Identification Of Resistance Of Corn Varieties To Three Species Of Lepidopteran Larvae Damaging Corn Ears

In recent years,the occurrence and damage of three species of lepidopteran insect pests(Conogethes punctiferalis,Ostrinia furnacalis and Helicoverpa armigera)on ears in the corn field has become more and more serious,especially the population of C.punctiferalis is increasing,its damage on corn ears is more serious than the other pests,O.furnacalis and H.armigera.All the pests not only cause a significant reduction in yield,but also cause a variety of ear rot diseases on corn,which has brought great risks to the safe production of corn.From the perspective of the resistance of crop to insect pests,the resistance and susceptibility of 72 corn varieties to the three pests were studied based on the amounts of three lepidopteran larvae in the field,some biological characteristics of corn varieties and the free amino acid contents in corn grains to provide scientific basis for breeding,extention and rational distribution of resistant corn varieties.1.The population dynamics of C.punctiferalis,O.furnacalis and H.armigera larvaeThe number of C.punctiferalis larvae was small from the early August to the middle of August.The key damage period occurred from the middle ten days of August when the corn began to enter the flowering and milking stages,and its population increased and rosed up dramatically.The population of O.furnacalis larvae was very small before the late of first ten days of August,afterwards began to rise,and peaked in the late of first ten days of September to the middle ten days of September when the corn entered the grain filling stage.After the middle ten days of September,its population declined with the O.furnacalis egg mass parasitized by Trichogrammatid.The population of H.armigera is very low from early August to the middle ten days of August.From the middle ten days of August to the early middle ten days of August,its larvae population began to rise and peaked.Subsequently,the population began to decrease with the maturation of corn.2.Identification of resistance of different corn varieties to three species of lepidopteran larvae based on the Larvae IndexFor the resistance of corn varieties to C.punctiferalis: among the 72 corn varieties,there was no high resistant corn varieties;6 resistant corn varieties,accounted for 8.3%;14 median-resistance varieties,accounting for 19.4%;34 suseptible varieties,accounting for 47.2%;18 kinds of high suseptible varieties,accounting for 25%.For the resistance of corn varieties to O.furnacalis: among the 72 corn varieties,there were 1 high resistant corn varieties,accounted for 1.4%;4 resistant varieties,accounting for 5.6%;14 median-resistance varieties,accounting for 19.4%;37 suseptible varieties,accounting for 51.4%;16 kinds of high suseptible varieties,accounting for 22.2%.For the resistance of corn varieties to H.armigera: among the 72 corn varieties,There was no high resistant corn varieties;2 resistant corn varieties,accounted for 2.8%;9 median-resistance varieties,accounting for 12.5%;50 suseptible varieties,accounting for 69.4%;12 kinds of high suseptible varieties,accounting for 16.7%.3.The correlation between the resistance/suseptibility of corn varieties and corn biological traitsBy investigating in the field and referring to the relevant information of different corn varieties,plant types compactness,colors of flower filaments,bracteal leaf and grain size compactness were discovered have no significant correlation with different resistance of maize.4.Corelation of resistance with free amino acid contents in corn varietiesTotal 17 free amino acid contents in grains of 72 corn varieties related to the amounts of C.punctiferalis larvae,not to those of O.furnacalis and H.armigera larvae.Among the 17 free amino acids,aspartic acid,glutamic acid,alanine,isoleucine,leucine and valine had possotive relationship with the amounts of C.punctiferalis larvae.