Submitted to: Molecular Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2001
Publication Date: N/A
Citation: Interpretive Summary: The soybean is able to grow in the far north as well as near central America. This wide range of adaptation makes the soybean a very economically important crop. It has the ability to grow and thrive in a wide geographic range because it has complex genes that respond to changing day lengths and seasons. It has the ability to extend or shorten the time it takes to mature. Understanding how the genes function that control thi ability would help breeders to manipulate the plant for even more productivity. In this paper the authors located the genes allowing the soybean to respond to day length and to alter its time to maturity. The authors placed the genes onto the genetic road map of the soybean. Interestingly, they found that the genes controlling several traits (recognition of day length, maturity, flowering time) were located in the same region. This meant that a single gene controlled all the traits, or, several genes controlled the traits, but the genes were located next to each other. This information may help breeders to manipulate the soybean so that it may extend its growing range even further and help to make marginal farming land more productive.
Technical Abstract: The objective of this research was to use molecular markers to identify and locate chromosomal regions that control traits for flowering time, maturity and photoperiod insensitivity in soybean. Two single-cross populations, IX132 (PI317.336 X'Corsoy'), and IX136 (PI317.334B X'Corsoy') were used for this purpose. Days to R1 was observed among F6:7RI lines in the field during 1991 and 1992 and in the growth chamber at 12 h and 20 h photoperiods using fluorescent and incandescent lamps. Days to R3 was observed in the field during 1991 and in the growth chamber with 12 h photoperiod. Days to R7 was observed in the field in 1991. A total of 139 markers (88 RFLPs and 52 SSRs) in the IX132 population and 125 markers (73 RFLPs and 52 SSRs) in the IX136 population were used to map quantitative trait loci (QTL) affecting these traits. Results show that a large-effect QTL for days to R1, R3, and R7, and photoperiod insensitivity was found at the same location on linkage group (LG) C2. This QTL was detected in all environments tested. In both populations, the QTL accounted for 35.4- 45.7%, 29.7-43.2%, 24.7-25.6%, and 22.4-25.7% of total phenotypic variances for days to R1, R3, R7, and photoperiod insensitivity, respectively. This result suggests that traits for photoperiod insensitivity, flowering time, and maturity may be controlled by the same gene(s) or by tightly clustered genes in the same chromosomal region. In addition to the large effect QTL, minor QTL were also detected. Minor effect controlling these four traits also were observed in these populations IX132 and IX136. These QTL account for as much as 18.1% and 17.9% of phenotypic variance in populations IX132 and IX136, respectively.