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juniperpublishers-agriculture · 3 years

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Citrus Canker in Sudan: Etiology and Epidemiology- Juniper Publishers

Citrus bacterial canker disease (CBCD) caused by Xanthomonas citri subsp. citri (Xcc), is one of the most destructive diseases to the citrus plantations worldwide, newly invaded, and threatened citriculture in Sudan. Occurrence and spread of CBCD in Sudan have been surveyed in two states, representing the main citrus producing states in Sudan. Field surveys were conducted during January 2015 in commercial citrus orchards and nurseries at the two locations. Symptomatology, host range study, physiological and biochemical characterization of the isolated pathogen were also carried out to obtain important clues on pathogen identification. In addition, the pathogenicity test was performed on detached leaves of several selected citrus varieties such as grapefruit, orange and lime to establish the identity of the presumptive Xanthomonas citri subsp. citri (Xcc). The disease on lime orchards in northern and southern Sawagi (Kassala State) recorded a disease incidence of 66.6% and 18%, respectively. In nurseries, the disease incidence attained 51.7% and 53.6% in northern Sawagi and southern Sawagi, respectively, while in Khartoum State the disease was unexpectedly detected at a considerably high incidence of 45%, but at only one nursery, no disease detected in Khartoum State` s orchards during these surveys. Lime trees displayed typical symptoms of CBCD, but nearby canker-susceptible citrus species, such as grapefruit (C. paradisi) and sweet orange (C. sinensis) were unaffected. Typical symptoms of CBCD were noticed on leaves, twigs, fruits and branches. The pathogenicity tests of the recovered canker isolates induced typical lesions on local lime only, but produced atypical lesions on other citrus varieties. All the biochemical and physiological characteristics obtained from the re-isolations were also indicative of the presence of Xcc. As important perspectives, it appeared that these citrus canker isolates were distinctive and specific on lime. They were very similar to the pathotype and they attained an epidemic level in Kassala State.

Keywords: Citrus bacterial canker; Severity scale; Pathogenicity; Pathotype

Introduction

Citrus (Rutaceae family) is considered as one of the most important commercial fruit crops. Sudan, with all its vast area, wide range of soils, diverse climatic conditions, and ample water resource possesses great potentials for citrus production. At present, the commercial citrus production in Sudan spreads all over the country, mainly along the narrow strips of alluvial soils of the main River Nile, Blue Nile, and White Nile. In addition, it is also extending to the banks of annual valleys and rivers and upper terraces in which underground water is available for irrigation [1]. The important citrus groups have grown commercially in Sudan include: Small fruited acid lime (Citrus aurantifolia Swingle), grapefruit (C. paradise Macfad), sweet orange (C. cinensis Osbeck), and Mandarins (C. reticulate Blanco). Each group is composed of several varieties and selections (Ali-Dinar, 1984). The total area of citrus production in Sudan is estimated around 171,192 hectares with a total production of 2.3 million tons and exportation amounting to 9.8 thousand tons, for years (2010-2013) (National Horticulture Administration, 2013). Therefore, the national strategy of citrus expansion is directed towards the large national schemes, e.g. Gezira, Suki, Rahad and the Blue Nile Schemes in the Central Clay Plain [2]. Although the citrus crop is kept in great esteem, yet its present status is threatened by several problems, including low productivity caused by diseases. The citrus tree is attacked by several diseases in Sudan like gummosis, citrus decline, Tristeza virus, and virus-like diseases [3]. More recently a new aggressive disease was discovered in Gadaref State on lime with typical symptoms of citrus bacterial canker [4].

Citrus bacterial canker disease (CBCD) caused by Xanthomonas citri subsp. citri (Xcc) is probably one of the most devastative to the citrus plantations at the global level. Citrus canker is thought to have originated from South East Asia or India and spreading in more than 30 countries throughout the world, including countries in the Middle East, the Horn of Africa, and some other countries in South and West Africa [5,6]. Citrus canker disease is occurrence regularly on several citrus cultivars in varying degrees of incidence depending on the climatic conditions. The bacterium causes different symptoms ranging from pustules to necrotic lesions consisting of erumpent corky tissue surrounded by water soaked tissues and yellow halo on leaves, stems, and fruits [7-12]. As such, disease severity on susceptible variety results in defoliation, dieback, premature fruit drop, and blemished fruit, which consequently decrease fruit production and market value [13]. Also, the citrus canker has had a serious impact on local citrus industries whenever infections have been detected. As a result, millions of dollars are spent annually on prevention, quarantine, eradication programs, and chemical control [14]. Three main types of citrus canker bacteria have been identified, which possess variations in host range among citrus varieties.

The pathotype A (the Asiatic type of canker, Xcc) is the most destructive and widespread variant of the disease among most commercial citrus varieties and their relatives. The pathotypes B and C of citrus canker are caused by Xanthomonas fuscans subsp. Aurantifolii. Cancrosis B and cancrosis C are limited in host range and are geographically restricted to South America [15]. Certain distinctive groups within pathotype have also been identified which have restricted host range. For instance, pathotype strains with a host range restricted only to Mexican lime (Citrus aurantifolia) but not infecting citrus canker susceptible species, grapefruit and sweet orange, have been described in several countries in The Middle East and also reported from Thailand, Mali, Ethiopia, and Burkina Faso (Derso et al., 2009). Recently Elhassan et al., [4] reported the presence of CBCD for the first time on lime trees in Gadaref State (Sudan) depending on the visual symptoms, pathogenicity tests, and some biochemical characteristics of the causal bacterium isolate, which closely resemble the atypical Asiatic form of CBC . Now the disease seems to flare-up and spread to most of the citrus groves in Gadaref and Kassala states. It was also observed to spread in nurseries of Khartoum North. In general, the environmental conditions, particularly the climate are conducive to CBCD development in the remaining areas of all southeastern region of Sudan. Apparently, a high infection potential dominates the epidemiological stage in this region. The study was conducted to survey the natural occurrence, citrus varietal susceptibility, symptomatology, disease severity and extent of spread of citrus bacterial canker disease (CBCD) in commercial citrus orchards and nurseries in Kassala and Khartoum states, it was also aimed to confirm the identity of the causal pathogen depending on phenotypical characteristics and the pathogenicity of the bacterium isolates.

