Author
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ROBINSON, S - FFR COOPERATIVE |
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Wilcox, James |
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Submitted to: Crop Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/6/1998 Publication Date: N/A Citation: N/A Interpretive Summary: Determinate is a term used to describe soybean varieties that stop growing in plant height when they begin to flower, resulting in very short-statured plants. Indeterminate is a term used to describe soybean varieties that continue to grow in height when they flower, resulting in tall plants with many nodes. Different management practices have been developed to optimize seed yields of the two plant types. It has been controversial whether or not separate breeding programs are needed to develop productive varieties of the two plant types. Determinate and indeterminate pairs of soybean, that are nearly identical genetically, were found to be similar in time of beginning flowering, time when the plants mature, and length of the reproductive period, whether planted early or late or in wide or narrow rows. There was virtually no relationship in seed yields between most determinate soybeans and their member of the pair. However, the highest yielding determinate soybean had an indeterminate counterpart that was the highest in yield among the indeterminate soybeans. The high yields of this determinate and indeterminate pair were consistent at two row spacings and two planting dates. This information will be useful to soybean breeders who are developing determinate and indeterminate soybean varieties and need to know the response of the two plant types to planting dates and row spacing. Technical Abstract: Determinate and indeterminate soybean [Glycine max (L.) Merr.] lines respond differently to planting date and row spacing, factors than can be varied to maximize seed yield for the two plant types. This study was conducted to determine the similarity for phenological and agronomic traits of determinate (DET) and indeterminate (IND) near-isolines. A second objective was to determine similarity of response of the isolines to planting date and row width. Thirty-eight F5-derived DET and IND near- isolines were randomly selected and were evaluated in three replications of a split (planting date), split (row spacing), split (isoline) plot design over a 2-yr period. Data were recorded on the phenological traits days to first flowering, days to maturity, length of the reproductive period, and on plant height, lodging, and seed yield. Lines within growth habit responded similarly to row spacing, but the interactions of planting dates with lines within growth habits were significant for all traits measured. The DET lines were very similar to their IND isoline counterparts for the phenological traits measured (r = 0.74** to 0.93**), less similar for plant height (r = 0.59** to 0.73**), and even less similar for plant lodging (r = 0.36** to 0.70**). There was no association between DET and IND isolines for seed yield in three of the four environments, suggesting that, in general, the two plant types respond differently to environmental factors that affect seed yield. The highest yielding DET and IND isolines, averaged over all environments, were derived from the same F5 plant, suggesting that loci affecting superior seed yield cause similar responses in both plant types. |
