Early Defoliation Research Articles

State of Knowledge of Apple Marssonina Blotch (AMB) Disease among Gunwi Farmers

Purpose: Fuji apples are one of the top selling exports for South Korea bringing in over $233.4 million in 2013. However, during the last few decades, about half of the Fuji apple orchards have been infected by Apple Marssonina Blotch disease (AMB), a fungal disease caused by Diplocarpon mali., which takes about 40 days to exhibit obvious visible symptoms. Infected leaves turn yellow and begin growing brown lesions. AMB promotes early defoliation and reduces the quality and quantity of apples an infected tree can produce. Currently, there is no prediction model for AMB on the market. Methods: The Precision Agriculture Laboratory (PAL) at the University of Florida (UF) has been working with the National Academy of Agricultural Science, Rural Development Administration, South Korea to investigate the use of hyperspectral data in creating an early detection method for AMB. The RDA has been researching hyperspectral techniques for disease detection at their Apple Research Station in Gunwi since 2012 and disseminates its findings to the local farmers. These farmers were surveyed to assess the state of knowledge of AMB in the area. Out of a population of about 750 growers, 111 surveys were completed (confidence interval of +/- 8.59%, confidence level of 95%, p-value of 0.05). Results: The survey revealed 32% of the farmers did not know what AMB was, but 45% of farmers have had their orchards infected by AMB. Twenty-five percent could not distinguish AMB from other symptoms. Overwhelmingly, 80% of farmers strongly believed an early detection method for AMB was necessary. Conclusions: The results of the survey will help to evaluate the outreach programs of the RDA so they can more effectively educate farmers on the identifying, treating, and mediating AMB.

Yield Response to Early Defoliation in Spring‐Planted Canola

Canola (Brassica napus L.) is a high‐value summer annual crop grown in the northern Great Plains of Canada and the United States. During the early stages of its life, the crop may lose leaf area as a result of spring hail storms, frost, herbicides, animal grazing, and insects. However, little information is available on the effect of defoliation during vegetative growth on yield for spring‐planted canola. To address this gap, a five site‐year study was conducted in central Saskatchewan, Canada, to test canola recovery from partial (50%) or full (100%) defoliation at five stages before flowering (2‐, 4‐, 6‐, 8‐, and 10‐leaf stages). Partially defoliated canola plots yielded, on average, 92% of untreated control plots, while fully defoliated canola yielded 75% of controls. The yield response to defoliation timings varied; in one site‐year yield loss was minimized with earlier timings, while in the remaining site‐years, seed yield response was inconsistent or unrelated to timing. Our study shows that partial or full defoliation of summer‐cropped canola at any point during vegetative growth is likely to cause a yield loss. However the crop's substantial compensation for loss of foliage means that reseeding is rarely profitable.

Identification of a defoliation severity threshold for changing fruitset, bunch morphology and fruit composition in Pinot Noir

Background and Aims Early defoliation has been proposed as a tool to reduce bunch susceptibility to fungal infections through a reduction in bunch compactness. This research aims to determine the desired level of defoliation producing looser bunches and to investigate the impact of the application of early defoliation on Pinot Noir vines under cool climate conditions. Methods and Results We applied leaf removal treatments at full flowering or EL-20 phenological stage on Pinot Noir in 2 consecutive years using five levels of defoliation: no leaves removed, and leaves removed from four, six, eight and ten basal nodes. The effects on fruitset, bunch morphology, fruit chemistry, yield and rot severity were recorded. We identified the defoliation of eight basal nodes as the threshold resulting in significantly lower fruitset. The removal of eight or ten leaves reduced bunch compactness but did not alter the proportion of rot. Finally, fruit composition at harvest of the treated vines was found to be improved compared with that of the control vines. Conclusions The defoliation of six to eight basal nodes at full flowering can regulate fruitset and bunch compactness in Pinot Noir under cool climate conditions. Application over 2 years showed no adverse effects on bud fruitfulness or vine performance the following year. Significance of the Study Early leaf removal can be an efficient tool to alter bunch architecture, yield and fruit composition without impacting vine health.

Effect of Early Defoliation on Fruit Yield, Reserve Accumulations and Flower Bud Formation in ‘Sinano Sweet’ Apple Trees

Effect of Early Defoliation on Fruit Yield, Reserve Accumulations and Flower Bud Formation in ‘Sinano Sweet’ Apple Trees

Short- and long-term effects of carbohydrate limitation on sugar and organic acid accumulation during mandarin fruit growth.

