PROGRESS IN BREEDING OF F1 PAPAYA HYBRIDS IN MALAYSIA
The Eksotika papaya variety developed by MARDI in 1987, is a pureline like many popular varieties in the world today. The seeds are produced easily by self-pollination and this can be carried on for many generations without loss of vigour. There is recent evidence, however, to justify the development of F1 papaya hybrids to exploit heterosis in increasing yield. At MARDI, three inbred lines (L7, L19 and Eksotika (formerly L20)) from the backcross breeding population, were crossed inter se and the hybrids were evaluated in two trials from 1985–1988. In the third trial conducted from 1989–1990, L19, Eksotika and Sunrise Solo were crossed to produce another hybrid set for evaluation. In this trial, the performance of tissue-cultured plants of L19 x Eksotika was compared with their seed-propagated counterparts. The results of the three trials indicated that there was no difference in plant vigour (estimated from diameter of stem), between the hybrids and the inbred parents but marked heterosis was exhibited for yield. The most impressive hybrid combination was L19 x Eksotika in which a consistent increase in yield of 2–22% over the better parent was shown in all three trials. Compared with Eksotika, the poorer parent, the hybrids were 14–33% higher yielding. In crosses with the Sunrise Solo, the hybrids showed yield increase of only 9–19% over the mid parent. However, compared with the poorer parent, Sunrise Solo, the hybrid yield was 40% higher. Both L19 x Eksotika and Solo F1 hybrids have the potential for replacing the contemporary varieties. Although the prospects of using hybrid varieties seem bright, certain aspects of F1 seed or planting material production need to be investigated further. Hybrid seeds produced from crosses using female flowers that obviated emasculation, had 50% segregation of undesirable female progenies. This problem may be resolved by using tissue culture for propagation of hybrid materials. In one trial, tissue cultured plants of L19 x Eksotika exhibited precocity, high yield and most importantly, established a pure stand of hybrid hermaphrodites.
Chan, Y.K. (1992). PROGRESS IN BREEDING OF F1 PAPAYA HYBRIDS IN MALAYSIA. Acta Hortic. 292, 41-50