Response of phosphate solubilizing bacteria in the rhizosphere of moso bamboo to phosphorus addition.

Moso bamboo forests are mainly distributed in subtropical regions characterized by phosphorus (P) deficiency. Moso bamboo exhibits a natural age structure of culms and a unique 'dual root system' of shoot roots and rhizome roots. Exploiting phosphate-solubilizing microorganisms (PSM) in the rhizosphere and their responses to P addition is essential for improving productivity and ecological functions of moso bamboo. We investigated the effect of P addition on the number and activity of PSM from the rhizosphere of shoot roots (1 year and 3 years) and rhizome roots across three levels of P addition (control: CK, 0 kg P·hm-2·a-1, low P: LP, 50 kg P·hm-2·a-1, high P: HP, 100 kg P·hm-2·a-1). We utilized the microporous plate high-throughput screening method to isolate PSM. A total of 125 strains were isolated from the rhizosphere, with 96.8% of the isolates belonging to Proteobacteria phylum. The main genus were Brucella and Burkholderia. The roots of 3-year-old bamboo (SⅢ) showed the highest number of PSM (52 strains), with the phosphorus solubilization activity of 171.24 mg·L-1, which was 1.5 and 1.4 times of that in 1-year-old shoot roots (SⅠ) and rhizome roots, respectively. Compared with CK, both the number and activity of PSM in SⅠ decreased in LP, while the number of PSM remained unchanged but the activity increased in HP. The number of PSM in SⅢ and rhizome roots decreased in LP, whereas the activity increased. Both the number and activity of PSM increased in HP. The activity of PSM was significantly positively correlated with soil total P content, pH, and microbial biomass P. Overall, the SⅢ demonstrated a higher number and activity of PSM compared to the SⅠ and rhizome, with positive response to P addition. We recommended to apply P fertilizer to the rhizosphere of 3-year-old shoot to maximize the microbial activity for P solubilizing in the intensive management of moso bamboo forests.