不同栽培模式下葡萄霜霉病菌遗传结构的时间动态分析

为明确不同栽培模式下葡萄霜霉病菌Plasmopara viticola的遗传结构、遗传多样性及遗传分化水平,于2014-2015年定期采集露地和避雨2种栽培模式下的葡萄霜霉病菌菌株,利用6对SSR引物对该病菌基因型、遗传多样性及遗传分化进行对比分析。结果表明,露地和避雨栽培模式下葡萄霜霉病菌群体的Nei’s基因多样性指数大于0.14,香农多样性指数大于0.31,2种栽培模式下群体具有丰富的遗传多样性,但避雨栽培模式可显著降低群体等位基因数和等位基因频率。露地栽培模式下该病菌群体的流行模式呈现中等水平无性繁殖,2年初侵染和再侵染对病害流行的贡献率分别约占26.1%和73.9%;避雨栽培模式下葡萄霜霉病菌群体的流行模式则呈现高等水平无性繁殖,初侵染和再侵染对病害流行的贡献率分别约占4.3%和95.7%。卵孢子的形成对于葡萄霜霉病菌种群遗传变异和有效越冬起着关键的作用。2014-2015年露地栽培模式下葡萄霜霉病菌群体的主效流行基因型对病害流行的贡献率分别为44.5%和51.8%;而其在避雨栽培模式下葡萄霜霉病菌群体的贡献率分别可达84.2%和87.1%。同一年份的露地和避雨栽培模式下葡萄霜霉病菌群体的主效基因型种类相同,2个群体间的等位基因频率呈现显著正相关性,且二者之间存在频繁的基因交流,推测避雨栽培模式下葡萄霜霉病的初侵染源自于避雨设施附近的露地栽培病株上再侵染形成的飞散传播孢子囊。

Temporal dynamics of the population genetic structure of grapevine downy mildew pathogen Plasmopara viticola under open field and rain-shelter cultivation

In order to determine the genetic structure and diversity levels of grapevine downy mildew pathgen Plasmopara viticola populations under open field and rain-shelter cultivations, their genotypes, genetic diversity and genetic differentiation were analyzed by using the samples collected from the two cultivations in 2014-2015 with six pairs of SSR primers. The results showed that the Nei''s genetic diversity index and Shannon''s information index of P. viticola populations under open field and rain-shelter cultivations were more than 0.14 and 0.32, respectively, indicating the existence of rich genetic diversity in the two populations. Rain-shelter could significantly reduce population allele number and allele frequency. The epidemic pattern of downy mildew under open field cultivation showed moderate level of asexual reproduction. The primary and secondary infections contributed 26.1% and 73.9% to the epidemic of downy mildew, respectively. The epidemic pattern of downy mildew under rain-shelter cultivation showed high level asexual reproduction. The primary and secondary infections contributed 4.3% and 95.7% to the epidemic of downy mildew, respectively. Oospores played a key role in genetic variation and effective overwintering of grape downy mildew. From 2014 to 2015, the main epidemic genotypes contributed 44.5% and 51.8% to the disease epidemic, respectively, while the contribution rate under rain-shelter cultivation were 84.2% and 87.1%, respectively. The main epidemic genotypes of the pathogen population were the same under open field and rain-sheltered cultivation in the same year. There was a significant positive correlation in the allele frequencies and frequent gene exchange was observed between the two populations. It was speculated that the primary infection of downy mildew in grape under rain-shelter cultivation mode originated from sporangial dispersion caused by reinfection on the pathogen plants in open field cultivation near rain-shelter facilities.