Screening of EGCG -tolerant growth promoting bacteria and their efficiency in enhancing tea plant growth

• Low concentration EGCG enhanced the growth of tea plants; • EGCG Reshaped Rhizosphere Microbiota and enriched Burkholdeiales and Acidothermus ; • The selected strains could tolerate and degrade EGCG; • The selected strains promoted the growth of tea cuttings with or without EGCG In recent years, plant growth-promoting bacteria were being valued and applied to enhance plant health and confer resistance. The tender shoots of tea plants are rich in polyphenols, especially epigallocatechin gallate (Hossen et al.), which will return to the rhizosphere soil after being pruned. Therefore, the screening of EGCG-tolerant strains is of great significance for the development of growth-promoting bacteria for tea plants. In this paper, EGCG treatment results showed that 0.6 mg/mL EGCG significantly promoted the growth of tea plants. 16S rRNA sequencing results revealed that after 0.6 mg/mL EGCG treatment, Pseudomonadota and Actinomycetota phylum were significantly enriched, and at genus level, the abundance of Burkholdeiales and Acidothermus were increased significantly. EGCG tolerance characteristics analysis exhibited that among the 75 bacteria of tea roots, 32 strains could tolerate 1.5 mg/mL EGCG. For strains Paraburkholderia (PPH), Micromonospora (FSS), and Sporosaricina (AME2), the optimal degradation concentration of EGCG was 0.6 mg/mL. With the extension of time, the content of EGCG decreased gradually. The Q-TOF-MS analysis showed that EGCG was degraded to gallic acid (GA) and epigallocatechin (EGC). Then the effects of growth-promoting and EGCG-tolerant strains PPH, FSS and AME2 on the growth of tea plants were explored. The results showed that PPH, FSS and AME2 strains all could promote the growth of tea cuttings with or without EGCG, particularly increasing the root weight. In conclusion, through comprehensive analysis, the growth-promoting and EGCG-tolerant strains were successfully identified, which hold great potential for development into microbial fertilizers to be applied in tea plantation management.