Identification Of Pathogen Caused Fusarium Wilt Of Muskmelon And Research On Screening Of The Disease Control Agent

Fusarium wilt of muskmelon（FWM）was increasingly serious in the muskmelon production in Jilin Province,which caused huge economic losses.It has been considered that the Fusarium oxysporum was the major pathogenic bacteria of FWM.Firstly,a pathogen caused FWM was isolated and identified by morphological and molecular methods from cultivated muskmelon fruits in field where FWM occurred seriously in Jilin Province,then the relationship between the incidence of FWM and the pathogenic bacteria carrying rate of seeds was defined,this study also screen out the high-efficiency chemical agents and Streptomyces 769 against FWM.Yet,the changes of growth,the control effect on FWM and muskmelon yield were investigated by applying gongzhulingmycin and chemical agents alone,this study was useful for biological control against FWM.The main results were as follows:1.In present study,F.verticillioides,isolated from symptomatic fruits and identified via morphological and molecular identification,from a serious FWM in fields,was identified as causal agent of the FWM by Koch’s rule.Meanwhile,the F.verticillioides carrying rates of four different melon varieties were detected by PCR method,and which incidence of FWM were evaluated.The results showed that the pathogen carrying rates of different species of muskmelon seeds were different,and which was positively correlated with incidence of FWM.2.For high-efficiency and low-toxicity chemical agents against FWM screening,eight kinds of chemical agents commonly used in production were defined by mycelium growth rate method,and the control effects of tested agent against FWM were tested indoor.The results showed that prochloraz gave the highest inhibitory activities against F.verticillioides among all tested chemical agents,which EC50 was 0.0295μg/m L,and the EC₅₀of tebuconazole and flusilazole were 0.1467μg/m L and 0.1901μg/m L,respectively.The minimum inhibitory concentration of prochloraz,tebuconazole and flusilazole were 0.048μg/m L,1.200μg/m L and0.800μg/m L,respectively.The mininal bactericidal concentration of prochloraz,tebuconazole and flusilazole were 0.052μg/m L,1.600μg/m L and 0.800μg/m L,respectively.The results of indoor control effects indicated that prochloraz established the highest control efficiency of82.88%against FWM at the concentration of 0.144μg/m L.3.The results of pot test showed that Gongzhulingmycin significantly promoted the root growth of muskmelon seedlings compared with control treatment.Furthermore,compared to control,the root length and root density of muskmelon seedlings soaked by 800X water extract of gongzhulingmycin were significantly increased by 9.82%and 18.23%,respectively.The fresh weight of root by 100X water extract of gongzhulingmycin and prochloraz were remarkably improved 25.00%and 16.67%higher than that of the control,respectively.The dry weight of root treated by gongzhulingmycin and prochloraz were remarkably improved 20.00%,respectively.On the 7^thday of FWM,the disease index of FWM were significantly changed in different treatments,which decreased 18.54%and 26.43%in gongyulingmycin and prochloraz treatment,respectively（P<0.05）,and disease index decreased 5.79%（P>0.05）and 39.49%（P<0.05）,respectively,on the 14^thday of FWM.4.The results of field experiment showed that gongyulingmycin played a positive role in promoting the emergence rate,plant height and leaf age of melon plants.The overall incidence of FWM treated with gongzhulingmycin and prochloraz alone was lower than that of the control,which improve the theoretical output value per unit area of muskmelon.Compared with the control,the emergence rate increased by 18.08%and 41.11%,plant height increased by 64.51%and 90.54%,and leaf age increased by 18.89%and 35.29%after applying gongzhulingmycin 50g/row and 100 g/row,respectively.The results of field experiment investigation in fruit setting stage showed that compared with the control,the incidence of FWM was decreased 38.45%and56.67%（P<0.05）,the theoretical output value per unit area of muskmelon was increased20.52%and 37.66%（P<0.05）after applying gongzhulingmycin and prochloraz,respectively.The control effect of gongzhulingmycin on FWM was lower than prochloraz,in any case,it still had obvious growth promotion and disease resistance,and was potential for biological control of FWM.