GENETIC DIVERSITY ASSOCIATED WITH AGRONOMIC TRAITS AND BIOTIC STRESSES USING SSR MARKERS IN SOME EGYPTIAN RICE GENOTYPES

Abstract

Genetic diversity underlies the improvement of crops by plant breeding. In Egypt, pedigree analyses indicate that the rice varieties currently under cultivation are closely related in there genetic background. Effective breeding programs, based on the information about of the genetic diversity of cultivars, are needed to broaden the genetic bases of local rice germplasm in the country. The present study has been conducted to evaluate the pattern, type and extent of genetic variability and relatedness among some rice varieties and new promising lines of Egypt based on important agronomic traits and some biotic stresses of some common diseases using simple-sequence-repeat (SSR) markers. In this study, we used a set of twelve SSR markers to assess the genetic diversity of 22 Egyptian rice cultivars and new promising lines, which released by the National Rice Breeding Program between years of 1975 and 2010. The 12 microsatellite markers used in this study produced a total of 73 alleles. The number of alleles per marker ranged from 3 (RM282) to 9 (RM488), with an average of 6.08. The polymorphism information content (PIC) values were high for all microsatellites with average of 0.588 and ranged from a low of 0.345 for RM249 to a high of 0.716 for RM488 and RM144. UPGMA-cluster-analysis based on genetic distance coefficients clearly separated all the genotypes, and showed that the Egyptian rice varieties are closely related. 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 relative relationship among Egyptian varieties are discussed. Varieties like Giza177, Sakha 102 and Sakha 103 are still resistant for most of the biotic stresses and become good sources for biotic stress resistance relating to different disease blast in the national breeding program.