Radiosensitivity studies and induction of restricted vine growth habit in bittergourd (Momordica charantia L.) through seed and pollen irradiation

Mutant phenotypes appeared in the M2 but not in the M1 generation. The most prominent mutant was the chlorophyll deficient or yellow seedling type which occurred at frequencies of 0.83% (3 kr) and 3.51% (9 kr). This trait appeared to be controlled by a lethal recessive gene, designated as Y. Furthermore, a suppressed shoot growth mutant was isolated from one M2 family and was studied further in the M3. The genetic analysis of this mutant revealed that it was due to a recessive gene, designated as ssq. In addition, a dwarf phenotype was selected in the M3 from progenies of normal looking M2 plants. The stability of expression and genetic basis of this trait are still to be determined. A separate study was conducted on pollen irradiation using the highly inbred line 9-108 (S8). Evaluation of radiation sensitivity was based on fertility and germination of irradiated pollen, fruit set percentage and number of seeds per fruit. The viability of M1F1 seeds and the fertility of M1F1 plants were also evaluated. A decreasing trend in all of these parameters was observed with increasing doses. Fertility of the irradiated pollen was least affected by the treatments but fruit setting percentage and number of seeds per fruit were greatly reduced with increased dosage. The effective dose for pollen irradiation was set between 3kr and 5kr. A number of M1F1 plants with reduced fertility appeared in all treatment groups except at 1kr. They were found to be associated with morphological aberrations. The aberrant phenotypes mainly exhibited a change leaf type such as incurved leaves, firm leaves, narrow lobed leaves, heart shaped leaves, deeply serrated leaves and pale green leaves. An aberrant plant with short internodes and erect growth habit was also obtained. Evaluation at the M2 generation did not show prominent morphological aberrations among progenies derived from normal looking M1F1 plants.