Characteristics of root-associated microbiomes and their responses to soil nitrogen levels in different wheat cultivars

Plant root-associated microorganisms play important roles in nutrient uptake and plant growth. In order to illustrate the differences in the root-associated microbial community structure of different wheat cultivars, four wheat cultivars (i.e., ‘Kenong 9204’ ‘Kenong 2011’ ‘Jing 411’ and ‘Bainong 207’) were planted under 0 kg(N)·hm⁻² (low nitrogen level) and 300 kg(N)·hm⁻² (high nitrogen level), and the rhizosphere and root samples were collected at the tillering, jointing, and filling stages. The bacterial diversity and community structure in the rhizosphere and root endosphere of different wheat cultivars were analyzed using 16S rRNA high-throughput sequencing, and the physiological parameters of wheat were determined. Compared with the other three cultivars, ‘Ke-nong 9204’ had higher aboveground nitrogen accumulation at the three growth stages and under two nitrogen levels, except at the tillering stage with a low nitrogen level. Proteobacteria and Actinobacteria were the dominant bacteria in the wheat rhizosphere and root endosphere. Compared to the other three cultivars, ‘Kenong 9204’ enriched Rhizobiales and Gemmatimonas in the rhizosphere soil bacterial community under low nitrogen level at the jointing stage and enriched Frankiales under high nitrogen level at the filling stage. Correlation analysis showed that Arthrobacter, Streptomyces, Rubrobacter, and Nocardioides in the rhizosphere soil bacterial communities were significantly positively correlated with aboveground biomass and nitrogen accumulation; Massilia, Arenimonas, Pseudomonas, and Flavobacterium were significantly positively correlated with aboveground nitrogen content. Our results indicate that wheat may affect nutrient uptake by regulating the composition of the microbial community in the root zone and that this effect is cultivar-specific. This study provides useful information for understanding plant-microbe interactions in wheat and harnessing beneficial microbes for agricultural production.