The physiological roles of organic acids in fruit cells are not fully understood, especially in citrus, whereas the decline in titratable acidity during ripening shown by many citrus fruits is due to the utilization of citric acid. We induced carbohydrate depletion by removing source leaves at two key periods in mandarin development (early and full citric acid accumulation). Then, we assessed the resulting changes in the short term (within 48 h) and long term (several weeks until ripening). Control mature fruits were characterized by elevated fresh weight, large diameters and high quantities of malic acid, citric acid and sucrose. At the same stage, fruits subjected to early or late defoliation had higher glucose, fructose, citric acid concentrations and lower sucrose concentrations. They differed only in their malic acid concentrations, which were higher in early defoliation fruits and similar in late defoliation fruits when compared to control fruits. Finally, fruits subjected to late defoliation were characterized by high proline and γ-aminobutyric acid concentrations, and low fructose and glucose concentrations. We have shown that short- and long-term carbohydrate limitation modifies sugar and organic acid metabolism during mandarin fruit growth. © 2015 Society of Chemical Industry.

Current status and management of coffee leaf rust in Brazil

In Brazil, coffee leaf rust, a fungal disease caused by Hemileia vastatrix Berk. et Br., was first detected in Coffea arabica in January 1970, in the southern region of Bahia state. Today, the disease is present in virtually all arabica and conilon (Coffea canephora) coffee-growing areas of Brazil, and continues to threaten coffee production with losses that range from 30 to 50 %. The disease is usually less severe at elevations above 1,200 m, where the environment is less conducive for the rust. Disease risk is increased in arabica coffee compared to conilon, and lower production is expected in the year following an epidemic due to early defoliation and drying of branches. Several varieties were developed in the country using sources of resistance from germplasm collections in Portugal. However, very few are completely resistant, instead exhibiting various levels of partial resistance. The disease is currently managed through the use of protectant and systemic fungicides including copper, triazoles and strobilurins that should be applied following rules of decision that vary according to the risk scenario. A review of the biology and epidemiology of coffee rust in Brazil is presented and the best management practices for controlling the disease based on advances in breeding for resistance and crop protection are discussed.

Impact of Early Defoliation on California Pima Cotton Boll Opening, Lint Yield, and Quality

Chemical defoliation is a necessary pre-harvest practice in Pima cotton (Gossypium barbadense L.) production in California. Growers begin defoliating as early as possible but yield and quality loss can occur if the bolls are not fully mature. Harvest aids can advance harvest dates, avoid late-season pests, and adverse weather conditions in California. A study was conducted on Pima cotton, cv. ‘Phytogen-802’. Different rates of Ginstar (ai thidiazuron/diuron, Bayer CropScience) or Ginstar plus Finish 6-Pro (ai ethephon/cyclanilide, Bayer CropScience) were applied at 6 to 7 nodes above cracked boll (NACB) or 4 to 5 NACB at various rates. Results showed that these harvest aids could be applied at the tested rates at both timings without any adverse effects on percent open bolls, and lint yield and quality. Therefore, application of these harvest-aid materials starting at 6 to 7 NACB can benefit Pima cotton growers in California as early harvests can be achieved without compromising lint yield or quality.

Leaf nitrogen is closely coupled to phenophases in a desert shrub ecosystem in China

The understanding of the seasonal dynamics of leaf nitrogen (N) relative to leaf traits for desert shrub species is limited. We investigated the seasonal changes in leaf N, soil N, specific leaf area (SLA) and photosynthetic capacity (Pmax) in relation to the phenology of Artemisia ordosica in a desert shrubland area in northern China during the growing season of year 2012. We found that the amount of leaf N per unit dry mass varied in different phenological phases, having higher values during the early leaf expansion and leaf coloration and early defoliation periods and lower values during the expanded leaf and flowering periods. Pmax was positively related to leaf N from the late leaf expansion period to the flowering and bearing period. Photosynthetic nitrogen use efficiency (NUE) correlated with SLA during the growing period. However, similar relationships were not observed for the leaf expansion and defoliation periods. During the flowering and bearing period, leaf N content per unit dry mass remained relatively stable, although fluctuations occurred due to precipitation. Our findings could help with modelling the dynamics of plant-soil N coupling of desert shrub-land ecosystems under changing environment.

