Differential heterosis in a natural population of Asian wild rice (Oryza rufipogon Griff.) due to reproductive strategy and edge effect

Authors: Kuroda, Yosuke1; Urairong, Hathairat2; Sato, Yo-Ichiro3

Source: Genetic Resources and Crop Evolution, Volume 52, Number 2, March 2005 , pp. 151-160(10)

Publisher: Springer

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Asian common wild rice (Oryza rufipogon) is a polycarpic perennial plant with a mixed inbreeder/outbreeder strategy. Seeds and clones are both reproductive components of the population. However, when collected in the flowering stage, the two differ substantially as to whether they have experienced natural selection directly or not. This study is aimed at evaluating mechanisms for the survival of a population by comparing genetic structure among subpopulations that are classified in terms of: (1) reproductive systems (clones or seeds); and also (2) location (fringe or inside). First, the genotypes determined at seven SSR (Simple Sequence Repeat) loci showed that parameters of observed heterozygosity (HO) and outcrossing rate (t) were clearly higher in clones (HO = 0.609, t = 82.4%) than in seeds (HO = 0.346, t = 35.5%), although the two had approximately the same values for the number of alleles (A) and expected heterozygosity (HE)(A = 4.43 in both clones and seeds, HE = 0.709, 0.692 in clones and seeds, respectively). This result indicates that the individuals showing ’heterosis’, with high numbers of heterozygous loci and outcrossing rates, are more likely to survive in the natural habitat. Secondly, parameters of observed heterozygosity and outcrossing rates were lower for seeds from the fringe area (HO = 0.238, t = 24.6%) compared to seeds from the inside area (HO = 0.443, t = 60.7%), although values were similar in clones of both the fringe and inside areas. This result suggests that the ’edge effect’ might be due mainly to the restriction of wind strength in fringe area of the forested swamp.

Keywords: Heterosis; Oryza rufipogon; Reproductive systems; SSR (Simple Sequence Repeat); Sampling locations

Document Type: Research Article

DOI: http://dx.doi.org/10.1007/s10722-003-4451-z

Affiliations: 1: Graduate School of Asian and African Area Studies, Kyoto University, Sakyo-ku, Kyoto, 606-8501, Japan, 2: Pathum-Thani Rice Research Center, Pathum-Thani, 12110, Thailand, 3: Faculty of Agriculture, Shizuoka University, Ohya, Shizuoka, 422-8259, Japan,

Publication date: March 1, 2005

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