Crossability of selected Progeny from interspecific crosses between Oryza Sativa and Oryza Glaberrima (Nericas)

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Sterility of F1 between Oryza sativa and Oryza glaberrima is well documented. It could be traced to the presence of sterility genes on Chromosomes 2, 3, and 6 of O. glaberrima as well as chromosome 6 of O. sativa. Biotechnological techniques were used to overcome the sterility barrier by Africa Rice Centre. This led to the development of New Rice for Africa (NERICAs). NERICA varieties differ in many characters and combining these characters into a desirable plant type will be easier through conventional crosses than repeating the original interspecific crosses. Some selected first and second generation upland NERICAs were, therefore, intercrossed to find out their level of cross compatibility and the extent of sterility in the NERICAs. All hybrids were highly sterile and showed significant differences in their seed set (0.6-33.09%). The direction of cross partly affected crossability in the NERICAs. Hybrids from crosses that maintained O. glaberrima cytoplasm showed significantly higher (p≤ 0.05) seed fertility than those that maintained O. sativa cytoplasm. Pollen fertility tests indicated reduced pollen viability in the hybrids. Seed set was improved (up to 65%) when hybrids were backcrossed to either NERICA parent. Raising a large F1 population through emasculation could result in increased F2 population. Ratooning the F1 plants could further increase F2 population. Cytoplasmic factors probably affected the degree of sterility in the NERICAs.
A thesis Submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology, in partial fulfilment of the requirement for the degree of Master of Science in Plant Breeding,