Inoculation with Clariodeoglomus etunicatum improves leaf food quality of tea exposed to P stress

Abstract

The present study aimed to evaluate the effect of an arbuscular mycorrhizal fungus (AMF), Clariodeoglomus etunicatum, on leaf food quality and relevant gene expression levels of tea (Camellia sinensis cv. ‘Fuding Dabaicha’) seedlings exposed to 0.5 μM P (P0.5) and 50 μM P (P50) levels. Twenty-four weeks later, the seedlings recorded higher root mycorrhizal fungal colonization in P50 than in P0.5. AMF-inoculated tea plants represented significantly higher leaf fructose and glucose contents and lower sucrose content than non-inoculated plants, irrespective of substate P levels. AMF treatment also increased total amino acids content in P0.5 and P50, accompanied with higher expression of glutamate dehydrogenase (CsGDH) and lower expression of glutamine synthetase (CsGS) and glutamine oxoglutarate aminotransferase (CsGOGAT). The total flavonoid content was higher in mycorrhizal versus non-mycorrhizal plants under P0.5 and P50, together with induced expression of phenylalanine ammonia-lyase (CsPAL) and cinnamic acid 4-hydroxylase (CsC4H). Mycorrhizal fungal inoculation improved catechins content, which is due to the up-regulated expression of flavanone 3-hydroxylase (CsF3H), flavonoid 3'-hydroxylase (CsF3'H), dihydroflavonol 4-reductase (CsDFR), leucoanthocyanidin reductase (CsLAR), anthocyanidin reductase (CsANR), and chalcone isomerase (CsCHI) under P0.5. However, under P50, the gene involved in catechins synthesis was not affected or down-regulated by mycorrhization, implying a complex mechanism (e.g. nutrient improvement). AMF also inhibited the tea caffeine synthase 1 (CsTCS1) expression regardless of P levels. Therefore, the results of this study concluded that inoculation with C. etunicatum improves leaf food quality of tea exposed to P stress, but the improved mechanisms were different between P0.5 and P50.

Arbuscular mycorrhizal fungi and phosphorus supply accelerate main medicinal component production of Polygonum cuspidatum

“…Low P levels favor root AM fungal colonization, but high P levels inhibit AM fungal colonization (Mora et al, 2008;Breuillin et al, 2010). The present study revealed that root mycorrhizal colonization rate was significantly lower at P 0 than at P 0.2 , which is consistent with the findings of Shao et al (2021), who reported that under P deficit conditions, P uptake by tea plants relied more on root hairs than on AM fungi, resulting in low AM fungal colonization under low P levels. Therefore, future work is needed to evaluate the response of root hairs and AM fungal colonization of P. cuspidatum to different P levels.…”

“…Inoculation with AM fungi also dramatically improved root average diameter, total length, and projected area independent of P levels, being superior at P 0.2 than at P 0 . Similar results were also observed in tea (Shao et al, 2021), walnut, and trifoliate orange exposed to P stress (Wu et al, 2015b;Huang et al, 2020). The improvement of root morphology triggered by AM fungi may be linked to the increase of root auxins and polyamine levels by AM fungi (Zhang et al, 2019;Zou et al, 2021).…”

“…Substrate phosphorus (P) levels have an impact on the colonization response of AM fungi ( Campos et al, 2018 ; Cao et al, 2021 ). High levels of substrate P inhibit AM fungal colonization ( Breuillin et al, 2010 ), and low levels of P and AM fungi have improved effects on the accumulation of secondary metabolites in plants ( Zeng et al, 2014 ).…”

Individual and combined effects of arbuscular mycorrhizal fungi and phytohormones on the growth and physiobiochemical characteristics of tea cutting seedlings

“…Meanwhile, inoculation with C. etunicatum significantly improved the leaf water content and antioxidant enzyme activity of tea plants under drought stress ( Liu et al., 2020 ). In addition, AMF inoculation promoted the flavor and quality (e.g., catechins, amino acids, and tea polyphenols) of tea under phosphorus stress conditions ( Shao et al., 2018 ; Cao et al, 2021a ).…”

Mycorrhiza improves plant growth and photosynthetic characteristics of tea plants in response to drought stress

“…A previous study showed that AMF had an important impact on nutrient uptake and physiological ecology in tea plants, manifested by increased chlorophyll content and leaf area, and reduced leaf water potential, thus enhancing plant water absorption capacity (Mathur et al, 2019). It can also significantly increase the mass fraction of proline, soluble protein, and glutathione glycopeptides, as well as the contents of various mineral nutrients required by tea plants, thereby improving the quality of tea (Cao et al, 2021). Based on these reports, it is of great importance to promote the positive effects of AMF on tea tree growth and to further research the effects of AMF on tea growth and quality under drought conditions, as well as the mechanisms of AMF on tea resilience.…”