Manipulation of in vivo pollination techniques to improve the fertilization efficiency of interspecies crosses in the genus Phaseolus

Phaseolus angustissimus A. Gray contains genes for traits of interest for dry bean (P. vulgaris) breeders. F₁ hybrids can be produced but introgression through backcrossing has been a problem. One of the main impediments is the time required between pollination and fertilization when F₁ hybrids of P. vulgaris/P. angustissimus are backcrossed with P. vulgaris. In an attempt to reduce this time, the effect of alternative pollination techniques was studied. The rate and the time of fertilization were ascertained using three different pollen types (pollen germinated in vitro, fresh pollen (FP) mixed in pollen‐germinating media and FP), and two methods of pollination (cut‐style and stigmatic pollinations). An optimal in vitro pollen germination medium for Phaseolus pollen was developed. Low temperatures (6–9°C) were demonstrated to be necessary for Phaseolus pollen germination. Pollination using a cut‐style technique coupled with pregerminated pollen reduced the time for fertilization in the backcrosses of interspecies hybrids by approximately 28 h. This technique improved the success rate of fertilization in wide crosses of Phaseolus designed to introgress genes from wild relatives.