Kiwifruit Cultivation Research Articles

D-PSA-K: A Model for Estimating the Accumulated Potential Damage on Kiwifruit Canes Caused by Bacterial Canker during the Growing and Overwintering Seasons.

We developed a model, termed D-PSA-K, to estimate the accumulated potential damage on kiwifruit canes caused by bacterial canker during the growing and overwintering seasons. The model consisted of three parts including estimation of the amount of necrotic lesion in a non-frozen environment, the rate of necrosis increase in a freezing environment during the overwintering season, and the amount of necrotic lesion on kiwifruit canes caused by bacterial canker during the overwintering and growing seasons. We evaluated the model’s accuracy by comparing the observed maximum disease incidence on kiwifruit canes against the damage estimated using weather and disease data collected at Wando during 1994–1997 and at Seogwipo during 2014–2015. For the Hayward cultivar, D-PSA-K estimated the accumulated damage as approximately nine times the observed maximum disease incidence. For the Hort16A cultivar, the accumulated damage estimated by D-PSA-K was high when the observed disease incidence was high. D-PSA-K could assist kiwifruit growers in selecting optimal sites for kiwifruit cultivation and establishing improved production plans by predicting the loss in kiwifruit production due to bacterial canker, using past weather or future climate change data.

기후변화 시나리오에 따른 미래 참다래 궤양병 피해 예측

RCP4.5와 RCP8.5 미래 기후 변화 시나리오자료와 참다래 궤양병 피해 예측 모형인 D-PSA-K, 미래 참다래 재배적지 지도를 활용하여 궤양병의 미래 피해를 예측하고 참다래 궤양병의 발생 변화의 경향성을 찾아 보았다. 병원 세균에 의한 감염이 충분히 있다는 가정 아래에서 RCP4.5와 RCP8.5 시나리오의 2020년대와 2050년대에서 궤양병의 최대이병주율은 제주도와 남해안 일부 지역을 제외한 대부분의 지역에서 75% 이상으로 나타날 것으로 예측되었다. 두 시나리오들 모두에서 월동기 저온 환경이 없다는 가정 아래에서의 참다래 궤양병에 의한 가지 피해량은 거의 모든 재배가능지에서 증가될 것으로 예측된 반면에 월동기 저온에 의한 가지 피해량 증가율은 거의 모든 재배가능지에서 감소할 것으로 예측되었다. 지역 및 시나리오별로 궤양병 피해의 증가 및 감소의 경향은 다르게 나타날 것으로 예측되었다. RCP4.5 시나리오에서 2050년대에 2020년대에 비하여 10% 이상 최대 이병주율의 증가가 일어날 것으로 예측된 참다래 재배 가능지는 전체 재배 가능지의 3.14%, RCP8.5 시나리오에서는 25.41%였다. We estimated the averaged maximum incidences of bacterial canker at suitable sites for kiwifruit cultivation in 2020s and 2050s using D-PSA-K model with RCP4.5 and RCP8.5 climate change scenarios. Though there was a little difference between the estimation using RCP4.5 and that using RCP8.5, the estimated maximum disease incidences were more than 75% at all the suitable sites in Korea except for some southern coastal areas and Jeju island under the assumption that there are a plenty of infections to cause the symptoms. We also analyzed the intermediate and final outputs of D-PSA-K model to find out the trends on the change in disease incidence affected by climate change. Whereas increase of damage to kiwifruit canes in a non-frozen environment caused by bacterial canker was estimated at almost all the suitable sites in both the climate change scenarios, rate of necrosis increase caused by the bacterial canker pathogen in a frozen environment during the last overwintering season was predicted to be reduced at almost all the suitable sites in both the climate change scenarios. Directions of change in estimated maximum incidence varied with sites and scenarios. Whereas the maximum disease incidence at 3.14% of suitable sites for kiwifruit cultivation in 2020s under RCP4.5 scenario was estimated to increase by 10% or more in 2050s, the maximum disease incidence at 25.41% of the suitable sites under RCP8.5 scenario was estimated so.

