Identification of Sources of Resistance Against Charcoal Rot in Cowpea

Abstract

Cowpea [Vigna unguiculata (L.) Walp.] is an important socioeconomic crop in Brazil, mainly in the Northeast and more recently in the Midwest of Brazil. Charcoal rot caused by Macrophomina phaseolina (Tassi) Goid, is an important disease in semiarid regions, where edaphoclimatic conditions are favorable to the development of disease. The aim of this study was to evaluate the response of 100 cowpea lines to two isolates of M. phaseolina. The experiments were conducted in a completely randomized design, with five replications (two plants per pot). The main variables evaluated were lesion length and relative growth compared to control (RGCC). Among the evaluated accessions, 15% of the lines were resistant to isolate 59 and 11% of the lines were resistant to isolate CMM 2106 of M. phaseolina. Therefore, these accessions can be used as a source of resistance to M. phaseolina by farmers directly as new cultivars or in future hybridizations of cowpea genetic breeding programs.

Identification of resistant cowpea genotypes and aggressiveness of Macrophomina phaseolina isolates by diallel analysis

“…L80 showed the worst reaction to the pathogen, so it can be inferred that this line has a smaller number of resistance genes for these M. phaseolina isolates. Although these lines were previously selected as resistant, it is worth mentioning that in the previous work, only two isolates were used (Araújo et al., 2022). In the present study, only isolate 59, was used because the other isolate did not grow.…”

“…One hundred cowpea lines, donated by Embrapa Meio‐Norte, were previously assessed for resistance to charcoal stem rot when inoculated with two isolates (CMM 2106 and ISO59) of M. phaseolina (Araújo et al., 2022). Among these, 10 lines were selected for the present study (L08, L19, L24, L29, L48, L51, L63, L76, L80, L95).…”

“…As a pathogen with a wide range of hosts, prospecting sources of resistance to different M. phaseolina isolates is essential. In this study, we showed the reaction of lines that are potential sources of resistance to this disease (Araújo et al, 2022) when inoculated with different M. phaseolina isolates. It was possible to verify the predominance of horizontal resistance to charcoal rot; however, vertical resistance was also present.…”