Effect of Pasteuria penetrans against Meloidogyne spp., on peanut cultivars

Twelve phytoparasitic nematode genera were found infected or associated with the rhizosphere of peanut plants. Meloidogyne arenaria was the most common nematode in all collected soil samples followed by Tylenchorhynchus spp., Helicotylenchus spp., M. javanica and Pratylenchus penetrans. All tested peanut cultivars were resistant to M. incognita race 2 and moderately resistant to M. javanica. Whereas, peanut cvs. Balady, Ismailia 1 and Giza 6 were found highly susceptible to M. arenaria race 1 and Giza 4 and Giza 5 cvs. were susceptible. The suppressive efficacy of using three isolates of Pasteuria penetrans (Pp) against M. arenaria race 1 infected peanut was tested through two microplot experiments during two growing seasons 2011-12. Treatments in 1st season with two concentrations of the three mixed Pp isolates caused the highest reduction of 74.8-86.9% in number of nematode root galls, egg-masses/root system and number of J2/250 cm3 soil compared with any single Pp isolate application. Meanwhile, all treatments in 2nd season with both concentrations of all Pp isolates either alone or as a mixed isolates resulted in 65.7-94.7% reduction in all nematode parameters. Treatments with high concentration of all Pp isolates either alone or as mixed resulted 61.4-72.2% encumbered J2 in the 1st season and increased to 93.2-97.9% in the 2nd season. Treatments with two concentrations of mixed isolates and PpT isolate resulted in a significant increase of 51.7-77.0% in dry weights of shoot and root systems and number of peanut pods/plant, followed by treatments with the same concentrations of PpB and PpG isolates, which showed 32.7-48.5% increase. Number of bacterial nodules/root system was significantly increased with Pp treatments in both seasons. However, numbers of adherent endospores on J2 cuticle were ranged 3.6-9.4 and 6.2-11.4 endospore/J2 in the 1st and 2nd season, respectively. High Pp concentrations resulted in the highest numbers of adherent endospores.