Epistasis and Maternal Effect in Resistance to Puccinia coronata Cda. f. sp. avenae Eriks in Oats （Avena sp.）

The objective of this paper was to investigate the mode of heredity for resistance in oats （Avena sp.） to crown rust caused by Puccinia coronata Cda. f. sp. avenae Eriks, Eight generations of 2 crosses were used to estimate genetic effects and narrow-sense heritability （NSH）. Separate generation means analysis （GMA） indicated a complex gene action controlling this trait with additive, dominance, epistatic and maternal effects （ME）. The genetic model which assumed no epistasis and no ME did not accurately describe the resistance to P. coronata. In both crosses, the digenic epistatic model with ME was sufficient to explain variation in generation means for isolate CRec58 and isolate CRec46. Additive dominance and epistatic components were negative in most cases, suggesting that gene effects contributed more to the resistance than to the susceptibility. The estimated values of NSH were 15-99% depending upon the cross and isolates. The results indicated that appropriate choice of maternal parent and recurrent selection would increase resistance to crown rust in oats.     

Diallel Crossing Analyses of Resistance to Main Diseases in Pepper （Capsicum annuum L.）

Fifteen capsicum combinations were made with 6 parents by （1/2）n（n-1） diallel crossing. Genetic parameters in the resistance to TMV, CMV, phytophthora blight, bacterial spot of these combinations were studied by Hayman. The results indicated that the resistance to TMV, CMV and bacterial spot conformed genetically to the “additive-dominant” model but the resistance to phytophthora blight did not and significant epistatic dominance effect existed in it. F1 hybrid＇s resistance to CMV was controlled by homozygous dominant gene （s）, but resistance to bacterial spot by heterozygous one （s）. There were little, or no sum of dominant effect and genomes controlling the dominant expression of F1 hybrids in its phytophthora blight resistance.     

Identiifcation and Molecular Mapping of the RsDmR Locus Conferring Resistance to Downy Mildew at Seedling Stage in Radish （Raphanus sativus L.）

Downy mildew （DM）, caused by the fungus Peronospora parasitica, is a destructive disease of radish （Raphanus sativus L.） worldwide. Host resistance has been considered as an attractive and environmentally friendly approach to control the disease. However, the genetic mechanisms of resistance in radish to the pathogen remain unknown. To determine the inheritance of resistance to DM, F1, F2 and BC1F1 populations derived from reciprocal crosses between a resistant line NAU-dhp08 and a susceptible line NAU-qtbjq-06 were evaluated for their responses to DM at seedling stage. All F1 hybrid plants showed high resistance to DM and maternal effect was not detected. The segregation for resistant to susceptible individuals statistically iftted a 3：1 ratio in two F2 populations （F2（SR） and F2（RS））, and 1：1 ratio in two BC1F1 populations, indicating that resistance to DM at seedling stage in radish was controlled by a single dominant locus designated as RsDmR. A total of 1 972 primer pairs （1 036 SRAP, 628 RAPD, 126 RGA, 110 EST-SSR and 72 ISSR） were screened, and 36 were polymorphic between the resistant and susceptible bulks, and consequently used for genotyping individuals in the F2 population. Three markers （Em9/ga24370, NAUISSR826700 and Me7/em10400） linked to the RsDmR locus within a 10.0 cM distance were identiifed using bulked segregant analysis （BSA）. The SRAP marker Em9/ga24370 was the most tightly linked one with a distance of 2.3 cM to RsDmR. These markers tightly linked to the RsDmR locus would facilitate marker-assisted selection and resistance gene pyramiding in radish breeding programs.     

Genetic Analysis of the Resistance to Aspergillus flavus Infection in Maize （Zea mays L.）

Maize （Zea mays L.）, one of main crops in the world, is easily susceptible to Aspergillusflavus （Link： fr） infection, resulting huge loses worldwide. Breeding for A. flavus resistance has been proved an efficient way to solve the problem of aflatoxin contamination. Genetic analysis of the sources of resistance to A.flavus in maize is necessary for this purpose. The complete diallel crosses of 6 inbred lines with different resistance to A.flavus infection were implemented. Inoculation categorical data of each cross were analyzed with the additive-dominant and additive-dominant-epitasis genetic models. Results indicated some crosses fitted the 2 major genes with additive-dominant-epitasis genetic model. Others fitted the major gene and polygene mixed model. Moreover, the additive, dominant, and epitasis effects varied in crosses. The A.flavus resistance was controlled by both major gene and polygene.     

