Characterization of novel rice germplasm from West Africa and genetic marker associations with rice cooking quality
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Genetic resource enhancement is the foundation of any good breeding program. Landraces from West Africa, interspecifics between Oryza sativa and Oryza glaberrima and improved lines from the West African Rice Development Association and other research centers were introduced to the Beaumont Rice Research center for in situ evaluation and characterization. Beside the introduction of seeds, milled samples were also introduced for grain chemistry analysis. Field evaluation combined with physicochemical and molecular characterization revealed unique characteristics among African germplasm. New rice for Africa (NERICA) lines performed well in the USA environment. Varieties like Nerica 2, Nerica 3, Nerica 4, and Nerica 5 need more attention because of their superior performance in yield and grain quality. Landraces did not perform well due to their height and late maturity and their resulting problems with lodging. The rapid visco analyzer RVA profiles showed that the cultivar Jaya has unusually strong paste viscosity features. Comparing West Africa samples grown in Cote d??????Ivoire with those grown in Texas, parameters like AA, ASV, Hot, Cool, and CT were not stongly affected by the environment. According to the Stbk value, cultivars grown in Cote d??????Ivoire will cook softer than when they were grown in Texas. The lack of the environmental effect is somewhat surprising considering the difference in latitude, soil types, weather patterns, and management practices between the two locations. Apparent amylose is a key element to characterize a rice cultivar; however certain varieties like Cocodrie and Dixiebelle have similar apparent amylose content but dramatically different functional qualities. A population derived from Cocodrie and Dixiebelle was developed for genotypic and phenotypic analysis of grain chemistry traits that affect functionality. It was concluded that the amount of soluble amylose in the grain had a significant effect on flour pasting properties, even when total apparent amylose content did not vary. Marker association studies revealed that the Waxy microsatellite and the Waxy exon 10 SNP markers were associated with soluble amylose content and RVA characteristics. These markers will speed up the development of new rice cultivars with desirable quality characteristics in West Africa and in the USA.