Biological control of chestnut canker, caused by Cryphonectria parasitica, by antagonistic organisms and hypovirulent isolates

摘要

Biological control of chestnut blight was investigated by using 3 hypovirulent isolates of Cryphonectria parasitica, 5 Trichoderma sp., 4 Penicillium sp., and 4 Bacillus sp. isolates. Hypovirulent isolates and antagonistic organisms were obtained from samples collected from the Black Sea region of Turkey, in 2008 and 2009. Effectiveness of the hypovirulent isolates and antagonistic microorganisms was tested on 3-year-old chestnut saplings. In the tests, bark disks of 6 mm were removed from the stem bases and culture disks of the virulent isolate of C. parasitica were first placed into the hole and then the hypovirulent isolate or the antagonistic fungi. Bacillus strains were applied as bacterial suspensions of 1010 cell mL-1 to the holes; then the virulent isolate of C. parasitica was placed. Evaluations were made by measuring the canker lengths in 3 periods and effectiveness was given as percent inhibition (PI) of the treatments. Antagonistic microorganisms yielded varying PI values in 3 time periods and the highest rate of inhibition (68%) was obtained from the Trichoderma sp. isolate T - 2. A Penicillium sp. isolate (P - 3) and 2 Bacillus spp. isolates (B - z and B - b) also provided 30%, 40%, and 31% disease inhibition, respectively, 58 days after the inoculation. Effectiveness of the hypovirulent isolates varied depending on the virulent isolates and the hypovirulent isolate Z - 1 provided 59% inhibition against the most virulent isolate K - 19, while it gave 32% inhibition against the less aggressive isolate K - 44. The other hypovirulent isolate Ba - 6 also inhibited the canker development of the virulent isolate by 42%. Key words: Cryphonectria parasitica, chestnut blight, biological control, hypovirulence, antagonists