Isolating And Screening Of Antagonistic Fungi On Vegetable Root-Knot Nematodes In Shaanxi Province

Root-knot nematodes (Meloidogyne spp.) are a major group of pathogens of important crops and cause great damage to the production of crops. Especially with the expansion of cultivated area of greenhouse vegetable, root-knot nematodes has become the biggest obstacle to the production of greenhouse vegetable, and the biological control has been taken more and more attention recently.In this study, 118 vegetable root samples infected by root-knot nematodes were collected from 9 countries covering Yan'an, Weinan, Xi'an, Xianyang, Yangling, Baoji, Shangluo of Shaanxi Province. 199 antagonistic fungal strains were obtained by direct dissection respectively from females, egg masses and eggs of root-knot nematodes. These antagonistic fungi were identified to 22 genera, including Fusarium, Cephalosporiopsis, Cladosporium, Alternaria, Paecilomyces etc. and 43 sterile fungi. Fusarium spp. was the dominant population, and its isolation frequency took up 34% of all the isolates in this study. The species and the amount of antagonistic fungi of different samples were distinctly different in regions.Through testing the relative percentage of inhibition to the eggs of M. incognita with the spore suspension of 131 non- Fusarium antagonistic fungi in vitro, we found that the majority of strains had inhibited the eggs of M. incognita. There are 8 strains suppressed the hatching of eggs over 60%. Isolate XPE-36 has higher parasitical abilitily to the eggs of M. incognita, which relative percentage of inhibition to the eggs of M. incognita reached 82.3%.The effect of the fermentation liquid extract of 68 strains Fusarium spp. to second stage juveniles(J2) of M. incognita was tested to screen the biocontrol strains, we found that the majority of strains had nematicital activity differently. The relative percentage of death to the J2 of M. incognita. of LGEM-5 reached 80.6%, and there are 7 strains which relative percentage of death to the J2 of M. incognita reached 60～80%, with a strong nematicital activity. In addition, the strain LGEM-5 has good thermal stability, which fermentation liquid extract still maintain higher nematicital activity after heat treatment. Based on morphological and cultural characters, strain XPE-36 and LGEM-5 were identified as Paecilomyces lilacinus and Fusarium oxysporum respectively.