I Made Tasma – Soybean Genetics Newsletter 27

Soybean Genetics Newsletter 27 [Online journal].

Inheritance of Genes Controlling Photoperiod Insensitivity and Flowering Time in Soybean

IM. Tasma1, L. L. Lorenzen2, D. E. Green1, and R. C. Shoemaker1,3
1Department of Agronomy, Iowa State University, Ames, Iowa 50011
2Office of Biotechnology, Iowa State University, Ames, Iowa 50011
3 USDA-ARS, Corn Insects and Crop Genetics Research Group,
Iowa State University, Ames, Iowa 50011


The objective of this research was to study the inheritance of genes controlling photoperiod insensitivity and flowering time in soybean. Two single-cross populations, IX132 (PI 317.336 X 'Corsoy'), and IX136 (PI 317.334B X 'Corsoy') were developed for this purpose. The populations were inbred to obtain 101 and 100 F6:7 lines, respectively, using a modified single seed descent. Flowering time (days to R1) of the RI lines from each population was observed in the growth chamber at 12 h and 20 h photoperiods using fluorescent and incandescent lamps. Results show that the RI lines have dramatically different responses to day length. A normal distribution of flowering times was observed when the lines were grown in growth chamber with 12 h photoperiod. When the lines were grown in growth chamber with 20 h photoperiod, however, a discontinuous distribution was observed. This suggested that the insensitivity of the RI lines on long day length may be controlled by few major genes. The time of flowering was delayed in almost all lines when grown in growth chamber with 20 h photoperiod compared to those grown in the growth chamber with 12 h photoperiod. The flowering delays were 5 to 75 days in population IX132 and 0 to 75 days in population IX136. Chi-square tests show that the segregation data fit a 1:6:1 ratio in population IX132 and IX136. Based on these tests a minimum of three genes are proposed to control photoperiod insensitivity in both populations.
Joint publication of the USDA-ARS-Corn Insect and Crop Genetics Research Unit and Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa (project no. 3236). Names are necessary to report factually on the available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be available. We thank the government of Indonesia for financial support for IMT.