New Zealand kiwifruit growers’ vulnerability to climate and other stressors

Commercial cultivation of kiwifruit in New Zealand is concentrated in a relatively small area of the North Island. Cultivation is economically significant and growing quickly. However, current understanding of vulnerability for this, and other primary sector activities in New Zealand, makes almost exclusive use of linear outcome-oriented frameworks. Drawing on in-depth, semi-structured interviews with kiwifruit growers and orchard managers, workshops and analysis of secondary data, a “bottom-up” contextual assessment of vulnerability was developed and empirically applied. The findings suggest that climate and markets are the main sources of exposure for growers, with sensitivity moderated by location. Growers employ mostly short-term, reactive adaptive strategies to manage climate exposure and sensitivity, but have less capacity to respond to market-related stressors. Warmer and drier conditions are likely to have adverse effects for kiwifruit production and compound existing vulnerabilities. An ageing population and other processes of rural change may also constrain future adaptation. In order to realise opportunities and minimise losses, longer-term strategic responses are required. The paper demonstrates the need to move beyond outcome-oriented and model-based vulnerability assessments in New Zealand, to consider the broad range of the factors that contribute to vulnerability in the nation’s agricultural sectors. It provides a basis for further consideration of multiple exogenous impacts in the industry and confirms the critical importance of qualitatively vulnerability assessments to determine spatially specific outcomes.

Studies on the Infection, Colonization, and Movement of Pseudomonas syringae pv. actinidiae in Kiwifruit Tissues Using a GFPuv-Labeled Strain.

Kiwifruit bacterial canker, an economically important disease caused by Pseudomonas syringae pv. actinidiae (Psa), has caused severe losses in all major areas of kiwifruit cultivation. Using a GFPuv-labeled strain of Psa, we monitored the invasion, colonization, and movement of the pathogen in kiwifruit twigs, leaves and veins. The pathogen can invade twigs through both wounds and natural openings; the highest number of Psa is obtained in cut tissues. We determined that, following spray inoculation, Psa-GFPuv could infect leaves and cause lesions in the presence and absence of wounds. Light and transmission electron microscopic observations showed that bacterial cells colonize both phloem and xylem vessels. Bacterial infection resulted in marked alterations of host tissues including the disintegration of organelles and degeneration of protoplasts and cell walls. Furthermore, low temperature was conducive to colonization and movement of Psa-GFPuv in kiwifruit tissues. Indeed, the pathogen migrated faster at 4°C than at 16°C or 25°C in twigs. However, the optimum temperature for colonization and movement of Psa in leaf veins was 16°C. Our results, revealing a better understanding of the Psa infection process, might contribute to develop more efficacious disease management strategies.

KIWIFRUIT RESEARCH AND PRODUCTION IN TURKEY

Total world kiwifruit production outside China is currently 1,412,455 t, the total planted area is 98,656 ha, and the production area is increasing each year (FAO, 2012). Cultivation of kiwifruit started in Europe in the 1960s. Towards the end of last century, kiwifruit were introduced to Turkey by the AtatA¼rk Central Horticultural Research Institute in Yalova. Since then, each year has seen increasing interest. Today, Turkey, in terms of kiwifruit plantings, is amongst the more important producers. But productivity is low as most orchards in Turkey are still young; total yields will increase rapidly in the next few years. Commercial orchards are generally A. deliciosa ‘Hayward’ and cultivation of other species or cultivars is very limited. Especially in the northern part of Turkey, climatic conditions are suitable for kiwifruit. The two most common support systems are the T-bar and the pergola and these are used, with some modifications. Psa (Pseudomonas syringae pv. actinidiae) is so far not a serious problem in Turkey but root rots and water-logging problems in heavy soils are very common, so ridge planting is widely used. Frost protection in the form of fogging is also beginning to be used at higher altitudes. In contrast to New Zealand, irrigation of kiwifruit in Turkey is essential and is commonly done by mini-sprinkler systems in the Marmara and the Central Black Sea Regions. In the past, there was little irrigation of orchards in the Eastern Black Sea Region, but more recently irrigation systems have been installed. Consumption of fresh kiwifruit is likely to increase as the Turkish kiwifruit industry develops. Kiwifruit producers in Turkey are organized into small producer associations. However, these have not yet combined to form a national association. Such a combined national organization would make it much easier to solve problems of production, storage, packaging and marketing of Turkish kiwifruit. Kiwifruit research in Turkey first began in the 1990s at the Yalova AtatA¼rk Horticultural Central Research Institute. The number of kiwifruit-related research programmes is increasing each year. The studies so far have concentrated on rooting of cuttings, climate change-adaptation, packaging, cold storage and fruit quality issues.

