GENETIC EFFECTS ON REPRODUCTIVE PHENOLOGY IN SOYBEAN ISOLINES DIFFERING IN MATURITY GENES

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Abstract
Soybean (Glycine max (L.)) reproductive phenology is influenced by genotype, photo-period, and temperature. Backcross-derived isolines for three maturity genes, E1, E2, and E3 were used. Three Harosoy and four Clark isolines were evaluated for flowering date (R1) in the Duke University Phytotron. Eight Clark isolines were tested in controlled-photoperiod and planting-date field experiments at Urbana, Illinois. The phytotron data showed a mean delay in flowering of 16, 7 and 2 d for E1, E2 and E3 vs. e1, e2 and e3, respectively. The genes were mainly additive, as were temperature and photoperiod on rate of progress to flowering. Flowering was delayed 14.4, 5.4, and 2.7 d and 16.0, 6.6 and 5.5 d in the controlled-photoperiod and planting-date experiments by E1, E2and E3, respectively. Maturity was delayed 16.1, 7.1 and 4.3 d, and 10.8, 10.6 and 5.8 d in the controlled-photoperiod and planting-date field experiments by E1, E2 and E3, respectively. Postflowering development (R1 to R8) was slowed by E2 and E3, E1 showed no effect in the controlled-photoperiod experiment, but hastened postflowering development in the planting-date experiment. Reproductive development periods prior to and after flowering can be affected by the same gene to different extents and in different directions.Key words: Soybean, Glycine max, photoperiod, temperature, flowering, maturity