Tackling the Context-Dependency of Microbial-Induced Resistance
2021-6-25, Lee Díaz, Ana Shein, Macheda, Desiré, Saha, Haymanti, Ploll, Ursula, Orine, Dimitri, Biere, Arjen
Plant protection with beneficial microbes is considered to be a promising alternative to chemical control of pests and pathogens. Beneficial microbes can boost plant defences via induced systemic resistance (ISR), enhancing plant resistance against future biotic stresses. Although the use of ISR-inducing microbes in agriculture seems promising, the activation of ISR is context-dependent: it often occurs only under particular biotic and abiotic conditions, thus making its use unpredictable and hindering its application. Although major breakthroughs in research on mechanistic aspects of ISR have been reported, ISR research is mainly conducted under highly controlled conditions, differing from those in agricultural systems. This forms one of the bottlenecks for the development of applications based on ISR-inducing microbes in commercial agriculture. We propose an approach that explicitly incorporates context-dependent factors in ISR research to improve the predictability of ISR induction under environmentally variable conditions. Here, we highlight how abiotic and biotic factors influence plant–microbe interactions in the context of ISR. We also discuss the need to raise awareness in harnessing interdisciplinary efforts between researchers and stakeholders partaking in the development of applications involving ISR-inducing microbes for sustainable agriculture.
Arbuscular mycorrhizal fungi prevent the negative effect of drought and modulate the growth-defence trade-off in tomato plants
2022-6-6, Orine, Dimitri, Defossez, Emmanuel, Vergara, Fredd, Uthe, Henriette, van Dam, Nicole M., Rasmann, Sergio
Introduction A wide range of arbuscular mycorrhizal fungi (AMF) can be applied to agricultural soils as biofertilizers for increasing crop growth and yield. Current research also shows that AMF can stimulate plant defences against a range of herbivores and pathogens. However, to date, the efficient use of AMF in agriculture is largely impaired by our inability to predict the performance of different AMF-plant complexes in variable environments. For instance, AMFs by increasing plant foraging capacity might alleviate allocation constraints in relation to growth versus defences. However, whether this effect occurs might depend on the in situ conditions. The main goal of this study was to investigate the context-dependency of the ability of AMF to modulate plant growth and resistance against herbivores under variable soil water availability. Materials and Methods To address our goal, we performed a greenhouse experiment for measuring the effect of different AMF inocula (Funneliformis mosseae, Rhizophagus irregularis, or both) on tomato plants (Solanum lycopersicum) growth and defences against an insect herbivore under two conditions: a normal watering regime or drought conditions. We measured the functional, physiological and chemical traits of the plants. Results We found that AMF presence generally decreased plant growth, but increased chemical defences and resistance against generalist caterpillars. Such growth-defence trade-off was nonetheless dependent on the identity of the mycorrhizal inoculum and on soil water content. Under drought, inoculated tomato plants lowered their investment to defence and noninoculated plants lowered their growth. Conclusion This study highlights the influence of abiotic factors and fungal identity on plant–AMF–herbivore interactions. In a broader sense, our results point to the necessity of finding AMF species that have reduced context-dependency to climatic factors, for more widespread use in organic agriculture.