Pollinator Density Effects on Frequency and Randomness of Male‐Sterile Soybean Pollinations 1

Genetic male‐sterility has been used to facilitate intermating in the recombination phase of soybean [ Glycine max ( L.) Merr.] breeding programs. Insect vectors of pollen do not move at random in these intermating blocks and this may restrict random pollination. This study was initiated to assess the amount of cross pollination to male‐sterile plants as affected by different proportions of pollinators in the intermating population. Seeds of ‘Century’ and CX602‐107‐1‐2 pollinators, both with tawny pubescence, were individually blended at 0, 20, 40, and 80% levels with F 2 seeds of a gray‐pubescent population segregating for male sterility ( ms 2 ms 2 ). Two replications of the intermating blocks were grown each of 2 years in the field at Lafayette, Indiana. Seeds were harvested from male‐sterile plants in each treatment and the numbero f tawny( Tt ) and gray ( tt ) pubescent plants developing from these seeds were recorded. Effects of years and interactions of years on pollinators and pollinator densities were not significant in the analyses. The incidence of tawny pubescent progeny from male‐sterile plants was linearly related to the amount of seed of tawny pubescent pollinators planted in the intermating blocks. The proportion of tawny progeny from individual male‐sterile plants was consistent irrespective of the numbero f seeds producedo n the male‐sterile plants. The data suggest that cross‐pollinations in recombination blocks using males teriles is directly related to the frequency of each pollinator genotype in the population. The data further suggest that foreign genes could readily each pollinator genotype in the population. The data further suggest that foreign genes could readily be introgressed into an intermating population containing male steriles by simply blending seeds of the foreign germplasm with those used to produce the intermating population.