NATURE OF RESISTANCE OF COWPEA ALECTRA VOGELII INFESTATION

Alectra vogelii (benth) is parasitic weed which causes significant yield reductions in cowpea ( Vigna unguiculata Walp) in Africa. The objective of this study was to identify the type of gene action controlling the trait for resistance to Alectra vogelii in cowpea and estimate the heritability of the trait. Seven genotypes of cowpea were mated in half diallel and their F2 progeny, including parents, were evaluated for reaction to Alectra vogelii infection in the field in two locations at Ilonga and Hombolo Agriculture Research Stations. Highly significant (P < 0.001) differences were found for Alectra emergency and infestation at Ilonga. General combining ability (GCA) and specific combining ability (SCA) effects for Alectra shoot emergency and infestation were significant (P < 0.05). The estimate of Baker\u2019s ratio for Alectra shoot emergency and infestation were 0.62 and 0.66, respectively. This indicates that both additive and non-additive gene actions influenced the trait for resistance to Alectra emergency and infestation. Narrow sense heritability estimates were 41.28 and 44.39 for shoot and emergency, respectively. These results imply that introgression of a desirable trait in an elite genotype would involve careful crossing with a resistance genotype, accompanied by selection in the advanced population.Alectra vogelii (benth) est une herbe parasite qui engender des reductions significatives dans les rendements du ni\ue9b\ue9 ( Vigna unguiculata Walp) en Afrique. L\u2019objectif de la pr\ue9sente \ue9tude \ue9tait d\u2019identifier le type d\u2019action de g\ue8ne controllant la r\ue9sistance \ue0 Alectra vogelii chez le ni\ue9b\ue9 et d\u2019estimer les valeurs d\u2019h\ue9ritabilit\ue9. Sept g\ue9notypes de ni\ue9b\ue9 ont \ue9t\ue9 crois\ue9s selon le mode half diallel et leurs descendants F2, ainsi que les parents, ont \ue9t\ue9 \ue9valu\ue9s pour leur reaction face \ue0 \u2018linfestation en plein champs du Alectra vogelii dans les stations de recherch\ue9 agricole de Ilonga et Hombolo. Des differences tr\ue8s significatives (P < 0,001) ont \ue9t\ue9 observ\ue9es pour l\u2019\ue9mergence, la croissance v\ue9g\ue9tative et l\u2019infestation de Alectra \ue0 Ilonga. L\u2019habilet\ue9 \ue0 la combinaison g\ue9n\ue9rale (GCA) et sp\ue9cifique (SCA) pour l\u2019\ue9mergence, la croissance v\ue9g\ue9tative et infestation de Alectra \ue9taient significative (P < 0,05). les valeurs du ratio de Baker pour l\u2019\ue9mergence, la croissance v\ue9g\ue9tative et l\u2019infestation de Alectra \ue9taient respectivement de 0,62 et 0,66. Ceci indique que les deux effets de g\ue8ne; additif et non-additif sont responsables de la r\ue9sistance \ue0 l\u2019\ue9mergence, la croissance v\ue9g\ue9tative et \ue0 l\u2019infestation de Alectra. Les valeurs de l\u2019h\ue9ritabilit\ue9 au sens strict \ue9taient respectivement de 41,28 et 44,39 pour la croissance v\ue9g\ue9tative et l\u2019\ue9mergence. Ces r\ue9sultats indiquent que l\u2019introgression d\u2019un caract\ue8re d\ue9sirable dans un g\ue9notype \ue9lite n\ue9cessiterait des croisements avec un genotype r\ue9sistant, suivi de selection au cours des g\ue9n\ue9rations avanc\ue9es

Effects of yellow witchweed (Alectra vogelii) strains on performance of improved cowpea (Vigna unguiculata (L) Walp.) Genotypes

Research articleWitchweed (Alectra vogellii) has continuously remained a great challenge for cowpea production in sub-Saharan Africa. Developing resistant and stable high yielding cowpea genotypes in Alectra infested areas requires evaluation of available cowpea germplasm for resistance against the weed. To achieve this, an experiment was conducted in the screen house at Ilonga Agricultural Research Institute (ARI- Iloga), Tanzania in 2017 to determine how selected cowpea genotypes fair in soils infested with different Alectra strains. The experiment comprised of two factors namely A. vogellii strains as the main factors and cowpea genotypes as sub-factors and was carried out as a spilt plot experiment arranged in randomized complete block design with three replications. Results revealed significant differences amongst cowpea genotypes on days to first Alectra emergence and number of emerged Alectra shoots. The cowpea genotypes B 301, Mkanakaufiti, Vuli AR1, Vuli AR2 and Vuli-1 allowed Alectra emergence at 42.83, 37.25, 36.75, 37.42 and 33.17 days after planting (DAP), respectively. There were variations in number of Alectra shoots supported by genotypes, as 1.0, 5.0, 4.0, 5.0 and 14.0 for B301, Mkanakaufiti, Vuli AR1, Vuli AR2 and Vuli-1, respectively. The genotype B 301 recorded the lowest number of Alectra shoots, reached 50% flowering earlier and had the highest seeds and pods weight and highest number of pods per plant. Contrarily, the genotype Vuli-1 produced the highest number of seeds per pod and was the first to reach 95% physiological maturity. The genotype B 301 was identified to possess a high level of resistance to A.vogelii infestation and accordingly was deemed as a useful source of resistance genes in cowpea resistance breeding programs

Effects of yellow witchweed (Alectra vogelii) strains on performance of improved cowpea (Vigna unguiculata (L) Walp.) Genotypes

Research articleWitchweed (Alectra vogellii) has continuously remained a great challenge for cowpea production in sub-Saharan Africa. Developing resistant and stable high yielding cowpea genotypes in Alectra infested areas requires evaluation of available cowpea germplasm for resistance against the weed. To achieve this, an experiment was conducted in the screen house at Ilonga Agricultural Research Institute (ARI- Iloga), Tanzania in 2017 to determine how selected cowpea genotypes fair in soils infested with different Alectra strains. The experiment comprised of two factors namely A. vogellii strains as the main factors and cowpea genotypes as sub-factors and was carried out as a spilt plot experiment arranged in randomized complete block design with three replications. Results revealed significant differences amongst cowpea genotypes on days to first Alectra emergence and number of emerged Alectra shoots. The cowpea genotypes B 301, Mkanakaufiti, Vuli AR1, Vuli AR2 and Vuli-1 allowed Alectra emergence at 42.83, 37.25, 36.75, 37.42 and 33.17 days after planting (DAP), respectively. There were variations in number of Alectra shoots supported by genotypes, as 1.0, 5.0, 4.0, 5.0 and 14.0 for B301, Mkanakaufiti, Vuli AR1, Vuli AR2 and Vuli-1, respectively. The genotype B 301 recorded the lowest number of Alectra shoots, reached 50% flowering earlier and had the highest seeds and pods weight and highest number of pods per plant. Contrarily, the genotype Vuli-1 produced the highest number of seeds per pod and was the first to reach 95% physiological maturity. The genotype B 301 was identified to possess a high level of resistance to A.vogelii infestation and accordingly was deemed as a useful source of resistance genes in cowpea resistance breeding programs