Characterization of adaptability components of Brazilian isolates of Macrophomina pseudophaseolina

Macrophomina pseudophaseolina is a new Macrophomina species reported on different crop and weed species in Brazil, India and Senegal, but to date there are no studies about its adaptability components. In this work, a collection of 62 M. pseudophaseolina isolates obtained from roots of the weed species Trianthema portulacastrum and Boerhavia diffusa collected in Northeastern Brazil, was used to: (a) study the effect of temperature and salinity on mycelial growth, (b) to determine their sensitivity to the fungicide carbendazim and (c) to assess their aggressiveness on melon and watermelon seedlings. Results showed variability among M. pseudophaseolina isolates. The optimum temperature for mycelial growth ranged between 26.4 and 38.1ºC. NaCl reduced the in vitro growth of all isolates, which were also highly sensitive to the fungicide carbendazim, exhibiting EC₅₀ values ranging from 0.013 to 0.089 mg/L a.i. Disease severity values on melon and watermelon seedlings showed that M. pseudophaseolina isolates were more aggressive in melon than in watermelon. Information about adaptability components of M. pseudophaseolina obtained in this study could be incorporated on breeding programs for melon and watermelon crops.