Evaluation of potential genetic marker traits and estimation of outcrossing rate in Stylosanthes guianensis

Abstract

The inheritance of flower, seed testa, and hypocotyl colour, and growth habit were studied in the F2 generation of biparental crosses between Stylosanthes guianensis accessions exhibiting contrasting phenotypes. Segregation ratios for flower colour in seven crosses and the pooled ratio supported a conclusion of single-gene inheritance, with yellow dominant to white. The data on seed colour (purple v. brown) gave inconsistent results in the two crosses evaluated. Neither red v. white hypocotyl colour nor normal v. dwarf growth habit appeared to be inherited monogenically, since a range of intermediate phenotypes was observed in the F2 populations examined. The open-pollinated progenies of 12 homozygous recessive (white-flowered) individuals within one F2 population contained yellow-flowered plants attributed to outcrossing. Overall outcrossing rate ( ¦ s.e.) was estimated as 0.138¦0.021. The proportion of yellow-flowered outcrosses in these 12 progenies was related to the number of yellow-flowered individuals adjacent to the F2 parent, indicating that pollen movement was limited within the F2 plot. Based on these findings a practical, recurrent population improvement scheme for S. guianensis is proposed.