Mejoramiento de la tolerancia al calor y a la desecación de tres nematodos entomopatógenos

Entomopathogenic nematodes (EPN) have potential to be used as biological control agents against white grubs (Phyllophaga spp.), but high temperatures and low water activity (A_W) may restrict their usefulness. The objective of this work was to generate lines tolerant to heat and desiccation of three species of EPN (Steinernema glaseri Steiner strain NC, Steinernema riobrave Cabanillas, Poinar and Raulston, and Heterorhabditis bacteriophora Poinar strain NC1). The treatments for selection of heat tolerance were applied to infective juveniles (IJ) reared in third-instar larvae of Galleria mellonella in six successive generations, at 25, 30, and 35°C for 48 h. For selection of desiccation tolerance, water activities of 0.86, 0.90, 0.97, and 1.0 were also applied for 48 h to IJ obtained from generations F1 to F6. As water activity decreased, survival also decreased. After the F3, S. glaseri became the most tolerant to desiccation, followed by S. riobrave. At the lowest A_W, these nematodes showed 45.6 and 33.8% survival, respectively. After the F3, the three species also increased their tolerance to high temperatures, especially S. glaseri and H. bacteriophora, which showed survival rates of 84.8 and 69.8%, respectively, at 35°C in the F6. The tolerant lines were evaluated using secondinstar larvae of Phyllophaga vetula Horn, an important pest in the region where the study was conducted. Steinernema riobrave and H. bacteriophora showed good control at low A_W (0.86), while S. glaseri and S. riobrave showed good control at high temperature (35°C).