Aluminum-Tolerant Wheat Genotype Changes Root Microbial Taxa and Nitrogen Uptake According to Soil pH Levels and Nitrogen Rates

Nitrogen (N) fertilizer induces soil acidification and aggravates aluminum (Al) toxicity in acid soil, while Al toxicity inhibits root growth and limits plant N acquisition. In this study, we explored the effect of enhanced Al tolerance on wheat (Triticum aestivum L.) N recovery efficiency (NRE) in acid soil and examined potential microbial mechanisms. Two wheat varieties (Al-tolerant Atlas 66 and Al-sensitive Scout 66) were cultivated with or without N fertilizer at soil pH levels 4.6, 5.0, and 5.4 in pots for 55 days. After harvest, we examined wheat growth and NRE, soil pH, Al toxicity, and microbial communities. The NRE and N loss of Al-tolerant variety were 2.4 times and 60% those of the Al-sensitive one at soil pH 4.6, respectively. This N superiority of Al-tolerant variety disappeared at soil pH levels 5.0 and 5.4 where soil toxic Al concentrations were decreased relative to soil pH 4.6. Compared with the Al-sensitive variety, the roots of Al-tolerant wheat at soil pH 4.6 recruited several specific bacteria (Granulicella, Phenylobacterium, Geodermatophilus, Noviherbaspirillum, Massilia, and Sinomonas) and fungi (Chaetomium, Arcopilus, and Microascus) associated with soil N transformation and plant growth promotion, but the number of genotype-specific microbial taxa dramatically decreased at soil pH levels 5.0 and 5.4. Enhanced Al tolerance combined with root-recruited genotype-specific microbial taxa improves wheat NRE and reduces fertilizer N loss in acid soil.