Study On Efficacy Of Purpureocillium Lilacinum Strain PLHN Against Tomato Root-knot Nematode

Root-knot nematode(RKN),Meloidogyne spp.,are important plant pathogenic nematodes.It causes serious economic losses to agricultural production every year.Using nematicide is one of the main methods to control RKN.However,extensive applications of nematicides have posed huge threat to ecological environment.In recent years,biological control has become one of the research hotspots.The thesis carried out a study on the control of tomato RKN with PLHN strain from Hainan Province.PLHN strain isolated from Hainan eggplant RKN female was identified as Purpureocillium lilacinum according to morphology and molecular biology.The optimal medium for this strain is PDA.The optimal p H for colony growth,spore production,and spore germination is 7.0,and the optimum culture temperature is 28 ℃.Darkness is beneficial to PLHN.Laboratory toxicity test suggests that PLHN spore suspension has poor knockdown effect on Meloidogyne incognita J2.Eggs hatching were reduced by spore suspension,and the inhibition rate was 28.01%.Parasitism on egg sacs and single egg also were seen.After treated by culture filtrate for 72 hours,the knockdown rate of J2 was 52.76%.And knockdown effect was positively correlated with filtrate concentration.Simultaneously,the inhibition rate of 100% culture filtrate on eggs was up to 95.85%.The control efficiency and colonization of PLHN strain were determined by different culture and application methods.PLHN fermentation broth was more effective against RKN than solid fermentation.And the efficiency of mixed application of PLHN and low-dosage abamectin to control RKN disease was comparable to that of abamectin alone.The soil colonization rate of solid fermentation was higher than that of fermentation broth after 60 days.Moreover,the mixed application of low-dosage abamectin and PLHN did not reduce the survival and colonization of PLHN in the soil.PLHN has a poor ability to colonize in the roots and parasitize in females,but its parasitic rate on egg sacs was more than 40%.The control effectiveness and colonization monitoring test were also carried out.PLHN fermentation broth showed a short-term effect for 30 d and almost no preventive effect for 60 d.But PLHN solid fermentation did not work until 60 d.It showed that,the persistence of PLHN was basically consistent with the colonization dynamics of different fermentations in soil.The community composition of soil nematode after application showed that,PLHN reduced the abundance of plant nematodes,but had no significant effect on the abundance of soil free living nematodes.It can be used safely to carry out field control tests.Based onHigh-throughput sequencing technology,field trails show that,PLHN solid fermentation would affect the raletive abundance of varioud trophic groups in soil.PLHN solid fermentation and low-dosage abamectin application had the least effect on nematode communities.The efficiency of mixed application of PLHN and low-dosage fosthiazate was up to 80% at 60 d and its efficiency remains 63.5% after 100 days.Both are higher than nematicide single-agent.It indicates that mixed application of PLHN and nematicide can achieve the purpose of chemical pesticide reduction.