Nematodes associated with andean papaya (Carica pubescens L.) in Sandia, Puno, Peru

Plant-parasitic nematodes cause 14 % of annual losses in different crops in the world and there are more than 35 genera of phytoparasitic nematodes associated with the rhizosphere of the papaya crop (Carica spp.), being the most important the root-knot nematode (Meloidogyne spp). The present study aimed to carry out the morphological identification of the genera of nematodes associated with the cultivation of Andean papaya (Carica pubescens), in Sandia district, Puno, Perú. One-hundred and fifty-five soil and roots samples from eight communities were evaluated. The samples were processed by the centrifugal fluctuation method in sucrose solution and subsequent identification of the nematodes at the genus level, using the dichotomous key of Mai and Mullin. We found the genus Meloidogyne, Pratylenchus, Helicotylenchus, Mesocriconema, Apelenchus, Dorilaymus, Tylenchus, Xiphinema, Mononchus, Discocriconemella, Trichodorus and other unidentified free-living nematodes. This information may allow the design of an integrated nematode management plan in Andean papaya crops.

A modified semi-selective medium for isolation and enumeration of Pochonia chlamydosporia (Goddard) Zare & W. Gams

Pochonia chlamydosporia, is one of the most promising biological control agents for managing phytoparasitic nematodes. Isolation and enumeration of viable colonies of P. chlamydosporia from soil and other substrates without contamination is a major limitation, when commonly available nutrient media are used. Development of a suitable selective/semi-selective media by incorporating one or more inhibitors of microbial growth can facilitate isolation of the fungus. In vitro studies were carried out to test the compatibility of commonly used pesticides, namely, metalaxyl, metalaxyl-mancozeb, carbendazim, copper oxychloride, and chlorpyrifos with P. chlamydosporia. The fungus showed relatively high tolerance to higher doses of metalaxyl and carbendazim and was used in the modified medium for better suppression of other soil borne fungi. In the present study, Kerry’s semi-selective medium was modified and evaluated by counting the viable fungal propagules in different substrates (rice, farmyard manure, maize, rice bran, barley, and sorghum) and soil artificially inoculated with the fungus. The results showed that the modified Kerry’s semi-selective medium can effectively be used for isolation and quantification of P. chlamydosporia in routine studies.

Draft Genome Sequence of Bacillus velezensis BZR 277, a Prospective Biocontrol Agent Against Phytoparasitic Nematodes

ABSTRACT Bacillus velezensis strain BZR 277 is a rhizobacterium isolated from the rhizoplane of a winter oilseed rape plant from the Krasnodar region in Russia. This study presents the genome sequence of the rhizobacterium Bacillus velezensis BZR 277, which exhibited high antagonistic activity against the root-knot nematode Meloidogyne incognita Kof. The data on the genome sequence can help to identify pathways for the biosynthesis of metabolites responsible for nematicidal activity in order to improve crop protection against plant-parasitic nematodes.

Bacteria as Biocontrol Tool against Phytoparasitic Nematodes

Phytoparasitic nematodes cause severe damage and yield losses to numerous agricultural crops. Considering the revision of the EU legislation on the use of pesticides on agricultural crops, control strategies with low environmental impact are required. The approach based on the use of bacteria seems particularly promising as it also helps to reduce the applied amounts of chemicals and stabilize ecological changes. This paper gives an overview of the main types of bacteria that can be used as biological control agents against plant parasitic nematodes and their interrelationships with plants and other organisms. Many experiments have given positive results of phytoparasitic nematode control by bacteria, showing possible prospects for their application. In vitro, greenhouse and field experiments have shown that bacteria can regulate the development of ecto- and endoparasitic nematodes by different modes of action. Triggering the induction of plant defense mechanisms by bacteria is seen as the optimum tool because the efficacy of bacterial treatment can be higher than that of chemical pesticides or at least close to it. Moreover, bacterial application produces additional positive effects on growth stimulation, raises yields and suppresses other pathogenic microorganisms. Commercial formulations, both as single bacterial strains and bacterial complexes, are examined.

Effects of paclobutrazol and mepiquat chloride on the growth and development of plantain Dominico Hartón (Musa AAB)

Colombia is the fourth largest producer of plantain in the world, with a harvest of 3,539,252 t. Various biotic and abiotic factors affect yields, including phytoparasitic nematodes that are a major constraint in this crop. For this reason, strategies are being sought to improve the performance of this plant with this cosmopolitan pest. This research evaluated the effect of two hormonal regulators on the growth and development of the Dominico plantain. The experiment design had treatments that were divided plots, where the main plot corresponded to the type of product, and the sub-plot corresponded to the concentrations of paclobutrazol and mepiquat chloride in the different doses: 0, 250 and 500 mg L-1. The experiment unit consisted of ten plants with four replicates. The evaluated variables were plant height, diameter of the pseudostem, number of functional leaves, length and diameter of the roots, number of nematodes and variables for production quality. The two growth regulators reduced the plant height before emergence of the flower; paclobutrazol reduced the height by up to 40%, while mepiquat chloride reduced the height by up to 6.7%. There were no statistical differences in the production per plant, where the production with paclobutrazol was 14 kg/plant and, with mepiquat chloride, was 15 kg/plant. The control was 14.5 kg/plant. The use of growth regulators did not significantly restrict the damage caused by nematodes; however, paclobutrazol performed better as a growth regulator in the Dominico Hartón plants.