Inheritance, stability, and validation of provitamin a markers in striga hermonthica-Resistant maize inbred lines

A research thesis submitted to the Directorate of Research and Graduate Training for partial fulfillment of the requirement for the award of Master of Science in Plant Breeding and Seed Systems of Makerere University

The development of maize varieties combining Provitamin A (PVA), high yield, and Striga resistance is an effective and affordable strategy to contribute to food security in sub-Saharan Africa where maize is a staple food crop. There has been limited research on introgressing PVA genes into Striga-resistant maize genotypes. The objectives of this study were to: i) determine the mode of gene action controlling PVA carotenoid accumulation in Striga-resistant maize, ii) identify Striga-resistant maize hybrids with high PVA content and stable yield, and iii) validate the presence of PVA functional markers in offspring. Six elite, Striga-resistant inbred females were crossed with six high-PVA inbred males in a North Carolina Design II to generate 36 hybrids. The offspring were evaluated in four environments, including Namulonge, Kasese, Bukedea and Namutumba, following a 5x8 alpha lattice design with four hybrid checks. Results revealed that both additive and non-additive gene action control carotenoid accumulation in the present study, with a predominance of non-additive gene effects for PVA. Inbred lines CLHP00286, CLHP1259, CLHP 1162 were selected as PVA donors’ parents based on their significant and positive. Hybrids STR1004xCLHP0352 and STR1004xCLHP0046 were identified as Striga-resistant because they supported fewer Striga plants – were the highest yielding genotypes with a moderate PVA concentration of 5.48 and 5.77 μg/g, respectively. However, those two hybrids were not stable in terms of yield across all environments. Hybrid STR1007xCLHP0046, however, supported fewer Striga plants, had a yield of 4.52 T/ha, a PVA concentration of 4.52 μg/g, and was also stable. Gel-based marker systems of CrtRB1 and LCYE were used to screen the hybrids and PVA parents’ lines. Favorable allele of CrtRB1 primers namely CrtRB1-3-’TE were detected in 20 hybrids, confirming good levels of PVA carotenoids, this marker can be used in MAS in Uganda. Hybrids with favorable alleles of LCYE had the highest concentration of non-PVA carotenoids. These findings will contribute to the development of high-yielding striga resistant-PVA-rich maize hybrids varieties in Uganda.