Occurrence of potato wart disease (Synchytrium endobioticum) in Bulgaria: identification of pathotype(s) present

Potato wart disease caused by Synchytrium endobioticum was detected for the first time in Bulgaria in 2004. Laboratory tests, pot tests and field tests were carried out to determine which pathotype is present, specifically in Prodanovtsi near the town of Samokov. In addition, potato cultivars were tested for levels of resistance, in order to be used in buffer zones surrounding infested fields. Based on the results obtained in this study, it was found that most probably pathotype 8(F1) is present in Bulgaria. Most of the commercial potato cultivars tested were found to be susceptible to this pathotype. The local cultivars Koral and Bor were resistant, but these are not very important cultivars commercially. The potato cultivars Panda, Désirée and Amorosa were recommended for cultivation in the fields adjacent to infested plots.     

The Relation Between Field and Laboratory Susceptibility of Potato Cultivars to Wart Disease1)

Potato wart disease has been effectively controlled legislatively by the growing of resistant cultivars. The testing of new potato seedlings for plant breeders is undertaken so that susceptibles can be removed from the breeding program at an early stage. In the laboratory, gradation of resistance and susceptibility is noted. The range of reactions is divided into 6 arbitrary groups, 3 with necrosis and 3 without (Hills , 1965), and Hille's infection patterns have been interpreted as a set of assessment keys. Susceptible cultivars show a variation in degree of susceptibility, but infections persist even though there may be a necrotic hypersensitive reaction of the host. With some less resistant cultivars, the fungus can become established in the host and complete its life cycle, but infected tissue mostly necroses and is sloughed off. These less resistant cultivars (intermediates) grow away from infection when grown on in pots. The cultivar Red Craigs' Royal showed no infection when inoculated in soil tanks (3 soil types) with heavy watering or when grown on infested land. All evidence collected gives indication that intermediate cultivars are field resistant and not affected to any measurable extent by Synchytrium endobioticum (Schilb.) Perc.     

History of potato wart disease in Europe – a proposal for harmonisation in defining pathotypes

Potato wart disease, caused by the chytridiomycete Synchytrium endobioticum, was first introduced into Europe in the late 19th century. It spread quickly, and today is reported in 15 European countries. Initially, only one pathotype was found, and the disease was efficiently controlled using resistant cultivars. In 1941, however, formerly resistant cultivars showed wart formation in the field simultaneously in Germany and South Bohemia (Czech Republic), indicating the occurrence of new pathotypes. New pathotypes have since been reported from Germany, The Netherlands, Czech Republic, Ukraine and Canada. Today the pathogen is present in The Netherlands (only in fields for ware and starch potatoes) but restricted to two demarcated areas and subject to official control. Outside these areas, the pathogen is absent. For pathotyping, different countries have used different sets of differential cultivars, and the usual system of numerical coding of pathotypes has not been consistently followed. In this review we propose a new standardised code to be used for the 43 pathotypes currently known and described in Europe. The code is a combination of a numerical and letter code, combining the two terminologies used by former West and East Germany, respectively. We also plead for harmonisation in the choice of differential cultivars used for pathotype identification. The set of differentials described in the international standard for diagnosis of S. endobioticum issued by the European and Mediterranean Plant Protection Organisation (EPPO), should serve as a basis. Through close collaboration of European countries dealing with new pathotypes of potato wart disease, a final agreed upon set of differentials, combined with a set of reference isolates, should ultimately be established, allowing a clear distinction between the most important pathotypes occurring in Europe.     

A biotechnological strategy involving monoclonal antibodies for improvement of potato farming by identification and quantification of potato cyst nematodes in soil samples1

The two closely related nematode species Globodera rostochiensis and G. pallida are one of the major problems encountered in potato cultivation. There is a spectrum of potato plant genes known, which confer resistance to these species and their pathotypes. Potato growing in The Netherlands has to follow strict rules to control spread of the pests. Since distinction between the two nematode species is difficult, a rapid and reliable identification method is needed to allow better use of existing and forthcoming resistant potato cultivars. The aims of this project were: (1) identification and partial purification of species-specific proteins from the nematodes, (2) production of species-specific monoclonal antibodies, and (3) development of a screening test for qualitative and quantitative determination of Globodera spp. in soil samples.     