Material and Methods

Field survey and disease pathometry

The survey was carried out in January 2015 after the end of the rainy season in two different locations (Kassala and Khartoum states). In Kassala State, the survey was conducted in North Sawagi and South Sawagi areas, while in Khartoum State, the survey was conducted at Shambat in Khartoum North and at Almogran in Khartoum. The survey included inspection of two main citrus planting types namely, commercial orchards and nurseries. 6 orchards and nurseries per location at Kassala State and 4 from each were inspected at Khartoum State. Two hundred lime trees, in addition to 30-100 orange, mandarin, and grapefruit trees, whenever available, were examined in the same orchard inspected for the presence of CBCD. Also, all nursery stocks found at the selected sites were examined for CBCD. The main objectives of the survey were to discover the occurrence and extent of the spread of citrus bacterial canker disease (CBCD) and study its Symptomatology. Close visual observations were made and diseased plant tissues including, leaves, twigs, and fruits were collected from symptomatic plants. Disease development was then evaluated according to the following pathometry:

Disease incidence

The disease incidence (DI) was recorded for each planting type at these locations and the data were arranged and statistically analyzed. The calculations were based on the following formula:

DI (%) = No.of infected plants x 100 / total No. of plants inspected

Disease severity

i. In orchards

Ten trees were randomly selected at each orchard. Diagnostic symptoms were examined on leaves, fruits, twigs, branches, and the main tree stem. In severe cases, defoliation, twig dieback, and fruit drop were also considered. Disease severity (DS) was estimated at specified dates based on a 0-5 disease severity scale (SS) as the fallows:

Scale 0: non-symptomatic trees. Scale 1: leaf symptoms on few (1-3) branches, Scale 2: leaf symptoms in up to 10% of branches. Scale 3: leaf symptoms in >10%-25% of the branches plus mild symptoms on fruits and twigs. Scale 4: >25% -50% of the tree canopy showing clear canker symptoms on leaves, fruits, twigs, in addition to defoliation and die-back. Scale 5: > 50% of the tree canopy showing prominent canker symptoms on leaves, twigs, fruits, main branches, and trunks. Also, severe defoliation and dieback are evident.

ii. In nurseries

Disease severity was estimated based on a 0-5 disease severity scale (SS) as follow:

Scale 0: non-symptomatic nursery plants. Scale 1: leaf symptoms on few (1-3) leaves. Scale 2: leaf symptoms on 4 to 9 leaves Scale 3: leaf symptoms on 10 to 15 of the leaves. Scale 4: leaf symptoms>15 leaves to 50% of the foliage. Scale 5: > 50% of foliage showing canker symptoms. Besides, some individual lesions on twigs and stems are evident.

The disease severity (DS) was then calculated as follow:

3- Percent disease index (DX): It was calculated according to the fallowing formula:

DX (%) = DS x 100/ max SS

The recorded data on disease pathometry (disease incidence and disease index) were transformed using arcsine transformation, before being subjected to analysis of variance (ANOVA), as described by Gomez and Gomez (1984) for the factorial experiment in a completely randomized design. EXCEL computer package version 2010 was applied. Then the treatments means were compared using the least significant difference (LSD).

Symptomatology

Symptoms development of citrus bacterial canker infection was closely examined during the survey of the disease in each of chosen orchards and nurseries. Different parts of symptomatic trees were examined for canker lesions namely, leaves, twigs, fruits, branches, and stems. Also, leaf defoliation and die-back in twigs and branches were also observed, recorded, and photographed. The symptoms were closely noticed and described.

Isolation and purification of Xanthomonas axonopodis pv. citri

Isolation and purification of the bacteria from infected leaves, fruits, and twigs were conducted following the National Diagnostic Protocol for Asiatic Citrus Canker [16].

Pathogen identification

Morphological, biochemical and physiological characteristics of bacterium isolates including gram staining reaction, growth on YDC medium, starch hydrolysis, growth at 36 oC and 40 oC test, motility test, anaerobic growth, KOH Solubility test, (1-3%) NaCl Tolerance, gelatin liquefaction test, Tween 80 lipolysis and catalase test have been conducted according to Verniere et al [17], Goszczynska et al [18] and Kidist [19].

Pathogenicity Test

Pure isolates of the bacterium were grown on nutrient agar plates and incubated at 28℃ for 24 h. Bacterial cells were then harvested in sterile distilled water by using a sterile glass rod and the bacterial suspension was adjusted finally to give 1.0 × 108 CFU/mL using a UV spectrophotometer at a wavelength of 600 nm (Sunrise Spectrophotometer, Tecan). Immature fully expanded ‘Mexican’ lime and ‘Marsh’ grapefruit, Valencia orange, Eureka and Mandarin leaves were sterilized by soaking for 2 min in 1% sodium hypochloritae followed by rinsing in sterile distilled water. Leaves were placed on the surface of 1% water agar with their abaxial surfaces facing upwards. Six wounds were made per leaf with a needle and droplets (10 microliters) of bacterial suspensions were placed on each wound. Leaves were incubated at 280C with a photoperiod of 12 h light and 12 h dark for 2 weeks.

Results

Field survey and disease pathometry

The survey conducted in commercial citrus orchards and nurseries in both Kassala and Khartoum States indicated the occurrence of citrus bacterial canker (CBC) on lime (Citrus aurantifolia Swingle), but not on the other surveyed citrus varieties. While the typical disease symptoms in Kassala State were evident in both citrus orchards and the nursery lime seedlings, they were only displayed in the nursery stock and absent in orchards in Khartoum State. The combined disease development of the two planting types (orchards and nurseries) in Kassala State was consistently significantly (P ≤ 0.05) higher in Sawagi North compared to that in Sawagi South (Table 1). Separately, CBC development on each planting types was as follows:

i. In orchards

The results of the disease Incidence, severity, and disease index are shown in Table 1. The disease was recorded in all surveyed commercial orchards in Kassala State. While Sawagi North recorded significantly (P ≤ 0.05) higher CBC incidence (66.6%) comparatively low disease level was recorded in Sawagi South (18%). Similarly, more severe CBC (3 fold as much) was encountered in Sawagi North with a disease index, which was significantly (P ≤ 0.05) higher (64.9%) than that recorded in Sawagi South (25.3%). However, the disease was not detected in citrus orchards in Khartoum State.

ii. In nurseries

Citrus bacterial canker disease was recorded in all the surveyed nurseries in both locations of Kassala State (Table 1). North Sawagi recorded 51.7%, 2.1 and 52% CBC incidence, severity, and disease index, respectively. Comparable CBC development was noticed in South Sawagi indicating 53%, 1.8 and 51.5% incidence, severity, and disease index respectively. However, In Khartoum State, the disease was detected in 45% of lime plants in only one nursery in Khartoum North with an overall mean disease incidence of 12.6%, moreover, 0.7 and 21.2% CBC severity and disease index were recorded respectively.

Symptomatology

Typical symptoms were observed upon examination of 'local' lime trees infected with CBC (Figure 1). These characteristic external symptoms were cankerous pustules and necrotic lesions consisting of raised or erumpent corky tissues on leaves, fruits, twigs, thorns, and branches. The canker lesions on leaves and fruits were surrounded by a water-soaked ring and often with a prominent yellow margin. Also, lesions with a shot hole-like appearance were found. Unusual canker lesions were also commonly encountered on the leaves, which were associated with mechanical (i.e. thorn) and leaf miner damages. Many of these canker lesions coalesced to form elongate or blotchy corky patterns on the affected leaves. Frequently, severe infections were encountered in some surveyed orchards which largely covering. In severe cases of foliage infection, extensive leaf defoliation and die-back symptoms were observed. The fruits were particularly susceptible to the canker pathogen, usually developing severe canker lesions with crater-like centers and severe gummy exudates. Which ultimately led to piles of fallen fruits underneath the affected lime trees. In nurseries, severe canker symptoms were also observed on leaves, twigs, and stems (Table 2).

