The genetic base of brazilian irrigated rice (Oryza sativa L.) cultivars

Abstract

We analyzed the genealogy of 42 irrigated rice varieties recommended for cultivation in Brazil from 1980 to 1992. We observed that 68% of the gene pool analyzed were derived from only 10 ancestors. Taking into account the cultivars most frequently grown in the main rice-producing states, we observed seven ancestors more often in the pedigrees, which are responsible for 70% of the genes. For this reason the genetic basis of the Brazilian irrigated rice cultivars should be broadened to overtake the yield plateau and to surpass the genetic vulnerability. We suggest four alternatives to broaden the genetic basis: a) use of genetically divergent parents and adequate characteristics introduced front other breeding programs; b) use of traditional varieties in multiple crosses with inbred elite lines; c) use of synthesized populations, with large genetic basis, through the use of male-sterile gene, and conduction under recurrent selection, and d) use of wild species of rice, maitily Oryza glumaepatula