Study on Resistance of Different Corn Varieties to the Aphid ( Rhopalosiphum maidis Fitch)

Comparison the resistance to nature infected aphid(Rhopalosiphum maidis Fitch) for 24 corn varieties in the field and greenhouse by the method of aphid index.The results indicated that there were 9 highly resistant varieties(Yunrui 7,YR88,YR220,Baoc09-6,Jingfeng 3,Deyu15,Jian 09-40,LL11Q447,LL11Q388),7 resistant and moderately resistant ones(YR6,YR7,YR8,YR47,YR99,Yunyou105,Baoyu13),2 susceptible varieties(YR68,LL11Q523),6 highly susceptible varieties(Haihe2,Baoyu9,Jingfeng6,Deyu14,Nongda68,LL11Q266).There was significant difference between highly resistant variety YR220 with average aphid number 221.111 1 per corn and highly susceptible variety Deyu14 with average aphid number 902.777 8 per corn in greenhouse,and there was significant difference on the average aphid number of varieties in different resistance level,the results of resistance on greenhouse was almost similar to that of field.