Hypovirulent Rhizoctonia spp isolates from New Zealand soils protect radish seedlings against dampingoff caused by R solani

Abstract

Of the 206 Rhizoctonia spp isolates obtained from 135 soil samples collected from different fields in the North and South Islands of New Zealand 55 were pathogenic on radish (Raphanus sativus cv Rex) seedlings Only 27 of the isolates that were strongly pathogenic on radish were also pathogenic on ryegrass (Lolium perenne) While 13 of the 92 hypovirulent isolates provided gt;50 protection to radish seedlings against dampingoff caused by Rhizoctonia solani in a screening experiment only three provided gt;50 protection in the final more detailed experiment The best protective isolates R8510 and R308 consistently protected approximately 70 of radish seedlings in at least two separate experiments There was no correlation between the growth rates of the hypovirulent Rhizoctonia spp isolates and their percentage protection of radish seedlings against dampingoff