Browsing by Author "Oloka, Bonny M."

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    Combining ability and heritability analysis of sweetpotato weevil resistance, root yield, and dry matter content in sweetpotato
    (Frontiers Media S.A., 2022-09) Mugisa, Immaculate; Karungi, Jeninah; Musana, Paul; Odama, Roy; Alajo, Agnes; Chelangat, Doreen M; Anyanga, Milton O; Oloka, Bonny M.; Gonçalves dos Santos, Iara; Talwana, Herbert; Ochwo-Ssemakula, Mildred; Edema, Richard; Gibson, Paul; Ssali, Reuben; Campos, Hugo; Olukolu, Bode A; Guilherme; Yencho, Craig; Yada, Benard; da Silva Pereira, Guilherme; Yencho, Craig
    Efficient breeding and selection of superior genotypes requires a comprehensive understanding of the genetics of traits. This study was aimed at establishing the general combining ability (GCA), specific combining ability (SCA), and heritability of sweetpotato weevil (Cylas spp.) resistance, storage root yield, and dry matter content in a sweetpotato multi-parental breeding population. A population of 1,896 F1 clones obtained from an 8 × 8 North Carolina II design cross was evaluated with its parents in the field at two sweetpotato weevil hotspots in Uganda, using an augmented row-column design. Clone roots were further evaluated in three rounds of a no-choice feeding laboratory bioassay. Significant GCA effects for parents and SCA effects for families were observed for most traits and all variance components were highly significant (p ≤ 0.001). Narrow-sense heritability estimates for weevil severity, storage root yield, and dry matter content were 0.35, 0.36, and 0.45, respectively. Parental genotypes with superior GCA for weevil resistance included “Mugande,” NASPOT 5, “Dimbuka-bukulula,” and “Wagabolige.” On the other hand, families that displayed the highest levels of resistance to weevils included “Wagabolige” × NASPOT 10 O, NASPOT 5 × “Dimbuka-bukulula,” “Mugande” × “Dimbuka-bukulula,” and NASPOT 11 × NASPOT 7. The moderate levels of narrow-sense heritability observed for the traits, coupled with the significant GCA and SCA effects, suggest that there is potential for their improvement through conventional breeding via hybridization and progeny selection and advancement. Although selection for weevil resistance may, to some extent, be challenging for breeders, efforts could be boosted through applying genomics-assisted breeding. Superior parents and families identified through this study could be deployed in further research involving the genetic improvement of these traits.
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    The use of multiplexed simple sequence repeat (SSR) markers for analysis of genetic diversity in African rice genotypes
    (African Journal of Biotechnology, 2015) Oloka, Bonny M.; Lamo, Jimmy; Rubaihayo, Patrick; Gibson, Paul; Vorster, Juan
    Rice is an emerging food and cash crop in Eastern Africa. Thousands of germplasm accessions have been introduced from major rice breeding centers, such as the International Rice Research Institute (IRRI), and Africa Rice but the genetic variability among the introduced rice germplasm is unknown. Knowledge on genetic diversity would be useful in designing measures for comprehensive breeding and conservation. To address this knowledge gap, 10 highly polymorphic rice simple sequence repeat (SSR) markers were used to characterize 99 rice genotypes to determine their diversity and place them in their different population groups. The SSR markers were multiplexed in 3 panels to increase their throughput. An average of 15.9 alleles was detected, ranging from 6 alleles detected by marker RM7 to 30 by marker RM333. The UPGMA dendogram based on Nei’s genetic distance cluster analysis, revealed 5 genetic groups among the genotypes tested. Analysis of molecular variance indicated that 97% of the diversity observed was explained by differences in the genotypes themselves, and only 3% was due to the sources from which the genotypes were obtained. This study sets the stage for further diversity analysis of all the available germplasm lines using SSR markers to ensure effective utilization and conservation of the germplasm.