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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

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The surface of agricultural soils affected with salinity causes degradation and reduction of crop production, negatively impacting the economy of farmers. The objective of this research was to determine the effect of water quality and soil salinity on rice production in the sub-basin of the Yaguachi River, Ecuador. For this purpose, 99 soil samples were georeferenced and analysed over an area of 19 027 ha, as well as water samples representative of the area under study. Soil pH and electrical conductivity (EC) maps were produced and a regression analysis between EC and rice yield was performed on 34 producer plots. The predominant texture of the soils was found to be clayey, with an average pH of 6.73; The 38.4 % of the samples had an EC between 3.8 and 7.1 dS m-1. Rice yield gradually decreased as it was grown in soils with higher salinity and 26.81 % of the yield loss was found to be attributed to the increase in EC. The salinity of the irrigation water and other quality indicators such as the percentage of soluble sodium (Na+) and the sodium adsorption ratio (RAS) classified the water as severely restricted for use. However, given that crop yields did not show as drastic a reduction as expected, it can be said that the rice plant responds to the conditions of the canton of San Jacinto de Yaguachi as moderately tolerant to salinity.