Seed size is an important quantitative character in vegetable soybean breeding program. The objective of this study was to detect simple sequence repeat (SSR) marker associated with quantitative trait loci for seed size. 183 F₂ and F₃ families were generated from the cross between ‘Chiangmai 60’ and ‘Kaori’. The data of seed size, including seed length, seed width and 100 seed weight were collected and narrow-sense heritability (h²[subscript n]) were calculated. It was shown that h²[subscript n] of seed length, seed width and 100 seed weight were 0.908, 0.656 and 0.753, respectively. These three seed size characters showed normal distribution in the F₃ population which were the effect of additive gene action. The correlation between F₂ and F₃ populations of these seed size characters were positive . DNA from the parents and F₂ population were extracted for determination of the polymorphism between parental soybean using 18 SSR markers. The markers, Satt143, Satt179, Satt184, Satt373 and Satt513 were found polymorphic between them. These makers were tested with the F₂ population, the linkage map was constructed using the computer program MAPMAKER version 3.0, and the simple linear regression between SSR markers and seed size characters were analyzed by SPSS which showed only 1 linkage map, containing Satt373 and Satt513. However no QTL was found associating with seed size characters in this study.