The effects of early leaf removal and cluster thinning treatments on berry growth and grape composition in cultivars Vranac and Cabernet Sauvignon

The aim of the present work was to investigate the effect of early leaf removal and cluster thinning treatments in the Mediterranean climate on berry growth and how these two techniques affect phenolic profile (especially proathocyanidins) and color characteristics for later wine production. The study was conducted in 2011 in Podgorica, Montenegro. Two grapevine cultivars were selected to compare different ability in flavonoid accumulation: Vranac, with moderate accumulation and Cabernet Sauvignon, usually showing very good accumulation of polyphenols. Four treatments were compared: only leaf removal, only cluster thinning, leaf removal combined with cluster thinning, and no treatment that was used for control (control set). Early defoliation reduced the yield in both varieties. In Cabernet Sauvignon, defoliation initially delayed berry growth, but at the end, defoliation slightly affected almost all yield parameters (cluster weight, berry weight, and number of berries per cluster), while in cultivar Vranac, defoliation did not modify the berry growth and berry weight. In both varieties, cluster thinning did not affect the berry weight. In the treatments where both defoliation and cluster thinning was applied, a reduction of the cluster weight, berry weight, and berry numbers per cluster was observed. Cabernet Sauvignon showed a greater reactivity to the applied techniques, while Vranac was less reactive. At harvest, no damaged bunches (caused by sunburn) were found in defoliated treatment. It can be concluded that for both varieties, early defoliation and cluster thinning lead to better soluble solids accumulation than in the control set. The treatments lead to raised concentration of anthocyanins and proanthocyanidins in both varieties. It is confirmed that the highest content of anthocyanins and proanthocyanidins was in the skin extracts of the grapes where both treatments were applied. This is followed by the treatment where only defoliation was applied. The enhanced contents of these compounds per berry in grape variety Vranac are the result of increased synthesis, while in Cabernet sauvignon variety, increased content was due to the less berry weight. The best wine characteristics (alcohol, color intensity, color hue, total anthocyanins, total polyphenols) were found in products, where defoliation was applied.

Identification of differentially expressed genes using digital gene expression profiles in Pyrus pyrifolia Nakai cv. Hosui bud release following early defoliation

“Returning bloom” is a major problem in the warm pear-producing regions during autumn–winter after the pear harvest and can cause tremendous pear production losses in the following year. The molecular mechanism causing this phenomenon is a mystery. We used high-throughput tag-sequencing (tag-seq) technology to analyze the gene expression profiling of pear (Pyrus pyrifolia Nakai) floral buds at three time points for completely defoliated plants after harvest. A total of 13.2–15.8 million reads were obtained for each of the six libraries, and approximately 61.81–67.11 % were mapped to Pyrus bretschneideri Rehd. genome sequences. A total of 2713 differentially expressed genes, categorized into 35 functional groups, were associated with 251 Kyoto Encyclopedia of Genes and Genomes pathways. Gene Ontology and pathway enrichment analysis showed differentially expressed genes linked to photosynthesis, hormone/signaling, and carbohydrate biosynthesis and metabolism. Six differentially expressed genes were selected for quantitative real-time PCR analysis, and the expression patterns were consistent with the tag-seq results. We concluded that bud release after artificial defoliation required compensatory mechanisms, which induce genes specifically expressed in association with the process of photosynthesis, endogenous hormones, carbohydrate, and reactive oxygen species. The differential expressions of genes found in pear tree defoliated by hand should play important roles in the reversion phase from paradormancy back to growth.

New Report of Black Leaf Spot Mold (Pseudocercospora fuligena) on Withania somnifera from India.

