The selection for resistance to charcoal rot in cowpea requires a better understanding of the responsible pathogen of the genus Macrophomina. The present study aims to morphologically characterize and determine the virulence of fungal isolates collected from 18 localities in two climatic zones of the country. The growth rate and coloration of the isolates cultivated in Petri dishes were evaluated. The isolates were then characterized for their pathogenicity by incorporating the inoculum into the culture substrate in the presence of a control. Thirty-six isolates exhibited rapid growth (>25 mm/day), 2 isolates showed slow growth (<20 mm/day), and 23 isolates had medium growth (20-25 mm/day), consisting of 42 isolates that were black and 19 that were gray. Seven isolates (Koubri-KomM11E3, Môgtédo-YiisYandM11, Yako-TilM19b, Dédougou-KomM30E1, Saria-TilM30a, Sapouy-KomM21b, Tenkodogo-TilM3b) were classified as highly pathogenic, 2 isolates (Dédougou-TilM2E2 and Farakoba-KomM16b) as moderately pathogenic, and 2 isolates (Livara2-KomM32E4, KamboinséTil M27b), in addition to the control, as weakly pathogenic. Considering the study areas, the isolates from the Sudano-Sahelian zone were found to be more pathogenic compared to those from the Sudanian zone. The morphological and pathogenic variabilities identified in this study represent a significant step in the implementation of control measures.

 

Key words: Macrophomina phaseolina isolates, charcoal rot, pathogenicity, cowpea, Burkina Faso.