Date of Award
Doctor of Philosophy
Two photoperiod insensitive plant introductions, PI317.334B (Maturity Group III, determinate growth habit) and PI317.336 ('Shinsei' - Maturity Group O, determinate growth habit) were crossed with photoperiod sensitive 'Harosoy 63' (Maturity Group II, indeterminate growth habit) and with each other to generate genetic variability for lengths of the seed filling and reproductive periods. The relationships of seed filling and reproductive periods with date of maturity and photoperiod sensitivity at flowering were also studied. The three resulting F(,2) populations were screened for photoperiod sensitivity in the greenhouse. F(,2)-derived lines were evaluated in field conditions in the F(,3) and F(,4) generations;Determinate F(,2)-derived lines displayed a shorter time period from growth stages R1 to R5 and a longer time period from stages R5 to R7 than indeterminate lines. This is probably due to the method of estimating growth stage R5 rather than to biological differences among growth habits in length of the seed filling period for any particular pod. Significant and heritable genetic variability for lengths of the seed filling and reproductive periods as well as dates of R1, R5, and R7 was observed among lines in all growth habit classes, except for length of the seed filling period in the indeterminate classes. Realized heritabilities of length of the reproductive period ranged from 0.63 to 1.17. Realized heritabilities of length of the seed filling period ranged from 0.46 to 1.02 in growth habit classes where variability existed;Early dates of R1, R5, and R7 of field-grown F(,2)-derived lines were closely associated with photoperiod insensitivity of F(,2) plants. However, lengths of the seed filling and reproductive periods were not. In crosses between Harosoy 63 and either photoperiod insensitive plant introduction, correlations of date of R7 with lengths of the seed filling and reproductive periods were considerably lower than correlations in the cross between PI317.334B and Shinsei or correlations previously reported in USA-adapted germplasm;Seed filling and reproductive periods of F(,4) generation lines could be lengthened by six days due to F(,3) selection for these traits. These changes were possible without substantially affecting date of R7.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Grant Loyal Metz
Metz, Grant Loyal, "Length of reproductive period and degree of photoperiod sensitivity in soybeans (Glycine max (L.) Merr) " (1982). Retrospective Theses and Dissertations. 7518.