Journal de pathologie végétale et de microbiologie

Abstrait

Efficacy and Durability of Paenibacillus sp. strain B2 in Co-Inoculation with Arthrobacter sp. SSM-004 and Microbacterium sp. SSM-001 for Growth Promotion and Resistance Induction in Wheat against Mycosphaerella graminicola and Drought Stress

Erika Samain, Cédric Ernenwein, Thierry Aussenac, Sameh Selim

Plant Growth-Promoting Rhizobacteria (PGPR) are able to promote plant growth and/or induce local and systemic resistance against biotic and abiotic stresses, but the stability and durability of their efficiency still need more investigation. The present work aims to identify a compatible-PGPR-mixture effective to stimulate wheat growth, resistance against Mycosphaerella graminicola, the causal agent of Septoria tritici leaf Blotch (STB), and tolerance to drought stress. The interactions between twenty-six PGPR and four wheat cultivars with different resistance levels to STB, in individual and co-inoculations, were tested. The results demonstrated higher external and internal root colonisation potential of Paenibacillus sp. strain B2 (PB2) in a mixture, referred hereafter as Mix-3, with strains Arthrobacter sp. SSM-004 and Microbacterium sp. SSM-001, and without an impact of wheat genotype and growth stage, as observed in its individual inoculations. Only with Mix-3 was wheat growth promotion observed. Interestingly, PB2 and Mix-3 eliminated the negative impact of drought stress on the Foliar Dry Biomass (FDB) and Root Dry Biomass (RDB), and only Mix-3 impacted root length. Moreover, Mix-3 induced pathogen strain and growth stage-dependent resistance, and conferred more than 73.5% protection against STB compared to 59.8% by PB2 in a single inoculation. Gene expression results showed the activation of basal defences, reactive oxygen species, phenylpropanoid and phytoalexins, salicylic acid and jasmonic acid pathways in the resistance induced by Mix-3. The PR1, chitinase, glucanase and flavonoid genes are strongly recommended as protection gene markers for wheat resistance to STB. To conclude, PB2 induced durable wheat resistance against M. graminicola and wheat tolerance against drought stress. Only in a mixture of three-compatible-PGPR (Mix-3) was plant growth promotion observed and the tolerance induced to drought stress was more effective. However, it seems that resistance induced against STB is PB2-dependent.