IMPACT OF GAMMA IRRADIATED POLLEN ON SEXUAL COMPATIBILITY, SEED SETTING, AND FRUIT ATTRIBUTES IN GUAVA (PSIDIUM GUAJAVA L.) CULTIVARS

Pollen irradiation technique has emerged as a novel tool to induce parthenogenesis. Round shaped guava cultivars including white flesh 'Gola', pink flesh 'Surkha' and pyriform shaped cultivar white flesh 'Surahi' were self-pollinated by Co-60 gamma irradiated pollen at variable gamma irradiation doses viz. 100, 200, 350, 500, 700 and 900 Gy to observe metaxenial impact and induce parthenogenesis. Fruit setting and harvesting were reduced to 10% and 8% at 900 Gy of gamma irradiation, respectively. Seed setting was also reduced to half in crosses of all cultivars with irradiated pollen (102-144 seeds/fruit) compared with non-irradiated control pollen (220-250 seeds/fruit). Seeds produced in irradiated crosses were 45% lighter compared with seeds of control fruit. Round cultivars 'Gola' and 'Surkha' showed better self -compatibility compared with pyriform cultivar 'Surahi'. Pollination by irradiated pollen at higher doses improved average fruit length (12%), FL: FD (15%) and TSS: TA (50%) whereas, it decreased fruit weight (30%), TSS (20%), TA (60%), total sugars (63%) and ascorbic acid (63%) compared with fruit attributes of control fruit. Number of seeds and seed weight were positively correlated with total sugars and ascorbic acid whereas fruit weight was positively correlated with seed cavity weight and TSS. Principle component analysis (PCA) revealed greater variation in fruit biochemical traits compared with physical traits. In cluster analysis of chemical traits, higher doses of gamma irradiation were grouped separately compared with control and other treatments indicating their greater contribution to enhance variability. The irradiated pollen reduced fruit and seed setting and also influenced most of the physico-chemical traits indicating the presence of a robust metaxenial effect. The developed mutant plant populations were characterized for morphogenetic diversity. Mutation breeding could further contribute towards haploidization using induced parthenogenesis and to enhance seedlessness.