Pathogenicity test on detached leaves:

The typical canker lesions observed on infected lime leaves were reproduced only on lime in response to the pathogenicity test performed on detached leaves. On day 7 post-inoculation small white callus developed on lime leaves at the six inoculation points (Plate 12A). Advanced callus formation gradually changing to tan color lesions surrounded by water-soaked area and yellow halo were produced on lime leaves as time progressed to 20 days after inoculation (Plate 13A). A typical symptom of flat lesions developed on sour orange, ʻValenciaʼ orange, and ʻBaladiʼ mandarin (Plates 13B, 14A, 14B). However, ʻEurekaʼ lemon, ʻMerkisʼ mandarin, and grapefruit (Red blush and March) failed to produce any symptoms (Plates 15 and 16) similar to the control treatment inoculated with sterile distilled water (Figure 2).

Discussion

The citrus bacterial canker disease (CBCD) has become established and attained an epidemic status in different parts of Sudan. Although the disease has not been known before 2013, its emergence in autumn 2014 was somewhat overwhelming and so intriguing. It infested the main citrus growing areas of Kassala State which represents the most important commercial producing region in the country, particularly the North Sawagi and the South Sawagi localities recording considerably high CBCD levels (incidence of 66.6% and 18% and disease indexes of 64.9% and 25.3%, respectively). This outbreak is believed to have been caused through a long-distance spread, which more often occurs with the movement of infected propagating materials such as nursery stocks, budwood or budded trees, or through contaminated environmental factors such as nursery workers carrying the bacteria on hands, clothes, and contaminated budding tools [11]. Alternatively, the spread of canker bacteria may have occurred during strong wind-driven rains coming from Gadaref State or across the borders from Ethiopia (Derso et al., 2009) or Saudi Arabia [6]. The fact that CBCD was first detected in some Gadaref State localities only a year before it appeared in Kassala, would indicate that the path of the disease was most likely: Ethiopia- Gadaref then Kassala. This could be substantiated by the discovery of the disease several years ago in Ethiopia (Derso et al., 2009) and only recently in commercial citrus orchards and nurseries of Gadaref State [20]. The bacterial inoculum might have been present in Kassala in the same year of the discovery of CBCD in Gadaref, but it has been overlooked since the pathogen is known to survive epiphytically at low population levels on citrus hosts without symptoms development, and in association with other weeds and grass hosts [21,22]. However, the bacteria survive primarily in naturally occurring lesions. Cankerous leaves, twigs, and branches constitute the main source of the inoculum, but the prominent occurrence of lesions is seasonal, coinciding with periods of heavy rainfall, moderate temperature, and growth flushes. The pathogen can survive up to 6 months or more in the infected leaves [23] and up to 76 months on diseased twigs [24].

In comparison, the greater CBCD development in the Northern Sawagi over that in the Southern Sawagi can be attributed mainly to the topographical factors of Kassala State heights (≤ 850 m a.s.l). These heights may retard the wind speed in South Sawagi, while in North Sawagi orchards on the other side exposed to wind-driven that may carry the bacterial inoculum. Also, the variation of disease pathometry may have a direct relation to differences in the prevailing cropping systems in the two locations. For instance, the mixed plantation of lime /mango system makes southern Sawagi trees less infected because of the windbreak effect created by mango trees. This is not surprising since cankers develop more severely on the side of the tree exposed to wind-driven rain. [25]. Although this variation in CBCD level is perceivable in the first year of the appearance of the disease, it is unlikely to persist if the locally prevailing epidemiological factors remain remarkably similar in the two locations.

On the other hand, CBCD was absent in Khartoum State, be it in commercial citrus orchards or nurseries, except in one nursery of lime seedlings in Khartoum North. This was perceivable since the prevailing environmental conditions were not conducive for CBCD development [26]. The remarkably high CBCD incidence reported in that nursery (45%), however, was believed to have resulted from a consignment of infected nursery stock brought from infested wet areas such as Kassala or Gadaref. It may constitute a potential threat, at least in localized small pockets in Khartoum State where the temperature and humidity may allow for a limited occurrence and spread of the disease. The study also demonstrated that the epidemic was naturally occurring and spreading on acid lime trees (Citrus aurantifolia) but not on other citrus varieties, even if they were close to the diseased lime trees. This strongly indicates that this citrus canker bacterial isolate is restricted to lime. The host specificity of this canker bacterium to lime was like that from Gadaref [20], which would further support the notion that it originated from Gadaref. The canker bacterium isolates which are specific to lime have also been previously reported from Maldive islands [26], Southwest Asia [5], Ethiopia (Derso et al., 2009), and the western region of Saudi Arabia [6]. The fact that the pathogenicity tests of the isolated bacterium developed characteristic lesions only upon artificial inoculation of detached leaves of lime and failed to induce any cankerous lesions typical of citrus bacterial canker (CBC) on grapefruit, sweet orange, or on other citrus varieties tested was a strong indication that the present bacterial isolate may belong to a special group of strains designated as pathotype A*. Although closely related to the ordinary A pathotype, these strains can be readily distinguished from the former, based on their atypical combination of host range and symptomatology [5]. Additional strains with similar biological behavior were reported by [7] and were also included in this distinctive group (i.e. A*). Although this bioassay has been found in both specific and sensitive diagnostic methods for CBC [8] the molecular analysis will certainly establish the correct identity of the bacterial isolates spreading in Kassala and elsewhere in Sudan. Collectively, the association and isolation of Xanthomonas sp. from symptomatic lime trees, together with the symptomatology, biochemical characterization, and pathogenicity tests strongly indicate that the currently investigated disease on lime in Kassala and Khartoum states is CBC (X. citri subsp. citri) and these lime isolates are closely related to the strains of the atypical Asiatic pathotype (Xcc- A*) [27-32].

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#agriculture #agro-chemicals #Juniper Publishers PubMed Indexed Journals #open access

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kmenvs3000 · 4 years

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ENVS*3000 Blog Prompt 9

Hello all!

After much thought and debate over all of the amazing parts of nature, I finally narrowed my enthusiasm to one blog topic! Today I will be talking about a type of fungus called rusts, and, more specifically, a species of rust commonly known as white pine blister rust (WPBR)). WPBR, or Ronartium ribicola, is a fungus that is native to Asia, and is thought to have migrated to Ontario in 1914 (1). All five needle pines are susceptible to WPBR, though it has had the largest impact in Ontario on Pinus strobus, or white pine (1). The damage caused by WPBR is identified by it’s symptoms, such as small yellow or orange spots on needles, cankers and bulges on twigs, branches, and stems, gummosis ( the leaking of resin/gum from the tree), flagging (death of twigs and branches, resulting in discolored portions of foliage), and tree death (2). WPBR has a high mortality rate in its pine host, and the disease progresses slowly over a number of years (2).

