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Copyright of Journal of Henan Agricultural Sciences is the property of Editorial Board of Journal of Henan Agricultural Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Tobacco Science & Technology is the property of Tobacco Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Clubroot, caused by Plasmodiophora brassicae, is a crucial oilseed rape disease worldwide. Information on the virulence of P. brassicae populations is essential to apply disease control with proper clubroot-resistant cultivars. In 2016–2020, 84 isolates of P. brassicae were collected in the Czech Republic (CZ), Germany (DE), Poland (PL), and Sweden (SW). Pathotypes were designated using 17 Brassica hosts, including the European Clubroot Differentials (ECD), Somé set, and clubroot-resistant oilseed rape cv. Mendel. According to the ECD set, virulence analyses differentiated the isolates into 42 pathotypes. The most common pathotypes were 16/31/31 (in DE, PL, and SW) and 16/06/12 (in CZ, DE, and PL). Six pathotypes were found according to the Somé set, including 1–4 pathotypes per country. P1 was most prevalent in DE, PL, and SW, while P3 was abundant in CZ, DE, and PL. The current study provides clear evidence for a shift towards increased virulence in P. brassicae populations compared to previous studies. Several isolates overcame the resistance of cv. Mendel and of Brassica rapa genotypes ECD 01 to ECD 04. Considering all investigated samples, significant negative correlations were found between clubroot incidence and the frequency of oilseed rape in crop rotation, as for clubroot incidence and soil pH. [ABSTRACT FROM AUTHOR]

Fusarium wilt is one of the most important diseases of tomato seriously threatening the cultivation and development of this crop worldwide. In this study, the biocontrol potential of four basidiomycota fungal endophytes isolated from wheat and wild oat, namely Rhizoctonia endophytica M32, R. zeae M9, Fomes inzengae M40 and Coprinopsis urticicola M2, was evaluated against fusarium wilt of tomato under laboratory and greenhouse conditions. In lab, identity and race of the pathogen was first determined using phylogenetic inference and specific primers. In addition, antagonistic potential of fungal endophytes in inhibiting the pathogen and possible plant resistance induction was assessed through dual culture, volatile metabolite production, pot cultivation, split-root and root-cutting tests. Molecular evidence determined the identity of the pathogen as Fusarium oxysporum f. sp. lycopersici race 3. Lab tests showed that in duel culture test all four fungal endophytes were able to reduction of colony diameter of pathogen significantly five and seven days after inoculation compared to control. In volatile metabolite test all isolates could reduce mycelial growth of the pathogen significantly compared to control except R. zeae M9 in third and fifth day. Under greenhouse condition, only C. urticicola M2 isolate could significantly reduce the severity of fusarium wilt of tomato and increase plant growth factors compared to the control and other fungal endopytes. Through split-root and root-cutting tests, the possible mechanism of disease severity reduction caused by C. urticicola M2 was identified as stimulation and induction of resistance in tomato plant. This study is the first report on the evaluation of the biocontrol ability of the endophytic fungus, C. urticicola M2, in suppression of fusarium wilt disease of tomato. [ABSTRACT FROM AUTHOR]

Clubroot, caused by Plasmodiophora brassicae, is a crucial oilseed rape disease worldwide. Information on the virulence of P. brassicae populations is essential to apply disease control with proper clubroot-resistant cultivars. In 2016–2020, 84 isolates of P. brassicae were collected in the Czech Republic (CZ), Germany (DE), Poland (PL), and Sweden (SW). Pathotypes were designated using 17 Brassica hosts, including the European Clubroot Differentials (ECD), Somé set, and clubroot-resistant oilseed rape cv. Mendel. According to the ECD set, virulence analyses differentiated the isolates into 42 pathotypes. The most common pathotypes were 16/31/31 (in DE, PL, and SW) and 16/06/12 (in CZ, DE, and PL). Six pathotypes were found according to the Somé set, including 1–4 pathotypes per country. P1 was most prevalent in DE, PL, and SW, while P3 was abundant in CZ, DE, and PL. The current study provides clear evidence for a shift towards increased virulence in P. brassicae populations compared to previous studies. Several isolates overcame the resistance of cv. Mendel and of Brassica rapa genotypes ECD 01 to ECD 04. Considering all investigated samples, significant negative correlations were found between clubroot incidence and the frequency of oilseed rape in crop rotation, as for clubroot incidence and soil pH.

