Factors Determining the Variability of Performance of Bio-Control Agents against Root-Knot Nematodes in Vegetable Plants

Sergio Molinari

doi:10.3390/agronomy11081602

Abstract

The application of management strategies against plant-parasitic nematodes (PPNs), an alternative to the use of toxic nematicides, has become of paramount importance due to the recognized environmental impact. Pre-treatments with bio-control agents (BCAs), such as bio-control fungi (BCF, Trichoderma spp.) and arbuscular mycorrhizal fungi (AMF), have been proved to protect many crop plants from endoparasitic sedentary nematodes (ESNs), the most damaging PPN group. However, the use of commercial BCA formulates is not always successful because of an array of variables that influence their performance. One AMF-based and 2 BCF-based commercial formulates were used as soil-drench pre-treatments to protect tomato, egg, and pepper plants from ESN attack. High variability of performance occurred according to the growth stage of treated plants and the amounts of formulates provided per plant. All formulates were highly effective in reducing both root-knot (RKN) and potato cyst (PCN) nematode infection when plants had reached an intermediate growth stage (3.5–5 g plant weight at treatment). However, only specific ranges of doses had to be used. Lower doses were ineffective against nematode attack; higher doses were often toxic to plants. When plants were grown from seeding in BCA-enriched soil, priming against RKNs was even more active. If plants were not challenged by nematodes, BCAs had a low bio-fertilizer effect.

Highlights

Plant-parasitic nematodes (PPNs) are small animal parasites of almost all crops worldwide
Data presented here confirm that arbuscular mycorrhizal fungi (AMF) and Trichoderma-containing bio-control agents (BCAs) are able to restrict endoparasitic sedentary nematode infection and reproduction, this capability is subjected to an array of factors that determine the high variability in performance
Despite the high number of studies reporting a protective effect of both Trichoderma and Mycorrhizal fungi against plant-parasitic nematodes [4], none has pointed out the crucial importance of the growth stages of the treated plants and the opportune dose ranges with which each stage should be provided

Summary

Introduction

Plant-parasitic nematodes (PPNs) are small animal parasites of almost all crops worldwide. They all have a protrusible stylet in their mouth apparatus by which they suck cell sap and inject an array of digestive compounds. These compounds are produced by three to five pharyngeal glands and act as effector molecules that alter gene expression and metabolism of the host [1]. Chemical control by using toxic nematicides, which has been the most reliable management strategy against RKNs and PCNs up to the recent past, is gradually being phased out by EU regulations (EC No1107/2009) because of the high impact on human and animal health and environment safety. The search for sustainable alternatives to nematicides by the scientific community has become of paramount interest [3]

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Conclusion