Beneficial and pathogenic plant‐microbe interactions during flooding stress

Abstract

The number and intensity of flood events will likely increase in the future, raising the risk of flooding stress in terrestrial plants. Understanding flood effects on plant physiology and plant-associated microbes is key to alleviate flooding stress in sensitive species and ecosystems. Reduced oxygen supply is the main constrain to the plant and its associated microbiome. Hypoxic conditions hamper root aerobic respiration and, consequently, hydraulic conductance, nutrient uptake, and plant growth and development. Hypoxia favours the presence of anaerobic microbes in the rhizosphere and roots with potential negative effects to the plant due to their pathogenic behaviour or their soil denitrification ability. Moreover, plant physiological and metabolic changes induced by flooding stress may also cause dysbiotic changes in endosphere and rhizosphere microbial composition. The negative effects of flooding stress on the holobiont (i.e., the host plant and its associated microbiome) can be mitigated once the plant displays adaptive responses to increase oxygen uptake. Stress relief could also arise from the positive effect of certain beneficial microbes, such as mycorrhiza or dark septate endophytes. More research is needed to explore the spiralling, feedback flood responses of plant and microbes if we want to promote plant flood tolerance from a holobiont perspective.

Warming Scenarios and Phytophthora cinnamomi Infection in Chestnut (Castanea sativa Mill.)

“…In the Mediterranean area, the dieback of Q. ilex induced by Pc was exacerbated by severe drought [ 80 , 81 ]. Waterlogging in combination with subsequent water deprivation is the worst scenario for Q. ilex if soils are infested with Pc [ 82 ]. A higher frequency of extreme rain events that saturate the soil might be particularly beneficial for Pc (and negative for the tree [ 14 ]), potentially boosting its soil density beyond any possible defence response of the susceptible hosts [ 82 , 83 ].…”

“…Waterlogging in combination with subsequent water deprivation is the worst scenario for Q. ilex if soils are infested with Pc [ 82 ]. A higher frequency of extreme rain events that saturate the soil might be particularly beneficial for Pc (and negative for the tree [ 14 ]), potentially boosting its soil density beyond any possible defence response of the susceptible hosts [ 82 , 83 ]. However, an average, drier climate might imply suboptimal conditions for Pc infections, allowing for the slower advance of the disease in infested areas [ 83 ].…”

Plant Beneficial Bacteria and Their Potential Applications in Vertical Farming Systems

“…There are abiotic stresses that are pertinent to vertical farming systems, such as root hypoxia and a high salinity due to the buildup of ions in recirculating water [ 30 ]. Root hypoxia may present a risk when hydroponic systems are improperly aerated, which can lead to impaired root respiration and elevated ethylene levels [ 30 , 115 ]. Ethylene, as a gaseous phytohormone, can be transported through the xylem to affect distal plant organs (e.g., leaves, fruit), where it can induce ethylene response factors, which can inhibit cell division and growth [ 116 ].…”

“…ACC is converted to ethylene by ACC oxidase. As mentioned, part of the plant response to elevated levels of ethylene includes the inhibition of growth [ 115 ].…”

Interactions between grasses and soil biota : From genes to climate change-induced drought

“…On the other hand, abiotic stress can increase a plant's susceptibility to disease with often detrimental consequences for the plant (Martínez Arias et al 2022). Consequently, the overall effect of soil biota on plant health will likely vary between environments (Lau and Lennon, 2012).…”