Genetics of resistance to 3 isolates of Ascochyta fabae on Faba bean (Vicia faba L.) in controlled conditions

Summary Genetics of resistance to Ascochyta fabae Speg. in Vicia faba L. was studied with a final objective to develop resistant faba bean varieties to Ascochyta blight. The study was conducted separately on 3 single spore isolates (AF10-2 and AF13-2 from Tunisia and AF4-3 from France) and belonging to different groups of virulence (GV1 and GV2). Important general combining ability (GCA) effects were found especially with isolates AF10-2 and AF4-3. Specific combining ability (SCA), although significant for the 3 isolates, was important only with AF13 -2, but less important than GCA. Additive gene effects were predominant to non-additive effects. Lines 29H and A8817 transmitted to their progenies resistance to the 3 isolates, whereas 14–12 and 19TB conferred resistance to their progenies only with isolates AF13-2 and AF4-3, respectively. In the material studied, resistance was generally controlled by dominant genes but also could be attributed to recessive genes although less frequent. Analysis of segregation in the F2 of 2 crosses between the resistant lines (A8817 and 29H) and the susceptible line (14–12) with isolate AF4-3 revealed dominant monogenic control at the level of leaves in the 2 resistant lines and, in addition, a recessive gene controlling resistance of stems. Non-allelic interactions were occasionally manifested and their origin appeared to be due to line 19TB. A recurrent selection scheme was proposed with the objective to develop improved open-pollination populations and synthetic varieties responding to the objective of the national Tunisian research programme on faba bean.     

太子参叶斑病病原菌鉴定及防治药剂筛选

采用形态学结合分子系统学方法对引起贵州黄平县和六枝道地中药材种植基地太子参叶斑病的病原菌进行鉴定,并以菌丝生长法对75%百菌清可湿性粉剂、70%甲基硫菌灵可湿性粉剂、37%苯醚甲环唑可湿性粉剂、40%氟硅唑乳油以及1%申嗪霉素悬浮剂进行了室内药效筛选。结果表明:引起贵州太子参叶斑病的病原菌为Ascochyta versabilis,该病原菌为太子参病害新记录;5种杀菌剂除75%百菌清可湿性粉剂2 000倍对A.versabilis的抑菌率较低外(51.4%),其余4种供试杀菌剂均具有较强的抑菌作用。70%甲基硫菌灵可湿性粉剂2 000倍、37%苯醚甲环唑可湿性粉剂2 000倍和40%氟硅唑乳油2 000倍对A.versabilis的生长具有较强的抑制作用,其抑制率均高于90%;1%申嗪霉素悬浮剂2 000倍对该病原菌的抑制率为72.3%。     

Structure and pathogenic variability in Ascochyta rabiei populations on chickpea in the Canadian prairies

A population study of Ascochyta rabiei from the Canadian prairies was conducted to assess pathogenicity among isolates with the objectives to investigate the existence of a race or pathotype structure and to evaluate whether there had been a shift to higher aggressiveness between 1998 and 2002. Ninety-nine isolates collected in 1998, 2001 and 2002 were inoculated onto seven differential chickpea genotypes. Significant isolate × differential interactions occurred, but accounted for a small proportion of the total variability. It was found that very few interaction effects between all combinations of differentials and isolates were significant and frequency distributions of disease severity of isolates tested on the differentials revealed continuous distributions. These results suggest that no genotype-specific relationship existed between A. rabiei and its host and that Canadian populations of the pathogen cannot be objectively classified into races or pathotypes. Isolates from 2001 and 2002 caused significantly more disease than isolates from 1998, suggesting that disease epidemics encountered since 1999 were in part caused by a shift in the population to higher aggressiveness.     

白头翁叶斑病菌黑色素的理化性质及其生物合成途径初步研究

对白头翁叶斑病菌胞壁结合黑色素和胞外黑色素进行了理化性质和红外光谱扫描测定, 结果表明两者具有相似的理化性质, 均易溶于KOH、H2O2和NaClO, 不溶于水、乙醇和丙酮。红外光谱分析表明, 白头翁叶斑病菌YS-24菌株的胞壁结合黑色素与胞外黑色素为同一种类型的黑色素。DHN黑色素的特异性抑制剂—三环唑, 对白头翁叶斑病菌黑色素的产生有明显的抑制作用; 以白头翁叶斑病菌基因组DNA为模板, 通过PCR扩增, 得到了聚酮体合成酶基因的同源片段 AaPKS , 初步推断白头翁叶斑病菌黑色素合成属于DHN途径。     

Genetics of resistance to ascochyta blight in chickpea (Cicer arietinum L.)

Summary Six chickpea lines resistant to Ascochyta rabiei (Pass.) Lab. were crossed to four susceptible cultivars. The hybrids were resistant in all the crosses except the crosses where resistant line BRG 8 was involved. Segregation pattern for diseases reaction in F₂, BCP₁, BCP₂ and F₃ generations in field and glasshouse conditions revealed that resistance to Ascochyta blight is under the control of a single dominant gene in EC 26446, PG 82-1, P 919, P 1252-1 and NEC 2451 while a recessive gene is responsible in BRG 8. Allelic tests indicated the presence of three independently segregating genes for resistance; one dominant gene in P 1215-1 and one in EC 26446 and PG 82-1, and a recessive one in BRG 8.Research paper No. 3600     

QTL mapping of resistance in lentil (Lens culinaris ssp. culinaris) to ascochyta blight (Ascochyta lentis)

Quantitative trait locus (QTL) analysis of ascochyta blight resistance in lentil was conducted using genomic maps developed from two F₂ populations, viz. ILL5588/ILL7537 and ILL7537/ILL6002. Five QTLs for ascochyta blight resistance were identified by composite interval mapping (CIM) across four linkage groups (LG) in population ILL5588/ILL7537. Three QTLs were identified by CIM in population ILL7537/ILL6002 (two in close proximity on LGI and one on LGII). Two of these coincided with regions identified using multiple interval mapping (MIM) and were shown to be conditioned by dominant and partial dominant gene action. Together, they accounted for approximately 50% of the phenotypic variance of disease severity. Comparison between the two populations revealed a potentially common QTL and several common regions that contained markers significantly associated with resistance. This study demonstrated the transferability of QTLs among populations and identified markers closely linked to the major QTL that may be useful for future marker‐assisted selection for disease resistance.     

