Isolate Neoscytalidium dimidiatum fungal pathogens from pytaya (Hylocereus undatus) and research controlling by microorganisms
In recent years, Neoscytalidium dimidiatum has caused severe white spot disease in Pytaya, while no effective controls have been taken. In this study, two strains of N. dimidiatum NdGV and NdBT were obtained by isolation on water agar medium containing streptomycin, morphological tests, in vitro and in vivo pathogenical tests, and molecular biology tests by sequencing the genes ITS1 and ITS4. By using dual culture technique on potato-glucose agar medium, 100% of Trichoderma spp., 75% of Bacillus spp. and 20% of Streptomyces spp. were able to antagonize N. dimidiatum. The mean antagonistic effect with N. dimidiatum of Trichoderma spp. was higher than Bacillus spp. and the lowest was Streptomyces spp. 56.8%, 55.3% and 54.3% respectively. Especially 5 strains Trichoderma sp. 8.3.5, 8.3.7, 8.3.14, 8.3.19, and 8.3.20 had antagonistic effects of over 60%. The application potential of the 5 selected Trichoderma strains to control N. dimidiatum disease was further strengthened when their antagonistic effect was relatively stable on Pitaya juice agar medium while all Bacillus sp. and Streptomyces sp. were lost the ability to antagonize. It was noteworthy that four of the five strains of Trichoderma sp. were highly compatible, suggesting further studies are needed to apply their combined potency in enhancing the control of N. dimidiatum NdBT and NdGV on Pitaya.