Control potential of Meloidogyne javanica and Ditylenchus spp. using fluorescent Pseudomonas and Bacillus spp

ABSTRACT Plant Growth Promoting Rhizobacteria (PGPR) have different mechanisms of action in the development of plants, such as growth promotion, production of phytohormones and antibiotic substances and changes in root exudates. These help to control plant diseases. In order to evaluate the potential of microorganisms in the control of Meloidogyne javanica and Ditylenchus spp., five rhizobacteria isolated from rhizosphere of garlic cultivated in the Curitibanos (SC) region were tested. Hatching chambers were set on Petri dishes, in which were added 10 mL of bacterial suspension and 1 mL of M. javanica eggs suspension, at the rate of 4500, on the filter paper of each chamber. The same procedure was performed with 300 juvenile Ditylenchus spp. The experimental design was completely randomized, with four replications. The evaluations were performed every 72 h for nine days. The antagonized population of nematodes was determined in Peters counting chamber, determining the percentage hatching (for M. javanica) and motility (for Ditylenchus spp). Isolates CBSAL02 and CBSAL05 significantly reduced the hatching of M. javanica eggs (74% and 54.77%, respectively) and the motility of Ditylenchus spp. (55.19% and 53.53%, respectively) in vitro. Isolates were identified as belonging to the genera Pseudomonas (CBSAL05) and Bacillus (CBSAL02).

Meloidogyne and Pratylenchus species in sugarcane fields in the state of Alagoas, Brazil / Espécies de Meloidogyne e de Pratylenchus em áreas cultivadas com cana-de-açúcar no estado de Alagoas

ABSTRACT: The objective of this study was to accomplish a survey on populations of Meloidogyne and Pratylenchus species in sugarcane farming areas in the state of Alagoas, Brazil. Twenty samples of soil and roots were processed to extract and quantify nematodes; however, the identification of Meloidogyne species was performed using only 12 samples. Pratylenchus spp. were reported at moderate population levels of 68-1556 specimens 50g-1 of roots and 2-298 specimens 100cm-3 of soil in twenty analyzed samples. For Meloidogyne spp., these values were of 12-487 specimens 50g-1 of roots and 0-140 specimens 100cm-3 of soil. Based on electrophoresis of esterase isozymes, M. incognita was reported to be the most frequent species, followed by M. javanica and M. arenaria. Pratylenchus species identified through morphometrical and morphological characteristics were P. zeae and P. brachyurus , with predominance for the first species. No significant correlation (P≤0.05) were reported between nematode populations and sugarcane cropping systems.

RESUMO: O objetivo deste trabalho foi realizar um levantamento de espécies de Meloidogyne e de Pratylenchus existentes em áreas de cultivo de cana-de-açúcar, no estado de Alagoas. Vinte amostras de solo e raízes foram processadas para a extração e quantificação, sendo a identificação das espécies de Meloidogyne realizada em 12 amostras. Detectou-se a presença de Pratylenchus spp. em níveis populacionais médios de 68-1556 espécimes 50g-1 de raízes e 2-298 100cm-3 de solo, em todas as amostras. Para Meloidogyne spp., esses valores foram de 12-487 50g-1 de raízes e 0-140 100cm-3 de solo. Com base na eletroforese da isoenzima esterase, M. incognita foi a espécie mais frequente, seguida por M. javanica e M. arenaria . As espécies de Pratylenchus identificadas pelas características morfológicas e morfométricas, foram P. zeae e P. brachyurus , com predomínio da primeira espécie. Não houve correlações significativas (P≤0,05) entre as populações de nematoides e as características dos sistemas de cultivo de cana-de-açúcar.

Structural and functional analysis of cathepsin S of Heterodera spp: A promising candidate for its control.

Cysteine proteinases are required for a wide range of physiological processes in all living organisms. In parasitic nematodes, they are particularly crucial for the digestion of host tissues and evasion of host immune responses. Therefore, in general, these are identified as primary targets for the control of parasitic nematodes. Herein, cathepsin S-like cysteine proteinase of Heterodera avenae (Hacp-s) has been cloned and analysed for the first time. The predicted protein is 298 amino acids long and showed significant similarity with cathepsin S of Heterodera glycines (Hgcp-s). The sequence of cathepsin S contains a signal peptide of 30 amino acids which suggests its role in extracellular functions. Multiple sequence alignment revealed the presence of ERFNIN motif and conserved catalytic residues. Three dimensional structure (3D) of Hgcp-s was modelled using homology modelling. In order to illustrate the plausible mode of interaction of cathepsin S (Hgcp-s), docking analysis was performed with E-64 cysteine proteinase inhibitor. Docking studies revealed the hydrogen bonding of E-64 with Gln153, His299 and Gly203 as well as close interaction with catalytic residues Cys159 and Asn320. Expression analysis of Hacp-s using qRT-PCR showed high expression of cathepsin S in pre parasitic J2s and female stages suggesting its significant role in both pre-parasitic and parasitic stages of the nematode life cycle.

Conjoint effect of oil-seed cakes and Pseudomonas fluorescens on the growth of chickpea in relation to the management of plant-parasitic nematodes

Soil application of organics has been explored as an alternative means of organic management of plant-parasitic nematodes. Efficiency of different oil-seed cakes of neem (Azadirachta indica), castor (Ricinus communis), groundnut (Arachis hypogaea), linseed (Linum usitatissimum), sunflower (Helianthus annuus) and soybean (Glycine max) were evaluated in field conditions with association of Pseudomonas fluorescens in relation to growth parameters of chickpea and population of plant-parasitic nematodes. Their efficacious nature was highly effective in reducing the population of these dominant soil nematodes. Significant improvement was observed in plant-growth parameters such as plant weight, percent pollen fertility, pod numbers, root-nodulation and chlorophyll content of chickpea, seemed to be due to reduction in disease incidence and might be due to growth promoting substances secreted by P. fluorescens. The multiplication rate of nematodes was less in the presence of P. fluorescens as compared to its absence. Most effective combination of P. fluorescens was observed with neem cake.