| Abstract |
Papaya (Carica papaya L.) is one among the most important fruit crops grown in tropical and subtropical areas of the world. It has long been known as ‘Wonder Fruit of Tropics’ due to its year-round bearing nature, high yield and ease of adaptation to various soil and climatic conditions. Although India is a major producer of papaya, the lack of high-yielding cultivars and adverse conditions restrict its commercial cultivation. Farmers adopt hybrids because of their increased yield potential and superior eating quality. Though there is a lot of scope for scaling up papaya production and export, one of the major challenges is the non-availability of high yielding hybrids in the public sector. Hence, developing a public sector hybrid for table purpose, value addition and export is the need of the hour. In this context, the present study on ‘Development of hybrids in papaya (Carica papaya L.)’ was undertaken in the Department of Fruit Science during 2021-2024. The first experiment was on hybridization in which six gynodioecious varieties (CO-3, CO-7, Arka Surya, Arka Prabhath, Coorg Honey Dew and Pusa Delicious) were selected as parents to carry out 6 x 6 full diallel crossing to develop 30 hybrids. These 30 hybrids were evaluated along with their parents and a standard check Red Lady, for growth, yield and quality parameters. Evaluation of vegetative characters showed that seed germination was found to be maximum in three hybrids viz., CO-7 x Coorg Honey Dew (96.84 %), Arka Surya x CO-7 (95.80 %) and Coorg Honey Dew x CO-3 (95.24 %), dwarf growth habit in Pusa Delicious x Arka Surya (176.90 cm), thicker stem in Coorg Honey Dew x Arka Surya (57.25 cm), more number of leaves in Arka Prabhath x CO-3 (29.05) and shortest petiole in Pusa Delicious x CO-3 (58.05 cm). With regard to floral characters viz., days to first flowering and height to first flower was minimum in CO-7 x Arka Prabhath (86.5 days) and Pusa Delicious x Arka Surya (74.85 cm) respectively. Regarding fruit characters, CO-7 x Arka Prabhath exhibited minimum number of days from flowering to fruit set (6.50 days) and Arka Prabhath x CO-7 recorded least fruit cavity index (16.00 %). Maximum fruit weight (2605.00 g), fruit length (18.55 cm) and fruit breadth (15.90 cm) were recorded in Arka Prabhath. The hybrid Arka Prabhath x CO-3 recorded the highest number of fruits per node (1.45) and fruit yield per plant (77.74 kg). Superiority with respect to fresh weight of seeds per fruit was observed in Arka Prabhath (125.50 g). With respect to quality attributes, CO 7 x Arka Prabhath was found to have the highest TSS (15.50 ˚B), total sugars (12.05 %) and reducing sugars (11.25 %) with low acidity (0.11 %). The estimated total carotenoids was found to be the maximum in Arka Prabhath x CO-7 (3.43 mg/100g). The fruits of the hybrid Arka Prabhath x Coorg Honey Dew exhibited the longest shelf life (8.85 days). Overall scoring of papaya hybrids for table purpose based on growth, yield and quality recorded highest rank for the hybrid Arka Prabhath x CO-3 followed by Arka Surya x Arka Prabhath. The observations on colour of mature leaf petiole, flower colour, fruit shape, fruit skin and flesh colour, seed colour and seed shape exhibited variations among the treatments. These qualitative parameters were recorded using IPGRI descriptor for papaya. The combining ability analysis revealed Arka Prabhath as the best general combiner for early flowering (-3.31) and Pusa Delicious for height to first flower ( 5.62). Arka Prabhath was estimated with highest GCA effect for fruit yield per plant (10.78), total sugars (0.92) and total carotenoids (0.32). The highest SCA effect for early flowering was noted in Arka Prabhath x CO-7 (-17.25) and height to first flower in Coorg Honey Dew x Arka Prabhath (-22.20). The hybrid, Arka Prabhath x CO-3 was estimated to have the highest SCA effect for fruit yield per plant (17.11), Arka Surya x Arka Prabhath for total sugars (1.53) and reducing sugars (1.38) and CO-7 x Arka Prabhath for total carotenoids (0.93). The estimation of heterosis for days to first flowering revealed that CO-7 x Arka Prabhath to have the lowest relative heterosis (RH -28.07 %), heterobeltiosis (HB 31.08 %) and standard heterosis (SH -20.27 %). The hybrid, Pusa Delicious x Arka Surya exhibited lowest relative heterosis (-27.33 %) and standard heterosis (-6.96 %) for height to first flowering, while CO-7 x Coorg Honey Dew showed lowest heterobeltiosis (-7.63 %) for the same trait. Highest significant heterosis on fruit yield per plant was exhibited by CO-3 x Arka Surya (RH 283.95 % and HB 213.12 %) and SH by Arka Prabhath x CO-3 (111.77 %). Other crosses with significant SH for fruit yield per plant were Arka Prabhath x CO-7 (91.14 %), Coorg Honey Dew x CO-3 (76.00 %), CO-7 x Arka Prabhath (66.50 %), Arka Surya x CO-7 (52.43 %), CO-3 x Arka Surya (51.70 %), CO-3 x Arka Prabhath (33.69 %) and CO-7 x CO-3 (14.60 %). With respect to total sugars, Arka Surya x Arka Prabhath exhibited highest (RH 31.86 %) and (HB 25.26 %) and CO-7 x Arka Prabhath exhibited highest SH (24.87 %). Highest significant heterosis for reducing sugars was exhibited by Arka Surya x Arka Prabhath (RH 47.59 %) and HB (25.15 %) and CO-7 x Arka Prabhath over SH (41.51 %). The hybrid, Arka Surya x Arka Prabhath recorded superiority in terms of RH (95.38 %), HB (67.15 %) and SH (131.31 %) for total carotenoids. Estimation of other genetic parameters revealed that there was wide variation in results among various characters indicating the presence of considerable diversity among the parents and hybrids for these traits. The difference between PCV and GCV was found to be low for characters like days to first flowering, height to first flowering, fruit weight, fruit length, fruit yield, total sugars and total carotenoids. Characters such as fruit weight, fruit length, fruit yield per plant and total carotenoids exhibited high GCV and PCV. Heritability (> 90 %) with high genetic advance was observed for plant height, height to first flowering, fruit weight, fruit length, fruit yield, total sugars, reducing sugars and total carotenoids. Yield and quality (in terms of total sugars and total carotenoids) are two prominent attributes in papaya for effective utilisation as table purpose. The result of correlation analysis with respect to yield revealed a significant positive correlation with stem girth, number of leaves, fruit weight, fruit breadth, fruit length, TSS, total sugars, reducing sugars and total carotenoids at both genotypic and phenotypic levels. Correlation analysis with respect to total sugars and total carotenoids exhibited positive and significant correlation with number of leaves, fruit weight, fruit breadth, fruit yield per plant, TSS and reducing sugars both genotypically and phenotypically. In the second experiment on the evaluation of hybrids for homogeneity, twenty plants from each cross were evaluated for homogeneity in terms of growth, yield and quality. The results revealed that majority of the crosses had shown low co-efficient of variation (CV) indicating low variability, thus proving homogeneity, while few crosses with respect to number of leaves, fruit length, fruit yield and TSS exhibited medium CV. The third experiment was on molecular characterization of hybrids and the results revealed that five (CP03, CP18, CP31, CP40 and CP94) out of 34 SSR primers were found to be polymorphic for the parents and their amplicon size ranged from 240 to 260 bp for CP03 and CP18, while it ranged from 160-170 bp for CP31, CP40 and CP 94. The identified five polymorphic SSR primers have confirmed the hybridity in papaya. The present investigation resulted in the development of two heterotic hybrids viz., Arka Prabhath x CO-3 and Arka Prabhath x CO-7 for fruit yield, while two hybrids viz., CO 7 x Arka Prabhath and Arka Surya x Arka Prabhath for fruit quality. The results on evaluation of hybrids for homogeneity revealed that all the hybrids showed homogeneity with respect to plant height, plant stem girth, petiole length, days to first flowering, height to first flower, fruit weight, fruit cavity index, total sugars and total carotenoids. Molecular characterization of hybrids for checking the hybridity using SSR markers explained that five polymorphic SSR primers have confirmed the hybridity in papaya by indicating alleles of both the parents in the respective hybrids. |
