IDENTIFICATION OF IMPROVED RICE VARIETIES USING DNA MOLECULAR TECHNIQUES

Abstract

The New Rice for Africa (NERICA) and Transgressive Segregate (TGS) which were developed from the two cultivated rice species O. sativa L. and O. glaberrima Steud. genomes are well adapted to the African rice growing ecology, offering opportunities for improvement in rice breeding. NERICA 1 and TGS 25 were crossed in the screen house to produce the first filial (F1) progenies. Seeds from F1 plant were then planted in a hydromorphic environment to produce the second filial (F2) progenies. Yield and yield component traits were studied on the field while leaf samples of each plant were taken for DNA extraction and isolation, amplification by polymerase chain reaction (PCR) with simple sequence repeat (SSR) markers, electrophoresed on agarose gel and analysed using numerical taxonomy system (NTSYS). Protein content of the F2 progenies was determined by kjeldahl method. Yield and its component traits analysed were seed size, plant height (Ht), fertility, tillering ability (Ti), heading days (HD), panicle length (PnL), panicle branching (Pbrch), 1000-grain weight, leaf blade colour (LBC), basal leaf sheath colour (BLSC). F1 seeds were homogenous and heterozygous. The segregation pattern observed for F2 progenies was transgressive. There were variations among the fifty-eight F2 progenies with respect to the phenotypic traits that were evaluated with 66% having phenotypic characteristics similar to TGS 25 and 94% of the progenies were similar genetically to NERICA 1. The genetic grouping has 93% coefficient of similarity as compared with 39% in the phenotypic grouping. Phylogenetic analysis revealed that over 50% of the F2 progenies were agronomically better and more than 25% had better protein content than the parents. There were sixteen putative Quantitative Trait Loci (QTL) residing in 6 regions of the rice genome. Using Single Point Analysis, Simple Interval Mapping and Composite Interval Mapping, nine (56%) of the 16 traits observed for yield and its component. Quantitative Trait Loci were not detected for seven (44%) traits. Eleven F2 progenies with better yield and protein content as compared with NERICA 1 and TGS 25 were identified in these studies.