Genetic Structure of Wild Rice Oryza Glumaepatula Populations in Three Brazilian Biomes Using Microsatellite Markers

Abstract

The existence of Oryza glumaepatula is threatened by devastation and, thus, the implementation of conservation strategies is extremely relevant. This study aimed to characterize the genetic variability and estimate population parameters of 30 O. glumaepatula populations from three Brazilian biomes using 10 microsatellite markers. The levels of allelic variability for the SSR loci presented a mean of 10.3 alleles per locus and a value of 0.10 for the average allelic frequency value. The expected total heterozygosity (H(e)) ranged from 0.63 to 0.86. For the 30 populations tested, the mean observed (H(o)) and expected heterozygosities (H(e)) were 0.03 and 0.11 within population, respectively, indicating an excess of homozygotes resulting from the preferentially self-pollinating reproduction habit. The estimated fixation index ( (IS) ) was 0.79 that differed significantly from zero, indicating high inbreeding within each O. glumaepatula population. The total inbreeding of the species ((IT) ) was 0.98 and the genetic diversity indexes among populations, (ST) and (ST), were 0.85 and 0.90, respectively, indicating high genetic variability among them. Thus, especially for populations located in regions threatened with devastation, it is urgent that in situ preservation conditions should be created or that collections be made for ex situ preservation to prevent loss of the species genetic variability.

Genetic structure of Brazilian wild rice (Oryza glumaepatula Steud., Poaceae) populations analyzed using microsatellite markers

“…The average apparent outcrossing rate is in agreement with the estimate obtained by Brondani et al (2005) for O. glumaepatula, namely t a = 0.135. The low t a estimate found in our study is a consequence of the high intrapopulation coefficient of inbreeding detected (average f = 0.750, Table 4).…”

“…These indices were superior to those reported by Buso et al (1998) (H o = 0.00 to 0.025 and H e = 0.00 to 0.21) and Akimoto et al (1998) (H o = 0.03 and H e = 0.044) with isozyme markers, probably due to the high degree of heterozygosity and higher allele number detected by the microsatellite markers in our study. However, Brondani et al (2005) found lower values for these indices (H o = 0.027 Karasawa et al 405 and H e = 0.113) with O. glumaepatula populations investigated using microsatellite markers (Table 7). The difference between our results and those of Brondani et al could be due to both the higher number of plants per population sampled in our study (an average of 27.4 in our study compared to 13.8 by Brondani et al) and also to the greater number of Amazon biome populations sampled by us.…”

“…(Poaceae) which has an AA genome, of the same type as the cultivated Oryza sativa, and occurs widely in Latin America from 23°N in Cuba to 23°S in Brazil (Vaughan et al, 2003). The Brazilian O. glumaepatula populations are found in the extensive river basins of the Amazon and Pantanal Matogrossense and the smaller river basins which occur in the states of Goiás and Tocantins (Oliveira, 1994;Brondani et al, 2005).…”

“…Molecular markers have been used for germplasm characterization, phylogenetic and population genetic studies in O. glumaepatula and several other Oryza species (Akimoto et al, 1998;Buso et al, 1998;Ge et al, 1999;Doi et al, 2000;Bautista et al, 2001;Oliveira, 2002;Gao et al, 2002aGao et al, , 2002bGao, 2004;Brondani et al, 2005). Buso et al (1998) used isozyme and random amplified polymorphic DNA (RAPD) markers to estimate genetic parameters for four South American O. glumaepatula populations and found high values for interpopulation differentiation.…”

“…Brondani et al (2005) used ten microsatellite markers to analyze 30 O. glumaepatula populations from the Brazilian Amazon, Cerrado and Pantanal biomes, assessing six to 24 plants per population, and found high genetic diversity between populations but high inbreeding levels within populations, suggesting a preferentially self-pollinating breeding system. We used eight microsatellite markers to estimate gene flow and genetic structure and analyze within and between population genetic variation in eleven Brazilian O. glumaepatula populations and to address specific strategies for the in situ and ex situ conservation of this species.…”