Biological control of Pythium aphanidermatum-induced cucumber and radish damping-off by an endophytic fungus, Cladosporium omanense isolate 31R

Cladosporium omanense has been recently described as a novel endophytic fungus from Zygophyllum coccineum in the desert habitat of Oman. The ability of this fungus to suppress Pythium aphanidermatum, the cause of cucumber and radish damping-off disease, was investigated. In vitro results showed effective suppression of P. aphanidermatum by C. omanense, producing an inhibition zone of 3.67 mm in dual culture assay. Light microscope and scanning electron microscope examination showed abnormalities in Pythium hyphae at the inhibition zone. The culture filtrate from C. omanense induced cellular leakage from Pythium mycelium and inhibited oospore production. A bioassay test was further conducted to examine the ability of C. omanense in suppressing P. aphanidermatum-induced damping-off disease of cucumber. It showed that C. omanense significantly increased the percent surviving cucumber seedlings up to 58.9%. Similarly, the addition of C. omanense significantly increased the percent surviving radish seedlings up to 80.4%. The in vivo and in vitro suppression effects of C. omanense were mainly due to the production of cellulase, β-1,3-glucanases and siderophores in the culture filtrate of C. omanense. This is the first report describing the biocontrol efficacy of C. omanense, especially in suppressing P. aphanidermatum-induced damping-off of cucumber and radish.