Ben J. Long

Societal Impact Statement: Sorghum bicolor is a globally important cereal crop with annual yields exceeding 50 million tons across more than 100 countries and can be grown on marginal lands where conventional agriculture is limited. We examined how eight genetically diverse sorghum genotypes shaped arbuscular mycorrhizal fungal (AMF) community assembly across two contrasting field environments. We found that sorghum genotype influences AMF community composition and that this showed a pattern over time. These findings suggest that crop genotype selection can be a useful practical tool to modulate root‐microbial interactions in low‐input and marginal agricultural systems, with implications for sustainable intensification strategies and microbiome‐informed crop breeding programs. Summary: Arbuscular mycorrhizal fungal (AMF) symbiosis can influence crop production but can be variable across environmental conditions, host‐partner complementarity, and temporal dynamics. Understanding how these factors interact to shape AMF community assembly allows for the selection of crop genotypes that may maximally utilize AMF associations in agricultural systems. We assessed the development of AMF communities colonizing the roots of eight genetically diverse genotypes of Sorghum bicolor across a growing season. We used two field sites with contrasting environments and management histories. Sorghum cultivated in Georgia (GA) sorghum harbored 3.7‐fold more species than Arizona (AZ). We observed evidence of host‐filtering of AMF communities, with genotypes displaying more distinct associations in GA than AZ. AZ showed rapid shifts from early Funneliformis mosseae dominance to increasing dominance by either Entrophospora etunicata or Diversispora aurantia . In GA, we observed temporal variation associated with turnover of low‐abundance taxa contributing to larger family‐level patterns. Our findings demonstrate that there is potential for leveraging intra‐species genetic variation in AMF community assembly as an extended plant phenotype.

Arbuscular mycorrhizal fungal (AMF) symbiosis can influence crop production, but can be variable across environmental conditions, host-partner complementarity and temporal dynamics. Understanding how these factors interact to shape AMF community assembly allows for the selection of crop genotypes that may maximally utilize AMF associations in agricultural systems. We assessed the development of AMF communities colonizing the roots of eight genetically diverse genotypes of Sorghum bicolor across a growing season. We used two field sites with contrasting environments and management histories. Sorghum cultivated in Arizona (AZ) contained low diversity AMF communities, while in Georgia (GA) sorghum harbored more diverse and evenly distributed AMF communities. We observed evidence of host-filtering of AMF communities, though with genotypes displaying more distinct associations in GA than AZ. AZ showed rapid shifts from early Funneliformis mosseae dominance to dominance by either Entrophospora etunicata or Diversispora aurantia. In GA, such drastic abundance shifts were not observed. Instead, consistent temporal turnover was associated more with higher level family abundance patterns driven by the combination of minor variations in multiple low-abundance taxa. Our findings demonstrate that there is potential for leveraging intra-species genetic variation in AMF community assembly as an extended plant phenotype.

Yaupon holly ( Ilex vomitoria ) is a shrub native to the southeastern US whose leaves can be roasted and brewed into a caffeinated infusion. While production and consumption of yaupon tea is growing, not much is known about what influences downstream levels of caffeine and other metabolites within the leaf. To address this question, we used ultra-high performance liquid chromatography-mass spectrometry to measure the effect of leaf stage and roasting on the metabolome of yaupon leaves. We found caffeine levels strongly decreased with leaf stage but were not significantly affected by roasting. We also tentatively identified 100 chemicals that were dramatically increased by roasting, including several lactones and probable Maillard products related to known flavor compounds. These findings will help the yaupon tea industry produce a more consistent and tailored product, as well as lend insight into how leaf biochemistry changes over time.