Abstract
An investigation was carried out to study the floral biology, anther culture, interspecific hybridization and genetic transformation of papaya. The male flowers of different Carica species emerged earlier than female flowers. The flower buds, petal, anther, fresh weight and dry weight of male flower at all stages were the highest in C. cauliflora. But the female flowers of C. pupuya cv. Ranchi performed the best in respect of all parameters. C. papaya cv. Shahi required the maximum time for initiation to receptivity followed by C. papaya cv. Ranchi. C. cauliflora required the minimum time in this respect. The anther dehiscence in all Carica species increased upto 12 p.m. The anthesis of female flowers of C. papaya cvs. Shahi and Ranchi gradually increased during 6 a.m. to 8 a.m., and declined during 8 a.m. to 11 a.m All Carica species showed the maximum receptivity on the day of anthesis. The pollen of C. cauliflora showed the maximum viability in March. The pollen stored in desiccator at 10% relative humidity at 0°C and room temperature showed the best results for storage. The pollen remained viable up to 5 months at 0°C temperature. The best medium for anther culture of Carica species was half strength MS medium with full strength Na-Fe- EDTA supplemented with 2.0 mg NAA, 1.0 mg BAP and 60 g sucrose per litre. The 12-14 mm long flower buds of C. goudotiana and 10-15 mm long flower buds of C. papaya cv. Shahi, C. papaya cv. Ranchi and C. cauliflora were found to be the best for anther culture. The anthers pretreated at 4°C temperature did not perform well. The anthers of different Carica species responded to medium supplemented with NAA for callus induction. Selfing of the genotypes under study gave the highest fruit set. The lowest fruit set was recorded from the cross of C. papaya cv. Ranchi x C. goudotiana. The fruits set from the crosses dropped 5-7 days after pollination. The lowest number of embryos per fruit was recorded in the cross of C. papaya cv. Ranchi x C. cauliflora. The maximum germination was recorded from the hybrid embryos of C. cauliflora x C. goudotiana on White's medium. The highest number of somatic embryos was obtained from the embryos of C. cauliflora x C. goudotiana on medium supplemented with 5.0 mg/l 2, 4-D. The hybrid seedlings obtained from the crosses of C. papaya cv. Shahi x C. cauliflora and C. papaya cv. Ranchi x C. cauliflora did not show any PMV symptom after 21 days of inoculation. Genetic transformation was carried out by co-cultivating papaya embryo axis with Agrobacterium tumefaciens and confirmed by histochemical staining for detection of GUS expression. Genetic transformation was higher in C. papaya cv. Shahi than in C. papaya cv. Ranchi