Selection to Improve Yield Components of Bacterial Pustule Resistant Soybean Lines

Abstract

                Selections on 7 soybean crosses were performed at Suwan Farm based on high number of pods per plant, high 100-seed weight and more resistance to bacterial pustule disease incited by the bacterium Xanthomonas campestris pv. glycine. Pedigree method of selection was employed starting with 101 F5-lines in the dry season of 1985. Selection of F6 and F7 were done in rainy season of 1986, respectively. Finally, thirty two F7-rows were selected and harvested separately for yield testing of F8-lines at Suwan Farm and Kamphaengsaen Campus, Kasetsart University in the rainy season 1986. The design employed was a 6 x 6 double lattice having SJ4, SJ5, Nakhon Sawan 1 and Doi Kham as check cultivars. Four agronomic characters were recorded, namely; yield per plot, number of pods per plant, 100-seed weight and number of seeds per pod.

                 Results from the yield testing at Suwan Farm revealed that lines and cultivars were different in all traits recorded. The selected lines were more resistant to bacterial pustule disease than SJ4 and SJ5. Simple correlations among the recorded characters of the selected lines showed that yield per unit area was positively correlated with 100-seed weight and number of seeds per pod.

                  Yield testing at Kamphaengsaen Campus revealed that yield per unit area among the tested lines and cultivars were not statistically significant, while all the other traits were significantly different. The selects F8-lines were more resistant to bacterial pustule disease than SJ4 and SJ5. Correlations among the recorded characters of the selected lines showed that yield per unit area correlated positively with number of seeds per pod.

                   Thus selection of soybean crosses having similar genetic background to the ones employed in this experiment should be based on 100-seed weight and number of seeds per pod. Selection based on number of pods per plant was not recommended since this character was easily affected by environment as compared to the former two characters. Besides, 100 seed weight and number of seeds per pod tended to correlate positively, thus should make good yield response from the selection.