Comparative virulence of bacterial blight (Xanthomonas campestris pv. vignicola) isolates and their effect on yield components of cowpea (Vigna unguiculata)

Abstract

The viruleiace of Ibadass, Ikeirne asid Kano isolates of bacterial blight pathogen and their effect on yield components were compared in cowpea cnltivars Ife Brown, TVx 3236 and 86D-721 artificially inoculated in the field. The isolates differed significantly (p< 0.05) in their virulence in each cultivar causing 6.3 - 33.8% disease incidence with associated disease severity ratings of 1.4 - 9.4. A significant area under the disease progress curve (AUDPC) was associated with each isolate/cultivar combination. The isolates caused significant reductions o f23.6-56.5% in number of pods/plant across the cultivars. Significant reductions of 7.6-13.8% and 12.1 - 20.8% were also recorded for pod length and number of seeds/pod, respectively. Yield depressions of 62.4%, 25.8% and 36.5% in Ife Brown; 64.9%, 13.1% and 29.4% in TVx 3236; and 62.3%, 5.4% and 38.1% in 86D-721, were associated with infections by Ibadan, Kano and Ikenne isolates of bacterial blight, respectively. Overall, Ibadan isolate was more virulent than Kano and Ikenne isolates which had comparable virulence in each of the cultivars.