COMPARISONS OF FRUIT QUALITY OF F3, F2 AND F1 HYBRID PAPAYA PLANTS AND THEIR PARENTS

Research was conducted between mid-1998 and early 2000 at the Chanthaburi Horticultural Research Center, Thailand, to select papaya breeding lines with improved eating quality for overseas and Thai domestic markets. Twenty-two lines, including F3, along with the other lines of F2, F1 seeds from the yellow-fleshed Australian cultivars (Richter and 2.001) and the red- or orange-fleshed cultivars from Thailand (Kheng Dum), were planted, together with Hawaii (Sunset) crosses and their parents. Fifteen characteristics were studied to compare these hybrids and their parents. The eating quality of the F3, F2 and F1 fruits varied from better than the better parent to intermediate between the parents. Most of the TSS measurements of the F3, along with the other lines of F2 and F1 fruits ranged from greater than the higher parent to intermediate between the parents. It revealed that the eating quality of F3, along with F2, F1 fruits showed improved quality as compared to their parents and this was especially true for the F3, along with F2, F1 fruits in the crosses involving Sunset, which had high sugar content. Three characteristics viz. % TSS, fruit weight and flesh thickness were considered important in evaluating papaya fruit quality to select specific hybrids. % TSS was poorly correlated with fruit weight and flesh thickness. It showed that the hybrids which produce a high sugar content have a smaller fruit size (weight) and thinner flesh thickness. Thirty-seven superior F3, along with F2, F1 fruits from the crosses involving Sunset have been selected on the basis that they produced a high sugar content of more than 13% TSS, had a fruit weight between 0.3 and 1.0 kg and a flesh thickness of more than 2 cm. Six superior F3 along with F2 fruits from the other line, in the crosses involving Khaeg Dum were selected on the basis that they produced a high sugar content of more than 11% TSS, had a fruit weight between 1.0 and 2.0 kg and a flesh thickness of more than 2.2 cm. These superior hybrid plants could be considered worthy of propagation by cutting or by tissue culture and their seeds could be planted to develop inbred lines.