![]() ![]() aphanidermatum is the main causal agent of damping-off of cucumber in Oman and elsewhere ( Al-Sadi et al., 2011, 2012 Hatami et al., 2013). Damping-off of vegetable crops is caused by several species of Pythium ( Kraus and Loper, 1992 Al-Sadi et al., 2010), Rhizoctonia solani ( Asaka and Shoda, 1996 Sadeghi et al., 2006), Phytophthora capsici ( Sharifi-Tehrani and Omati, 1999), and Fusarium ( Berg et al., 2017 Hrunyk et al., 2017 Lamprecht and Tewoldemedhin, 2017). However, cucumber production suffers from Pythium-induced damping-off disease which is responsible for over 75% mortality in cucumber seedlings ( Al-Kiyumi, 2006 Al-Sadi et al., 2012). In Oman, over 90% of greenhouses are dedicated exclusively for cucumber ( Cucumis sativus). terreus can help suppress Pythium-induced damping-off of cucumber, which is suggested to be through the effect of A. terreus isolates did not have any negative effects on the growth of cucumber seedlings. No disease symptoms were observed on cucumber seedlings only treated with the isolates 65P and 9F of A. aphanidermatum to 38–39% when the biocontrol agents were used. ![]() terreus increased the survival rate of cucumber seedlings from 10 to 20% in the control seedlings treated with P. In bioassay tests, the two isolates of A. aphanidermatum compared to the control ( P < 0.05). Also, the CFs of 65P and 9F isolates significantly reduced spore production by P. In addition, Aspergillus isolates produced siderephore, which is suggested to be involved in inhibition of Pythium growth. This suggests that the cell walls of Pythium, which consist of glucan, are affected by the glucanase enzyme produced by A. terreus isolates showed a significant increase in glucanase activity. Testing glucanase enzyme activity by both A. terreus resulted in significant rise in cellular leakage of P. aphanidermatum with the culture filtrate (CF) of A. ![]() aphanidermatum hyphae close to the inhibition zone showed that the hyphae showed abnormal growth and loss of internal content. In vitro tests showed that the two isolates inhibited the growth of P. The study investigated the efficacy of two isolates of Aspergillus terreus (65P and 9F) on the growth, morphology and pathogenicity of Pythium aphanidermatum on cucumber.
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