[Objective] Clarifying the composition of physiological races and virulence of Magnaporthe oryzae in rice blast nursery in Taojiang of Hunan province will provide a reference basis for utilization and development of rice varieties for resistance to rice blast disease in Hunan Province. [Method] The spore-generating ability of 64 rice blast isolates from Taojiang nursery was determined by inducing spore production on oat tomato agar medium ( OTA), and the physiological races of 53 strains were identified and their virulence was further analyzed by using in vitro leaf inoculation technology. [Result] Among 64 isolates collected from Taojiang nursery in 2018, 53 isolates could produce > 1 x 105 spores/mL after induced on OTA meidum, which met the requirement of in vitro leaf inoculation for spore concentration. Based on the reactions to seven Chinese differential varieties of rice, these isolates were divided into 4 groups and 12 physiological races, in which the dominant population was ZB with the frequency of 79. 2 %, and the dominant physiological race was ZB15 with the frequency of 39. 6%. Furthermore, ZB1 had strong pathogenicity and the second highest frequency, and ZA1 possessing the strongest pathogenicity was also isolated from Taojiang nursery. [Conclusion] The population of rice blast fungus from Taojiang nursery is very strong in virulence to Chinese differential varieties of rice, in which the dominant physiological race is ZB15. [ABSTRACT FROM AUTHOR]

Copyright of Acta Agronomica Sinica is the property of Crop Science Society of China and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Control Theory & Applications / Kongzhi Lilun Yu Yinyong is the property of Editorial Department of Control Theory & Applications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Wheat stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), is a fungus that causes the devastating fungalwheat stem rust disease in wheat production. Rapid identification of the physiological races of Pgt are very importance for the prevention of wheat stem rust. In this paper we developed a molecular method to identify the most prevalent race of Pgt, as a supplement for traditionally used host-specific methods. Amplified fragment length polymorphism (AFLP) was employed as a means of analyzing DNA polymorphisms in six common physiological races of Pgt in China and Ug99. In total, 64 pairs of primers were used for AFLP screening of race-specific molecular markers. One primer pair-namely, E7/M7 (5′-GACTGCGTACCAATTCG G-3′/5′-GATGAGTCCTGAGTAACGG-3′)-yielded a unique band for the race 34MKG that was purified and cloned into the pGEM-T vector for sequencing. We then designed a new primer pairs (sequence—characterized amplified region marker) to amplify the 171-bp fragment and confirmed that the marker was highly specific for 34MKG. These results provide a new tool for monitoring different races of Pgt for improved control of wheat stem rust in China. [ABSTRACT FROM AUTHOR]

The present study investigated the changes in total and individual glucosinolates (GSLs) in roots and leaves of different clubroot-resistant and -susceptible oilseed rape cultivars following artificial inoculation with Plasmodiophora brassicae isolates with different virulence. The results showed significant differences in clubroot incidence and severity as well as in the amount of total and individual glucosinolates between oilseed rape cultivars in response to virulence of the pathogen. Single among with total aliphatic and total indolic glucosinolate contents were significantly lower in leaves of susceptible cultivars compared to resistant ones due to the infection. Similarly, single and total aliphatic as well as indolic glucosinolate contents in roots were lower in susceptible cultivars compared to resistant cultivars analyzed. The different isolates of P. brassicae seem to differ in their ability to reduce gluconasturtiin contents in the host. The more aggressive isolate P1 (+) might be able to suppress gluconasturtiin synthesis of the host in a more pronounced manner compared to the isolate P1. A possible interaction of breakdown products of glucobrassicin with the auxin receptor transport inhibitor response 1 (TIR1) is hypothesized and its possible effects on auxin signaling in roots and leaves of resistant and susceptible cultivars is discussed. A potential interplay between aliphatic and indolic glucosinolates that might be involved in water homeostasis in resistant cultivars is explained.

