Viability of pollen grains of isogenic sibling bean (Phaseolus vulgaris L.) selections of known tolerance of sensitivity to high temperatures (HT), as previously determined by pod retention and seed yield, was compared to that of a common parent bean selection and a cowpea [Vigna unguiculata (L.) Walp.] cultivar. Exposure of newly opened flowers to temperatures of 35° or 41°C reduced the viability of pollen grains in all bean selections. Pollen of all sibling selections was less affected by HT than pollen of their common parent suggesting transgressive segregation of factors for HT tolerance. At 41°, most pollen grains were destroyed in the parent bean selection and the 2 HT-sensitive siblings, whereas 44% to 55% of the pollen grains appeared to be viable in the 2 HT-tolerant siblings. Pollen viability of the HT-tolerant cowpea cultivar was not reduced by temperatures to 41°. Pollen staining indicated an interrelationship between pollen viability and tolerance to HT stress among the bean selections. The technique described has the potential for rapid selection of HT-tolerant genotypes in hybrid populations.
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