Screening Of Corn Cultivars Resistant To And Effective Pesticide Against Curvularia Maydis

Corn is an annual herb of Gramineae,native to South America and Central America.It is an important food and economic crop in China,with an annual planting area of 30-30.67 million hm2,which plays an important role in China's agricultural economy.At present,there are more than 40 kinds of corn diseases reported in China,which seriously affect the yield and quality of corn.In recent years,because of the increase of global temperature and the change of farming system in corn field,Curvularia leaf spot disease has increased year by year.When the disease is mild,it causes 10%-30% yield loss of corn,and when it is serious,it causes more than 50% yield loss,or even have no harvests.At present,the effective methods of controlling Maize Curvularia leaf spot are breeding resistant varieties,agricultural control and chemical control.In this paper,the resistance of maize strains to Curvularia leaf spot was identified and the effective fungicides were screened.The main results are read as follows.1.We identified the resistance of 260 corn cultivars to Curvularia leaf spot and obtained 80 resistant cultivars.Curvularia lunata Boed was inoculated onto sorghum medium to obtain a spore suspension at a concentration of 1.0 × 10~6 spores / m L.Spore suspension was sprayed to 260 maize cultivars when the corn plants were tasseling,and the incidence of Curvularia leaf spot was investigated during the corn wax ripening period.The results show that there were no corn cultivar was highly resistant to Curvularia leaf spot,80 corn cultivars were resistant to Curvularia leaf spot,104 corn cultivars showed moderate resistance,while 72 corn cultivars were susceptible to Curvularia leaf spot,4 corn cultivars were highly susceptible to Curvularia leaf spot.2.We screened 4 agrochemicals than could significantly inhibit Curvularia lunata Boed and obtained the optimal ratio with increase effects.The mother liquor of each agrochemical was prepared into a drug solution of equal gradient concentration,mixed with the PDA culture medium in a ratio of 1: 9,poured into a petri dish to make a toxic plate,and a 9 mm diameter fungus cake was inverted with an inoculation needle Inoculate into the middle of the plate,seal the petri dish with a parafilm,and incubate in a 28 ° C constant temperature incubator for 5 days,measure the colony diameter with a ruler,and process the data with DPS software.According to the laboratory bioassay,four kinds of fungicides,Tebuconazole,Carboxin,Difenoconazole and Pyraclostrobin,were screened out,with EC50 of 1.0883mg/l,4.8362mg/l,1.926mg/l and 1.9524mg/l,respectively.According to the ratio of 1:2,1:2,1:3,2:1 and 3:1,the compound types and proportion of Tebuconazole + Difenoconazole(3:1),Tebuconazole + Pyraclostrobin ester(1:3),Carboxin + Difenoconazole(1:3),Carboxin + Pyraclostrobin ester(1:2)and Difenoconazole + Pyraclostrobin ester(1:3)were screened out.3.We tested the control efficiency of the optimized chemical ratios to corn Curvularia leaf spot in the field.The selected Tebuconazole,Carboxin,Difenoconazole,Pyraclostrobin ester and their optimized mixtures were tested by the Corn cultivar Jiangyu 898 planted in the field.The 8-leaf stage corn plants were evenly sprayed with 1.2 × 10~6 spores/m L Curvularia lunata Boed from the sorghum medium,and the incidence of Curvularia leaf spot was investigated 30 days after the inoculation.Results showed that the application of Carboxin + Pyraclostrobin ester(1:2)and Carboxin + Difenoconazole ester(1:3)obtained better control effects to Curvularia leaf spot in the field.