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Makerere University (2019)

Genetics of Cowpea Resistance to Bruchid (Callosobruchus maculatus Fab.)

Weldekidan, Miesho Belay

Titre : Genetics of Cowpea Resistance to Bruchid (Callosobruchus maculatus Fab.)

Auteur : Weldekidan, Miesho Belay

Université de soutenance : Makerere University

Grade : DOCTOR OF PHILOSOPHY IN PLANT BREEDING AND BIOTECHNOLOGY 2019

Résumé
Cowpea Vigna unguiculata (L.) is an important indigenous legume crop providing dietary protein, minerals, carbohydrates, fats, vitamins and income to many people in Africa, Asia, and Central and South America. However, its production is limited by insect pests in general and bruchids attack in particular. Bruchids particularly Cowpea weevil (Callosobruchus maculatus) is the most destructive pest causing complete storage loses in quality and quantity. This makes the grain unfit for consumption, marketing and planting. To minimize losses due to bruchids infestations, the majority of farmers in Sub-Saharan Africa are using chemical pesticides. The use of pesticides however is expensive, pose health hazards to farmers and consumers, and their continuous use can lead to development of insecticide resistant bruchids. The use of resistant genotypes is, therefore, a promising alternative control method to the hazardous pesticides for the management of C. maculatus. However there is a paucity of information on genetics and sources of cowpea resistance to bruchids. Thus the objectives of this study were to : (i) Identify new sources of cowpea germplasm that are resistant to bruchids ; (ii) determine the biochemical traits involved in the resistance to bruchids ; (iii) determine the mode of inherence of resistance to cowpea bruchids and combining ability and (iv) identify candidate genes that control bruchids resistance traits in the cowpea association mapping panel using individual SNP markers. The study was conducted at Makerere University Agricultural Research Institute - Kabanyolo (MUARIK) between May 2015 and March 2018. One hundred and forty five (145) cowpea genotypes were evaluated, in a completely randomized design (CRD), for their reaction to C. maculatus. As a result 18 genotypes (ACC23 × 3B, NE39 × SEC4, ALEGI×5T, ACC2 × ACC12, 3B × 2W, SEC1 × SEC4, IT84s-2246, TVu-2027, IT97K-499-35, IT95K-207-15 and IT90K-76) were identified as being resistant, suggesting that they could serve as donor source/parent to breed for cowpea resistance to bruchids. To study the mechanism of cowpea resistance to bruchids, different biochemicals were extracted from seed coat and cotyledons of seven cowpea genotypes, four susceptible and three resistant to bruchids.

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