Withania somnifera (family solanaceae) commonly known as ashwagandha and Indian ginseng, originated in India is one of the most powerful medicinal plants for more than 3,000 years (1). It is commercially cultivated for its roots, a natural rich source of glycowithanolides, tannins, potassium nitrate, etc., which are an anti-inflammatory, anti-tumor, anti-oxidant, anti-ulcer, and regulator of the nervous system and sleep (2). During the monsoon of July 2011, black spots on the leaves of infected plants were observed in the ashwagandha growing Lucknow, Raibareilly, and adjoining areas of Uttar Pradesh province with 10 to 20% disease incidence. Early stage of disease were characterized by the presence of light chlorotic spots on both sides of old leaves that later turned into dark black spots resulting in early defoliation. About 27 samples were collected from different locations of the fields for isolation of the causal organism and microscopic studies. Infected leaves were cut into small pieces, surface sterilized with 1% sodium hypochlorite for 1 min, rinsed thrice with sterilized distilled water, and placed onto potato dextrose agar (PDA) plates. After 21 days of dark incubation at 25°C, 8- to 10-mm grayish-brown colonies were observed. Microscopic studies at early and mature stages of infection showed production of conidia in conidiophores. Conidiophores were mostly 5 to 9, few dense pale brown, simple unbranched, septate, geniculate and 14 to 55 × 3 to 5.5 μm. Conidia were subhyline, obclavate to cylindrical, some were straight to slightly curved, multiseptate, base long obconic to long obconically truncate, and 12 to 85 × 3.5 to 5 μm. On the basis of cultural and morphological studies, the pathogen was identified as Pseudocercospora fuligena (3). The pathogen identity was further confirmed at molecular level using universal primers ITS1/ITS4 through PCR (4). An amplification of the expected size (~550 bp) was generated, eluted from agarose gel by QIAquick gel extraction kit (Qiagen), cloned into pGEM-T Easy vector (Promega), sequenced, and deposited in GenBank (Accession No. KF881898). NCBI BLASTn showed 99% identity with P. fuligena (GU214675) strain CPC 12296, isolated from Lycopersicon sp. Pathogenicity test was carried out on 10 plants of W. somnifera cv. Poshita through two approaches, one using mycelia from culture and another using spore suspension from naturally infected leaves. In the first approach, fungal mycelia were applied onto the healthy ashwagandha leaves, whereas in the second approach, infected leaves were washed with distilled water and spore suspension of 106 spores/ml was sprayed on healthy plants. Plants sprayed with sterilized distilled water served as controls. Inoculated plants were placed in a growth chamber at 28°C under 90% humidity for 3 days. After, pots were placed in the glasshouse at 27 ± 2°C with 70 to 80% humidity for 21 days. Initial symptoms appeared on the 7th day while typical symptoms appeared on all the inoculated plants after 12 to 17 days. Control plants remained free of infection. Re-isolation of the pathogen on PDA fulfilled Koch's postulates. Black leaf mold caused by P. fuligena has been reported on tomato (5). This is the first report of black leaf mould caused by P. fuligena on W. somnifera from India. P. fuligena has the potential to reduce yield of W. somnifera.

First Report of Quinoa Downy Mildew Caused by Peronospora variabilis in Republic of Korea.

Quinoa (Chenopodium quinoa Willd.) has become increasingly popular due to its high nutritional value and adaptability to harsh environments. Several field trials have recently been conducted to determine the ability of quinoa cultivars to grow under climate and soil conditions of Republic of Korea. During July 2013, which is the rainy season, plants showing typical symptoms of downy mildew were first observed in an experimental plot in Iksan City, Korea. Infection resulted in small to large, irregular chlorotic areas on the upper leaf surface with a gray mildew developing on the abaxial surface, and often leading to early defoliation. The same symptoms of downy mildew were also found in Pyeongchang County and Imsil County, Korea. A sample from Iksan City was deposited in the Korea University Herbarium (Accession No. KUS-F27388) and used for microscopy and molecular studies. Microscopic examination revealed colorless conidiophores emerging from stomata, straight to slightly curved, 350 to 550 × 10 to 18 μm, and sub-dichotomously branched in 5 to 7 orders. Ultimate branchlets were mostly in pairs, flexuous to curved, 10 to 30 μm long, and had obtuse tips. Conidia were pale brown to olivaceous, broadly ellipsoidal to ellipsoidal, and 25 to 32 × 22 to 25 μm with a length/width ratio of 1.20 to 1.35. These characteristics fit well with Peronospora variabilis, which was previously recorded to be parasitic to C. quinoa and C. album, although P. farinosa f. sp. chenopodii has often been considered a causal agent of downy mildew on quinoa (1). To confirm this morphological identification, amplification and sequencing of the internal transcribed spacer (ITS) region of the rDNA of the Korean specimen were performed using procedures outlined by Choi et al. (1) with oomycete-specific primers DC6 and LR0. The resulting 796-bp sequence was deposited in GenBank (Accession No. KF887493). A comparison with the ITS sequences available in GenBank revealed that it is identical to P. variabilis found on C. album (EF614959, EF614961), and shows only one base pair substitution with another isolates from C. quinoa (EU113305, EU113306). Therefore, the pathogen found in Korea was confirmed to be P. variabilis. Downy mildew is the most damaging disease of quinoa in Argentina, Bolivia, Colombia, Ecuador, and Peru (1). Increasing reports of this disease from India, Canada, the United States, Portugal, and Denmark (2,3,4) have revealed its worldwide occurrence and spread. To our knowledge, this is the first report of a downy mildew on quinoa in Korea (3). It suggests that quinoa downy mildew poses a new and serious threat to production of this crop in Korea.

