新疆北疆棉田立枯丝核菌不同菌丝融合群致病力的研究

从新疆北疆棉区采集了典型的棉花立枯病病苗及棉田土标样686份,按常规分离方法分离得到399个分离物,从中鉴定出272个纯化的立枯丝核菌(Rhizoctonia solani Kühn)菌株。用标准菌株,通过载玻片菌丝融合试验测定,将纯化的272个菌株划归为3个菌丝融合群:即AG-2、AG-4和AG-5,分别占总菌株的6.24%、84.2%和1.1%。另有23个菌株不与任何标准菌株融合,占8.46%,说明新疆北疆棉田立枯丝核菌的优势菌系是多核丝核菌的AG-4融合群。通过从10种不同配方培养基中筛选效果好的麦芽蛋白胨(MPDA)配方培养基(Ⅱ)进行对峙培养,将纯化获得的272个丝核菌菌株,划分为6个不同的营养亲和群。将多核的不同菌丝融合群及其各营养亲和群代表菌株在3种不同主栽棉花品种上(每品种都加不接菌的对照)进行温室盆栽致病力测定,结果以AG-4对棉花的致病力最强,其次是非融合类,AG-2和AG-5虽致病,但并不致死苗,其平均病指数分别为94.9、81.4、53.1、43.5。

Study on the anastomotic group of Rhizoctonia solani isolated from cotton fields and their pathogenicity in Northern Xinjiang

Three-hundred and ninety-nine fungal isolates were obtained from 686 diseased cotton seedlings and soil samples collected from cotton production areas in Northern Xinjiang by using the conventional method,among which 272 strains of R.solani were identified.Based on Giemsa staining,all strains were identified as multinucleate Rhizoctonia solani. The results from cover glass mating and anastomosis with the tester isolates showed that the 272 multincleate strains of R.solani could be divided into 3 anastomotic groups,namely AG-2,AG-4 and AG-5.The frequency of AG-4 was 84.5% of the total strains tested,which was the major strain of R.solani in Northern Xinjiang,with AG-2 having a frequency of 8.4% and AG-5 of 1.1%.Twenty-three strains of them belong to non-fusion strains,accounting for 8.4% in frequency.A comparative assay of the pathogenicity of the representative strains of different anastomotic groups and their vegetative compatibility was conducted.The results indicated that AG-4 had the strongest pathogenicity-with mean disease index as 94.9,whereas AG-2 and AG-5 had the weakest pathogenicity,with mean disease indices as 53.1 and 43.5,respectively,leading to less virulence and causing no death.Non-fusion was medium in pathogenicity,with mean disease index as 81.4.