Screening of Closnostachys strains against Phytophthora nicotianae

Abstract:

[Background] Tobacco black shank, induced by Phytophthora nicotianae, is one of the major soil-borne diseases that cause serious stem and root rot in flue-cured tobacco production. [Objective] Screening of strong antagonistic strains is the basis of biological control. [Methods] In this study, the dual culture assay was used to screen Closnostachys strains against P. nicotianae. Sixty-five strains of Closnostachys belonging to eight species were tested. According to their abilities of sporulation on colony of P. nicotianae and hyphal coilings produced surrounding hyphae, sporangiophores, and sporangia of the pathogen, the antagonism of Closnostachys was classified into four degrees:strong, moderate, weak, and absent. [Results] A total of 6 tested strains had strong antagonistic ability, 27 moderate antagonistic ability, 22 weak antagonistic ability, and 10 no antagonistic ability. The inhibition rates of Closnostachys strains tested to P. nicotianae were 20.0%-86.7%. [Conclusion] The strains tested with strong antagonistic ability were C. rosea 7901 and 11361, C. byssicola 5072, 6729, and 7507, and C. grammicospora 6730. Their potential as biocontrol resources needs further pot experiment confirmation.