EVALUATION OF EFFICACY OF PASTEURIA PENETRANS ALONE AND IN COMBINATION WITH VERTICILLIUM CHLAMYDOSPORIUM AGAINST MELOIDOGYNE JAVANICA

The potential control of Meloidogyne javanica using Pasteuria penetrans (Pp) alone and in combination with Verticillium chlamydosporium (Vc) was tested in earthen pots following a cropping sequence "tomato-tomato-tomato” over three crop cycles. After the final harvesting, analysis of variance showed significant effect of treatments (P0.01) regarding number of eggmasses, galls and nematode female populations. Similarly, significant effect of treatments (P0.01) was also recorded in case of infected nematode females with Pasteuria and number of eggs/eggmass while no significant effect (P 0.0 5) was observed in case of endospore production. Higher numbers of eggmasses (360) and root galling (6.2) was observed where biocontrol agents were absent (control). The treatments showed 46.58, 58.85 and 33.13 percent reduction in number of galls, eggmasses and nematodes in Pp alone and 43.34, 55.21 and 30.09 percent reductions in Vc+Pp treatments respectively. Numbers of females infected with the endospores of P. penetrans were recorded higher in Pp-3 alone treatment (13.2) followed by Vc+Pp combined treatment (13.0) and maize rotated treatment (10.4) respectively. Significantly lesser number of eggmasses, galls and nematodes were recorded in pots where tomato was rotated with maize (treatment 3) compared with control. Thus rotation prevented the buildup of nematode population and resulted in a 72% decrease in numbers of eggmasses, 38% in root galling and 46% regarding female populations over the control after the final harvest. Maximum colony forming units of V. chlamydosporium per gram of soil were recorded after its addition to the soil. The fungus established in the soil during the first crop and soil colonization of the fungus was also observed after final crop.

Development of Pasteuria penetrans on different field populations of Meloidogyne spp. from Pakistan

Summary Pasteuria penetrans is a hyperparasite with potential as a biological control agent of root-knot nematodes, Meloidogyne spp. In this study two exotic Pasteuria isolates (PP-3 and PP-J) were developed on different Meloidogyne spp. collected from different districts of Punjab, Pakistan. The development of PP-3 and PP-J on different field populations of Meloidogyne spp. showed differential infectivity in terms of nematode reproduction variables. The development of PP-3 and PP-J was maximum on tomato as compared to cucumber. It was probably due to more invasion sites for nematodes present in the tomato roots. However, a bigger root system has not always been a guarantee for development of Pasteuria on Meloidogyne spp. For successful development of Pasteuria, the key parameters are the percentage of infected females, number of endospores (female)−1 or endospores (mg root powder)−1. The results of these parameters are greater in tomato as compared to cucumber.

De novo assembly of the Pasteuria penetrans genome reveals high plasticity, host dependency, and BclA-like collagens

1.ABSTRACTPasteuria penetrans is a gram-positive endospore forming bacterial parasite of Meloidogyne spp. the most economically damaging genus of plant parasitic nematodes globally. The obligate antagonistic nature of P. penetrans makes it an attractive candidate biological control agent. However, deployment of P. penetrans for this purpose is inhibited by a lack of understanding of its metabolism and the molecular mechanics underpinning parasitism of the host, in particular the initial attachment of the endospore to the nematode cuticle. Several attempts to assemble the genomes of species within this genus have been unsuccessful. Primarily this is due to the obligate parasitic nature of the bacterium which makes obtaining genomic DNA of sufficient quantity and quality which is free from contamination challenging. Taking advantage of recent developments in whole genome amplification, long read sequencing platforms, and assembly algorithms, we have developed a protocol to generate large quantities of high molecular weight genomic DNA from a small number of purified endospores. We demonstrate this method via genomic assembly of P. penetrans. This assembly reveals a reduced genome of 2.64Mbp estimated to represent 86% of the complete sequence; its reduced metabolism reflects widespread reliance on the host and possibly associated organisms. Additionally, apparent expansion of transposases and prediction of partial competence pathways suggest a high degree of genomic plasticity. Phylogenetic analysis places our sequence within the Bacilli, and most closely related to Thermoactinomyces species. Seventeen predicted BclA-like proteins are identified which may be involved in the determination of attachment specificity. This resource may be used to develop in vitro culture methods and to investigate the genetic and molecular basis of attachment specificity.