PEDOCLIMATIC WEB MONITORING SYSTEM FOR PSEUDOMONAS SYRINGAE PV. ACTINIDIAE (PSA) AND ORCHARD MANAGEMENT

The collection of soil and climate data from kiwifruit orchards can constitute a reference for the proper management of kiwifruit cultivation, in particular for control of Pseudomonas syringae pv. actinidiae (Psa), plant nutrition and irrigation. The optimization of irrigation, fertilization, and copper treatment resulted in sustainable production of kiwifruit at reduced costs. The climate monitoring system can also be applied in field trials to study diseases epidemiology and orchard management.

Field detection of canker-causing bacteria on kiwifruit trees: Pseudomonas syringae pv. actinidiae is the major causal agent

Bacterial canker of kiwifruit, caused by Pseudomonas syringae pv. actinidiae (Psa), is thought to be responsible for severe damage to kiwifruit cultivation and production worldwide. However, several etiology issues impede disease management. As similar symptoms on kiwifruit could be affected by P. syringae pv. syringae (Pss), it is not known whether Psa is the only pathogen causing the current canker disease. In this study, we identified a P. syringae strain M209 isolated from canker tissue of kiwifruit based on biochemical characteristics, pathogenicity test and multi-locus sequence analysis. M209 caused mild canker lesions and leaf spots on kiwifruit, and it belongs to P. syringae genomospecies 2, showing distinct differences compared to the previously reported Psa-LV (less virulent) strains in pathogenicity and classification. We developed a multiplex PCR to evaluate the distribution of Psa, Pss and M209-representing populations. The PCR procedure was optimized and further validated for detecting pure isolates, as well as in artificially and naturally infected plant tissues. We used the PCR assay to detect 130 representative samples from 50 orchards in Shaanxi Province of China during 2013–2014, which covers the largest area of kiwifruit cultivation. The results indicated that Psa was the dominating pathogenic microbe responsible for canker symptoms on kiwifruit, while Pss and M209 were infrequent and less important pathogens in kiwifruit orchards in Shaanxi. In summary, a new canker-inducing strain on kiwifruit was identified, a reliable multiplex PCR for detecting three canker-inducing P. syringae populations was developed and applied, and the pathogen causing severe kiwifruit canker disease was determined in Shaanxi such that Psa should be the focus of disease management.

Pollen effects on fruit attributes and seed properties in colchicine-induced autotetraploids of red-fleshed kiwifruit (Actinidia chinensis Planch.)