Potato production and protection in Poland in the 1990s1

Potato is an important crop for Polish agriculture, now grown on an area of 1.8 million ha, with an annual production of about 35 million t. The crop is used for fodder (pork production), human consumption and as a raw material for various branches of industry. High quantity and quality are essential for proper utilization. The main limiting factors in Polish potato production are: water (shortage or excess), seed potato quality, cultivation practices, and damage by pests, diseases and weeds. Improving the economics of potato production depends on decreasing the acreage and increasing the extent of proper protection. The major constraint is late blight (Phytophthora infestans) which causes yield losses estimated at 22.8%. Blight control is indispensable. The level of resistance among Polish cultivars, both in haulm and tuber, is not satisfactory, so more intensive resistance breeding is needed. Chemical control has increased in popularity, but improper use of phenylamides has created new problems. Further progress will depend on cost-effective methods of control and reliable use of fungicides.     

Current situation and prospects of potato production in Ukraine1

Total potato production has been maintained in Ukraine, but the share of production on private plots has recently increased from 65% to 97% and the efficiency of production has declined. Protection of the potato crop from pests has suffered particularly. Scientific institutions continue to breed new cultivars (particularly with resistance to wart and cyst nematodes), and the seed-potato production system is being maintained and improved. However, these systems were designed for large-scale production on collective and state farms and have to be adapted to the realities of private production.     

Diversity of populations of Phytophthora infestans in relation to patterns of potato crop management in Latvia and Lithuania

Potato crop losses can be substantial when conditions for late blight (Phytophthora infestans) development and spread are favourable. In this study, drivers of differences between the P. infestans population structures in Latvia and Lithuania, two neighbouring countries with similar potato-growing traditions, were investigated. Genotypes of P. infestans and population genetic diversity were analysed using a 12-plex simple sequence repeat (SSR) marker assay. High genetic diversity was demonstrated in both populations, with population diversity being higher in Latvia. It would appear that local populations established from soilborne oospores early in the season are well adapted to the conditions in the region. However, somewhat greater spread and survival of local clones was detected in Lithuania, suggesting that potato cropping there is more vulnerable to clonal invasion than in Latvia. For effective disease management, current strategies should be adjusted according to the specific pathogen populations in the region, considering the reproduction and survival of the pathogen. Potato growers should implement late blight preventive measures such as longer field rotation to prevent oospore infections, especially in Latvia, and should use more disease resistant cultivars and high-quality seed potatoes.     

The 2019 Potato Wart Disease workshop: shared needs and future research directions

Potato wart disease is caused by the fungus Synchytrium endobioticum. A workshop on this disease was held in June 2019 at the Dutch National Plant Protection Organization (NPPO-NL) in Wageningen, the Netherlands. Over 60 participants from 20 countries and 36 organizations came together to share their knowledge via presentations and posters, to strengthen professional networks, and to identify shared needs and future directions for S. endobioticum research. The three major topics of the workshop were disease occurrence and management, understanding the pathogen, and host breeding and resistance. Many aspects of this disease were discussed and summarized in a shared statement. Future directions identified were (1) research initiatives are currently being initiated to develop standardized molecular viability tests and a molecular pathotyping test, (2) coordination is needed to come up with better standardization of the pathotyping bioassays and the set of differential cultivars described in EPPO PM 7/28 needs to be better available for testing, and (3) stacking of resistance genes is strongly recommended but resistance breeding alone is not enough and should be combined with other management strategies to contain potato wart disease. Furthermore, the attendees remarked that organizing a workshop every 2 or 3 years would be of great benefit to the potato wart disease research community.     

