Wed, Aug 17, 2022: 5:00 PM-6:30 PM
ESA Exhibit Hall
Background/Question/MethodsAccurate predictions of how plants respond to our rapidly changing climate should consider symbiotic interactions with micro-organisms and how they change with the environment. Previous SoyFACE (free air CO2 enrichment) studies show that elevated CO2 levels shifted the assembly of foliar microbial communities in Glycine max (soybean). In particular, composition of three dominant endophytes changed such that an isolate of the nitrogen-fixing bacterium Methylobacterium decreased in abundance in elevated CO2, while two fungal isolates (Colletotrichum sp. A2.15.12 and Colletotrichum sp. A2.10.2) increased in abundance. The purpose of this study was to determine the phenotypic effects of these endophytes in soybean under two conditions: a greenhouse study in sterile soil and a field study at the SoyFACE facility at ambient (416ppm) and elevated (550ppm) CO2 levels. We grew fungal and bacterial isolates in the lab and inoculated them onto soybean both independently and in combination, then measured parameters of aboveground biomass, pod number, plant height, and chlorophyll content as indicators of plant phenotypic response to dominant endophytes.
Results/ConclusionsIn the greenhouse, at ambient CO2 with sterile soil, endophyte treatments increased soybean growth compared to the control. Furthermore, plants inoculated with Colletotrichum sp. A2.15.12 and Colletotrichum A2.15.12+Methylobacterium elicited the largest increase in plant biomass at 49% and 51%, respectively, compared to uninoculated control plants. However, the results were not consistent in the field where there were no significant differences in soybean biomass with endophyte treatment in either ambient or elevated CO2. We can possibly conclude that these foliar endophytes, while commonly found in the field and having positive effects, might only affect plant phenotypes under controlled conditions when plants lack other microbial symbionts. Nitrogen fixation and other nutrient assimilation by mutualistic root endophytes may well outweigh the effect of foliar endophytes, and unless the soil is devoid of a microbial community, the foliar endophytes explored in this experiment may be mostly commensal. It is possible that they serve another function in plant defense or nutrient acquisition in non-agricultural plants. It will be important in future studies on plant-microbe responses to climate change to be mindful of the community context in any given environment.
Results/ConclusionsIn the greenhouse, at ambient CO2 with sterile soil, endophyte treatments increased soybean growth compared to the control. Furthermore, plants inoculated with Colletotrichum sp. A2.15.12 and Colletotrichum A2.15.12+Methylobacterium elicited the largest increase in plant biomass at 49% and 51%, respectively, compared to uninoculated control plants. However, the results were not consistent in the field where there were no significant differences in soybean biomass with endophyte treatment in either ambient or elevated CO2. We can possibly conclude that these foliar endophytes, while commonly found in the field and having positive effects, might only affect plant phenotypes under controlled conditions when plants lack other microbial symbionts. Nitrogen fixation and other nutrient assimilation by mutualistic root endophytes may well outweigh the effect of foliar endophytes, and unless the soil is devoid of a microbial community, the foliar endophytes explored in this experiment may be mostly commensal. It is possible that they serve another function in plant defense or nutrient acquisition in non-agricultural plants. It will be important in future studies on plant-microbe responses to climate change to be mindful of the community context in any given environment.