关键词: 小麦条锈菌, 小麦条锈病, 群体遗传多样性, 基因流, 有性生殖

Abstract:

【Objective】In order to clarify the relationship about migration and inoculum source exchange of Puccinia striiformis f. sp. tritici (Pst) in spring epidemic time in Gansu and Qinghai provinces, and provide a theoretical basis for the epidemic prediction of wheat stripe rust and tracing the initial over-summering inoculum source and benefiting the effective disease management, the population genetic diversities and the potential spring epidemic migration of Pst were investigated. 【Method】The regions where stripe rust occurred frequently in the past years were selected as the investigation and studying regions. Four test sites were included in Gansu Province: Wenxian in Longnan City; Kongtong District in Pingliang City, Longdong; Linxia County, and Lintao County in Dingxi City, Longzhong; Two test sites were included in Qinghai Province: Chengbei District, Xining City; Huzhu County, Haidong City. In autumn of 2017, 82 wheat materials for trap nurseries were seeded sequentially in six regions according to the local wheat planting date in Gansu and Qinghai provinces. Field investigation was performed and molecular genotyping for 551 Pst samples collected from 82 materials with known resistant genes in six test sites of Gansu and Qinghai provinces from April to August 2018 was carried out by using 15 pairs of primers simple sequence repeat (SSR) markers. The GenAlEx and POPPR v2.5.0 software were used to analyze the data and the non-significant rbarD value might indicate linkage equilibrium was used to infer whether sexual recombination does occur or not. 【Result】The severity of the 82 wheat materials for trap nurseries of Pst in Gansu was more severe than that in Qinghai Province. The 15 SSR markers produced a total of 81 polymorphic alleles, ranging from 2 to 12 for each of the locus. A total of 505 unique multi locus genotypes (MLGs) were identified after clone correction cross the 551 Pst individuals, 32 MLGs were cloned and resampled between 2 and 6 times at six test sites. The entire genetic diversity (G) was 0.917 in six test sites from two provinces, the G value of Pingliang population (0.974) from Gansu was the highest, then it was Huzhu from Qinghai (0.957), and the Lintao population from Gansu was the lowest (0.841). The genetic variations of Pst mainly existed within the population. In spring epidemic, the migration occurred frequently among the populations. The gene flow was higher between Qinghai and Pingliang/Linxia than that was between Qinghai and Wenxian. The minimum spanning networks (MSN) and non-parametric discriminant analyses of principal components (DAPC) showed that the Huzhu and Xining populations from Qinghai had the closest relationship for the source of inoculum with the Pingliang and Linxia populations from Gansu, and the differences were the smallest. The genetic distance from the Lintao population was relatively far and the Lintao population was relatively independent. The Wenxian population was a completely independent population, with the largest difference from the other five populations. The analysis of linkage disequilibrium showed the presence of insignificant rbarD values in the Wenxian and Linxia populations from Gansu, and Xining population from Qinghai. The Wenxian population (rbarD=0.0139, P=0.186) showed obvious sexual recombination characteristics with a significant rbarD value. 【Conclusion】In spring epidemic season, the Pst source in Qinghai might originate from both Pingliang/Linxia and Wenxian, but it was mainly from Pingliang/Linxia. Signs for sexual reproduction were found in populations from Linxia and Wenxian of Gansu and Xining of Qinghai. The sexual reproduction might contribute to the richness of genetic diversity of Pst in Gansu and Qinghai.

Key words: Puccinia striiformis f. sp. tritici (Pst), wheat stripe rust, population genetic diversity, gene flow, sexual reproduction