Cloning of TaCYP707A 1 Gene that Encodes ABA 8′-Hydroxylase in Common Wheat（Triticum aestivum L.）

The plant hormone abscisic acid （ABA） regulates many important physiological and developmental processes in plants. The objective of this study was to clone the ABA 8′-hydroxylase gene in common wheat. In the present study, we used the eDNA sequence of barley HvCYP707A1 gene （GenBank accession no. AB239299） as a probe for BLAST search against the common wheat （Triticum aestivum L.） EST database in GenBank. All wheat ESTs sharing high similarity with the reference gene were subjected to contig assembly. Primers were designed based on the constructed contigs to clone the wheat CYP707A1 gene, designated as TaCYP707A1. The genomic DNA sequence of TaCYPTO7A1 gene comprised five exons and four introns, with a size of 2225 bp. The corresponding cDNA sequence of TaCYP707A1 was 1737 bp, containing an open reading frame （ORF） of 1431 bp, a 42-bp 5′-untranslated region （UTR） and a 264-bp 3′UTR, with 94.9% of identical sequences to HvCYP707A1 gene （AB239299）. The neighbor joining tree indicated that the deduced amino acid sequences of TaCYP707A1 gene was highly similar to those of barley and rice. The TaCYP707A1 gene was located on chromosome 6BL using a set of Chinese Spring nullisomic-tetrasomic lines and ditelosomic line 6BS. These results will be of high importance in understanding of molecular mechanism of ABA catabolism.     

Genetic Diversity of Recurrent Selection Populations with Ms2 Gene Assessed by Gliadins in Common Wheat （Triticum aestivum L.）

The male-sterile lines with Ms2 gene were highly evaluated in recurrent selection in wheat （Triticum aestivum L.）. Three populations C6 （population after six cycles of selection）, C7 （population after seven cycles of selection）, and C8 （population after eight cycles of selection） were constructed through recurrent selection with 12 parental materials （P）. Acid polyacrymide gel electrophoresis （A-PAGE） analysis was used to identify gliadin patterns and evaluate the genetic diversity in 12 parents and three populations. A total of 63 bands were identified, of which 17 polymorphic bands and 7 unique bands were present in populations and seven polymorphic bands and four unique bands were present in parents. The number of polymorphic and unique bands decreased gradually from C6 to C8, especially for to- and y-gliadins. The genetic distances in C6, C7, and C8 were calculated. The distributions of genetic distance were different in three recurrent selection populations. From C6 to C8, the genetic distance was 0.2687, 0.2652 and 0.1987, respectively. Statistically significant differences were detected between C7 and C8 with the T value of 37.9718. The result of cluster analysis based on genetic similarity matrix of three populations fitted well to those of principle coordinates analysis （PCoA）. Compared with 12 parents, almost all individuals of three populations are new genotypes. Most of the individuals from C6 and C7 could be divided into two groups, while most individuals of C8 were in one cluster. In conclusion, the results indicated that the genetic diversity was decreased severely according to the information revealed by A-PAGE, although some variations could be created in the recurrent selection. It was necessary to introduce diverse germplasm based on the genetic database of recurrent population to maintain and improve the breeding efficiency in the further program.     

小麦抗条锈病基因对中国条锈菌主要流行小种的抗性分析

[目的]培育和广泛应用抗病小麦品种是防治条锈病最经济有效和环境友好的措施.由于条锈菌(Puccinia striiformis f.sp.tritici,Pst)群体中毒性变异频繁,发生新生理小种常导致主栽品种抗病性'丧失',引发条锈病大规模流行,严重威胁我国主粮安全供给.本研究通过监测和评价已知抗条锈病基因对我国目前...     