Leaf phenological characters of main tree species in urban forest of Shenyang.

BackgroundPlant leaves, as the main photosynthetic organs and the high energy converters among primary producers in terrestrial ecosystems, have attracted significant research attention. Leaf lifespan is an adaptive characteristic formed by plants to obtain the maximum carbon in the long-term adaption process. It determines important functional and structural characteristics exhibited in the environmental adaptation of plants. However, the leaf lifespan and leaf characteristics of urban forests were not studied up to now.MethodsBy using statistic, linear regression methods and correlation analysis, leaf phenological characters of main tree species in urban forest of Shenyang were observed for five years to obtain the leafing phenology (including leafing start time, end time, and duration), defoliating phenology (including defoliation start time, end time, and duration), and the leaf lifespan of the main tree species. Moreover, the relationships between temperature and leafing phenology, defoliating phenology, and leaf lifespan were analyzed.FindingsThe timing of leafing differed greatly among species. The early leafing species would have relatively early end of leafing; the longer it took to the end of leafing would have a later time of completed leafing. The timing of defoliation among different species varied significantly, the early defoliation species would have relatively longer duration of defoliation. If the mean temperature rise for 1°C in spring, the time of leafing would experience 5 days earlier in spring. If the mean temperature decline for 1°C, the time of defoliation would experience 3 days delay in autumn.InterpretationThere is significant correlation between leaf longevity and the time of leafing and defoliation. According to correlation analysis and regression analysis, there is significant correlation between temperature and leafing and defoliation phenology. Early leafing species would have a longer life span and consequently have advantage on carbon accumulation compared with later defoliation species.

Cultivation technology influences the occurrence of potato early blight (Alternaria solani) in an organic farming system

Nowadays, organically produced products have become more popular than ever and interest in them is still growing fast. The early blight causal pathogen Alternaria solani has not been considered a great threat to potato in northern climate conditions in the past and has not been routinely sprayed against. During our study early blight was evaluated in 2010 and 2011 on the plants of a potato cultivar ‘Reet’ in an organic farming experiment. In our study, both growing seasons were very favourable for early blight development. Significant differences between the two cultivation technologies were found (F1,12 = 4.84, p = 0.048). In 2010, the area under disease progress curve (AUDPC) value was 303 on cover crop (CC) plots and 990 on CC + M (manure) plots that is three times higher, whereas in 2011, the AUDPC value was 967 on CC plots and 1195 on CC + M plots. Our results confirm that potato early blight has become a serious problem in North-East European organic potato fields and thus susceptible potato cultivars cannot be recommended for growing in an organic farming system. However, it is possible to influence the development severity of early blight by selecting the proper growing technology. Since, in the changing climate conditions and in susceptible cultivars, early blight is a potato disease that can cause early defoliation of plants and crop death, there is a need for resistant potato cultivars.

Impact of Pima Defoliation Timings on Lint Yield and Quality

Chemical defoliation is a necessary pre-harvest practice in Pima cotton (Gossypium barbadense L.) production in the San Joaquin Valley of California. Cotton growers are advised to begin defoliation as early as possible with both Pima and Upland cotton, but not so early that it results in yield and quality loss Potentially harvestable bolls often fail to reach full maturity due to the recommended defoliation timing. Applying harvest aids before the recommended maturity can advance the start of harvest, avoiding late-season pests and adverse weather that can damage lint quality. The objective of this research was to compare different rates of Ginstar® (thidiazuron/diuron, Research Triangle Park, NC) or Ginstar plus Finish® (ethephon/cyclanilide, Research Triangle Park, NC) on defoliation, yield, and fiber quality of Pima cotton when applications began at an earlier timing, six to seven NACB (nodes above cracked boll), versus the common four to five NACB timing. ‘Delta Pine DP-340’ (Monsanto Company, St. Louis, MO) was treated with harvest aid materials in field trials and was analyzed as a factorial split-plot design with four replications. Starting the defoliation of Pima at six to seven NACB rather than four to five NACB brought about a potential seven to ten day earlier harvest and did not significantly affect yield or cotton fiber quality characteristics except for micronaire in one year of the study. These data indicate that earlier defoliation could be beneficial when later-maturing crops or worsening harvest-season weather necessitate the initiation of an earlier harvest.

