Biological control of southern stem rot caused by Sclerotium rolfsii using Trichoderma harzianum and arbuscular mycorrhizal fungi on Jerusalem artichoke (Helianthus tuberosus L.)

Efficacy of Trichoderma harzianum and the arbuscular mycorrhizal fungus (AMF) Glomus clarum for suppression of southern stem rot caused by Sclerotium rolfsii in Jerusalem artichoke was investigated in Thailand under greenhouse conditions. Experimental factors included two Jerusalem artichoke genotypes (HEL 246 and JA 37), two levels of T. harzianum and G. clarum (inoculated and blank). The biological control agents were added to the potting medium immediately before seedlings of Jerusalem artichoke were transplanted into it; 20 days later, seedlings were inoculated with S. rolfsii by placing infested sorghum seeds at the base of the stem. The combination of cv. HEL 246 with addition of both G. clarum and T. harzianum had the lowest disease incidence (30%) and required the longest time to permanent wilt (11 days after inoculation). Inoculation of cv. JA 37 and HEL 246 with G. clarum alone gave better control of the disease than did inoculation with T. harzianum alone. The results are the first published report of biological control of S. rolfsii on Jerusalem artichoke.