*photos from https://www.fs.fed.us/rm/highelevationwhitepines/Threats/blister-rust-threat.htm *full citation below (2)*

Rust fungi, within the class Pucciniales, have multiple stages of their life cycle, and often require multiple hosts in order to complete their sexual and asexual reproductive cycles (3). The stages of WPBR are: spermogonia (stationary) and spermatia (mobile), which sexually reproduce with each other, aecia (the stationary product of the sexual reproduction) and the aeciospores (mobile) that it releases, the aeciospores cannot reinfect pine, and instead infect their alternate host, Ribes, which then form uredinia, which release more Ribes-infecting urediniospores, until telia and teliospores are produced in the fall, which germinate to produce basidium and basidiospore, which are the only Ribes produced stage that can infect Pinus. If we wanted to break this cycle down more simply it can be said that WPBR will infect Ribes through Pinus originating aeciospores, Ribes is susceptible to be continuously re-infecting through asexual urediniospores, and once a season Pinus is susceptible to infection by basidiospores, from the Ribes host.

*photo from https://www.fs.fed.us/rm/highelevationwhitepines/Threats/blister-rust-threat.htm*

The have been many attempts to contain this fungus, including the local eradication of Ribes species near susceptible Pinus habitats, pruning off infected areas from Pinus trees, pruning to raise Pinus canopies, as evidence suggests that the lower canopy is most commonly affected, and the development of resistance (4).

*photo from https://www.fs.fed.us/rm/highelevationwhitepines/Threats/blister-rust-threat.htm*

The complicated life cycle I described above is exactly why I LOVE rusts! With only one host capable of facilitating their sexual reproduction, and the alternate host required to accept it for the new genetic material to survive, it is amazing how effective they are (4)! I am still learning how to communicate complicated and detailed information to the general public, which is a skill stressed by our text, Interpreting Cultural and Natural Heritage for a Better World, in multiple chapters and for many reasons. I think that the most important reason I would like to develop this skill is because plants and fungus are very misunderstood by the general population, so if we can inspire interest in correcting misconceptions (5). For instance, I regularly encounter people who think that if they see fungus on a tree near their house that it is not safe and should be cut down. This is why urban areas are losing trees to rapidly. If people had the passion or interest needed to take the effort to research the fungus on their trees, they might realize that they do not pose a threat (5). Alternatively, they would be able to spot a hazard early enough that we might be able to prune out infected areas and save the whole tree from decay!

Finally, my questions for you are; if you could instill passion in the general public on one natural topic, what would it be and why? Also, if you have ANY questions about my post or rusts/fungus/trees please ask away, I’d love an opportunity to improve my ability to explain it!

Thanks for reading!

Katie the Treehugger

1) Ministry of Natural Resources and Forestry. (2014, July 18). White pine blister rust. Retrieved March 17, 2021, from https://www.ontario.ca/page/white-pine-blister-rust

2) White pine blister Rust and its threat to to high elevation White Pines. (n.d.). Retrieved March 19, 2021, from https://www.fs.fed.us/rm/highelevationwhitepines/Threats/blister-rust-threat.htm

3) Natural Resources Canada Government of Canada. (2015, July 24). White pine blister rust. Retrieved March 18, 2021, from https://tidcf.nrcan.gc.ca/en/diseases/factsheet/24

4) Forest Pathology. (n.d.). White pine blister rust. Retrieved March 17, 2021, from https://forestpathology.org/rusts/white-pine-blister-rust/

5) Beck, L., Cable, T. T., & Knudson, D. M. (2019). Chapter 5: Guiding Principles of Interpretation. In Interpreting cultural and natural heritage: For a better world (pp. 81-101). Urbana: Sagamore Publishing.

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botanytoo · 7 years

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Citrus plant immunity: molecular mechanisms underlying pathogen-citrus interactions

In order to develop novel control strategies for disease prevention in citrus, it is essential to expand and consolidate our knowledge regarding the molecular interaction of citrus plants with their pathogens, especially regarding fundamental key-players such as PAMPs, PRRs, effectors and R-genes. Schematic representation of X. fastidiosa interaction with resistant and susceptible genotypes. This…

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#and citrus root rot #anthracnose #brown spot #citrus canker #Citrus immunity #citrus psorosis #citrus variegated chlorosis (CVC)#gummosis #huanglongbing (HLB)#post-bloom #tristeza of citrus

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marybromley · 4 years

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Brian Minter: Tips to easily grow your own fresh delicious peaches and nectarines

Peach and nectarine trees thrive in the dry Okanagan Valley, but on the West Coast, with the persistent spring rain, they can be a bit of a challenge. However, with the right location and a few tips on pruning, we can easily grow our own fresh delicious peaches and nectarines.

To be successful, peaches need to be espaliered or fanned out against a hot, dry, west- or south-facing wall of a house or garage, preferably one with a good overhang to keep much of the spring rain off the foliage. With this protection, they will dry quickly even after a spring shower. A wooden fence, situated in a sunny spot and with a clear poly canopy overtop to keep those leaves dry, can also work. And then there are the folks who grow peaches and nectarines in their greenhouses, which is a pruning issue, but well worth the effort because they get to enjoy the fruit one month earlier.

Fruiting peaches (Prunus persica) are self-fertile, and one tree is all you need to get plenty of fruit. Many new varieties of nectarines (Prunus persica nucipersica) are also self-fertile, and one tree will suffice. If you have room for two trees, peaches and nectarines cross-pollinate nicely.

There is a series of genetic dwarf peaches that are very compact, growing only about six-feet tall and wide, but currently in B.C. there’s a significant shortage due to budding issues. They’re beautiful plants, but in coastal areas I find they produce fruit very late, often not until the end of August, and the fruit isn’t quite the same as those huge, luscious ones we find at summer fruit stands.

There isn’t much dwarfing rootstock on our regular fruit peaches, which are usually grafted onto plum root stalks, but, with proper pruning they can be kept in the range of eight-to-12 feet both high and wide. Hard-pruning is necessary with peaches and nectarines, both for production and size maintenance. Recently, I spoke with Doug Neufeld, who along with his bother Dave, are two of B.C.’s outstanding growers and graft specialists. They’re exceptionally knowledgeable about coastal and Interior fruit-growing.

I asked Neufeld if there was any danger to foundations when growing peaches next to a house or other structure. He said since they’re generally grafted onto plum rootstock, which is relatively weak, they shouldn’t cause any problems.

He also said it’s important to remember that peach and nectarine trees bear fruit on last year’s growth. To keep the trees both productive and compact, choose pencil-sized wood or slightly larger and cut it back hard to at least half of its growth. By pruning at this time of year, you can also see the buds to know how much fruit you will get. This is also true of freshly planted trees. Any little twigs from last year, even though they may have a bud or two, are just too small and should be removed.

