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Central University of Technology, Free State (2020)

Genetic Diversity And Screening Of Cowpea (Vigna unguiculata L. Walp.) Genotypes For Drought Tolerance In South Africa

Nkomo, Gabriel, Vusanimuzi

Titre : Genetic Diversity And Screening Of Cowpea (Vigna unguiculata L. Walp.) Genotypes For Drought Tolerance In South Africa

Auteur : Nkomo, Gabriel, Vusanimuzi

Université de soutenance : Central University of Technology, Free State

Grade : DOCTOR TECHNOLOGIAE : AGRICULTURE 2020

Résumé partiel
A survey was carried out to assess the farmers’ production constraints, traits and preferred cowpea varieties. A semi-structured questionnaire was used in a survey in Buhera District, Zimbabwe, in March and April of 2018. Women farmers dominated the survey as they were 52% of the surveyed population, while men occupied 48% of the total population. All participants concurred that cowpeas were used for domestic consumption. Eighty-three percent of the farmers cited shortage, unavailability, and cost of fertiliser, 16% of the farmers acknowledged that they do not have access to quality seed, and 1% cited labour as the major constraints in cowpea production. Farmers ranked heat (86%), drought (10%), and soil fertility (4%) as the most important abiotic factors. Ninety-one percent of the farmers’ ranked rust as the major disease, while 2% ranked storage rot, 1% ranked anthracnose, and 1% ranked downy mildew. Eighty-one percent of the farmers ranked aphids as the main pests, while 3% ranked thrips, 3% ranked legume borers, and 2% ranked pod borers. Fifty-two percent of the farmers preferred varieties that are resistant to diseases such as rust, whereas 48% were not concerned about diseases. For qualitative traits, 50% of the farmers had no specific colour preference, 32% preferred white colour, 14% brown colour, 3% red colour, and 1% tan colour. Ninety-four percent of interviewed farmers were not concerned about the pod shape, 3% preferred the kidney shape, 2% preferred the spherical shape and 1% preferred the globular shape. Ninety-nine percent of farmers agreed that they needed high yielding varieties per unit area and only 1% were unsure. For quantitative traits such as grain size, pod size, plant height, and head size, the preferences of farmers varied. Forty-four percent of the farmer respondents preferred larger cowpea grains, while 56% were not concerned about the size of the grain. A paltry 2% of the farmers were interested in pod size, while 98% did not regard it as important. Thirteen percent of the farmers were interested in climbing varieties, while 87% considered high grain yield as of the utmost importance. The top ranked accessions were CBC1, IT 18, and “Chibundi Chitsvuku”, respectively, while the least ranked was “Kangorongondo”. The survey showed that there is a need to breed for both biotic and abiotic factors, such as drought and moisture stress, as well as against pests and diseases. In order to assess the genetic diversity and population structure among cowpea accessions, diversity arrays technology (DArTSeq) genotype by sequencing technique was used. A total of 85 cowpea accessions (45 from the International Institute of Tropical Agriculture [IITA], 25 from South Africa, and 15 from Zimbabwe) were investigated in this study using 284 single-nucleotide polymorphisms (SNPs). Fifty-one percent of SNPs were polymorphic across the 85 accessions and fulfilled the selection criteria.

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Page publiée le 24 juin 2022