Potato cultivars from the mexican national program: sources and durability of resistance against late blight

ABSTRACT The Mexican National Potato Program has produced several cultivars with high levels of field resistance. We evaluated the durability of resistance to potato late blight of a selection of 12 such cultivars using data from 1960 to the present. Data were extracted from the field notebooks located in the archives of the Mexican National Potato Program in the John S. Niederhauser Library in Toluca, Mexico. There was a trend indicating that field resistances to potato late blight of Mexican cultivars released between 1965 to 1999 were durable. At least two of the cultivars, namely 'Sangema' and 'Tollocan', have been grown on at least 4 to 5% of the potato acreage and over long periods of time without decay in levels of field resistance. Pedigrees of the 12 cultivars indicate that most of the field resistance was introgressed from Solanum demissum. Field resistance might also be derived from commonly grown land-race cultivars such as 'Amarilla de Puebla' and 'Leona'. These have been grown in Mexico since about the 1780s. They have the appearance of S. andigena-derived material but their genetic background is unknown.     

Phytopathological situation in potato in Belarus1

The control of potato diseases in Ukraine is reviewed. Control of potato blight (Phytophthora infestans) has only been adequate for limited periods in the past (when resistant cultivars were available and when the systemic fungicides were introduced). Currently, the disease is in a new epiphytotic phase and control has failed again, probably connected with the introduction of new mating types and the existence of greater variability. Blight now occurs earlier in the season and in most years (instead of only years when climatic conditions are favourable). Control has now to be essentially preventive, rather than based on forecasting. The importance and control of other potato diseases is also considered (Alternaria spp., Rhizoctonia solani, Geotrichum candidum, Phytophthora erythroseptica, Sclerotinia sclerotiorum, Streptomyces scabies).     

Stability of partial resistance in potato cultivars exposed to aggressive strains of Phytophthora infestans

Potato cultivars were evaluated for their resistance responses to aggressive strains of Phytophthora infestans in field and laboratory experiments. Analysis of variance revealed differential cultivar-by-isolate interactions for both foliar and tuber blight resistance. Differential responses occur as revealed by specific susceptibilities of cultivars to certain pathogen genotypes and changing rank order. In general, severity of late blight epidemics as observed in the haulms did not correlate well with foliar blight resistance ratings as presented in the National List of Recommended Potato Varieties. No significant correlation was found between tuber blight incidence under field conditions and the tuber blight rating in the National List. Also, there was no relation between the field and laboratory tuber blight resistance assessments. A significant association was demonstrated between late blight infection in the foliage and tuber blight incidence under field conditions. The presence of differential interaction, independent of R-gene-based resistance, indicates some adaptation of P. infestans to partial resistance and consequently adverse effects on the stability and durability of partial resistance to potato late blight.     

中国马铃薯晚疫病监测预警系统“China-blight”的组建及运行

马铃薯晚疫病是严重威胁世界马铃薯生产和粮食安全的重要病害之一,同时也是植物病害中流行速度最快的病害之一。由于品种多不抗病,目前国内外主要依靠化学防治控制该病害。为了提高用药的时效性,将信息技术与植物病害流行学原理相结合,设计并组建了中国马铃薯晚疫病监测预警系统"China-blight"(www.china-blight.net)。该系统由"中国晚疫病实时分布"、"未来48小时不同区域晚疫病菌侵染危险性预测"和"晚疫病化学防治决策支持系统"等子系统构成,此外还包括"晚疫病防治方法"、"品种抗病性"、"化学药剂库"、"其他病虫害"、"问题与经验交流"和"用户田间管理电子档案"等知识信息与服务功能。通过对2009年我国北方马铃薯一作区6-7月份病害侵染时段出现次数与晚疫病实际发生情况进行比较,预测信息与病害实际发生程度相符,该系统可以用于对马铃薯晚疫病田间防治的指导。     

Assessment of varietal reactions to potato wart (Synchytrium endobioticum) in Germany

A key for official assessment of potato cultivars for their resistance to Synchytrium endobioticum (potato wart) is presented. The margin between resistant and susceptible reactions is determined solely by the intensity of necrosis. Low numbers of ripe wart sori can be tolerated, if substantial necrosis occurs simultaneously. The key is a combination of the testing procedures of the two former German States and has been officially applied in Germany since 1992.     

