Microsatellites and agronomic traits for assessing genetic relationships among 18 New Rice for Africa (NERICA) varieties

The Africa Rice Center ( WARDA) has developed several interspecific rice varieties by crossing the high yielding Asian rice ( Oryza sativa subsp. japonica) with the locally adapted African rice ( Oryza glaberrima). Eighteen varieties were named with the prefix NERICA ( New Rice for Africa) but their genetic difference and patterns of relationship is largely unknown. A total of 102 polymorphic microsatellite markers were used to genotype 18 NERICAs. A subset of seven NERICAs ( NERICA 1 to 7) was further characterized for 10 agronomic traits. The microsatellites data revealed no genetic difference between NERICA 8 and 9. The absence of genetic distance and identical SSR haplotype distribution ( banding pattern) observed between NERICAs 8 and 9 is highly likely to be due to lack molecular difference at the DNA level but the possibility for seed admixture remains to be explored. This study, however, revealed the presence of a wide range of genetic differences among all other NERICAs, with the highest being between NERICA 6 and 17. Cluster and principal component analyses of the SSR data revealed distinct separation of NERICA 1 to 7 from NERICA 8 to 18. The possible reasons for such separation and the implications for breeding programs are discussed.