Self-alleviation of continuous-cropping obstacles in potato via root-exudate-driven recruitment of growth-promoting bacteria

Continuous-cropping (CC) obstacles are among the primary factors limiting the development of global agriculture. Although most plants are negatively affected by barriers that develop with CC, they may also overcome such obstacles by altering the soil biological and chemical environment to favor plant growth. In this study, we investigated the mechanism by which plants recruit beneficial microorganisms using root exudates to alleviate obstacles in a 10-year CC potato system. On day 20 after potato emergence, soil microorganisms in the CC system promoted an increase in adventitious root (AR) numbers by increasing the indole-3-acetic acid (IAA) content of the rhizosphere soil. Analysis of rhizosphere bacterial communities using 16S rRNA sequencing revealed that CC alters community structure, increasing the abundance of Pantoea sp. MCC16. Irrigation with root exudates from CC potato significantly increased AR numbers and Pantoea sp. MCC16 abundance. Through untargeted metabolomic analysis, we identified nobiletin as key metabolite that promotes Pantoea sp. MCC16 colonization in the rhizosphere. Furthermore, application of either nobiletin or Pantoea sp. MCC16 significantly improved the yield of CC potatoes. These findings demonstrate that CC plants can actively secrete the unique metabolite nobiletin to recruit Pantoea sp. MCC16, a high IAA producer, to help plants recover functional traits and mitigate CC obstacles.