Evaluation of foliar resistance in potato to Phytophthora infestans based on an international field trial network

During the period 2000–03, local potato cultivars in Estonia, Latvia, Lithuania, Poland and Denmark were tested for foliar resistance to Phytophthora infestans (late blight) in an international field trial network. Four standard cultivars were included in the trials: Sava, Oleva, Danva and Kuras. Primary disease-assessment data were entered into a common database, and parameters from the disease progress curves were calculated and made available on interactive web pages. A regression model, using relative area under disease progress curve (RAUDPC) values for cv. Oleva as a reference, was developed for the estimation of 1–9 scale values, where 1 = most susceptible. Standard deviations for the estimated 1–9 scale values and a nonparametric rank stability analysis of RAUDPC were used to evaluate the stability of resistance of the cultivars. Overall, the results showed stability of resistance for cvs Sava, Oleva and Danva, but not for Kuras. Use of the Internet-based Web-Blight service in this study facilitated comparison of results among countries for the level and stability of resistance. The estimated 1–9 scale values were similar to, or slightly lower than, those from official cultivar lists or from the European Cultivated Potato Database, especially for the more resistant cultivars. Possible reasons for discrepancies from different sources and locations are discussed. It is concluded that RAUPDC and the derived 1–9 scale values are useful for ranking cultivars for resistance to P. infestans , but this information is not detailed enough for use in a decision support system for late blight control.     

National control measures for Synchytrium endobioticum1

Although Synchytrium endobioticum has been found in almost all potato-growing countries of the EPPO region, it is absent from the great majority of fields. A few plots scattered across the potato-growing areas have been ‘scheduled’ as infested but potatoes are not grown on them. The disease is accordingly hardly ever seen. This is the result of continent-wide multiyear campaign of potato wart control within countries, according to which it is prohibited to grow potatoes on infested plots, and only resistant cultivars may be grown in a safety zone around them. S. endobioticum can persist for several decades in soil, as resting spores, but it is now dying out in plots that have been subject to the control campaign for a sufficiently long period. Procedures are now being agreed for officially ‘descheduling’ such plots.     

Identification of the pathotype of Synchytrium endobioticum,causal agent of potato wart disease,present in Georgia

Potato wart is one of the most important quarantine diseases of potato in the world. In Georgia, symptoms of wart were first seen in 2009–2013 during observations on potato in home gardens in Khulo district, although they may have been present since 2006. However, potato wart presence was only confirmed by PCR in 2013. Isolates pw13N and pw13 of Synchytrium endobioticum collected from the infested area of the village Didadjara, Khulo municipality were tested using laboratories in Georgia and the Netherlands in the framework of collaboration between scientists of Batumi State University and the National Plant Protection organization of the Netherlands. Additionally, pot tests were carried out in Georgia. Based on the results obtained, the pathotype found in Georgia is not known from Europe, and based on its reactions this pathotype resembles pathotype 38 (Nev?ehir) detected in (the non‐European part of) Turkey.     

Invasion of Phytophthora infestans at the landscape level: how do spatial scale and weather modulate the consequences of spatial heterogeneity in host resistance?

Strategic spatial patterning of crop species and cultivars could make agricultural landscapes less vulnerable to plant disease epidemics, but experimentation to explore effective disease-suppressive landscape designs is problematic. Here, we present a realistic, multiscale, spatiotemporal, integrodifference equation model of potato late blight epidemics to determine the relationship between spatial heterogeneity and disease spread, and determine the effectiveness of mixing resistant and susceptible cultivars at different spatial scales under the influence of weather. The model framework comprised a landscape generator, a potato late blight model that includes host and pathogen life cycles and fungicide management at the field scale, and an atmospheric dispersion model that calculates spore dispersal at the landscape scale. Landscapes consisted of one or two distinct potato-growing regions (6.4-by-6.4-km) embedded within a nonhost matrix. The characteristics of fields and growing regions and the separation distance between two growing regions were investigated for their effects on disease incidence, measured as the proportion of fields with ≥1% severity, after inoculation of a single potato grid cell with a low initial level of disease. The most effective spatial strategies for suppressing disease spread in a region were those that reduced the acreage of potato or increased the proportion of a resistant potato cultivar. Clustering potato cultivation in some parts of a region, either by planting in large fields or clustering small fields, enhanced the spread within such a cluster while it delayed spread from one cluster to another; however, the net effect of clustering was an increase in disease at the landscape scale. The planting of mixtures of a resistant and susceptible cultivar was a consistently effective option for creating potato-growing regions that suppressed disease spread. It was more effective to mix susceptible and resistant cultivars within fields than plant some fields entirely with a susceptible cultivar and other fields with a resistant cultivar, at the same ratio of susceptible to resistant potato plants at the landscape level. Separation distances of at least 16 km were needed to completely prevent epidemic spread from one potato-growing region to another. Effects of spatial placement of resistant and susceptible potato cultivars depended strongly on meteorological conditions, indicating that landscape connectivity for the spread of plant disease depends on the particular coincidence between direction of spread, location of fields, distance between the fields, and survival of the spores depending on the weather. Therefore, in the simulation of (airborne) pathogen invasions, it is important to consider the large variability of atmospheric dispersion conditions.     

