立枯丝核菌的衰退及其生防潜能的研究

THE DECLINE OF RHIZOCTONIA SOLANI KUHN AND ITS POTENTIAL IN BIOLOGICAL CONTROL

从棉苗上分离到一株立枯丝核菌(Rhizoctonia solani),属第4融合群(AG—4),经连续转代得到一衰退菌株。同正常菌株相比较,衰退株生长缓慢,菌丝变细,菌落淡黄色,基质菌丝稀疏,气生菌丝絮状,极少产生菌核,致病力显著降低。经热水(52C)、抗菌素和吖啶橙类染料治疗说明衰退不是由细菌的污染所致,与丝核菌中的质粒也没有关系。衰退株的自然恢复率为4%,通过菌丝融合,衰退因子可传递给健康的立枯丝核菌。盆栽试验表明,健康株和衰退株混合接种时,棉苗发病程度明显减轻,尤其是先接种衰退株培养物的处理,这就表明衰退株具有一定的防病潜力。

A declined strain R-ld of Rhizoctonia solani was obtained from the healthy one R-1(AG-4), which was isolated from the diseased cotton seedling, by routine transfer. The cultural characteristics of R-ld are a slow growth rate, thin hypha and sparce substrate mycelia, light yellowlish eolour, floceose surface texture and production of a few or no sclerotia on the PDA plate. The decline could neither be caused by the bacterial contaminations and the special plasmids of the hypha owing to the results of treating the hypha of R- ld with hot water (52C), the antibiotics and the acridine dyes, nor controlled by the nucleus of R. solani because only 4% of the hyphal tips of R-1d recovered naturally to R-1. The anastomosis between R-ld and R-1 revealed that the decline agent could transmit through fungal fusions to the healthy hypha of R-1. The potting test showed that the pathogenicity of R-ld decreased significantly compared to that of R-1. The disease index was much lower when R-ld was inoculated 2 days before R-1. So R-Id has a high potential in controlling the damping-off of cotton seedlings caused by Rhizoctonia solani.