Effect of Soft and Hard X-Ray Irradiated Pollen on Pod and Seed Development Following Cross-Pollination in Phaseolus Vulgaris

The freshly opened flowers of Phaseolus vulgaris cv. Mexican Black were collected and exposed to 0, 45, 90, 135, 180, 225 Gy of hard X-rays (250 kV, 15mA) and. 45, 90, 135, 180, 225, 450, 675 and 900 Gy of soft X-rays (30 kV, 4mA). Irradiated pollen was used to pollinate flowers of cv. Concord to compare the biological effects of soft and hard X-rays based on success in pollination, pod and embryo development. There was negative relationship between hard X-ray exposures and percentage of successful pollination and pod set. Soft X-rays increased pod abscission and decreased seed bearing pods only up to 225 Gy. At higher doses of soft X-rays (450-900 Gy), the trend of damage either reversed or remained unaltered, i.e. similar to that of hard X-rays. The effects of both types of X irradiation were different at the same doses. There was substantial increase in the parthenocarpic pods per successful pollination with soft X-rays. Such pods were seedless and smaller In size than those obtained after setting or crossing with unirradiated pollen. However, there was no difference in the number of ovules present in both types of pods.