Evaluation of breeding strategies for resistance and tolerance to late blight in potato by means of simulation

A field experiment with three potato cultivars, where plants were inoculated withPhytophthora infestans, was used to parameterize a model of potato growth and blight population dynamics. The model was validated by accurately simulating a field experiment conducted in another year. Sensitivity analysis with the model showed that late cultivars are longer able to maintain a green canopy in the presence of disease, but still suffer more yield loss than early cultivars. The level of partial resistance of a cultivar was more important than its level of tolerance, and other plant characteristics. The model calculations showed that only between 4 and 15% of the yield loss in the experiments was due to accelerated leaf senescence caused by the disease; the major part of the loss was caused by lesion coverage of leaves.     

马铃薯与致病疫霉互作研究进展与展望

马铃薯是重要的粮食作物, 由致病疫霉侵染引发的晚疫病长期严重制约马铃薯产业的健康发展, 因此, 国内外均将马铃薯晚疫病列为重大病害。目前, 抗病品种选育栽培、晚疫病预测预报和化学防治等相结合的晚疫病综合防治手段已得到普遍推广, 但晚疫病局部大流行在全世界范围内仍时有发生, 给粮食安全和生态安全带来巨大挑战。本文回顾了我国晚疫病的部分研究历史, 集中关注致病疫霉与寄主的互作机制领域, 梳理了近年来关于致病疫霉侵入机理、效应蛋白毒力功能、病原菌变异规律、马铃薯抗病机理等方面的重要研究结果并展望未来主要的研究方向, 以期为晚疫病基础研究和防治技术革新提供参考。     

Inheritance of resistance in <Emphasis Type="Italic">Solanum nigrum</Emphasis> to <Emphasis Type="Italic">Phytophthora infestans</Emphasis>

Solanum nigrum, black nightshade, is a wild non-tuber bearing hexaploid species with a high level of resistance to Phytophthora infestans (Colon et al. 1993), the causal agent of potato late blight, the most devastating disease in potato production. However, the genetic mode of resistance in S. nigrum is still poorly understood. In the present study, two S. nigrum accessions, 984750019 (N19) and #13, resistant (R) and susceptible (S), respectively, to three different isolates of P. infestans, were sexually crossed. The various kinds of progeny including F1, F2, F3, and backcross populations (BC₁; F1 × S), as well as two populations produced by self-pollinating the R parent and S parent, were each screened for susceptibility to P. infestans isolate MP 324 using detached leaf assays. Fifty seedling plant individuals of the F1 progeny were each resistant to this specific isolate, similarly to the seedling plants resulting from self-pollination of the resistant R parent. Thirty seedling plants obtained from self-pollination of the S parent were susceptible. Among a total of 180 F2 plants, the segregation ratio between resistant and susceptible plants was approximately 3: 1. Among the 66 seedling plants of the BC₁ progeny originating from crossing an F1 plant with the susceptible S parent, there were 26 susceptible and 40 resistant plants to P. infestans. The segregation patterns obtained indicated monogenic dominant inheritance of resistance to P. infestans isolate MP 324 in S. nigrum acc. 984750019. This gene, conferring resistance to P. infestans, may be useful for the transformation of potato cultivars susceptible to late blight.