Cladosporium fulvum, the causal fungus of leaf mould of tomato, is present in most countries that grow tomatoes, and is an economic problem, particularly in Japan. The diverse, complex race structure of C. fulvum in Japan enables the fungus to overcome all resistant commercial cultivars. It was noted that C. fulvum lesions on tomato leaves in the greenhouse were overgrown with white mycelia and that leaf mould did not spread further. Two isolates from the white mycelia, designated 414‐2 and 414‐3, were identified from morphological and phylogenetic analyses as the mycoparasite Dicyma pulvinata. Scanning electron microscopy of inoculated leaves showed the mycoparasite had coiled around C. fulvum hyphae around stomata. Microscopic analysis revealed that C. fulvum, engineered to express green fluorescent protein, died when entwined by the isolates only when cocultured in the absence of a carbon source. These results indicate that these isolates are mycoparasitic fungi that absorbed nutrients from C. fulvum. Two isolates and four strains were evaluated according to their abilities to control disease caused by C. fulvum, form conidia and produce an antifungal agent. Isolate 414‐3 parasitized hyphae of C. fulvum on plants in the greenhouse and inhibited leaf mould caused by all physiological races that cause problems for tomato production in Japan. This indigenous isolate of D. pulvinata may thus serve to control the foliar pathogen C. fulvum. [ABSTRACT FROM AUTHOR]

Clubroot resistance of oilseed rape (OSR) cultivars frequently relies on a major resistance gene originating from cv. Mendel. The efficacy of this resistance was studied in greenhouse experiments using two Plasmodiophora brassicae isolates, which were either virulent (P1(+)) or avirulent (P1) on Mendel. Seeds of clubroot-susceptible cultivar Visby and clubroot-resistant cultivar Mendel were sown in soil mixtures inoculated with different concentrations of resting spores (101, 103, 105, and 107 resting spores/g soil). Clubroot severity, plant height, shoot and root weight as well as resting spore propagation were assessed for each isolate and cultivar separately at four dates after sowing. The OSR cultivars behaved significantly different in the measured parameters. The threshold of inoculum density to cause disease depended strongly on the virulence of the pathogen and susceptibility of the host plant. In Visby grown in soil infested with P1, clubroot symptoms and increases in root weight and the number of propagated resting spores occurred at inoculum levels of 101 resting spores and higher, whereas Mendel was not affected in soils under the three lowest inoculum densities. In contrast, the P1(+) isolate led to earlier and more severe symptoms, heavier galls, and a significantly higher number of new resting spores in both cultivars.

Copyright of Chinese Journal of Oil Crop Sciences is the property of Oil Crops Research Institute of Chinese Academy of Agricultural Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

【Objective】The present paper aims to figure out physiological races variation and genetic structure of Magnaporthe oryzae in Guangxi and providea basis for breeding and distribution of rice resistant varieties in the future. 【Method】 Physiological races identification with seven differential varieties and genetic diversity analysis with SSR of M. oryzae from 2012 to 2014 in Guangxi were conducted in the present work. 【Result】24 physiological races belonging to 7 groups which included ZA, ZB, ZC , ZD , ZE , ZF and ZG were identified from 142 isolates collected from 2012 to 2014. Among them, the predominant group was ZB with an occurrence frequency of 67. 61 % , and the predominant races were ZB9and ZB13with an occurrence frequency of 19. 01 % , respectively. The UPGMA method was used to analyze the genetic diversity of 107 isolates and 14 lineages at similarity coefficient of 0. 88 were obtained. Among them, lineage L01 was the dominant lineage accounting for 44. 86 % of the isolates, lineage L03 , L06 and L11 were subordinate lineages accounting for 19. 63 % , 13. 08 % and 10. 28 % of the isolates, respectively. In addition, the number of isolates and their corresponding physiological race of every lineage was counted and the result showed that there was no correlation between genetic lineages and races. ' Conclusion】 Between the year of 2012 and 2014 in Guangxi, the predominant group of M. oryzae was ZB while the predominant races were ZB9 and ZB13, and there was no correlation between genetic lineages and races. [ABSTRACT FROM AUTHOR]

