Abstract
In Venezuela, pedigree analyses indicate that the rice varieties currently under cultivation are closely related. Effective breeding programs, based on knowledge of the genetic diversity of cultivars, are needed to broaden the genetic bases of rice germplasm in the country. In this study, we used a set of 48 simple-sequence-repeat (SSR) markers to assess the genetic diversity of 11 Venezuelan rice cultivars, released by the National Rice Breeding Program between 1978 and 2007. A total of 203 alleles were detected, the number of alleles ( NA ) per marker ranged from 2 to 9, with an average of 4.23. The average genic diversity ( H ) over all SSR loci for the 18 genotypes was 0.524, ranging from 0.105 to 0.815. Positive correlations were found between H at each locus, NA , the allele size range and the maximum number of repeats. Venezuelan cultivars showed lower H (mean = 0.37) and NA (total = 124, mean = 2.58) than the whole sample. UPGMA-cluster-analysis based on genetic distance coefficients clearly separated all the genotypes , and showed that the Venezuelan rice varieties are closely related. Molecular identification of 7 Venezuelan cultivars could be done with 9 primers pairs which produced 10 genotype-specific-alleles. Although the genetic diversity was low, SSRs proved to be an efficient tool in assessing the genetic diversity of rice genotypes. Implications of the low genetic diversity detected and relatedness of Venezuelan cultivars are discussed.
Highlights
We used a set of 48 simple-sequence-repeat (SSR) markers to assess the genetic diversity of 11 Venezuelan rice cultivars, released by the National Rice Breeding Program between 1978 and 2007
The limited use made of the rice genetic diversity available worldwide has been a concern in Latin America since the late 1980s
Venezuelan rice germplasm is represented by 11 irrigated cultivars/breeding lines (‘Araure1’, ‘Araure 4’, ‘Araure 50’, ‘Centauro’, ‘Cimarrón’, ‘Fonaiap1’, ‘Fonaiap 2000’, ‘Fundarroz PN-1’, ‘Línea 17’, ‘Palmar’ and ‘Venezuela 21’,) from the Venezuelan Rice Breeding Program at the National Institute for Agricultural Research (INIA) (Table 1)
Summary
SSRs are an excellent molecular marker system for many types of genetic analyses, including linkage mapping, germplasm surveys, and phylogenetic studies They have been used for characterizing genetic diversity in several crop species including sorghum SSRs have been used to assess the genetic diversity of both wild and cultivated species (Yang et al 1994; Gealy et al 2002; Ni et al 2002; Ren et al 2003; Sarla et al 2003; Yu et al 2003; Siwach et al 2004; Xu et al 2004; Brondani et al 2005; Jeung et al 2005; Neeraja et al 2005) These studies showed that SSR markers are efficient in detecting genetic polymorphisms and discriminating among genotypes
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