Winter wheat cultivar improvement impacts rare bacterial communities in the rhizosphere more than abundant bacterial communities

Understanding the impact of genetic improvements in wheat cultivars on microbial communities is crucial for enhancing nitrogen utilization efficiency and increasing crop yields. This study analyzed 20 wheat cultivars released between 1964 and 2018, revealing shifts in abundant and rare bacterial communities in the rhizosphere , with distinct patterns over time. The α-diversity of abundant bacterial communities significantly declined with newer cultivars, while rare communities increased. The β-diversity of abundant groups remained stable, while rare groups decreased. Stochastic processes influenced these communities, with abundant groups maintaining a constant stochastic element and rare groups experiencing increased stochasticity. Functional predictions revealed decreased anaerobic chemoheterotrophy and fermentation and increased ureolysis and aromatic compound degradation in rare communities. Random forest analysis showed that the composition of the rare bacterial communities explained more variation in cultivar improvement than that of abundant communities. In abundant bacterial communities, increases in F_Rhizobiaceae and G_Pedobacter correlated with higher grain yield and nitrogen ultilization efficiency. In rare bacterial communities, higher grain yields were associated with increases in S_Pelomonas_aquatica , S_Dyadobacter_hamtensis , G_Erwinia , and G_Sphingobacterium , while P_Candidatus_Saccharibacteria and S_Dyadobacter_hamtensis contributed to enhanced nitrogen efficiency. These findings offer valuable insights into how genetic improvements in wheat cultivars influence soil bacterial communities, potentially optimizing nitrogen ultilization and boosting grain yields. • Abundant and rare bacterial communities exhibited distinct responses to wheat cultivar improvement. • Wheat cultivar improvement affected rare bacterial communities more than abundant bacterial communities. • Stochastic processes predominantly shaped the assembly of both bacterial communities. • Functional shifts in rare bacterial communities were closely linked to carbon and nitrogen cycling.