Physical characteristics of seed and seed coat in relation to seed quality in soybeans

Study on physical characteristics of seed coat in relation to seed quality in soybeans was conducted with 40 lines/varieties under 2 seasons i.e. dry season 1995 and rainy season 1996 at Kasetsart University, Kamphaeng Saen Campus. The seeds were subjected to standard germination test, accelerated aging test, field emergence test, electrical conductivity test and also counted hard seed percentages. The results revealed that seed quality differed among lines/varieties. In dry season, hard seed percentages were higher than those in rainy season. The physical characteristics significantly correlated with quality i.e. seed weight, seed volume, surface area, eccentricity, seed coat percentage, seed coat thickness and seed colour. Lines/varieties with small seed, thicked-seedcoat, oblong-seed shape and seed coat with black colour gave higher quality than large seed, thin seed coat, round-seed shape and yellow colour. Path-coefficient for standard germination and field emergence of soybean in rainy season 1996 was analysed. The physical characteristics of soybean seed that showed the significant direct effects and indirect effects were seed weight, seed volume, surface area, seed gravity, eccentricity, seed coat percentage and specific weight of seed coat. The physical characteristics that showed indirect effects by other characteristics were seed weight, seed size and seed shape (eccentricity). In the study of seed coat under scanning electron mocroscope of 6 soybean varieties i.e. Chiang Mai 60, Williams, SJ 4, Utsaha A, Sukhuthai 1 (SSR DMR 34) and SSR 8502-2-2. The results revealed that Chiang Mai 60, Williams and Sukhuthai 1 (SSR DMR 34) had larger pore size comparing to SJ 4, Utsaha A and SSR 8502-2-2. Physical characteristics that plant breeders should consider for selecting varieties with high seed quality were seed size, seed coat thickness, seed shape (eccentricity) and seed colour.