Implication of the hydrogen recycling capacity of rhizobia inoculants on the drought stress resistance of legume crops

除了豆科作物支持的土壤中氮素的输入外，从固氮根瘤中泄漏的分子氢(H2)被认为是作物轮作效应的重要贡献者。作为固氮反应的必然副产物，农业生态系统产生了大量的氢气，根据先前的估计，每个生长季每公顷产生24万升氢气。然而，有一些固氮根际细菌具有捕获产生的H2的能力，但后者在自然共生体中很少发现，而在商业接种剂中占主导地位。有两个学派试图解释这一悖论。第一条规定，根瘤菌-豆类共生体循环H2(Hup+)在改善共生的能量平衡方面更有效，证明将它们整合到商业接种剂中的兴趣是合理的。第二种观点认为，从根瘤菌-豆类共生体中泄漏出的氢，不会将H2(Hup-)作为浓缩H2氧化细菌(Boh)的货币，而是将这种气体用作土壤中的能源。BOH在土壤中普遍存在，以几种促进植物生长和抗逆性的物种为代表。向Hup-固氮根瘤菌接种剂的过渡是否有助于提高作物对气候变化的适应能力？这一问题将通过将在西班牙举行的指导编写审查文章的讲习班和将开展的研究活动来解决，以研究氢气泄漏对植物抗旱性的影响。理论和实验数据将首次提供关于固氮根瘤释放的氢气对“根瘤菌-植物-微生物-土壤”相互作用的影响的机制信息。结果将与面临干旱事件频率增加的加拿大豆类种植者分享，巩固新的合作伙伴关系，并指导他们选择接种剂。

Besides the input of nitrogen in soil supported by legume crops, leakage of molecular hydrogen (H2) from nitrogen-fixing nodules is envisioned as a significant contributor to the crop rotation effect. Being an obligatory by-product of the nitrogen fixation reaction, large amounts of H2 are produced in agroecosystems, representing 240 000 liters per hectare per growing season according to previous estimates. However, there are nitrogen-fixing rhizobacteria endowed with the ability to capture the H2 produced, but these latter are rarely found in natural symbioses, whereas they are dominant in commercial inoculants. Two schools of thought attempt to explain this paradox. The first stipulates that rhizobium-legume symbioses recycling H2 (Hup+) are more effective in improving the energy balance of the symbiosis, justifying the interest in integrating them into commercial inoculants. The second sees H2 leakage from rhizobium-legume symbioses that do not recycle H2 (Hup-) as a currency for the enrichment of H2-oxidizing bacteria (BOH), using the gas as a source of energy in soil. BOH are ubiquitous in soil and are represented by several species that promote plant growth and stress tolerance. Could a transition to Hup- nitrogen-fixing rhizobium inoculants help improve crop resilience to climate change? This issue will be addressed through a workshop guiding the preparation of a review article to be held in Spain and through research activities that will be carried out to examine the impact of H2 leakage on plant tolerance to drought. Theoretical and experimental data will provide the first mechanistic information on the impact of H2 emitted by nitrogen-fixing nodules on "rhizobium-plant-microbe-soil" interactions. The results will be shared with Canadian pulse growers facing an increase in the frequency of drought events, consolidating new partnerships and guiding their selection of inoculants.