Towards the first linkage map of the<Emphasis Type="Italic">Didymella rabiei</Emphasis> genome

A genetic map was developed for the ascomyceteDidymella rabiei (Kovachevski) v. Arx (anamorph:Ascochyta rabiei Pass. Labr.), the causal agent of Ascochyta blight in chickpea (Cicer arietinum L.). The map was generated with 77 F₁ progeny derived from crossing an isolate from the U.S.A. and an isolate from Syria. A total of 232 DAF (DNA Amplification Fingerprinting) primers and 37 STMS (Sequence-Tagged Microsatellite Site) primer pairs were tested for polymorphism between the parental isolates; 50 markers were mapped, 36 DAFs and 14 STMSs. These markers cover 261.4cM in ten linkage groups. Nineteen markers remained unlinked. Significant deviation from the expected 1:1 segregation ratios was observed for only two markers (Prob. of χ²<0.05). The implications of our results on ploidy level of the asexual spores are discussed. http://www.phytoparasitica.org posting Sept. 5, 2002.     

Sympatric ascochyta complex of wild Cicer judaicum and domesticated chickpea

The aim of this study was to isolate, identify and characterize ascochyta blight pathogens from Cicer judaicum , a wild annual Cicer species which grows in Israel and other Mediterranean countries in sympatric distribution with legume crops, and determine their virulence and aggressiveness to other wild and domesticated legumes. Native C. judaicum plants exhibited symptoms resembling ascochyta diseases of grain legume crops. Two distinct pathogens were isolated and identified as Phoma pinodella and Didymella rabiei using morphological and molecular tools; their infectivity was verified using Koch's postulates. The virulence of these pathogens was examined on 13 legume species, of which P. pinodella was virulent to Pisum sativum , P. fulvum , C. judaicum , C. arietinum , C. reticulatum , C. pinnatifidum and C. bijugum . Didymella rabiei infected all these Cicer species, but not the other legume species tested. Aggressiveness of the pathogens was tested on wild and domesticated chickpea and pea. Didymella rabiei isolated from C. judaicum had significantly higher ( P  < 0·001) aggressiveness than P. pinodella from C. judaicum on both wild and domesticated chickpea. Disease severity on the former species ranged from 62·5% to 70% and on the latter from 41% to 56%. Phoma pinodella isolates from C. judaicum were more aggressive on C. arietinum and P. sativum than on C. judaicum and P. fulvum . Results of the current study suggest that C. judaicum may serve as an alternative host to ascochyta pathogens that endanger chickpea and possibly other crops and wild species growing in close proximity.     

广州地区6种野生蔬菜上的病原真菌记述

通过对广州地区规模种植的野生蔬菜秋葵Abelmoschus esculentus（L.）Moench、紫背天葵Gynura bicolor DC．、香麻叶Corchorus capsularis L．、黄花菜Hemerocallis citrina Baroni、四稜豆Psophocarpus tetragonolobus（L．）DC．、一点红Emilia sonchifolia（L．）DC等的病害进行调查及病原菌鉴定，明确了8种真菌病害，分别是秋葵链格孢叶斑病Alternaria malvae Roum.et Letendre、秋葵壳二胞叶斑病Ascochyta abelmoschi Harter、紫背天葵链格孢叶斑病Alternaria tenuissima（Fr）Wiltshire、紫背天葵棒孢叶斑病Corynespora cassiicola Berk．＆Curt．、香麻叶炭疽病Colletotrichum capsici（Syd．）Butl．＆Bisby、黄花菜炭疽病Colletotrichum gloeosporioides（Penzo）Sacc．、一点红壳针孢叶斑病Septoria lactucae Passerini和四棱豆小球腔叶斑病Leptosphaeria blumeri E.Muller，并对各病原真菌的形态进行了描述。除黄花菜炭疽病外，其它7个均为国内未报道的植物真菌新病害。     

新疆鹰嘴豆壳二孢疫病病菌Ascochyta rabiei交配型、致病力及其对3种杀菌剂的敏感性测定

新疆是我国鹰嘴豆主要生产地,然而随着鹰嘴豆种植面积的扩大,集约化种植模式的发展以及广泛从国内外引种,鹰嘴豆壳二孢疫病(Ascochyta blight)开始发生。由于该病害在新疆发生历史较短,相关的研究还甚少。本研究对新疆鹰嘴豆壳二孢疫病病菌Ascochyta rabiei的交配型、致病力及对3种杀菌剂敏感性进行测定,结果表明,A.rabiei的交配型MAT1-1和MAT1-2在新疆木垒地区的分离频率明显偏离1∶1,以MAT1-2为优势种群,但其致病力与MAT1-1无显著差异,而MAT1-1对30%醚菌酯EC的敏感性显著低于MAT1-2。