Resistance response of cowpea genotypes to scab disease

Abstract

Cowpea is among the ancient crops known to man globally. After cereals, grain legumes are the most important family of agricultural crop species worldwide. The crop has been attributed to several production limitations such as pests and diseases, soil infertility, drought and water logging. Cowpea scab is one of the major serious fungal diseases in cowpea production, capable of causing yield losses of up to 100%. The research study directed to determine the resistance response of fifty one (51) cowpea genotypes assessed for two rain seasons at Busitema University Faculty of Agriculture and Animal Sciences (Arapai Campus), in Soroti district using a 5 by 11 alpha Lattice design with three replications. The analysis of variance showed significant differences (P<0.001) for grain yield, scab severity, scab incidence, and area under disease progress curve (AUDPC) across genotypes, season and genotype by season interaction except scab incidence for genotype by season interaction. The mean grain yield of 563.4 Kg ha was recorded across the cowpea genotypes with genotype, Par47*LGC074/30 having the highest grain yield of 911.1Kg ha-1. Most of the cowpea genotypes with cowpea scab resistance had low grain yield, with the lowest grain yield recorded by genotype MUAL19-143, Par47*LCG074/29, NAROCOWPEA5, MUALMP-17, MUAL19-118-4, MUALMP-12, MUALMP-42, NAROCOWPEA 2. Correspondingly the cowpea genotypes had low scab incidence except in genotypes MUALDT-05, MUALCP-21, Bruc2019B-470, and Eblate*NE51 respectively. The area under disease progress curve was equally low except in genotypes MUAL19-119, Bruc2019B-17, MUALDT-05, MUALCP-21, Bruc2019B-470 and Eblate*NE51 respectively. The Scab resistant cowpea genotypes can be used as parental breeding lines for development of scab resistant cultivar with farmer preferred traits. Grain yield had a significant positive correlation damage index on the pods (r = 0.336, p<0.001), scab incidence on pods (r = 0.347, p<0.001), scab severity on pods (r = 0.330, p<0.001). The identified cowpea genotype such as Eblate*NE5, NAROCOWPEA 2, NAROCOWPEA 4, MUAL19-118-4, Par47*LGC074/29, NAROCOWPEA 3, and others (Table 6) with scab resistance capability as parental lines in the cowpea breeding program to develop cultivars with improved yield and extensive horizontal resistance to the scab disease. Key words: Response, resistance, cowpea scab disease, incidence, severity