Co-inoculation of Trichoderma and tea root-associated bacteria enhance flavonoid production and abundance of mycorrhizal colonization in tea (Camellia sinensis)

Tea is one of the most popular nonalcoholic beverages, that contains several medicinally important flavonoids. Due to seasonal variation and various environmental stresses, the overall consistency of tea flavonoids affects the tea quality. To combat stress, plants stimulate symbiotic relationships with root-associated beneficial microbiomes that sustain nutrient allocation. Therefore, a study has been designed to understand the role of the tea root microbiome in sustaining tea leaf flavonoid production. To enumerate the microbiome, tea root and rhizoplane soil were collected from 3 years of healthy plants from Jalpaiguri district, West Bengal, India. A culture-independent approach was adopted to identify root and rhizosphere microbial diversity (BioSample: SAMN31404869; SRA: SRS15503027 [rhizosphere soil metagenome] BioSample: SAMN31404868;SRA:SRS15503030 [root metagenome]. In addition to diverse microbes, four mycorrhiza fungi, i.e., Glomus intraradices, Glomus irregulare, Paraglomus occultum and Scutellospora heterogama were predominant in collected root samples. A culture-dependent approach was also adopted to isolate several plant growth-promoting bacteria [Bacillus sp. D56, Bacillus sp. D42, Bacillus sp. DR15, Rhizobium sp. DR23 (NCBI Accession: OR821747-OR821750)] and one fungal [Trichoderma sp. AM6 (NCBI Accession:OM915414)] strain. A pot experiment was designed to assess the impact of that isolated microbiome on tea seedlings. After six months of microbiome inoculation, tea plants' physicochemical and transcriptional parameters were evaluated. The results confer that the microbiome-treated treatments [(T1-without any microbial inoculation; NCBI Accession: SAMN33591153), Trichoderma sp. AM6 (T2; NCBI Accession: SAMN33591155) and Trichoderma sp. AM6 +VAM containing tea root+synthetic microbial consortia (T5; NCBI Accession: SAMN33591154)] could enhance the total flavonoid content in tea seedlings by upregulating certain transcripts associated with the flavonoid biosynthesis pathway of tea.