Early defoliation reduces cluster compactness and improves grape composition in Mandó, an autochthonous cultivar of Vitis vinifera from southeastern Spain

In the old-world viticulture autochthonous varieties are an important inheritance because they can provide wines with authenticity and distinction. Cultivar Mandó is an almost extinct variety from southeastern Spain, which is used by a few wineries for elaborating premium quality wines. The aim of this 3-seasons long experiment was to assess the usefulness of early defoliation to reduce cluster compactness and to improve grape composition. Early defoliation, consisting of removal of all leaves from the first eight nodes, was tested at 3 different timings: just before anthesis, at flowering, and at fruit set. Non-defoliated vines were considered as a control. Yield and grape composition parameters were evaluated. Early defoliation, especially at fruit set, reduced cluster compactness and yield but increased total phenolics, anthocyanins and tannins concentration in berries. In the three seasons, total soluble solids concentration showed a tendency to increase in defoliated vines, while titratable acidity and pH were not clearly affected by the leaf pulling applications. Berry tasting was also improved by defoliation. As a consequence, defoliation carried out at fruit set is now widely conducted in the Mandó vineyards in the area for premium wine production.

Modeling the effects of individual-tree size, distance, and species on understory vegetation based on neighborhood analysis

Quantifying how understory vegetation responds to individual neighboring trees is critical to understanding forest dynamics. To do so, we used a spatial neighborhood approach to quantify the competitive effect of individual trees on the density and height of dwarf bamboo (Sasa senanensis (Franch. et Savat.) Rehder) in a mixed conifer–broadleaf forest on the island of Hokkaido, northern Japan. Using hierarchical Bayesian models, we analyzed how the effect of neighboring trees varies with stem size, distance to the dwarf bamboo, and tree species. The effect of neighbors peaked when the tree reached a medium size (33.0–45.0 cm in diameter at breast height) and decreased for larger trees. The effect of neighbors decreased with increasing distance to the dwarf bamboo. The slope of the decrease was gentler for larger trees. Conifers exerted an average of 7.2 times the effect of broadleaved trees. Species with higher shade tolerance exerted larger effects. Species with late leaf flush and early defoliation tended to exert smaller effects. Our results provide evidence that neighborhood analysis is an effective approach for quantifying the effects of individual trees on understory vegetation and represents a critical step toward understanding how fine-scale interactions between understory vegetation and trees influence overall forest dynamics.

Early defoliation in a temperate warm and semi-arid Tempranillo vineyard: vine performance and grape composition

Background and Aims Early defoliation (ED) can reduce vine yield and improve fruit composition in vigorous vineyards. The objective of this study was to test the effectiveness of this technique for the Vitis vinifera (L.) cultivar Tempranillo under the temperate warm and semi-arid climatic conditions of south-eastern Spain. Methods and Results Four treatments were applied over three seasons to drip-irrigated vines, planted with rows orientated north–south and shoots vertically positioned. Non-defoliated vines (control) were compared with vines defoliated either just before anthesis (phenological stage H, treatment ED) or at fruitset [phenological stage J, treatment late defoliation (LD)]. In the fourth treatment, only the leaves facing east were removed at phenological stage H (treatment east ED). In the fourth experimental season, all treatments were managed similarly. Defoliation did not reduce fruitset but reduced berry mass, particularly in the ED and the LD treatments. Defoliation, however, had a cumulative negative effect on vine bud fertility. Even in the fourth experimental season, the yield of the ED treatment was 18% lower than that of the control. Both the ED and particularly the LD treatments increased berry total soluble solids (TSS) and phenolic concentration. The effect of leaf removal on berry TSS and phenolic concentration was not significant in the east ED treatment. Conclusions Defoliation at fruitset was the most effective treatment for increasing berry phenolics and TSS while maintaining must acidity. Growers should take into account, however, the important yield penalty because of defoliation, particularly in the mid-term. Significance of the Study Early defoliation of Tempranillo grapes growing in semi-arid and temperate climates needs to be applied with caution and probably limited to specific seasons while consecutive defoliations should be avoided.

