Genotype Differences in Seed Germination and Growth, Pollen Fertility and Fruit Traits of Three Promising Papaya (Carica papaya L.) F1 Hybrids

Papaya F-1 hybrids are generally grown by many growers for their hybrid vigor, superior fruit characteristics and moderate tolerance to the Papaya ringspot virus (PRSV). A single-factor experiment conducted in completely randomized design (CRD) with three replications was done to test seed germination, assess seedling growth, and evaluate pollen fertility and horticultural characteristics of three promising papaya F-1 hybrids - 5648 x 336 (Liyag), 097 x 4172 (Hirang), and 4173 x 5648 (Timyas). There were significant differences in percent seed germination and seedling height between the three papaya F-1 hybrids. Hybrid 5648 x 336 (Liyag) had the highest seed germination rate (92.20%) and the tallest seedlings (44.73 mm). In terms of root characteristics, there were significant differences between the hybrids in fresh and dry weights of roots, number and length of secondary roots. Hybrid 5648 x 336 (Liyag) had the heaviest fresh and dry weights of roots and had the highest number of secondary roots while hybrid 097 x 4172 (Hirang) had seedlings with the longest secondary roots. There were significant differences in pollen viability in the three hybrids. F-1 hybrid 4173 x 5648 (Timyas) had the highest percent pollen viability (83.33%), and hybrid 097 x 4172 (Hirang) the lowest (73.33%). Pollen viability and pollen germination were high for the six parental inbred lines of the three F-1 hybrids, but no significant differences were found. In addition, there were significant differences between the three F-1 hybrids in fruit weight, fruit length and flesh thickness. Hybrid 097 x 4172 (Hirang) had red flesh, while hybrid 5648 x 336 (Liyag) and hybrid 4173 x 5648 (Timyas) had yellow orange flesh. The three hybrids are moderately tolerant to PRSV similar to the control cultivar Sinta.