北方麦区120个小麦品种抗秆锈病基因的推导

利用含已知Sr5～38、SrGT和SrWld基因的42个单基因系和19个不同毒性的秆锈菌系,对北方麦区的120个生产品种和后备品系进行了抗秆锈病的基因推导．研究结果表明：黄淮冬麦区和北方冬麦区抗病品种（系）含有的抗秆锈病基因相似,绝大多数品种（系）主要含有Sr5、Sr31,少量品种含有Sr11、21、29等抗病基因;东北春麦区的小麦抗病品种（系）主要含有Sr5、6、8a、9b、9e、11、21、27、30、31、34、36等多基因组合。     

中国47个小麦新品种（系）苗期抗叶锈基因推导

 【目的】探明中国47个小麦新品种（系）携带的苗期抗叶锈基因状况，改进和完善基因推导方法。【方法】选用17个具有较高鉴别能力的致病类型，在不同温度和（或）光照强度下测定，结合系谱分析进行基因推导。【结果】在供试的47个小麦品种（系）中，推导出Lr1（存在于11个品种或品系中）、Lr3（7）、Lr3bg（3）、Lr9（3）、Lr10（3）、Lr13（10）、Lr16（6）、Lr23（2）、Lr26（14）和Lr34（1）共10个已知抗病基因，另有42个品种（系）含有未知基因。【结论】在苗期进行基因推导时，尽量多地选择鉴别能力强的致病类型，在相对稳定均一的环境条件下重复测定，并结合系谱分析，才能获得可靠的结果。结合温度与光照强度梯度，具有持久抗病性潜质的抗叶锈基因Lr13和Lr34可在苗期进行推导。     

52个重要小麦品种抗条锈基因的推导

根据对 13个具有不同毒性基因组合的条锈菌系的反应,采用基因推导方法,分析 52个重要小麦品种(系)所携带的抗条锈基因。结果表明:在已知的 19个抗条锈基因中,Yr1、Yr2、Yr6、Yr7、Yr8、Yr9、Yr11、Yr12、Yr17、Yr18、Yr24和Avocet12个基因以单基因或基因组合的形式分布在 28个小麦品种 (系 )中;携带Yr11基因的小麦品种最多,有 17个,携带Yr2、Yr6和Yr17基因的小麦品种各有 15个;抗源品种 92R137、92R149等可抵抗包括当前流行小种在内的所有供试条锈菌系,正在大面积种植的品种如陕 160、济南 17、烟 188、烟 361等感染所有的菌系,由此推导它们不含任何已知抗条锈基因。培育和推广具有有效抗条锈基因的新品种迫在眉睫。该文还讨论了基因推导的局限性。     

河北省21个小麦品种抗叶锈基因的推导

选用了18个小麦叶锈菌菌系对河北省的21个小麦品种(系)进行了抗性基因推导。通过与31个抗叶锈的单基因系的反应作比较,在河北省的品种中鉴定出Lr1,Lr3,Lr3Bg,Lr18,Lr26和Lr30共6个抗性基因。冀麦15有Lr3,冀麦3号有Lr3Bg;有8个品种有3个基因,其中7个品种例如冀麦23等,有Lr3,Lr3Bg 和Lr26,另一品种冀麦20有Lr18,Lr26和Lr30。有两个品系88-5424和84—5103有4个基因;前者有Lr1,Lr18,Lr26和Lr30,后者有Lr3,Lr3Bg,Lr18和Lr26。冀麦26和冬协4号有与供试的已知基因不同的基因;在丰抗8号等3个品种中没有鉴定出抗性基因。Lr26最为普遍,在13个品种中存在。     

94个小麦重要抗源品种抗秆锈病基因的推导

利用含已知Ｓｒ５～Ｓｒ３８基因的３９个单抗基因系和１９个不同毒性的小麦秆锈菌系,对９４个小麦抗源品种进行了抗秆锈病基因的推导。结果有４个品种可能含有Ｓｒ３８基因或含有国际上尚未命名的新的抗病基因,有７２个品种可能含有Ｓｒ２２,Ｓｒ２６和Ｓｒ３１中的某些抗病基因或含有国际上尚未命名的新的抗病基因,有３个品种含有Ｓｒ３３基因,有１个品种含有Ｓｒ２１等基因。我国的小麦秆锈病菌对这８０个抗源品种表现无毒力或毒性频率很低,这些抗源品种是我国小麦抗秆锈病育种的有效抗源。     

