PS 20-9 - CANCELLED - Disentangling the effects of drought length and host age on biofuel sorghum biomass

Abstract: Increasing environmental pressures like drought challenge crop productivity. In response to drought, plants can alter root exudation to facilitate the recruitment of beneficial microbes like arbuscular mycorrhizal fungi (AMF) to ameliorate stress. Bioinoculants made from AMF are proposed as an alternative to increase plant tolerance to drought. However the efficacy of AMF depends on many factors including the root microbiome, the host and environment. Most studies that test the effects of drought on plant biomass and root microbiome overlook the confounding effects between the length of drought and host age, resulting in a major gap in our understanding of plant responses to drought. The goal of this study was to disentangle drought length, drought severity and host age to fully comprehend the climate-dependance of AMF, its effects on plant biomass, root exudates and AMF-root microbiome assembly. We grew plants in a mixture of turface and field soil to obtain a realistic soil microbial species pool including AMF, and manipulated the drought length, drought severity, and plant age. We applied drought treatments to plants at five different ages to disentangle the effects of drought length and host age for the first time. Each treatment combination included 10 replicates (total 290 plants). After the drought period, we harvested above-ground biomass, collected root exudates and roots for microbiome sequencing. Here, I will focus on the biomass results. I used a linear model to test the effect of length of drought, plant age, drought severity and their interactions on aboveground biomass. I found that drought severity did not significantly affect plant biomass (F1,219 =0.64, p =0.42). Thus, I analyzed the complete data set using a linear model with plant age, length of drought, and their interaction as explanatory variables. I found that plant age, length of drought, and their interaction had significant effects on plant biomass (F1,273 =364.13, p < 0.001; F1,273 = 111.64, p < 0.001; F1,273 = 5.52, p = 0.02 respectively). The slope of the interaction between plant age and length of drought was negative, meaning that as plants get older the effect of drought is more negative. This demonstrates that disentangling host age and length of drought is important to better predict plant responses to drought. Future work will analyze root exudates composition, and characterize the structure, composition and functional diversity of the AMF-root microbiome to understand the mechanisms driving AMF-root microbiome assembly and observed outcomes on plant biomass.