2003 Volume 69 Issue 4 Pages 384-392
Fungal strains in the genus Fusarium and Trichoderma that were isolated from the rhizosphere of some plants were screened for inhibition of “Bakanae” disease (Giberrella fujikuroi) and bacterial seedling blight (Burkholderia plantarii) that are very serious diseases, caused by seedborne pathogens of rice (Oryza sativa) seedlings. Of the tested 350 Fusarium and 66 Tricho-derma strains, frequency of the strains that inhibited “Bakanae” disease was very high when the seeds were treated with conidi-al suspensions and/or cultural filtrated and sown in small pot. Among those strains with high inhibitory activity against “Bakanae” disease by treatments at comparatively low inoculum doses, many strains also had high inhibitory activity against bacterial seedling blight as well. Among those strains, Fusarium oxysporum SNF-356 and Trichoderma sp. SKT-1 isolated from the rhizosphere of tomato (Lycopersicon esculentum) and Japanese lawgrass (Zoysia japonica), respectively, were the most effective and had equivalent inhibiting activity as some chemicals, including ipconazole, copper flowable and oxolinic acid when seeds were soaked in 1.0×107 and 1.0×105 conidia/ml or higher suspensions. Particularly, the activity of SKT-1 against “Bakanae” disease was stable and not influenced by the degree of seed infection. The occurrence of “Bakanae” disease at the heading stage of rice plants that emerged from the seeds treated with either of the isolates and were transplanted and grown in paddy fields was significantly lower than that on untreated seeds.
