การควบคุมโรคใบจุดวงแหวนในพืชวงศ์ผักกาดโดยใช้ยีสต์ปฏิปักษ์

Abstract

This research investigated the biological control of ring spot disease of Brassicales caused by Alternaria brassicicola, which is agriculturally important pathogen using antagonistic yeasts. One hundred fifteen epiphytic yeasts were isolated from 38 fruits and vegetable leaves. The antagonistic effect of yeasts was tested by dual culture method. Twenty-nine yeast isolates were tested for the inhibitory activity of A. brassicicola. The result shows three isolates of antagonistic yeasts: Y107, Y123 and Y16 with higher growth inhibitory percentages of 75.00%, 73.52% and 70.33%, respectively. Hence, isolates: Y107, Y123 and Y16 were tested for the efficacy of A. brassicicola spore germination inhibition using slide culture technique. After 12 h., Y107, Y123 and Y16 inhibited the spore germination by 90.26%, 87.82% and 80.90% respectively. Efficacy of the antagonistic effect of yeast against leaf spots on Pak Choi and Cabbage seedling was tested in greenhouse. Antagonistic yeast isolate Y107 significantly reduced the disease incidence by 71.42% (Pak Choi) and 72.75% (Cabbage seedling). The efficacy of Y123 and Y16 were not significant with disease inhibition of 69.83% and 68.92% respectively in Pak Choi and 66.67% and 66.08% respectively in Cabbage seedlings. Moreover, the phylogenetic analysis shows the relatedness of three antagonistic yeast isolates. The isolates were identified using analysis of the D1/D2 domain of the large subunit ribosomal RNA gene (LSU rRNA gene) and they were identified as Hanseniaspora thailandica (Y107) and Kurtzmaniella quercitrusa (Y16 and Y123).