Evaluation of Some Promising Soybean Genotypes to Infestation with Cotton Leafworm (Spodoptera littoralis) under Field Conditions

A two-year study was carried out in Giza Agricultural Experiments and Research Station, Agricultural Research Center (ARC), Giza, Egypt in the 2020 and 2021 summer seasons to evaluate the relative tolerance of ten soybean genotypes for cotton leafworm infestation under field conditions. Soybean genotypes H11L145, H155, H113, H4L4, H15L17, H129, H30, H19L96, Giza 111, and Crawford were distributed in randomized complete blocks design with three replications. Soybean genotypes differed significantly for cotton leafworm at the 6th, 7th, and 8th week from sowing. Low values of cotton leafworm assemblages were recorded for H113, H4L4, H15L17, Giza 111, and H129. Low percentages of the larval survival number and weight, as well as the number of the survival of pupa were recorded by feeding on leaves of genotypes H4F4, H15L17, and Giza 111 under laboratory conditions. There were significant differences among the studied genotypes in most yield attributes in both seasons. Soybean genotypes H15L17, Giza 111, H113, H129, H19L96, and H4L4 gave higher seed yield per ha, meanwhile soybean genotypes H155, H19L96, H30, Giza 111, and H15L17 had higher seed oil content than the other genotypes in both seasons. The number and weight of larvae surviving, as well as the number of pupa survival, were negatively correlated with leaf total phenols and seed oil content. It can be concluded that soybean genotypes H15L17, H4L4, and Giza 111 are promising genotypes with desirable seed oil content for tolerating cotton leafworm infestation in breeding programs.

Assessment on Phosphorus Efficiency Characteristics of Soybean Genotypes in Phosphorus-Deficient Soils

A glasshouse study compared the growth and phosphorus （P） efficiency of 96 genotypes of soybean [Glycine max （L.） Merrill] in a P-deficient soil. The soybean genotypes differed greatly in growth, nodulation and P uptake after growing in the soil for 45 days, with shoot biomass ranging from 0.91 to 1.75 g per plant. The application of P improved biomass production, nodulation and P uptake and decreased root to shoot ratio, root length and surface area and P utilization efficiency. The 96 soybean genotypes were divided into 3 categories in P efficiency using the principal component analysis and cluster analysis, and 4 categories according to F values in combination with growth potentials. The Pefficient genotypes were associated with high biomass production, root to shoot ratio, root length and surface area and P uptake but low shoot to root P concentration ratio under P deficiency. The results indicate that there is a substantial genotypic variation in P efficiency in existing germplasm, and that P efficiency was correlated positively with dry weights of shoots and roots, ratio of root to shoot dry weight, root length and surface area, root P content and total P uptake. The shoot dry weight under P deficiency and relative shoot dry weight （deficient P/adequate P supply） are effective and simple indicators for screening P-efficient genotypes at the seedling stage.