Browsing by Author "Gepts, Paul"

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    Inoculum sources and management of bean scab caused by Elsinoë phaseoli
    (UoEm, 2024-06-24) Masheti, Yona; Muthomi, James W.; Muiru, William M; Arunga, Esther E.; Gepts, Paul
    Bean scab caused by Elsinoë phaseoli is a major challenge to common bean cultivationin Kenya. However, knowledge about its epidemiology and management is limited.This study conducted three experiments in Kakamega, Kenya, evaluating scab inocu-lum sources and control options. The first experiment evaluated three different inoc-ulum sources over two seasons; bean crop residue caused the highest scab incidencein both the 2021 (62.1%) and 2022 (81.1%) seasons. The second experiment assessedthe effect of rotation history on scab over three seasons. Scab incidence consist-ently surpassed 90% within the first 30 days after planting in half-yearly rotated fieldsacross all seasons, while the disease was absent after planting in fields with no recenthistory of legumes. Fields rotated out of legumes consistently had the highest grainyield, averaging 1.5 t ha−1 over the seasons. Additionally, the rotation land treatmentdisplayed significantly more pods per plant during the 2021 (9.7), 2022a (9.8), and2022b (12.5) seasons. In the third experiment, the impact of five fungicides and fourcropping systems on bean scab was investigated over two seasons. Neither fungicidetreatments nor cropping systems had an effect on bean scab incidence even whenonly severe symptoms were considered. Carbendazim had the highest yield (1.9 t ha−1)outperforming the unsprayed control only in the 2022 season while none of the otherfungicides outperformed the control treatment in yield parameters in either season.This study emphasizes the challenge of managing bean scab without proper crop rota-tion and underscores the role of crop residue as a critical inoculum source.
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    QTL mapping for pod quality and yield traits in snap bean (Phaseolus vulgaris L.)
    (UoEm, 2024-08-12) Njau, Serah Nyawira; Gepts, Paul; Parker, Travis A.; Duitama, Jorge; Arunga, Edith Esther
    Pod quality and yield traits in snap bean (Phaseolus vulgaris L.) influence consumer preferences, crop adoption by farmers, and the ability of the product to be commercially competitive locally and globally. The objective of the study was to identify the quantitative trait loci (QTL) for pod quality and yield traits in a snap × dry bean recombinant inbred line (RIL) population. A total of 184 F6 RILs derived from a cross between Vanilla (snap bean) and MCM5001 (dry bean) were grown in three field sites in Kenya and one greenhouse environment in Davis, CA, USA. They were genotyped at 5,951 single nucleotide polymorphisms (SNPs), and composite interval mapping was conducted to identify QTL for 16 pod quality and yield traits, including pod wall fiber, pod string, pod size, and harvest metrics. A combined total of 44 QTL were identified in field and greenhouse trials. The QTL for pod quality were identified on chromosomes Pv01, Pv02, Pv03, Pv04, Pv06, and Pv07, and for pod yield were identified on Pv08. Co-localization of QTL was observed for pod quality and yield traits. Some identified QTL overlapped with previously mapped QTL for pod quality and yield traits, with several others identified as novel. The identified QTL can be used in future marker-assisted selection in snap bean.