ScienceAsia 33 (2007): 229-234|doi: 10.2306/scienceasia1513-1874.2007.33.229

Yield Improvement of Early Maturing Soybeans by Selection for Late Flowering and Early Maturity

Thitiporn Machikowa^a, Aree Waranyuwat^a, Joseph W. Burton^b and Paisan Laosuwan^a*

 
ABSTRACT: In Thailand, soybean varieties classified as early, medium and late maturing can be harvested in about 85, 100 and 115 days, respectively. The early maturing varieties generally have small plant stature, flower in about 30 days after planting and produce lower yield than others. Breeding to increase days to flowering of early maturing varieties while keeping their days from flowering to maturity intact or reducing them might indirectly increase seed yield. To test this hypothesis, three crosses were made between early maturing varieties (NS1, CM2) and a late maturing variety (CB1) and a late maturing line (LJ4). These crosses, CB1 × NS1, LJ4 × NS1 and LJ4 × CM2, were used to produce advanced populations. The three populations were subjected to two methods of inbreeding, conventional single-seed descent (CSSD) without selection and modified single-seed descent (MSSD) which included early generation selection for late flowering and early maturing plants. In the MSSD F2 and F3 generations, a single seed was taken from late flowering and early maturing plants. With CSSD, single seeds were sampled from all plants without selection. In the F6 generation, regardless of the number of tested lines, 17 lines, which flowered three days or more later and matured earlier than or on similar date to their respective early parent were selected from all three populations and both CSSD and MSSD methods of selection. These lines were evaluated for yield, days to flowering, days to maturity, seed size, nodes per plant, branches per plant, pods per plant, seeds per plant and plant height. It was found that in the F7 generation for all crosses the CSSD method gave a higher number early maturing lines outyielding their respective early parents (CM2, NS1) and the location check (SJ5) than the MSSD method. These lines flowered later than their respective early parents but matured on a similar date to their early parents. Therefore, this study showed that breeding early maturing soybeans for later days to flowering while keeping days to maturity intact or reducing them resulted in increased yield.


KEYWORDS: Late flowering, early maturity, indirect selection, single seed descent.

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