SUMMARYThe effect of the ploidy level of the polleniser has not been considered during the characterisation and evaluation of colchicine-induced autotetraploids of Actinidia chinensis (kiwifruit). It is therefore possible that few induced autotetraploids reach their potential size. Five genotypes of tetraploid pollenisers were used for controlled pollination of red-fleshed autotetraploids. Fruit of colchicine-induced autotetraploids from two genotypes of female red-fleshed A. chinensis plants were, on average, 25–30% larger than fruit arising from open-pollination in an orchard containing only a diploid male as polleniser. Fruit dimensions increased more in cross-section than in length, so the fruit were more round. Seed set increased up to two-fold and the number of filled seeds also increased significantly (P ≤ 0.01). The average filled-seed weighed two-to-three times more than that of seed from open-pollination with pollen from a diploid male, and were heavier than those in fruit of their diploid progenitors under open-pollination. The distribution of the red-flesh pigmentation increased, although its intensity was not significantly improved. The total soluble solids content (TSSC) increased by 1–2% and the size of the core cavity at the stylar end was significantly reduced (P ≤ 0.01) and sometimes completely. All these effects on fruit attributes would benefit the commercial cultivation of red-fleshed kiwifruit. It is therefore recommended that, as for diploids, pollenisers of tetraploid red-fleshed kiwifruit should be of matching ploidy. Two abnormal fruit with soft red cores were found on a branch of a tetraploid regenerant during the evaluation of fruit generated by controlled pollination. The possible origin and application of this mutation for novel kiwifruit breeding are also discussed.

Effect of Artificial Pollination, Pollination Time, and Pollen Bulking Agent on Seed Formation and Fruit Quality in the Shelter Greenhouse Cultivation of Kiwifruit

Effect of Artificial Pollination, Pollination Time, and Pollen Bulking Agent on Seed Formation and Fruit Quality in the Shelter Greenhouse Cultivation of Kiwifruit

The Italian inter-laboratory study on the detection of Pseudomonas syringae pv. actinide

A severe form of bacterial canker of kiwifruit, caused by Pseudomonas syringae pv. actinidiae (Psa), has been detected in all the main areas of cultivation of kiwifruit (Actinidia deliciosa and A. chinensis). Since 2010 several research groups have been assessing methods and procedures to detect and identify Psa, both from symptomatic and symptomless host material. In 2011, a study to compare Psa diagnostic methods was performed with reference to Psa strains and related pathovars, and with plant extracts or DNA obtained from healthy and naturally infected leaves, pollen or wood. The study revealed the strengths and the weaknesses of the assessed methods. The procedure included screening tests for Psa detection and for identification of Psa colonies. The methods assessed were bacterial isolation on generic and semi-selective media, PCR analysis (single, duplex and rep-PCR assay, the latter for identification only). The results highlighted the best performance of semi-selective with respect the generic media; the usefulness of the direct-PCR as screening tests for Psa detection; and the greater specificity of duplex-PCR and sensitivity of simple-PCR. The use of semi-selective medium for isolation and of two PCR-based methods - in parallel - for Psa detection are suggested. Both rep-PCR and duplex-PCR, were found to be specific, and are recommended as an identification test for this pathogen.

English

Bacterial canker of kiwifruit (Actinidia chinensis) has become one of the most serious factors that limit the cultivation of kiwifruit in Sichuan, China. Therefore, it is urgent to develop a rapid and precise method to detect the disease at its early infection stage. A 1300 bp specific fragment of pathogenic bacteria was obtained by random amplified polymorphic DNA (RAPD) analysis. This fragment was cloned and sequenced. Based on the sequences of the specific fragment, a pair of specific primers（F7’/R7’）that generated 994 bp single fragment only from the strains of Pseudomonas syringae pv. actinidiae were designed and synthesized. Then, for the detection of diseased kiwifruit trunk tissues collected from orchard and inoculated kiwifruit trunk tissues, the result indicated that the genomic DNA of P. syringae pv. actinidiae can be detected by the specific primers. The sensitivity of the primer set for genomic DNA of P. syringae pv. actinidiae was 100 fg µl-1. Compared with the designed primers with four pairs of published primers. The comparison concluded that only the primers designed in this study was specific to detect bacterial canker of kiwifruit in Sichuan. The result of this experiment showed that the designed and synthesized specific primers F7’/R7’ made it possible to diagnose the kiwifruit canker rapidly and precisely at its early infection stage. Key words: Bacterial canker, kiwifruit, primer, RAPD, SCAR, P. syringae pv. Actinidiae.

