Pathogenicity of Macrophomina phaseolina in cultivars and accessions of Cucumis melo

Abstract

The productivity of melon crops is affected by several soilborne pathogens. The objective of this work was to assess the susceptibility of different melon hybrids to infection by the fungus Macrophomina phaseolina. Seeds of 42 melon genotypic accessions were sown in 750 mL plastic vessels with a mixture of Tropstrato® substrate and Ecofertil® compost in a 3:1 ratio. Inoculations were carried out 10 days after sowing using toothpicks colonised by the pathogen. A completely randomised design with 42 treatments and four replications was used in two successive trials. Plant health was scored using a 0–5 diagrammatic scale, 45 days after sowing. All melon genotypes developed disease symptoms but susceptibility varied across accessions. While 42.8% of tested accessions were highly susceptible, 50.0% were susceptible, and 7.2% were moderately resistant. No genotypes were resistant to M. phaseolina. Although the results presented here may lower the overall disease severity in melon crops, melon breeding programs need to identify sources of resistance to this pathogen.