小麦条锈菌条中32号及水14致病类型毒性基因分析

利用Flor基因对基因学说原理对条锈菌生理小种条中32号和水14所含的毒性基因进行推导,结果表明,条中32号含有VYr-1、VYr-2、VYr-3、VYr-6、VYr-7、VYr-8、VYr-9、VYr—11、VYr-12、VYr-18、VYr—Su、VYr—C5、VYr—SD、VYr—SpP等毒性基因,水14含有VYr-1、VYr-2、VYr-3、VYr-6、VYr-7、VYr-8、VYr-9、VYr—11、VYr-12、VYr-18、VYr—Su、VYr—C5、VYr—C591、VYr—SD、VYr—SpP等毒性基因。对条中32和水14的毒性基因谱的比较发现,水14含有较条中32号特异的VYr—C591毒性基因,致使近年来抗病品种C591田间抗病性丧失。     

Ultrastructural Changes in the Interaction Between Puccinia striiformis and Wheat Cultivar with Slow-Rusting Resistance

Ultrastructural changes in both pathogen and host cells in the interaction between Puccinia striiformis and wheat cultivar （Libellula） with slow-rusting resistance were observed by transmission electron microscopy. Observations revealed marked changes in ultrastructure of both pathogen and host cells. In the pathogen respect, there were many vesicles appeared in the intercellular hyphae and gradually fused into bigger vacuoles, a number of fat drops and electron-dense granules accumulated, mitochondria became swollen and some of them degraded into vesicles, and the plasmalemma of intercellular hyphae became dark. In the haustoria, the cytoplasm degraded gradually and developed a vacuole in the center, fat drops increased, the extrahaustorial matrix widened with a great amount of electron-dense fibrillar and granular materials, and most of the haustoria died with in conjunction with the disappearance of fat drops and other organelles. Structural defense of the host, including formation of cell wall apposition, collar and papilla, occurred in the host respect. Host resistance expression and cytological features occurring in the slow-rusting resistance were discussed.     

中国40个小麦农家品种和甘肃南部40个生产品种抗条锈病基因推导

【目的】明确中国小麦农家品种与甘肃南部生产品种抗条锈性类型及可能含有的抗性基因和遗传多样性,为抗源的选择与利用提供参考。【方法】苗期于自控温室内使用中国当前小麦条锈菌（Puccinia striiformis f. sp. tritici）流行小种CYR32,成株期于大田病圃使用当前主要流行小种和重要致病类型共12个菌系组成的混合菌种对80个供试材料进行抗病性鉴定与评价。基因推导在温室用25个毒性谱不同的小麦条锈菌系于苗期接种30个已知抗条锈病基因载体品系及对照铭贤169、17个国际鉴别寄主和供试品种,根据供试品种和标准品系对不同菌系的侵染型,对农家品种和生产品种进行抗性谱比对分析和系谱分析,解析其可能含有的抗条锈病基因或基因组合及抗性谱,并通过NTSYSpc-2.2软件计算遗传相似系数,以UPGMA法进行聚类分析,将其抗性归类。【结果】供试品种大多具有良好的成株期抗性,除清农1号、清农2号、红壳小麦(2)在成株期表现感病,兰天3号、兰天4号、兰天6号等20个品种在成株期表现慢锈性外,其他品种均表现中抗至免疫的抗性水平。品种抗性多由全生育期抗性、部分由成株抗性提供。甘肃生产品种中抗病基因以Yr9、Yr24、Yr26为主,有的还含有其他未知抗条锈病基因。其中,兰天1号、兰天14号、兰天17号、兰天21号、清农4号等含Yr9;兰天24号、中梁04335、天选51号可能含Yr24;兰天17号、兰天23号、兰天25号、中梁17号、中梁04260、天选43号、天选48号可能含Yr26。农家品种中有19份材料含有未知抗条锈病基因,其余21份材料不能确认含已知抗病基因Yr1、Yr2、Yr4、Yr6、Yr7、Yr8、Yr40,可能含有未知基因。聚类分析发现,甘肃生产品种大都抗性谱较宽,遗传相似性较高;40份材料的抗条锈性相似系数范围在0.30-1.00,在抗性相似系数为0.70水平上可分为3大类,其中兰天15号单独聚为1类,清农1号和清农2号聚为1类,其余37份材料聚为1大类。农家品种抗性谱宽窄不一,显示出遗传多样性水平较高;40份材料的抗条锈性相似系数范围在0.38-1.00,在抗性相似系数为0.70水平上可分9大类。【结论】供试品种均有良好的抗条锈性,相对于甘肃南部生产品种,供试的农家品种更具丰富的遗传多样性和有效抗条锈病基因,可作为抗源在育种中加以利用。