Effects of pastueria penetrans endospore rate of attachment on root penetration and fecundity of meloidogyne arenaria race 1

Abstract

Pasteuria penetrans is an obligate mycelial endospore-forming bacterial parasite of root-knot nematodes that has shown great potential for their biological control. Endospores of P. penetrans attach to the cuticle of second-stage juveniles (J2) of Meloidogyne spp. when they move through soil in search of a host. The percentage of J2 with endospores attached and number of endospores per J2 are correlated with infection in adults and therefore are often used as an indirect measure of biocontrol potential. This study was carried out to test the effect of different rates of endospore attachment on the ability of root-knot nematodes to penetrate a host, produce galls and the nematode’s fecundity under environmentally controlled conditions. Different attachment levels were achieved using different ratios of J2 to endospores. The number of J2 penetrating host roots was highest in the control where the J2 were not exposed to P . penetrans endospores and lowest at higher endospore attachment levels of 10.2 and 18.1. As few as 3.5 endospores/J2 reduced their ability to infect roots. Egg mass numbers were reduced by higher levels of endospore attachment but galling was not. This study confirms that P. penetrans induced soil suppressiveness is dependent on endospore concentrations and is manifested at the level of root penetration by J2 and loss of nematode fecundity