Between 2012 and 2015, 49 new clubroot-infested fields were identified in 12 German federal states. Clubroot disease incidence varied within these fields from 22% to 92%. Field information revealed that in 85% of fields, oilseed rape was grown in rotation once every 2 or 3 years. Frequency of OSR in the rotation was significantly correlated with the incidence and prevalence of clubroot disease. The disease was detected in fields with soil pH ranging from 5.1 to 8.3, and a significant negative correlation was found between soil pH and the disease incidence of infested fields. Furthermore, more cases of disease and severe incidences were observed in sandy loam and loamy sand as compared with other soil types. Pathotype classification of the 49 Plasmodiophora brassicae populations was conducted on two differential sets, the European Clubroot Differential set and the set of Somé (1996). Additionally, the degree of virulence of the collected isolates was analysed on the clubroot-resistant oilseed rape cv. Mendel. The results showed variation in pathotype distribution in different regions in Germany. The majority of isolates according to Somé were pathotypes 1 and 3, respectively, with pathotypes 2 and 5 in the minority. Detailed classification according to Buczacki showed the dominance of 16/31/31, 16/14/30 and 16/14/31 populations among 20 distinct virulence patterns of collected isolates. From all populations tested for virulence on cv. Mendel, 15 isolates were found to be moderately or highly virulent. These virulent populations were not restricted to a small geographical area in the country. [ABSTRACT FROM AUTHOR]

In order to study the effects of different physiological races of rice blast fungus on different resistance of rice materials of different yield traits, the sundry physiologic races of spores of Magnaporthe grisea were used to inoculate the restore line R725, R720 and R727 at booting stage of rice. The results showed that each of the physiological races of rice blast fungus could cause reduction of rice output. Among them, ZA5 had the greatest effect on the R725; ZC8 had the greatest effect on the R720; ZA17 had the greatest effect on R727. Multi factor regression equation showed that after inoculating the Magnaporthe grisea, setting percentage and 1000 grain weight was a major factor limiting the yield of rice. [ABSTRACT FROM AUTHOR]

Fusarium oxysporum f.sp. cubense (Foc) is the causative agent of Fusarium wilt of bananas ( Musa spp.). To clarify the colonization patterns of Foc in bananas, two green fluorescent protein-tagged isolates, NT320 (race 1) and B2-gfp (race 4), were used to follow infection of the banana varieties Pisang Awak and Brazil. Penetration and colonization of both isolates in roots of these two banana varieties were observed within 6 days, but sporulation in xylem vessels was not observed until day 30 postinoculation. Interestingly, B2-gfp penetrated into xylem vessels of Pisang Awak banana roots more quickly than NT320, implying that the race 4 isolate is more virulent than the race 1 isolate. This result was further confirmed by comparing the disease severity of plants inoculated with NT320 with that of plants inoculated with B2-gfp. Quantitative real-time PCR revealed that some pathogenicity-associated genes, including Fga1, Fhk1, Fow2 and Ste12, were upregulated by B2-gfp during exposure to Brazil bananas, while they were either downregulated by NT320 or not significantly changed. These data might partly explain why the race 4 isolate was more virulent than the race 1 isolate. [ABSTRACT FROM AUTHOR]

The economic importance of oat stem rust is becoming more recognized with the increases of oat cultivated acreage and the disease damage in China. However, there is still no information on races of the pathogen and resistance of oat cultivars. In 2012 and 2013, 26 Puccinia graminis f. sp. avenae ( Pga) isolates were obtained from 11 oat stem rust samples collected from oat fields in Hebei province, one of China's major oat growing provinces. The isolates were tested on 16 Pg single-gene lines that have been used to differentiate Pga races in North America. From the isolates, three races, TKR, TJM and TKM, were identified at 61.6, 30.8 and 7.6 % frequencies, respectively. Virulences to resistance genes Pg1, Pg2, Pg3, Pg4, Pg8, Pg9, Pg12, Pg16 and the gene(s) in the universally susceptible variety 'Marvellous' were detected at 100 % frequency, to Pg10 at 69.2, to Pg13 at 61.6, to Pg-a at 61.6 %, and to the gene(s) in Rodney 0 at 84.6 %. No virulence to Pg6 and Pg15 was observed. The above races were used to evaluate the resistance in oat cultivars as seedlings grown in a greenhouse. Of 35 oat cultivars tested, only 13 (37.1 %) were resistant to all three races. This is the first study to identify Pga races and oat stem rust resistance in Chinese oat cultivars. [ABSTRACT FROM AUTHOR]

