Efficacy ofGliocladium virens and Trichoderma longibrachiatumas biological control agents of groundnut root and stem rot diseases

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Abstract
The biocontrol potential of Gliocladium virens (G1 and G2) and Trichodenma longibrachiatum (T1 and T2) against groundnut root and stem rot diseases, their survival patterns and effects on the pathogen survivability have been investigated. Isolates G1 and T1, delivered as a wheat bran‐sawdust (WBSD) preparation gave significant protection (65–74%) against root rot incited by Rhizoctonia solani. A linear correlation was obtained between the dosage (g/kg soil) of antagonists and their disease control efficacy. Seed coating with spore suspension (1 × 109spores/ml) also considerably reduced the root rot incidence but to a lesser degree than the WBSD preparation. On the other hand, only moderate protection (21–36%) against stem rot caused by Sclerotium rolfsii was recorded with either of the antagonists. The antagonists applied to soil, despite a sharp decrease by the 7th day, gradually increased in their population density over a period of time. G1 exerted a 65% reduction in R. solani viability followed by T1 (59.7%), T2 (46.9%) and G2 (21.6%); survival of S. rolfsii was reduced by 30–40%. The results are discussed in relation to the mechanisms underlying the biocontrol potential of these antagonists.