조기낙엽에 따른 참다래(골드러쉬) 무착과 유목 액아의 발아와 착화

BACKGROUND: Kiwifruit, which was introduced to Korea in late 1970s, is a warm-temperate fruit tree, whose leaves are easily damaged by wind because of their large size. To produce high quality fruits, efficient windbreak is necessary to protect leaves until harvest. In Korea, typhoons from July onwards usually influence the production of kiwifruit. Damages from typhoons include low fruit quality in the current year and low flowering ratio the following year. This study was conducted to investigate the effect of early defoliation of kiwifruit vines from July to October on the regrowth of shoot axillary buds the current year and bud break and flowering the following year. METHODS AND RESULTS: Scions of kiwifruit cultivar 'Goldrush' were veneer grafted onto five-year-old Actinidia deliciosa rootstocks, planted in Wagner pots (13L) and grown in a rain shelter. Kiwifruit leaves in the proximity of leaf stalk were cut by lopping shears to simulate mechanical damage from typhoon since only leaf stalks were left when kiwifruit vines were damaged by typhoons. Kiwifruit vines were defoliated from July 15 to October 14 with one monthintervals and degrees of defoliation were 0, 25, 50, 75 and 100%. All experiments were conducted in the rain shelter and replicated at least five times. Defoliation in July 15 resulted in a high regrowth ratio of 20-40% regardless of degree of defoliation but that in August 16 showed only 5.8% of regrowth ratio in the no defoliation treatment; however, more than 25% of defoliation in August 16 showed 17-23% of regrowth ratio. In September 15, regrowth ratio decreased further to less than 10% in all treatments and no regrowth was observed in October 14. Percent bud break of all defoliation treatments were not significant in comparison to 64.7% in no defoliation except for 42.1% and 42.9% in 100% defoliation in July 15 and August 16, respectively. Floral shoot in the no defoliation treatment was 70.2% and defoliation of 50% or less resulted in the same or increased floral shoot ratio in July 15, August 16, and September 15; however, defoliation in October 14 showed no difference in all treatments. In flower number per floral shoot, 2-3 flowers appeared in no defoliation and only 1 flower was observed when the vines were defoliated more than 50% in July 15 and September 15. In October 14, contrary to the floral shoot ratio, flower number decreased with increased defoliation. CONCLUSION(S): Therefore, it is suggested that dormancy of 'Goldrush' axillary buds, was started in August and completed in October. The effect of defoliation on bud break of axillary buds the following year was insignificant, except for 100% defoliation in July 15 and August 16. From July 15 to September 15, floral bud ratio was significantly reduced when more than 50% of leaves were defoliated compared to no defoliation. Also, the number of flowers per flower-bearing shoot the following year decreased by less than 50% when compared to no defoliation, and this decrease was more prominent in September 15 than July 15 and August 16.

Susceptibility of almond cultivars to Tranzschelia discolor

The susceptibility of 34 almond cultivars to rust [Transchelia discolor] was evaluated over a period of 4 years at two locations in South Australia on naturally and artificially inoculated trees. Cultivar tolerance to rust was measured by leaf area infection, uredia density or defoliation. At both sites the severity of rust leaf infections were positively correlated with defoliation at harvest. All cultivars were susceptible to rust, with the level of susceptibility varying between cultivars. Two major varieties grown in Australia, Nonpareil and Carmel, were susceptible to rust infection and/or early defoliation. Inoculation studies showed Carmel and Nonpareil produced more uredia than Price, while fewer urediniospores per uredia developed on Nonpareil compared to Carmel. With natural infections, more disease developed in Carmel and Nonpareil compared to Price. Masbovera, Mod Alnem 15, Mod Alnem 8, Ferraduel and Ferragnes were less prone to natural infection or produced fewer uredia after inoculation than more susceptible cultivars such as Nonpareil. Early defoliation was less on Masbovera compared with Nonpareil, Ne Plus Ultra, Sauret and Carmel. While no immune cultivars were identified, tolerant cultivars were identified that are less prone to rust infection, produce fewer uredia after infection and are less likely to defoliate prematurely. Future work should focus on artificial inoculation to screen cultivars for use as potential parents in almond breeding programs.