[Objective] The present study was conducted to identify the type, composition and distribution of Phytophthora infestans in Guizhou Province in 2013-2014 so as to provide references for late blight resistance breeding in potato and preventing and controlling potato late blight disease. [Method ]260 isolates from potato plant of 13 counties and cities in Guizhou Province during 2013-2014 were tested with 11 mono-gene R1 -R11 potato clones of potato late blight differential host.[Result]16 different races were found out of 260 isolates. Race 2.5.6.8.9.11 was most common with the frequency of 26.5%, followed by 2.5.6.8 with frequency of 20.8%. Race 2.5.6.8.9.11 was distributed mostly in Weining, Qianxi, Hezhang, Dafang, Qixingguan, Panxian, Anshun and Zunyi, while race 2.5.6.8 was distributed mostly in Zunyi, Anshun, Qianxi and Dafang. In the composition of Phytophthora infestans in Guizhou Province from 2013 to 2014, complex races were dominant, with the race 1.2.4.5.6.8.9.11 being the most complex one. In Anshun, Zunyi, Daozhen and Li-bo, the composition of the physiological race of Phytophthora infestans was complex. There were 4 or 6 types. In Qianxi and Leishan, the composition of the physiological race was simple. There were 2 types. [Conclusion ]There are 16 physiological races of Phytophthora infestans in Guizhou Province in 20&3-20&4 and the dominant race is 2.5.6.8.9.&&, followed by 2.5.6.8. The tendency of physiological race of Phytophthora infestans in Guizhou Province is diversified and complicated [ABSTRACT FROM AUTHOR]

Northern corn leaf spot, a foliar disease caused by Cochliobolus carbonum, has become prevalent in southwestern China, especially in the Yunnan Province. Races and mating types were identified for 169 isolates collected from 13 prefectures of Yunnan by artificial inoculation using six hybrid corns as differential hosts and by crossing with three standard mating strains: CC092 ( MAT1-2), CC120 ( MAT1-1) and CC026 ( MAT1-1). Results showed the existence of three races: CCR1 (one isolate), CCR2 (43 isolates) and CCR3 (125 isolates). Most isolates were moderately or weakly virulent with only five being highly virulent. CCR3 was widely distributed and significantly more virulent than CCR2 that coexisted with CCR3 in many locations. On Sach's nutrient agar, 20.71% of the Yunnan isolates self-mated, forming sterile perithecia. Fully developed perithecia could be formed between isolates of different geographic origins, but only 15.98% strains mated successfully with CC092 and 5.33% formed mature perithecia with 4-6 ascospores per asus. Similar results were obtained in crossing with CC026 or CC120. Mating could also occur between CCR3 and CCR2. Both mating types were found in Yunnan with 84 MAT1-1 strains (one CCR1, 10 CCR2 and 73 CCR3) and 85 MAT1-2 strains (33 CCR2 and 52 CCR3) and they coexisted in most areas. To identify the mating type rapidly, three specific primers were successfully developed and employed to amplify the mating-type genes, with stable patterns of 1627 and 876 bp fragments obtained from MAT1-1 and MAT1-2 isolates, respectively. The ratio between MAT1-1 and MAT1-2 was 1 : 1, indicating that the mating-type genes segregated randomly in the field naturally. [ABSTRACT FROM AUTHOR]

In order to clear the composition and distribution of physiological races of Pyricularia oryae in Heilongjiang Province, 299 single spore isolates of P. oryae collected from five rice regions (30 cities, counties or farms) in Heilongjiang Province form 2007 to 2011 were identified by seven differential varieties in China, and a total of seven groups with 31 physiological races had been identified. The results showed that ZA, ZD and ZB groups were the dominant groups in Heilongjiang Province, with the occurrence frequencies of 34. 8% , 31. 1% and 16. 1% , respectively. ZD5 was the dominant race with the occurrence frequency of 17.1 % ; followed by ZA4, and ZD2, with the occurrence frequencies of 13.7% and 10.7% , respectively. The types and compositions of physiological races of P. oryae varied with rice regions. [ABSTRACT FROM AUTHOR]

The article offers information on stripe rust resistance in wheat or Triticum aestivum with the wheat-rye. It is said that wheat lines were developed with the rye chromosome arm, which is translocated from rye inbreds. A study is conducted to evaluate wheat cultivars for reaction to races CYR31 and CYR32 of Puccinia striiformis.