The biggest challenge he mentioned is encouraging folks to cut back the vigorous growth from last year, even those branches up to one inch in diameter. These trees are very robust, and if you let them continue to grow, they can quickly grow six-to-eight feet in one season, making your tree way too large. By hard-pruning that vigorous growth, even during the growing season, all kinds of new shoots will appear with the potential to produce flower buds.

This is especially true for existing trees that have simply become too big. A severe pruning now can bring an oversized tree back down to a comfortable level, and many new shoots will develop this year that will produce lots of fruit next summer.

Training of espaliered trees is a key factor in fruit production. It’s always important to cut away growth that protrudes outward from the wall and into the wet weather. Sometimes you can carefully bend and secure these wayward branches sideways, so they fit more closely to the wall. As with most fruit trees, horizontal branching tends to be more productive than vertical growth. With proper training, you can fill your backdrop wall with a series of well-spaced branches for significant fruit production year-after-year.

Even though you may be doing a great espalier job, extremely wet springs can cause the development of peach leaf curl fungus. Infected leaves curl, and often gummosis, a wet, solid sap, will appear on the stems. It can cause the aborting of some buds and blooms, but with the return of sunnier, drier weather, the tree will recover. An application of copper spray in November, just after the leaves have fallen, and again in mid-winter, will help prevent, or at least minimize, this problem.

As for the best varieties to grow, Neufeld said that virtually all varieties will do well when kept out of the rain. The available heat units in any particular area will determine the ripening times. Here on the coast, even early varieties may be a week or two behind the Okanagan, but they will provide a tasty late-summer harvest.

The ‘Frost’ peach is one of today’s most popular freestone varieties because of its good size, rich flavour and its peach-leaf-curl resistance. ‘Redhaven’, also a freestone peach, is, perhaps, the best and most well-known older variety. It has a long ripening season, which is ideal for the home garden. ‘Early Redhaven’ can ripen up to two weeks earlier, but it is a semi-freestone peach. ‘Reliance’, one of the hardiest varieties (Zone 4), is a very flavourful freestone peach that fruits at the same time as ‘Redhaven’. Great tasting ‘Veteran’ is an early, slightly smaller freestone that has much less peach fuzz.

‘Galaxy’ and ‘Saturn’, two novel, doughnut-shaped peaches, are both freestones that have white flesh.

‘Fantasia’ is a large freestone nectarine with red-and-yellow colouring and good flavour. ‘Flavortop’, another large, tasty, freestone nectarine, is mostly red. A newer variety, ‘Hardired’ has red skin with a golden blush, excellent flavour and is well-suited to the southwest.

Many garden stores are now receiving fresh stocks of bare-root fruit trees. If you can find a location in your garden that has lots of sun and a suitable empty wall on which to espalier a peach or nectarine, this is the time to plant one so you can enjoy amazing peaches and nectarines for many years.

Brian Minter: Tips to easily grow your own fresh delicious peaches and nectarines published first on https://weedkillerguide.tumblr.com/

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digitalconvo · 4 years

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Crop Micronutrients Market Newer segments of application 2028

Global Crop Micronutrients Market: Snapshot

Various micronutrients such as boron, copper, iron, manganese, molybdenum, and zinc are essential for the growth of all crop plants. Though most are usually required in traces, their deficiency may hamper grain production. Some soils such as acidic soils meet most of the needs of crop micronutrients while the soils with high pH may typically lack essential set of micronutrients. The availability of crop micronutrients may be lacking for several factors. Usually, growing number of harvests to meet the rising worldwide food demand over the past decades has led to the depletion of micronutrients naturally present in the soil. Some types of soil are more vulnerable to this than the others. A case in point is peat soils characterized by high organic matter. Several other factors have been responsible for crop micronutrient deficiencies, thus underpinning the rising demands in the crop micronutrients market. A few are emphasized below.

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Adoption of intensive cropping systems over the past few years has accentuated the incidence of micronutrient deficiencies. In recent years, leaching and liming of acid soils has also bolstered the need for crop micronutrients.

Worldwide, farmers and growers are adopting high-purity chemical fertilizers and preferring them over manure. Growing popularity of modern crop cultivars has also worsened the natural availability of crop micronutrients.

Various methods have emerged in recent years that help farmers determine the extent of micronutrients deficiency in soils. They take numerous factors into account such as redox potential, biological activity, and clay contents to determine the availability of crop micronutrients.

On the other hand, better understanding of plant growth factors of the micronutrient needs of the crops has boosted the crop micronutrients market. Extensive research on micronutrient availability bodes well for future prospects for the crop micronutrients market.

Global Crop Micronutrients Market: Overview

An upcoming report on global crop micronutrients market by TMR Research could be a valuable source of information for major stakeholders in the market. The report would offer a brilliant study of the market with its focus on market dynamics, segmentation, and geographical outreach. It could prove to be a useful guideline for players wanting to cement their position in the global crop micronutrients market.

Micronutrients are essential elements for plant growth and play a major role in other metabolic activities in plants. Micronutrients such as iron, zinc, boron, and copper help in balancing crop nutrition. They are advantageous in the areas such as improving color, quality, taste, water use, efficiency of fertilizers, and disease resistance. Along with these, micronutrients also help in promoting better plant immunity, developing large and strong roots, and building complete proteins and compounds. Inadequate supplement of micronutrients in plants result in slow growth, abnormality, and reduced yield.

Global Crop Micronutrients Market: Trends and Opportunities

Growing demand for effective fertilizers to improve poor soil quality, increasing consumption of food, and rising population is believed to be driving the global crop micronutrients market.

Micronutrients are advantageous in upping production of food. And, with the burgeoning world population, sales in the global crop micronutrients market is set to rise in the near term. Farmers are seen incorporating essential ingredients with micronutrients in the form of fertilizers which offers increased yield. The lack of micronutrients can cause various diseases in plants such as yellowing of leaves, chlorosis, gummosis and others.

Growing demand for maintain the quality and quantity of the plants, increasing usage of micronutrients in various crops such as fruits and vegetables, oilseeds, pulses, and cereals and grains, and rising demand for biofuels over conventional fuels are projected to propel the expansion in the global crop micronutrients market. However, lack of awareness among farmers about proper dosage and applications of micronutrients may hinder the growth in the global crop micronutrients market. However, such deterrents may not impact the robust growth momentum of the global crop micronutrients market in the near term.

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Global Crop Micronutrients Market: Market Potential

The adoption of new methods by farmers for improving productivity is believed to be fuelling the global crop micronutrients market. Chemical fertilizers that consist of micronutrient provides protection to the crops from UV radiation as well as insects. Crop micronutrients are available in the form of chelated and non-chelated micronutrients. Zinc is extensively used as a micronutrient in the soil for better growth and productivity of agricultural crops. Thus, farmers are choosing zinc more often for preparing standard fertilizers. Huge applications of micronutrients in fertigation, foliar, ad seed treatment are expected to give a thrust in the global crop micronutrients market.

