小麦品种(系)抗叶锈病基因Lr10位点基因型的多样性

小麦抗叶锈病基因Lr10的表达需与其紧密连锁的RGA2基因调控, 按照这2个基因的连锁关系, Lr10基因位点分成H1和H2两个古单倍型。为揭示我国小麦品种中Lr10的遗传多样性, 对189个来自12省的小麦育成品种和58个品系的该基因位点变异进行了鉴定分析。绝大多数供试品种(系)为H2古单倍型, 其频率在育成品种和品系中分别为95.2% (180/189)和96.6% (56/58)。这2种古单倍型可进一步分为9种单倍型亚型, 其中H1-2、H2-4、H2-5、H2-6和H2-7亚型为首次报道。育成品种包含所有单倍型亚型, 以H2-1频率最高(69.3%), H2-3和H2-6频率最低(0.5%); 而在选育品系中仅检测到5种单倍型亚型, 其中H2-1频率最高(27.6%), H1-2频率最低(3.5%)。除H2-1与H2-2型外, 其他亚型与育成地显著相关(P < 0.05)。本研究结果支持Lr10基因位点的古单倍型和单倍型亚型在育种中保持相对稳定的推断, 同时由于在育种过程中持续重组和变异而产生了新的单倍型亚型, 而且重组可以发生在H2和H1两种古单倍型之间。在现代育成品种和品系中, H1古单倍型所占比例已降至5%以下, 应加以保护。

Genotypic Diversity at the Lr10 Locus for Leaf Rust Resistance in Various Hexaploid Wheat Varieties (lines)

Genotypes H1 and H2 are two ancient haplotypes on Lr10 locus, which is a resistance gene to wheat leaf rust. They are identified based on the presence of both Lr10 and RGA2 in full length (H1), and the absence of Lr10 and chromatin rearrangement of RGA2 (H2) due to chromosome 1AS reorganization during species evolution. Both haplotypes contain several subhaplotypes. To understand genetic diversity on Lr10 locus, we tested the frequencies of H1 and H2 haplotypes and their subhaplotypes in 189 wheat cultivars and 58 breeding lines originating from various provinces of China. The H2 haplotype was dominant in the developed cultivars and breeding lines with the frequencies of 95.2% (180/189) and 96.6% (56/58), respectively. Five novel subhaplotypes were detected in the developed cultivars, namely H1-2, H2-4, H2-5, H2-6, and H2-7. In cultivars, subhaplotype H2-1 was the most frequent (69.3%), whereas subhaplotypes H2-3 and H2-6 had the lowest frequencies (0.5%). Among the five subhaplotypes detected in breeding lines, subhaplotype H2-1 had the highest frequencies (27.6%), whereas subhaplotypes H1-2 was the least frequent (3.5%). Interestingly, the subhaplotypes except for H2-1 and H2-2 were highly breeding location-dependent (P < 0.05). These results support the hypothesis that both haplotypes have been maintained through a balanced polymorphism mechanism during wheat domestication. Furthermore, the five novel subhaplotypes suggest that genetic diversities resulting from recombination and other types of chromatin reorganizations (e.g., origin of the H2 haplotype and polymorphism for the Lr10 locus) have been going on since the formation of the hexaploid wheat. Significantly, identification of the H1-2 subhaplotype is a clear evidence of occurrence of recombination between the two ancient haplotypes, which disagrees with the previous notion. Importantly, because the frequencies of H1 is lower than 5% in developed cultivars and breeding lines, actions for protecting germplasm with the H1 haplotype are highly recommended.