Anthracnose disease of common bean ( Phaseolus vulgaris), caused by Colletotrichum lindemuthianum, is responsible for extensive yield losses worldwide. This pathogen is known to vary greatly in its pathogenicity. Control strategies include chemical control and, mainly, the development of resistant cultivars, taking into account the population structure of C. lindemuthianum. The objective of this study was to investigate the pathogenic and genetic diversity and population structure among C. lindemuthianum isolates collected in Minas Gerais state, Brazil. When these isolates were inoculated on 12 differential cultivars, a total of 10 races were identified within a series of 48 isolates collected in Minas Gerais, Brazil. Races 65, 81 and 73 were the most frequent races and occurred in most of the regions. This study also detected race 337, which had not been reported previously in the literature. Random amplified polymorphic DNA (RAPD) analysis performed on the same 48 isolates revealed great genetic diversity, clustering the series into five groups at a maximum similarity value of 89.6%. There was no clear relationship between the loci sampled by RAPD markers and the pathogenic characterization. Analysis of molecular variance showed that 96.06% of the variability was contained within regions and 3.94% among regions, indicating a high exchange of genetic material among the regions of the State. Most of the variability was detected within races (75.24%). The pathogenicity and RAPD assays corroborated the broad genetic diversity of the pathogen and the results have been useful in breeding for resistance to anthracnose. [ABSTRACT FROM AUTHOR]

Angular leaf spot disease of common bean ( Phaseolus vulgaris), caused by Phaeoisariopsis griseola, is one of the most important disease of this crop in Brazil. Control strategies for the disease include cultural practices, chemical control and genetic resistance. This pathogen is known to vary greatly in pathogenicity. For durable use of genetic resistance to control this disease, it is necessary to manage resistant cultivars by taking into account the population structure of P. griseola. Isolates of the pathogen from Goias, Brazil exhibited an important virulence polymorphism when inoculated on 12 differential cultivars. A total of 13 pathotypes was identified within a series of 96 isolates collected in Inhumas and Damolandia counties. Only pathotypes 63-15, 63-23, 63-31 and 63-63 were identified in both counties. Since all the isolates were capable of inducing disease in both Andean and Mesoamerican differential cultivars, they were considered to be of Mesoamerican origin. Random amplified polymorphic DNA (RAPD) analysis performed on the same 96 isolates revealed a great genetic diversity clustering the series into five groups at an Euclidean distance of 62.5%. Although the results did not show any clustering according to the isolate origin, it was possible to observe a tendency of the isolates to cluster in different groups according to their origin. No pathotype-specific band was observed in the present study. [ABSTRACT FROM AUTHOR]

Reports the incidence, severity and virulence spectrum of Puccinia graminis sp. tritici and Puccinia graminis f. sp. avenae populations. Identification of stem rust as a disease of cereal crops controlled in Canada; Annual stem rusts survey conducted to provide early detection of novel races with virulence to grown cultivars and to identify changes in virulence frequency in the pathogen population; Finding of stem rust on cultivated wheat.

Qualitative observations of Hevea spp. resistance to Phyllachora huberi were carried out on 200 clones in a collection and 21 full-sib progenies under natural conditions of infestation. A total of 42 clones, mostly originating from the natural range of the Hevea genus, and at least two species ( H. brasiliensis and H. benthamiana) revealed total resistance to the parasite. For nine of the thirteen `resistant ×susceptible' and `resistant × resistant' progenies studied, the ratio of susceptible: resistant plants suggested the existence of a total resistance mechanism produced by a dominant allele at a single locus for the P. huberi race(s) present at the study site. For three of the progenies involving the same resistant parent, it was possible to locate the gene (called Phr) at 14.7 cm from the adhisozyme locus. [ABSTRACT FROM AUTHOR]

