Acinetobacter calcoaceticus SJ19 and Bacillus safensis SJ4, two Algerian rhizobacteria protecting tomato plants against Botrytis cinerea and promoting their growth

Abdelhamid Foughalia,Yousra Bouaoud,Charlotte Chandeysson,Kamel Aissat,Mohamed Tahirine,Mawahib Djedidi,Philippe Nicot

doi:10.1186/s41938-022-00511-z

Abstract

BackgroundBotrytis cinerea, the causal agent of grey mould, is a polyphagous fungus that infects a wide range of plants, including tomato. In many countries, including Algeria, the management of grey mould is a challenging problem, even with chemical control. This necessitates the search for other strategies. The objective of this study was to evaluate the biocontrol potential of two rhizospheric bacterial isolates for the protection of tomato against B. cinerea.ResultsOn tomato plants, the two bacterial isolates consistently provided high levels of protection (on average 72.1% for SJ19 and 52.3% for SJ4). Their applications as a 1:1 mixture reinforced their effect (87.8% protection), indicating their compatibility and a potential use as a consortium. In vitro, the isolates significantly inhibited the mycelial growth of B. cinerea strains, both through direct confrontation in dual-culture assays (12–69% inhibition) and through the production of volatile compounds (36–46% inhibition). The two isolates, applied as seed treatment and as drench on seedlings, also showed strong growth-promoting effects on tomatoes. They substantially increased the length and fresh weight of shoots and roots, as well as stem diameter, leaf number and chlorophyll content, compared to untreated plants.ConclusionThe two bacteria tested in this study showed a high potential for use as biostimulants and as biofungicides against tomato grey mould.

Highlights

Botrytis cinerea, the causal agent of grey mould, is a polyphagous fungus that infects a wide range of plants, including tomato
Bacterial isolates The two bacterial isolates used in this study (SJ4 and SJ19) were isolated in 2018 from the rhizospheric soil of healthy tomato plants cultivated in unheated greenhouses near Jijel, Algeria
In vitro inhibition of Botrytis cinerea by the bacterial isolates Direct confrontation In dual culture tests, both bacterial isolates significantly inhibited the mycelial growth of the five strains of B. cinerea (Table 1 and Fig. 1)

Summary

Introduction

The causal agent of grey mould, is a polyphagous fungus that infects a wide range of plants, including tomato. Tomato grey mould caused by Botrytis cinerea Pers (anamorph of Botryotinia fuckeliana (de Bary) Whetzel) is becoming one of the most serious concerns in Algeria’s unheated greenhouses (Aissat et al 2008) This necrotrophic and polyphagous fungus can attack the tomato’s. Undesirable side effects of pesticides have increasingly generated concerns about possible public health and environmental issues All of these limitations have prompted researchers and agronomists to seek out alternate strategies of disease and pest management (Walia et al 2021). No microbial bio-fungicide is authorized for agricultural use in Algeria (Anonymous 2017) In this context, this study was initiated with the objective of evaluating biocontrol potential of two indigenous rhizobacteria, applied singly or in combination, for the protection of tomato against B. cinerea.

Objectives

Methods

Results

Discussion

Conclusion