Mutation breeding as an effective tool for papaya improvement in South Africa
Previous plant improvement efforts at the Institute for Tropical and Sub Tropical crops of the Agricultural Research Council (ARC-ITSC) concentrated on conventional breeding of papaya which subsequently led to the release of 'Bh65' and 'Selection 42' to the local industry. Gamma irradiation has proved to be an effective method to improve cultivars in several crops and in recent years, the seed of promising papaya selections were irradiated in order to develop dwarfed and/or disease-resistant selections. Seeds were irradiated at different dosages ranging from 0 to 120 Gy. Results showed that gamma irradiation has an effect on seed germination. The higher dosages of 100 and 120 Gy were lethal and almost no seeds germinated. Furthermore the different irradiation dosages showed a correlation between higher irradiation dosage and lower plant height and stem circumference on cultivars 'Bh65', 'Maradol' and 'Sunrise Solo' whereas the cultivars 'OShew Mee', 'Tainung' and 'V3' were less affected by radiation. The higher dosage of 80 Gy had the most profound effects, reduced plant height and stem circumference. Radiation did not affect yield negatively except for 'Shew Mee' and 'V3' where some differences were observed. The higher dosages especially 80 Gy resulted in smaller fruit. No effect on disease resistance for black spot (Asperisporium spp.) was observed in the irradiated treatments as the leaves on all the plants were infected.
Husselman, J.H., Daneel, M.S., Sippel, A.D. and Severn-Ellis, A.A. (2016). Mutation breeding as an effective tool for papaya improvement in South Africa. Acta Hortic. 1111, 71-78
Caricaceae, Carica papaya, gamma irradiation, growth