Natural Variations In Morphological,biochemical,nutritional And Metabolic Profiling Of Different Tea [Camellia Sinensis(L.) O. Kuntze] Cultivars Throughout The Growing Seasons

The main biochemical components,leaf morphological and yield characteristics for four rounds of tea leaves in a panel of 87 elite tea cultivars suitable for black,green,or oolong were evaluated tea in this study.Additionally,the fundamentals of natural variations for macro and micronutrients requirements,nutrient utilization and remobilization efficiencies,and seasonal fluctuations of these features were also evaluated.The current study aims to examine the natural variation of major quality components,morphological traits,and seasonal variations in tea leaves in a panel of 87 tea cultivars;to assess the natural variation and dynamics of macronutrients’use and remobilization efficiency across various tea varieties and growing seasons;and to comprehend the molecular mechanisms behind the synthesis of TFs,TRs,and TBs from catechin oxidation.The key findings are given below.1.Natural variation of main biochemical components,morphological and yield traits among a panel of 87 tea[Camellia sinensis（L.）O.Kuntze]cultivarsIn this research,significant variations were observed among the tea cultivars,as well as seasonal differences in the levels of the free amino acid（FAA）,caffeine（CAF）,tea polyphenols（TP）,water extract（WE）and TP to FAA ratio（TP/FAA）.Results showed that the average levels of FAA showed a seasonal change in the 1^st spring tea in the cultivars suitable for green tea and the lowest in summer tea in the cultivars suitable for black tea.The average CAF content was the highest in the cultivars suitable for oolong tea in the 1^stspring and the lowest in the cultivars suitable for green tea in the summer.The TP in the analyzed tea cultivars ranged from 13.6%to 23.7%,11.6%to 27.5%and 14.9%to 24.5%for the black,green,and oolong tea,respectively.Limited seasonal and varietal variations were noticed in the average levels of WE among the three categories of tea.In addition,significant variation of the morphological characteristics,bud length,bud density,mature leaves biomass,yield component traits of 100 buds dry weight,and tea yield/round,were observed in the 87 tea cultivars.2.Natural variations and dynamics of macronutrients indices for 87 tea plant varieties throughout the growing seasonsIn this study,the dynamics in macronutrients,nitrogen（N）,phosphorus（P）and potassium（K）levels,the nutrient use and remobilization efficiencies and requirements were quantified among the diverse tea plant varieties over the four harvesting rounds.The results revealed that the highest average N were observed in the young and mature leaves of the 2^nd spring tea and autumn tea,respectively,while the lowest average N levels in the young leaves was detected in summer tea and in mature leaves was detected in the 1^st spring tea.The maximum average P levels were noticed in summer tea,whereas the minimum average P levels in the 1^st spring tea.Similarly,the maximum average K levels were observed in the young leaves of summer tea.On the other hand,the minimum average K levels were observed in the 1^st spring.The results further revealed that a highest average nutrient utilization efficiency for nitrogen（NUt.E）was identified in the summer followed by autumn.The average NUt E-P in autumn and NUt E-K in the 1^st spring was relatively higher.In terms of requirements,N was the most required for optimal tea yield,followed by K,and then P.Seasonally,maximum N,P and K requirements were coincidentally observed in the 2^nd spring tea,whereas the minimum requirements were in summer tea.3.Tea quality responses to foliar application of Fe,Zn,Cu and MnA field experiment was carried out to explore the effects of iron（Fe）,zinc（Zn）,copper（Cu）and the hyperaccumulator of manganese（Mn）foliar application on the biochemical components of FAA,CAF,and TP in the black tea made from the tea（Camellia sinensis）cultivar‘Huangdan’.The foliar application of Fe,Zn,Cu,and Mn showed significant effects on FAA and TP contents of black tea（P<0.05）,but had no significant effect on the CAF content.Iron and zinc spraying significantly increased thearubigin and theabrownin content,whereas copper spraying significantly decreased thearubigin content while increasing theabrownin content.Additionally,the gene expression patterns of the POD family members CsSPX1,CsAPX1,CsGPX1,CsGPX3,CsPOD13,and CsPOD18 were identified to investigate the roles of these phenolic constituents influenced by the foliar application.The expression patterns of CsGPX3 and CsAPX1 were found to be involved in the production of TFs.PPO/POD-catalyzed TFs formation might serve as a molecular marker to identify varieties of tea plants suitable for brewing high-quality black tea beverages by regulating catechin oxidation throughout the tea processing process.