Evaluation Of Soybean Resistance To Leaf-Feeding Insects And Inheritance Of Antibiosis To Cotton Worm (Prodenia Litura)

Based on previous seven years studies, Forty-six resistant or susceptible soybean entries screened out from 6724 accessions together with six released cultivars, three breeding lines and the parents of the recombinant inbred lines (RIL), NJRILKY were evaluated for their resistance to the natural population of leaf-feedig insects(LFIs) in field by visually estimating the percent defoliation in 2000 and 2001. The results showed that there existed significant difference in the resistance of soybeans among varieties, record dates and years, and there also existed significant interactions between varieties and record dates, and between varieties and years. According to the results of identification of soybeans germplasm to LFIs from 1993 to 2001, the level of resistance remain relatively steady, although the result of every year is not completely identical. In addition, the result according to many years' identification is steadier, and so more reliable, than that according to only one year's. So, it can be applied as a standard method of evaluation soybean resistance to LEFs. According to the nine years' resistance grading result, ten accessions were selcted as standard varieties for later grading. They include five highly resistant varieties N3697, N21551, N21565, N3039 and N1178-2-2 and five highly susceptible N20839, N20793, N21249, N4938 and N21266.The accessions were also identified for their antibiosis to cotton worm (Prodenia litura Fabricius) under inoculation condition according to the ten days' larval weight and pupal weight (bioassay). The results showed that there existed significant difference in the antibiosis of soybeans among varieties. Low larval and pupal weight indicates the high level of antibiosis. Laval weight is positively related to pupal weight(r=0.92). They show the same reaction of soybeans resistance and can be applied to evaluate soybean resistance (antibiosis) to the insect. Accordingly, N21551, N21249, N20922, N23860, N1594, N20793 and N21565 were screened as highly resistant germplasms while N3108, N83259, N4029-3, N2395, 74906-08 and N3155-1, highly susceptible.The resistance levels of a variety in bioassay, netroom screening and field screening are not identically the same to each other. However, the results of bioassay and netroom screening have some relationship. On the contrary, either of them have obvious relationshipwith that of field screening. In consideration of the characteristic of every identification method, it is recommended that the result of bioassay could be more suitable to evaluate the resistance of soybean to only one insect (cotton worm, for example) in screening resistant resource and in the early generation selection of breeding program. But the ultimate evaluation of the resistance has to refer to the result in the natural environment in field.The antibiosis of the recombinant inbred lines (RILs) population derived from the cross between N21297 and N1178-2-2 was measured employed a larval weight gain assay to study the resistance inheritance of soybean to cotton worm. The segregation analysis of identifying mixed major genes and polygene inheritance model of quantitative traits showed that the inheritance of antibiosis accorded with a two major genes plus polygene mixed inheritance model. The heritability values of major genes were 69.18% and those of polygene were 24.45%.