Clubroot resistance of oilseed rape (OSR) cultivars frequently relies on a major resistance gene originating from cv. Mendel. The efficacy of this resistance was studied in greenhouse experiments using two Plasmodiophora brassicae isolates, which were either virulent (P1(+)) or avirulent (P1) on Mendel. Seeds of clubroot-susceptible cultivar Visby and clubroot-resistant cultivar Mendel were sown in soil mixtures inoculated with different concentrations of resting spores (101, 103, 105, and 107 resting spores/g soil). Clubroot severity, plant height, shoot and root weight as well as resting spore propagation were assessed for each isolate and cultivar separately at four dates after sowing. The OSR cultivars behaved significantly different in the measured parameters. The threshold of inoculum density to cause disease depended strongly on the virulence of the pathogen and susceptibility of the host plant. In Visby grown in soil infested with P1, clubroot symptoms and increases in root weight and the number of propagated resting spores occurred at inoculum levels of 101 resting spores and higher, whereas Mendel was not affected in soils under the three lowest inoculum densities. In contrast, the P1(+) isolate led to earlier and more severe symptoms, heavier galls, and a significantly higher number of new resting spores in both cultivars. [ABSTRACT FROM AUTHOR]

Twelve expressed sequence tags-derived markers were isolated from Plasmopara halstedii (Oomycetes), the causal agent of sunflower downy mildew. A total of 25 single nucleotide polymorphisms and five indels were detected by single-strand conformation polymorphism analysis and developed for high-throughput genotyping of 32 isolates. There was a high level of genetic diversity ( HE = 0.484). Observed heterozygosity ranged from 0 to 0.143 indicating that P. halstedii is probably a selfing species. These markers were also useful in detecting significant genetic variations among French populations ( FST = 0.193) and between French and Russian populations ( FST = 0.23). Cross-amplification tests on three closely related species indicated that no loci amplified in other Oomycete species. [ABSTRACT FROM AUTHOR]

The present study investigated the changes in total and individual glucosinolates (GSLs) in roots and leaves of different clubroot-resistant and -susceptible oilseed rape cultivars following artificial inoculation with Plasmodiophora brassicae isolates with different virulence. The results showed significant differences in clubroot incidence and severity as well as in the amount of total and individual glucosinolates between oilseed rape cultivars in response to virulence of the pathogen. Single among with total aliphatic and total indolic glucosinolate contents were significantly lower in leaves of susceptible cultivars compared to resistant ones due to the infection. Similarly, single and total aliphatic as well as indolic glucosinolate contents in roots were lower in susceptible cultivars compared to resistant cultivars analyzed. The different isolates of P. brassicae seem to differ in their ability to reduce gluconasturtiin contents in the host. The more aggressive isolate P1 (+) might be able to suppress gluconasturtiin synthesis of the host in a more pronounced manner compared to the isolate P1. A possible interaction of breakdown products of glucobrassicin with the auxin receptor transport inhibitor response 1 (TIR1) is hypothesized and its possible effects on auxin signaling in roots and leaves of resistant and susceptible cultivars is discussed. A potential interplay between aliphatic and indolic glucosinolates that might be involved in water homeostasis in resistant cultivars is explained.

A group of differential tomato lines was used to identify the races of Fusarium oxysporum f. sp. lycopersici in Zhejiang, China. Marmande verte carries no resistant genes and Marporum carries gene I-1. Both lines Motelle and Mogeor have Gene I-1 and I-2. Tomato seedlings of eighteen days after sowing were inoculated with an isolate of Fusarium oxysporum f. sp. lycopersici, No. 98-2 and kept in a growth chamber. The seedlings were evaluated at fourteen days after inoculation. Results showed that Marmande verte and Marporum were severely infected by the pathogen and established as susceptible. Motelle and Mogeor were not infected and established as resistant. These results indicated that the isolate No. 98-2 represented the race 2 of Fusarium oxysporum f. sp. lycopersici and gene I-2 is necessary for obtaining resistance to this pathogen in the Zhejiang region. [ABSTRACT FROM AUTHOR]