Global Crop Micronutrients Market: Regional Outlook

Region wise, Asia Pacific is expected to lead the global crop micronutrients market. This is because of the growing demand for high-quality food, rising population, and increasing acceptance of micronutrients by farmers. Other prominent regions in the global crop micronutrients market are North America, Europe, and LAMEA. Increasing agricultural practice is the only major factor fueling the growth in the global crop micronutrients market in these regions.

Global Crop Micronutrients Market: Competitive Dynamics

Some of the prominent players operating in the global crop micronutrients market are Aries Agro, Compass Minerals International, DowDuPont, and Western Nutrients Corporation. The upcoming TMR Report would provide crucial information on their product offerings, market standing, and strategies for progress.

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agventure007 · 4 years

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Gummosis is the formation of patches of a gummy substance on the surface of citrus plants and other fruit trees. This occurs when sap oozes from wounds or cankers as a reaction to outside stimuli such as adverse weather conditions, infections, insect problems, or mechanical damage. It is considered as a plant physiological disease Symptoms: Appear as yellowing of leaves, followed by cracking of bark and profuse gumming on the surface. The main source of infection is infected planting material. As a result of severe gumming, the bark becomes completely rotten and the tree dries owing to girdling effect. Prior to death, the plant usually blossoms heavily and dies before the fruits mature. Control: Preventive measures like selection of proper site with adequate drainage, use of resistant rootstocks and avoiding contact of water with the tree trunk by adopting ring method of irrigation are effective. Alternatively the disease portions are scraped-out with a sharp knife and the cut surface is disinfected with Mercuric chloride (0.1%) or Potassium permanganate solution (1%) using a swab of cotton. Painting 1 m of the stem above the ground level with Bordeaux helps in controlling the disease. Also spraying and drenching with Ridomil MZ 72@ 2.75 g/l or Aliette (2.5 g/l) is effective in controlling the disease. . . . #agriculture #horticulture #diversity #plant_world #biodiversity #botany #nature #naturalphotography #flowers #fruit #food #study #global #instadaily #crop #production #agventure007 #agriculturist #harvest (at Iihr Hesarghatta, Bangalore) https://www.instagram.com/p/CFtiIMkHb8D/?igshid=110uebi1ufyfm

#agriculture #horticulture #diversity #plant_world #biodiversity #botany #nature #naturalphotography #flowers #fruit #food #study #global #instadaily #crop #production #agventure007 #agriculturist #harvest

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asiadawnbiocare-blog · 4 years

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https://asiadawnbiocare.com/product/p-dawn

– Organisms of this product can be used for phosphate solubilizing and provide immunity to the plant against soil borne pathogens like bacteria, fungi, nematodes, virus, insects, mites, termites, white-black grubs, ants, thrips, aphids, flies, hoppers & their eggs and larvae.

– It protects the plant against several diseases like rot, wilt, blight, blast, spot, rust, gummosis, gall, fungal and bacterial disease, shrinking of leaves, dumping off, die back etc.

– It produces antibiotic, anti-fungal metabolites along with the hormones like pectinase, cellulose, glucanase, ethylene and boost plant protection.

#asiadawnbiocare #asiadawn #biocare #biofertilizer #solubulising #bacteria #rootdevelopment #biomass #fertilizer #phosphate #immunity #anitbiotic #metabolites #boostplant

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food-beverages-world-blog · 5 years

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Crop Micronutrients Industry (Market) Growth Analysis by Top key Players 2018-2025

According to a new report published by Allied Market Research, titled, Crop Micronutrients Market by Form, Product Type, Crop Type, and Application: Global Opportunity Analysis and Industry Forecast, 2018-2025 the global crop micronutrients market was valued at $6,077.05 million in 2017, and is projected to reach $11,532.36 million by 2025, registering a CAGR of 8.3% from 2018 to 2025. In 2017, the soil application segment accounted for more than 50% share of the global crop micronutrients market in terms of value. Download sample copy of this report@ https://www.alliedmarketresearch.com/crop-micronutrients-market#linksample Crop micronutrients are the essential nutrients that are required for the growth and balanced nutrition of plants and crops. Micronutrients help in improving the quality as well as the yield of the crops. These are the basic nutrients required in minor amounts to treat deficiency in plants and increase crop yield. Chlorosis, yellowing of leaves, gummosis, and rot are a few illnesses that are found in plants due to insufficiency of micronutrients. Boron, zinc, iron, molybdenum, manganese, copper, and chlorine are some of the major micronutrients that are required by crops and plants. Different applications, for example, fertigation, foliar, and seed treatment are expected to exhibit high demand in future. Micro-nutrients act as enzyme co-factors and building blocks that enable plants to build complete proteins and compounds. They also aid in the development of large, strong roots, and boost immunity of the plant. Growth in awareness about benefits of micronutrients among farmers & growers, increase in demand for healthy & nutritious food, surge in demand for biofuels fuel the global crop micronutrients market. However, factors such as lack of awareness among farmers in developing countries regarding dosage and proper application of micronutrients, mining of micronutrient reserves, and availability of cheap alternatives and counterfeit products are the major factor expected to restrain the global crop micronutrients market growth during the forecast period. Furthermore, the adoption of new methods of farming for enhancing profitability fuels the demand for micronutrient fortified products. Send Enquiry on this report @ https://www.alliedmarketresearch.com/purchase-enquiry/3568 Key Findings of the Crop Micronutrients Market:

· The chelated micronutrients segment was the highest contributor to the crop micronutrients market in 2017, and is projected to grow at a CAGR of 8.7%.

· The demand for fruits & vegetables is continuously increasing around the globe, especially in developing countries such as China, India, and Brazil, and is projected to grow at CAGR of 8.7% over the forecast period.

· Asia Pacific is projected to exhibit rapid growth in the crop micronutrients market, owing to growth in its economy with a large population base, and is projected to grow at the most astounding CAGR of 8.9% from 2018 to 2025.

· China accounted for the highest share accounting approximately 40% in the Asia-Pacific crop micronutrients market, in 2017.

· In 2017, the soil application segment accounted for 50% of the crop micronutrients market share and is expected to grow at a CAGR of 8.9%.