THE IMPORTANCE OF THE MAIN COLONIZATION AND PENETRATION SITES OF PSEUDOMONAS SYRINGAE pv. ACTINIDIAE AND PREVAILING WEATHER CONDITIONS IN THE DEVELOPMENT OF EPIDEMICS IN YELLOW KIWIFRUIT, RECENTLY OBSERVED IN CENTRAL ITALY

SUMMARY During the years 2008-2011 repeated isolations from symptomatic organs and plant parts of Actinidia chinensis cvs Hort16A and Jintao, grown in the provinces of Latina and Rome (Latium, central Italy), were done with the aim of determining the main colonization and penetration sites exploited by Pseudomonas syringae pv. actinidiae (Psa). Isolations were also made from exudates, pruned twigs and from tissues surrounding elastic laces used to tie young shoots. Artificial inoculations were performed to identify the main avenues for pathogen colonization. Climatic data (maximum, minimum and average temperature as well as rainfall) were recorded by weather stations established in the areas of yellow-fleshed kiwifruit cultivation. The bacterium appeared to be capable of colonizing the host all year round and to systemically migrate from young leaves to twigs. Unprotected lenticels, fruit stalks and leaf scars, as well as pruning wounds and tissues surrounding the elastic laces were easily colonized by the pathogen. The whitish exudates yielded, in many cases, pure cultures of the bacterium. A clear-cut relationship was found between the occurrence of frost events during winter 2007-2008 and the first outbreaks of bacterial canker on A. chinensis in the following spring-autumn. Moreover, in 2008, in the infected area, the rainfall was 30-35% higher than the average, which may have promoted the massive spread of the pathogen on the very susceptible yellow-fleshed cultivars. The disease cycle of Psa on A. chinensis in central Italy is postulated and described.

First report ofPseudomonas syringaepv.actinidiaeon kiwifruit plants in Spain

Bacterial canker caused by Pseudomonas syringae pv. actinidiae is the most harmful disease affecting kiwifruit (Actinidia spp.) cultivation worldwide reported so far. Reported in the 1980s in Asia (China, Japan, Korea), it was then described in the most important kiwifruit areas in other parts of the world (Italy, Portugal, France, New Zealand, Chile). The disease occurred on the main kiwi species (A. deliciosa and A. chinensis) and on different cultivars of kiwifruit. In 2011 the disease was observed during spring on two-year-old plants of cultivars of A. deliciosa (cv. Hayward) and of A. chinensis (cv. Jin Tao). Kiwifruit orchards with trees showing suspected symptoms were found located in Burgueira, Tomino Government, Provincia de Pontevedra - Galicia (Spain). The symptoms were similar to those recently reported in Portugal (Balestra et al., 2010) and characterised by typical symptoms on leaves (brown spots surrounded by yellow haloes), red browning on canes, with red sap production (Fig. 1). The disease incidence was estimated to be as high as 70 to 90% on the basis of the proportion of trees with evident symptoms in each orchard. Bacterial colonies were isolated from infected leaves on nutrient agar containing 5% sucrose. Four representative isolates were Gram-negative, negative for oxidase, potato soft rot, arginine dehydrolase, presence of tyrosinase and urease, nitrate and fluorescent pigment production. They were positive for levan production, presence of catalase and induction of a hypersensitive response on tobacco cv. Virginia Bright (Lelliott & Stead, 1988). Pathogenicity was confirmed by spraying a bacterial suspension calibrated at 10 7 cfu/ml on two-year-old plants of A. deliciosa (cv. Hayward) and A. chinensis (cv. JinTao). The assay was conducted on ten plants. Leaf symptoms were observed within 15 days after inoculation. No symptoms were observed on control plants. Bacteria with morphological, biochemical and molecular characteristics identical to the original isolate were re-isolated from tissue showing symptoms. The isolates (PSA 827, PSA 828, PSA 829, PSA 830) selected for molecular identification were compared to P.s. pv. actinidiae reference strains (CFBP 7285, CFBP 7286,