Selection for resistance to economically important diseases in soybean
1992
Pornpote Dansrichanchai
High number of pods per plant and resistance to downy mildew disease incited by the fungus Peronospora manshurica (Naoum.) Syd. and bacterial pustule disease incited by the bacterium Xanthomonas campestris pv. glycines. The selection was carried out from F3 to F6 generations until 45 F7-lines were identified as carrying resistance to both diseases, yet having high yield, large seeds and large number of pods per plant. They were yield-tested in a 7x7 double lattice at Kamphaeng Sean Campus and Suwan Farm in the rainy 1989. The check cultivars were SJ4, NS1, CM 60 and KUSL 20004. Eight agronomic characters were recorded and analyzed, namely yield per unit area, 100 seed weight, number of pods per plant, number of seeds per pod, plant height, days to flowering, days to harvest and number of plants harvested. The progress from selection was not detectable since the data were collected from different seasons or locations. Environments played major role in the variability of yield and yield components of the selected lines. Result from the yield testing revealed that lines and cultivars were different in all traits recorded. Most of the selected lines were more resistant to both downy mildew and bacterial pustule disease than the check cultivars, NS 1 SJ 4. Simple correlation coefficients among the recorded characters of the selected lines showed that yield per unit area did not correlate with yield components. However, it correlated negatively with days to flowering. Besides, number of pods per plant was negatively correlated with number of seeds per pod. Correlation study between generations showed that 100 seed weight was the most stable yield component, while number of pods per plant was easily affected by environment.
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