Relationship of parental genetic diversity with heterosis in two-lines and three-line Philippine rice hybrids
2003
Moreno, L.S. | Ordoñez, S.A. | Cruz, I.A. dela | Redoña, E.D.
Heterosis in rice has been acknowledge to be associated with the genetic divergence of the parents used in hybridization. We investigated the nature and extent of the correlation between microsatellite marker heterozygosity and heterosis for some quantitative traits in 48 three-line and 13 two-line F1 rice hybrids. The parental lines used represented the breadth of genetic diversity in the Philippine hybrid rice gene pool. F1 heterozygosity was deduced from parental genotypes at 43 to 108 microsatellite loci spanning the 12 rice chromosomes. Results revealed simple sequence repeat (SSR) heterozygosity and heterotic performance (measured as the superiority over the male parent) to be significantly correlated at the 1% probability level for the number of productive tillers per plant (r=0.41**) and leaf area index (r=0.39**), whereas grain yield (r=-0.30*) was correlated with heterosis at the 5% probability level in the three-line F1 hybrids. When the analysis was based on hybrids with positive heterosis, significant correlations were observed for leaf area index (r=0.45*), number of productive tillers per plant (r=0.40*), and harvest index (r=0.77*) at the 5% probability level. SSR heterozygosity in the two-line hybrids ranged from 0.43 to 0.66, suggesting a moderate extent of genotypic divergence among the parental cultivars. Heterotic performance of the hybrids was highest for grain yield and percent spikelet fertility at 62% and 25.6%, respectively. However, the relationship between heterosis and molecular genetic diversity was usually weak for most of the traits studied in the two-line hybrids.
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