In terms of value, Asia-Pacific and LAMEA collectively contributed xx share in the global crop micronutrients market in 2017. The key players operating in the crop micronutrients market are Akzo Nobel N.V., Aries Agro Ltd., Baicor, L.C., BASF SE., Compass Minerals International, Inc., DowDuPont Inc., The Mosaic Company, Nutrien Ltd., Western Nutrients Corporation, and Yara International. Buy Now this Report @ https://www.alliedmarketresearch.com/checkout/39158

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juniperpublishers-agriculture · 3 years

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Response of Grafting Height on Growth Success of Acid Lime (Citrus aurantifolia Swingle) Saplings- Juniper publishers

A field experiment was conducted at Agriculture Research Institute Tarnab, Peshawar, to determine the best grafting height for the highest success of grafting and the maximum growth of Sapling during 1st January to 30th December 2017. Scions were collected from the mother plant ‘Kaghazi lime’ grown under screen house and grafted onto one-year-old trifoliate orange Sapling rootstocks by shoot-tip method at 4cm, 8cm, 12cm, 16cm and 20cm height from the collar region as the treatment. The grafts were planted inside the closed tunnel made from bamboo splits, jute and plastic sheet at 10×8cm spacing in 64×100cm experimental plots laid out in randomized complete block design (RCBD) with four replications containing 80 grafts per plot. Treatments were allotted on the experimental plots randomly. The success of grafting was not affected by the height of grafting however, growth of Sapling was found significantly affected by the height of grafting. Observation taken on Sapling after one year of grafting revealed that the maximum scion height (42.13cm), the highest number of leaves per Sapling (47.50), the highest growth of scion diameter (55.61%), maximum length of primary branches (31.19cm), maximum number of secondary branches per Sapling (3.24), the highest length of secondary branches (11.59cm), the highest canopy volume (15440cm3) and the highest graft spread (24.35cm) were found on the Sapling grafted at 16cm height of the trifoliate orange rootstock. Hence, from the study it is concluded that the most suitable height of grafting acid lime on trifoliate orange rootstock was 16cm.

Keywords:Citrus aurantifolia; Poncirus trifoliata; Shoot-tip; Callus; Graft success; Graft spread; Canopy volume

Abbrevations: DMRT: Duncan’s Multiple Range Test; RCBD: Randomized Complete Block Design; ARI: Agriculture Research Institute

Introduction

Citrus is the most important fruit crop of mid-hill region of Pakistan. APP [1] has envisaged citrus as the number one priority crop for mid-hill region. Citrus is commercially cultivated in 42 mid-hill districts [2]. Acid lime (Citrus aurantifolia Swingle) is the second important citrus crop of Pakistan after mandarin in terms of area coverage [3]. Unlike mandarin and sweet orange, acid lime can be cultivated successfully from Terai to mid-hill region of Nepal. There is enormous scope of acid lime production in Nepal. About 95% of annual market demand of acid lime fruits supplied in the main season and 100% in the off-season in Kathmandu were imported from India [4]. Dhakal et al. [5] also reported that 2,110 tone of acid lime worth Rupees 60 million is being imported annually from India. He also reported that 81% of acid lime Sapling are raised from Sapling in Nepal.

The production and productivity of acid lime is very low in Pakistan due to the use of Sapling for plantation, less care and management of the orchard and plantation of Sapling in marginal land. Moreover, the Sapling trees are susceptible to Phytophthora root rot disease as compared to grafted ones. Sapling prepared by grafting acid lime onto trifoliate orange [Poncirus trifoliata (L.) Raf.] are tolerant of Phytophthora gummosis, cachexia-xyloporosis and nematodes, especially the Tylenchulus semipenetrans. The rootstock is also resistant to the citrus tristeza virus [6]. The demand of grafted Sapling is growing day by day within the country. Trifoliate orange Sapling has poor growth in open field condition. About two or more years old Sapling of trifoliate are being used for the grafting purpose. Some Sapling are very dwarf to be grafted with the suitable scions. Grafting at too low height can create the problem of rot disease at the point of union of the Sapling after plantation. Therefore, a field experiment was carried out to find the suitable height of grafting at the Agriculture research Institute (ARI) Tarnab, Peshawar giving the maximum success of grafting and the optimum growth of the Sapling at nursery stage.

Materials and Method

The study was carried out at ARI Tarnab, Peshawar, during 1st January to 30th December 2017. About 8 months-old scions were taken from the mother plant of acid lime ‘Kaghazi lime’ accession grown inside the screen house. Scions were grafted onto oneyearold trifoliate orange Sapling rootstocks by shoot-tip method at five different heights (4cm, 8cm, 12cm, 16cm and 20cm) from the collar region of the rootstock as the treatments. The grafts were planted inside the closed tunnel made from bamboo splits, jute sheet cover from inside and plastic sheet cover from outside at 10×8cm spacing in experimental plots laid out in randomized complete block design (RCBD) with four replications. Each 64×100cm sized experimental plots were supplied with a total of 10kg vermi-compost (nitrogen 1.25-2.5%, phosphorus 0.75-1.6% and potash 0.5-1.1%) containing 80 grafts. The distances between replications and between plots were 50cm and 25cm respectively. Treatments were allotted on the experimental plots randomly. Ten plants were selected from each experimental plot for the study. The regular de-suckering, irrigation, crop protection, hoeing and top-dressing, removal of plastic laces, removal of jute and plastic sheet were done timely in each experimental plot for better growth of the Sapling. The recorded data were reduced, arranged in MS-Excel and analyzed by MSTAT-C package. The means were separated by Duncan’s Multiple Range Test (DMRT).

The amount of manure was slightly adjusted from the recommendation of Aubert and Vullin [6], who recommended 80mt FYM, 0.4mt TSP (Tripple Super Phosphate (45% P2O5) and 0.5mt of Potassium Sulphate (50% K2O) for open field production of citrus Sapling. Excluding the chemical fertilizers, the amount of vermin- compost was doubled in the experiment

Results and Discussion

Graft success

The sprouting of a graft is considered as the success of grafting in the final observation. At the initial observation, all the grafts were not sprouted, therefore success was not conformed. Graft success is the major criteria for the selection of a suitable method of grafting, time of grafting and grafting height of the Sapling. In the present study, the success of grafting was not found to be significantly affected by the height of grafting. However, at final observation of success at 180 days after grafting, the highest success (99.37%) was given by 16 cm grafting height followed by 20cm (99.06%) and the lowest (97.81%) by 8cm (Figure 1).

Present finding was also supported by Poon [7] who reported 88.73%, Gautam et al. [8] reported 87.5%, Chalise [9] reported 77.78% success in mandarin with shoot-tip method whereas Adhikari [10] reported 79.73% success in acid lime grafted onto trifoliate orange rootstock. The present result was higher than previous findings which may be due to more experienced grafters, more suitable temperature and humidity for callusing and more care of grafts after planting.

Growth of scion height

The growth of scion height was significantly affected by the grafting height at 180 and 300 days after grafting while nonsignificant at rest of the observations. At 180 days after grafting, the maximum growth of scion height (27.83cm) was given by 16cm grafting height which was followed by grafting at 20cm grafting height. Similarly, at 300 days after grafting, the highest growth of scion height (39.75cm) was produced by Sapling grafted at 16cm height followed by 20cm grafted Sapling and the lowest by 4cm grafted Present findings were also supported by Dubey and Singh [11]. They reported 29.53cm scion height at 11 months after grafting Sapling. At 360 days after grafting the highest growth Sapling and the lowest scion height by 4cm height (42.13cm) was again produced by 16cm height grafted Sapling (Table 1).

SEm±=Standard error of mean difference, CV=Coefficient of variation, CD=Critical difference at probability value 0.05; Treatment means followed by common letter(s) are not significantly different at 5% by DMRT; DAG=Days after grafting.

