A Dwarf Outcrossing Mutant in Common Bean1

Abstract

This study was conducted to determine if a dwarf mutant in common bean (Phaseolus vulgaris L.) could be used to facilitate outcrossing. In one M2 progeny line of common bean, seven plants were discovered with a dwarf mutant phenotype. Tests of M3 progenies derived from field grown M2 plants revealed outcrossing rates of 5 to 47%. Pollen staining tests using potassium iodide or acetocarmine indicated no unusual pollen abortion rates. Pod set from plants grown in insect‐proof enclosures were comparable to unprotected dwarf plants. Open flowers of dwarf plants manually crossed between 0630 and 1430 h with either ‘Sprite’ or University of Florida breeding line ‘7‐1404’ pollen resulted in cross‐pollinated progeny at the rate of 26 to 86%. The frequency of cross‐pollination declined with time of day. Evidence is presented supporting the hypothesis that delay of anther dehiscence is responsible for the elevated levels of cross‐pollination. The exploitation of this mutant in a breeding program to increase rates of genetic recombination is discussed. The proposed name for this mutant is dwarf outcrossing (do).