FIELD APPLICATION OF SCLEROTIAL MYCOPARASITES AS BIOCONTROL AGENTS TO STROMATINIA CEPIVORA THE CAUSE OF ONION WHITE ROT
I.E. Elshahawy, N.M. Saied, F. Abd-El-Kareem, A.A. Morsy
Three fungal isolates from a total of 30 were selected on the basis of their antagonistic activity against the most pathogenic isolate (Sc2) of Stromatinia cepivora (Berk)Wetzel, the causal agent of onion white rot. These isolates were identified as Chaetomium globosum (Chg6)Kunze, Clonostachys rosea (Cr12)(Link) Schroersand Penicillium oxalicum (Po9)Currie & Thom. In vitro,the selected isolates were seen to colonize the surface of sclerotia and cause collapse to their outer rind. Parasitized sclerotia appeared degraded and failed to germinate when they were transferred onto fresh PDA plates indicating that the sclerotia of S. cepivora had been killed by these mycoparasites. Also, cultural filtrates of these isolates inhibited the growth of S. cepivora (Sc2) and decreased germination of sclerotia.Control of onion white rot disease by soil treatment with the inoculum of these sclerotial mycoparasites was attempted. Under greenhouse and field conditions, all sclerotial mycoparasites significantly reduced the incidence and severity of onion white rot disease.P. oxalicum (Po9)was the most effective with the lowest percentages of white rot incidence and severity. Ch. globosum (Chg6) and C. rosea (Cr12) occupied the second rank in this respect. Also, these treatments increased vegetative growth of a live onion plants in greenhouse and increased onion bulb yield in field compared with control. Mycoparasites enhanced biocontrol activity of peroxidase, polyphenoloxidase and chitinase enzymes in onion plants grown in field to resist infection with S. cepivora.