Phenotyping of Striga gesnerioides (Willd.) and Megalurothrips sjostedti (Trybom) resistance in cowpea (Vigna unguiculata (L.) Walp.) population in northern Ghana

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Parasitic weed Striga gesnerioides (Willd.) and flower Thrips (Megalurothrips sjostedti Trybom) are among the major constraints of cowpea (Vigna unguiculata (L.) Walp.) production. The single approaches used for their control appears to be highly insufficient. Host-Plant Resistance seems to have merit in efficiently and economically controlling these pests. The objectives of this study were to evaluate recombinant inbred lines developed between Striga and Thrips resistant parents, IT97K 499-35 and Sanzi respectively by Single Seed Descent (SSD), for Striga and Thrips resistance in Northern Ghana. The study also evaluated the promising Striga gesnerioides resistant lines for yield loss assessment. Studies involved field and pot screening under artificial inoculation. Twenty-seven (27) RILs out of the 251 RILs screened were completely resistant to Striga gesnerioides. The level of Thrips infestation was very low (0 to 11 flower Thrips per plot) making it difficult to rank the genotypes into the categories (resistant and susceptible). The damage index (scores) were therefore not recorded due to the total absence of flower Thrips in a good number of plots. The percentage reduction in the grain yield and dry biomass among the RILs was lower in the resistant RILs (0.55% to 3.08% and 1.11 to 7.7% respectively) than the susceptible ones (28.45% to 58.88% and 47.29% to 61.71% respectively). The negative effect of Striga infestation on cowpea grain yield and dry biomass can then be reduced when resistant genotypes are used.
A thesis submitted to the Department of Crop and Soil Sciences, Faculty of Agriculture, College of Agriculture and Natural Resources, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana in partial fulfilment of the requirements for the award of degree of Master of Philosophy in Plant Breeding.