A Procedure to Identify Genes Affecting Maturity Using Soybean Isoline Testers¹

Abstract

Maturity genes in soybean [ Glycine max (L.) Merr.] have been discovered through accidental cotransfer during backcrossing of other traits. This study evaluated a test for identification of maturity genes in soybean strains that does not require backcrossing such genes into a common genetic background. All eight maturity isolines with homozygous combinations of the genes E 1 e l , E 2 e 2 , and E 3 e 3 have been developed by backcrossing with the cultivar ‘Clark’. These isolines were used in testcrosses with Clark, ‘Harosoy’, or ‘Mukden’. Maturity dates (R8) for single field‐grown plants of parental and populations were taken in 1982. In 1983, flowering dates (RI) were also recorded, and pod‐picked bulk F 3 populations were included for the Harosoy testcrosses and Clark isolines. Genotypes were proposed after examining the changes in ranges and variances between testcrosses, and by comparison with the Harosoy and Clark testcross progenies in which the segregating loci were known. Harosoy and Clark were confirmed to have the alleles e l e 2 E 3 and e l E 2 E 3 , respectively. The genes E l and E 2 could be detected singly or together using either flowering or maturity data. The gene E 3 could not be reliably detected unless a photoperiod sensitivity follow‐up test was utilized. Mukden had the genotype e 1 e 2 e 3 . This test will allow the maturity genotype of unrelated soybean strains to be determined, and make discovery of other genes possible without backcrossing into a common genetic background.