Effect of soil pH on the pathogenesis of Heterodera glycines and Meloidogyne incognita on Glycine max genotypes

Abstract The effect of soil pH 4.3, 4.6, and 5.9 on the pathogenicity of Heterodera glycines and Meloidogyne incognita on acid soiladapted soybean genotypes (Davis and PI 416937) was investigated in three glasshouse experiments over 28 days after inoculation with 0 or 1000 (Experiments 1 and 2) and 0 or 5000 (Experiment 3) second-stage juveniles. Although nematodes of both species infected both genotypes at all of the soil pH, the numbers decreased with decreasing soil pH. Both genotypes seem to be better hosts for M. incognita than for H. glycines, Davis more so than PI 416937. Both nematodes decreased shoot weight at high inoculum levels, indicating that H. glycines may be more pathogenic than M. incognita. Nematode development after infection of roots was not affected by soil pH or by genotypes. Overall, the results suggest that adaptation of these nematodes should be considered in breeding programmes to develop low pH tolerant soybean cultivars.