The Effect of Plant Genotype, Growth Stage, and Mycosphaerella graminicola Strains on the Efficiency and Durability of Wheat-Induced Resistance by Paenibacillus sp. Strain B2

Abstract

Plant-growth-promoting rhizobacteria are known as potential biofertilizers and plant-resistance inducers. The current work aims to study the durability of the resistance induced as a response to the inoculation of wheat grains with Paenibacillus sp. strain B2 (PB2) and its influence by plant genotype, growth stage, and Mycosphaerella graminicola strain (the causal agent of Septoria tritici blotch or STB). The results of the plate-counting method showed that PB2 has high potential for wheat-root external colonization [>10 6 colony-forming unit (CFU)/g of root], and the quantitative real-time polymerase chain reaction (qPCR) analysis demonstrated its internal root-colonization capacity on all tested cultivars. However, the colonization seems to be dependent on wheat-growth stage. The durability of PB2-induced resistance (PB2-IR) was tested at the 3-leaf, tillering, and flag-leaf-growth stages. Additionally, the results showed that the PB2-IR is durable and able to protect the flag leaf, the most important leaf layer during grain fill. It conferred a high protection efficiency (55–94%) against four virulent strains of M. graminicola and over 11 wheat cultivars with different resistance levels to STB. Although, PB2-IR is dependent on M. graminicola strains, wheat genotypes and growth stages, its efficiency, under field conditions, at protecting the last wheat-leaf layers was not an influence. However, it showed 71–79% of protection and reached 81–94% in association with half of the recommended dose of Cherokee ® fungicide. This may be explained using laboratory results by its direct impact on M. graminicola strains in these leaf layers and by the indirect reduction of the inoculum coming from leaves infected during the earlier growth stages. Gene expression results showed that PB2-IR is correlated to upregulation of genes involved in defense and cell rescue and a priming effect in the basal defense, jasmonic acid signaling, phenylpropanoids and phytoalexins, and reactive oxygen species gene markers. To conclude, PB2 induces a high and durable resistance against M. graminicola under controlled and field conditions. The PB2-IR is a pathogen strain and is plant-growth-stage and genotype dependent. These results highlight the importance of taking into consideration these factors so as to avoid losing the effectiveness of induced resistance under field conditions.

Tomato Domestication Attenuated Responsiveness to a Beneficial Soil Microbe for Plant Growth Promotion and Induction of Systemic Resistance to Foliar Pathogens

“…Many studies have demonstrated that plant genotype can affect the expression of induced resistance mediated by biological (Martinelli et al, 1993;Korolev et al, 2008;Banani et al, 2014;Alkooranee et al, 2015;Hossain and Sultana, 2015;Prashar and Vandenberg, 2017;Samain et al, 2019;Adam, 2020) and chemical (Herman et al, 2007;Ishikawa et al, 2007;Sharma et al, 2010Sharma et al, , 2012Walters et al, 2011;Cordova-Campos et al, 2012;Banani et al, 2014;Pawlowski et al, 2016) inducers in a wide variety of crops. Therefore, it is not surprising that like Tucci et al (2011), we observed genetic differences in ISR by Trichoderma against Botrytis.…”

Insights on the Structural and Metabolic Resistance of Potato (Solanum tuberosum) Cultivars to Tuber Black Dot (Colletotrichum coccodes)

“…According to additional field trials (data not shown), overall disease severity was higher in the greenhouse experiment than in field trials, suggesting that the artificial inoculation resulted in a disease pressure higher than that found in the field. It is possible that a higher inoculum than that found in the field was applied to the greenhouse experiment, since soil inoculum correlates with disease severity ( Lees et al, 2010 ) Furthermore, inoculum concentration correlation with disease severity is genotype dependent ( Alonso-Villaverde et al, 2011 ), and both the pathogen strain and the plant genotype influence host resistance in other phytopathogenic interactions ( Ors et al, 2018 ; Samain et al, 2019 ). These results suggest that a high disease pressure as applied in the greenhouse might negatively influence the resistance of Cheyenne and Lady Christl to black dot.…”

“…Metabolomics and cytological analysis have been used to highlight pathogenesis related metabolites in several host-pathogen interactions, including interactions between S. tuberosum and microbial pathogens. Although recent studies showed the importance of the host variety and pathogen strain on quantitative resistance ( Ors et al, 2018 ; Samain et al, 2019 ), studies of plant-pathogen interactions often rely on the use of a model using a single susceptible and a single resistant genotype. Furthermore, the effect of the inoculation of C. coccodes on the metabolome of potato tubers has not been studied so far.…”

Plant Beneficial Bacteria as Bioprotectants against Wheat and Barley Diseases

“…For example, Paenibacillus sp. strain B2 was demonstrated to significantly reduce the symptoms caused by S. tritici by inducing an overexpression of different plant genes involved in defense and cell rescue [ 151 ]. In the same way, Petti et al (2010) [ 178 ] carried out one of the first transcriptomic analyses on barley to understand the impact of the Pseudomonas fluorescens strain MKB158 to protect from Fusarium head blight.…”