兼抗白粉、条锈病小偃麦渗入系CH7124抗性遗传及细胞学鉴定

CH7124是通过八倍体小偃麦TAI8335与感病小麦杂交、回交育成的兼抗白粉病、条锈病的小偃麦种质系。利用抗性接种鉴定、细胞学和基因组原位杂交(GISH)技术相结合的方法,对CH7124的抗性来源、遗传方式及细胞学特征进行了分析和鉴定。结果表明,CH7124在苗期和成株期对条锈菌系CYR29、CYR31、CYR32、CYR33和白粉菌系E09、E20、E21、E26表现为免疫或近免疫,其抗性来自中间偃麦草,受1对显性核基因控制;CH7124的根尖细胞染色体数目为2n=42,花粉母细胞减数分裂中期I(PMC MI)绝大多数细胞内可观察到21个二价体,平均配对构型为2n=0.30 I+20.79 II+0.04 III;与普通小麦中国春、绵阳11的杂种F1中,有80%以上的花粉母细胞可观察到2n=21Ⅱ的染色体构型,其平均配对构型均为2n=21II。说明CH7124具有与普通小麦相似的染色体结构和规则的配对构型。由于利用以中间偃麦草总DNA为标记探针的原位杂交未观察到可见的外源DNA杂交信号,进一步证明CH7124是一个小麦-中间偃麦草的隐形异源渗入系。

Cytological Characterization and Resistance Inheritance in Alien Introgression CH7124 from Thinopyrum intermedium

Stripe rust and powdery mildew, caused respectively by Puccinia striiformis f. sp. tritici (Pst) and Blumeria graminis f. sp. tritici (Bgt), are globally important diseases of wheat. Genes transferred to wheat from wild species are often associated with deleterious traits. In this study, a wheat-Thinopyrum intermedium germplasm line CH7124 was characterized by a combination of resistance evaluation, cytological observation and genomic in situ hybridization (GISH). Disease screening demonstrated this line was highly resistant to both Pst races CYR29, CYR31, CYR32 and CYR33 and Bgt isolates E09, E20, E21 and E26, which are the most widely virulent pathotypes in China and virulent to most of the known resistance genes, and the resistance derived from Th. intermedium. Genetic analysis of the F1, F2, F3 and BC1 populations from resistant line CH7124 revealed that the resistance to powdery mildew and stripe rust was controlled by a single dominant allele. Mitotic observation showed that CH7124 had 42 chromosomes, and the chromosomes in most pollen mother cells of its F1s involved wheat genotypes Chinese Spring and Mianyang 11 at PMC MI formed 21 bivalents, averaging, respectively, 20.73 in 102 cells and 20.74 in 87 cells, suggesting stability of CH7124 in cytology and regular pairing with common wheat. As no signal could be detected when using genomic Th. intermedium DNA as a probe in the GISH experiment, the introgressed alien chromatin in this line was very small and cytologically undetectable, further indicating that CH7124 is a cryptic wheat-alien introgression line. This study showed that CH7124 appears to serve as a novel resistance source for wheat breeding.