Study On Screening, Identification And Application Of Fungi Inhibiting Vegetable Root-Knot Nematodes (Meloidogyne Incognita)

Vegetable root-knot nematode is the most important pathogenotic nematodes of crop in China nowadays.It causes huge economic losses of crops each year.Chemical nematocide have caused environment pollution,ecological imbalance and other problems. It is secure and effective of using fungi to control vegetable root-knot nematode.The fungi inhibiting vegetable root-knot nematodes screening,characterization and biocontrol study provide basis for the exploitation of new biocontrol agents to root-knot nematodes.1 Isolation and screening of fungi inhibiting root-knot nematodesA total 316 pure isolates were obtained from soil samples using select medium.The strains were fermented in the PS cultural medium.The ferment filtrate were used to deal with sweet-potato stem nematodes(Ditrlenchus destructor).The result showed that the majority of the fungi strains broth has a certain inhibition effect to J2 of sweet-potato stem nematodes.The 2 times dilution of the three fungi strains broth ZB-4,ZW-3,XX-8 always maintained a high inhibitory effect to J2.In 24 and 72 hours treatment,the inhibiting efficiencies have reached more than 80%.2 Greenhouse evaluation of three fungal strains metabolites against vegetable root-knot nematodesBiocontrol effects of the metabolites of three fungus ZB-4,ZW-3 and XX-8 were tested and evaluated to control vegetable root-knot nematodes(Meloidogyne incognita) in vitro bioassay and in the greenhouse.The results showed that there were certain inhibitory effects to root-knot nematodes at different dilution ratio of the three fungi strains ZB-4,ZW-3,XX-8 after 24,48,72 hours treatment.In 72 hours treatment,the 2 times dilution of the three fungi strains broth showed the rectified inhibiting efficiencies to J2 as 95.27%,91.27%,86.58%respectively;The rectified inhibiting efficiencies to J2 of 4 times dilution were 68.52%,84.05%,60.33%in 72 hours.In greenhouse pot experiment,the 2 times broth of three fungus were used to treat tomato seedlings.After 45 days,compared to the control,the reducing rate of nematodes were up to 46.7%, 43.3%,36.7%respectively,The controlling efficiencies reached 23.81%,19.52%, 35.71%respectively.Furthermore,our investigation in 22 days and 45 days showed that the 2 times broth could promote the growth of tomato plant.3 Study on identification and culture characteristics of the three fungi strainsBy the morphological observation,comparison of its rDNA-ITS and phylogenesis tree analysis,The three fungi inhibiting vegetable root-knot nematodes ZB-4,ZW-3 and XX-8 was identified as Mocor.By observing the strains grown in different cultural medium and different temperature,the growth speed of the three fungi strains grown in PDA medium is slower than WA medium.The speed of spores emergence in 20℃is faster than in other temperature.4 Sequence analysis of rDNA-ITS of some fungus inhibiting root-knot nematodes(Meloidogyne spp.)By determine the rDNA-ITS gene sequences and construct phylogenetic trees of fourteen fungus having high inhibitory effect.The results showed that the strains 5-8,BLZW-3,NGHG-7,1-2,Ⅱ-2-5,1-1-6,HN-11,XXHS-3 belong to mocor sp.,the strains SDY-12,V-2-3,8-2-1 belong to Cryptococcaceae branch;the strain SM-3 was identified as monascus purpureus;the strains 18-1,GSR belong to Aspergillus sp.