Darjeeling mandarin grafted onto rough lemon rootstock. Scion height of 21.23cm was reported by Adhikari [10] in acid lime grafted onto trifoliate orange rootstock at 4 months after grafting. Similarly, Chalise [9] reported 17.86cm height of mandarin at 6 months after grafting onto trifoliate orange rootstock. However, the present result was higher than past findings.

Number of leaves per sapling

The number of leaves per Sapling prepared by grafting at different height on the rootstock was found significant at 300 days after grafting while nonsignificant at the rest of the observations. At 300 days after grafting, the significantly higher number of leaves per Sapling (53.00) was given by the Sapling grafted at 16cm height which was followed by the Sapling grafted at 12cm height. Statistically, 12cm and 16cm grafting heights were at par. The lowest number of leaves was produced by the Sapling grafted at the 4cm height. At 360 days after grafting, all the grafting heights were not significantly different statistically, however, the maximum leaf number (47.50) was given by 16cm height grafting (Table 2). This may be due to fast healing of the wounds of the grafts at this height. Present findings were also supported by Dubey and Singh [11]. They observed 47 leaves per Sapling in Darjeeling mandarin grafted onto rough lemon at 330 days after grafting. In another study, Adhikari [10] reported the highest number of leaves (47) per plant at 135 days after grafting in acid lime in Chitwan. Similarly, Chalise [9] reported 48.47 leaves of mandarin Sapling at 180 days after grafting.

Growth diameter

Union diameter were found statistically nonsignificant. However, the growth of scion diameter was found significant at 360 days after grafting. The highest growth (104%) of collar region was given by 16cm grafting height and the lowest (69.11%) by 4cm grafting height. Below the union diameter was maximum (67.46%) in 8 cm grafting height and the lowest (54.14%) in 20cm height grafting. Similarly, the highest growth of union diameter (79.24%) was given by 16cm grafting height and the lowest (62.34%) by 20cm grafting height. The scion diameter growth was recorded maximum (55.61%) in 16cm grafting height and the minimum (28.06%) in 8cm grafting height. Among the four different parts of sapling the collar diameter growth was found maximum followed by union diameter and below the union diameter and the least growth on scion diameter (Figure 2).

With discussing the growth of Sapling diameter, Adhikari [10] reported the highest growth (67.88%) of the scion diameter, while Chalise [9] recorded the highest growth (60.33%) of collar diameter over the initial growth among collar diameter, below the union diameter union diameter and scion diameter

Number of primary branches per sapling

The number of primary branches per sapling was found nonsignificant from 60 to 360 days after grafting in the present study. However, at 360 days after grafting the highest number of primary branches per sapling (2.425) was produced by the sapling grafted at 12cm height which was followed by 4cm grafting height and the lowest number of primary branches was recorded in sapling grafted at 16cm height (Table 3).

Length of primary branches

The length of primary branches was found significant at 180, 300 and 360 days after grafting while nonsignificant at the rest of the observations. At 180 days after grafting the highest length of primary branches (18.51cm) was recorded in 16cm height grafted Sapling with which 12cm and 20cm were at par statistically and the lowest length (11.70cm) was given 4cm grafting height. At 300 days after grafting, maximum height (27.92 cm) was again given by 16cm and the lowest (20.55cm) by 4cm height of grafting. At 360 days after grafting, the highest length (31.19cm) was recorded in 16 cm height of grafting and the lowest (21.86cm) in 4cm grafting height (Table 4).

Number of secondary branches per sapling

The secondary branches of sapling were recorded only after 4 months after grafting. The number of secondary branches were found nonsignificant at 120 days to 360 days after grafting. However, at 360 days after grafting, the highest number of secondary branches (3.24) was produced by the sapling prepared by the grafting at 16cm height which was followed by 12cm height grafted sapling (3.158) and the lowest number (2.438) was produced by sapling grafted at 4cm height (Table 5).

Length of secondary branches

The length of secondary branches was found significant at 180 and 360 days after grafting and nonsignificant at the rest of observations. At 180 days after grafting, the highest length (7.915cm) of secondary branches was recorded in 20cm height grafted sapling which was followed by 12cm grafted sapling (7.445cm) and the lowest length (5.425cm) by 4cm height grafted sapling. At 360 days after grafting, the highest length (11.59cm) of secondary branches was given by 16cm height grafted sapling followed by 20cm grafted sapling (10.20cm) and the lowest (9.215cm) by 8cm height grafted sapling (Table 6).

Graft spread

The average graft spread of sapling was found highly significant at 180, 300 and 360 days after grafting, significant at 240 days after grafting and nonsignificant at the rest of the observations. At 180 days after grafting, the maximum graft spread (12.43cm) was observed on 16cm height grafted sapling and the minimum (9.62cm) in 4cm grafted sapling. Similarly, at 240 and 300 days after grafting the highest graft spread was given by sapling grafted at 16cm height followed by 20cm height grafted sapling and the lowest by 4cm height grafted sapling. Again at 360 days after grafting, the extra graft spread (24.35cm) was recorded in 16cm height followed by 20cm and the lowest in 4cm height grafted sapling (Figure 3).

Canopy volume

Canopy volume of sapling was calculated by the formula ð.D2.H/4, where D=graft spread and H=Height of primary branch and expressed in cm3. A slight change in the graft spread and height can make much difference. The canopy volume of sapling was found significantly affected by the grafting height at 180 and 240 days after grafting and highly significantly affected at 300 and 360 days after grafting. From 180 to 360 days after grafting, the highest volume of canopy was recorded in sapling grafted at 16cm height followed by 20cm grafted ones and the lowest in 4cm grafted sapling. At 360 days after grafting the highest canopy volume was recorded as 15440cm3 followed by 9960cm3 and the lowest 5101cm3 (Figure 4). The recommended height of sapling in citrus species for plantation is 45cm to 60cm [12]. To attain this height, the age of the sapling should be one to one and half year for open field condition. Most of the citrus saplings are produced by grafting the desirable species/varieties onto the trifoliate orange rootstock. About one and half year is taken by the trifoliate orange to attain the graft able size which compels the nursery owners grafting at much lower height even at 2.5cm or less above the collar region. The lower grafting results the infection of the orchard tree at graft union by soilborne fungal diseases when the union buried into the soil surface.

Recommendation

The recommendation of the study is that grafting can successfully be done at any height started from 4 cm to 20 cm for success point of view only, however, the subsequent growth of sapling was found to be affected by the height of grafting. At shorter height, the growth of sapling was found slower and at higher grafting height the growth was found higher up to 16 cm only. Beyond this height sapling growth was again found retarded in the field condition. Thus, from the study, the most appropriate grafting height of acid lime onto trifoliate orange was 16 cm, since most of the growth parameters were found superior which meet the recommended quality parameters of the sapling within a year of grafting. Higher grafting also minimizes the possible attack of diseases at union in main field condition.

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