Polyphenols as Potential Indicators for Drought Tolerance in Tea (Camellia sinensisL.)

Abstract

Plant polyphenols have gained prominence in quality of plant products and in human health. An experiment was conducted to determine the association of tea polyphenols with water stress and their suitability as indicators for drought tolerance. The experiment was conducted in a 'rain-out' shelter, and consisted of six tea clones (BBK 35, TRFK 6/8, TRFK 76/1, TRFK 395/2, TRFK 31/30, and TRFK 311/287) and four levels of soil water contents (38, 30, 22, and 14% v/v), which were maintained for a period of 12 weeks. The treatments were arranged in a completely randomized design and replicated three times. Plant growth was monitored over 6 weeks, and a water stress index was calculated to determine water-stress tolerant clones. Total polyphenols in tea shoots was analyzed and a regression analysis done. The results indicate that declining soil water content (SWC) reduced both growth and content of polyphenols in tea. Tolerant clones maintained a high polyphenol content at low SWC, and also showed less fluctuation in phenolics when subjected to changes in SWC. There was significant (P < 0:001) correlation of total polyphenol content with shoot growth and WSI of tea, and a linear relationship (r 2 ¼ 0:97) between SWC for tea and both, water stress index and shoot polyphenol content. We report that there is a potential to use polyphenols as indicators for selection of droughttolerant tea cultivars.Key words: tea (Camellia sinensis L.); polyphenols; soil water content; drought tolerance Tea (Camellia sinensis L.) is rich in polyphenol compounds which have been a subject of study as to their effects on human health. [1][2][3][4][5][6][7][8] The crop is the source of manufactured tea, which is consumed worldwide but its production is constrained by frequent recurrence of drought in major production areas.9-11) Tea germplasm that can tolerate low soil water content (SWC) can reduce the losses occasioned by drought in production areas. Readily identifiable indicators for drought tolerance would hasten development and selection of tea germplasm for water stress environments. Plant response to stress is often manifested by its physiological and biochemical reactions, which can provide a basis for screening and selection of individual varieties and germplasm resistant to stress factors. For instance, plants are known to accumulate organic osmolytes, such as proline, glycine betaine, non-reducing sugars, and polyols 12,13) in response to stress factors. Though these organic compounds are species specific, their role is not clearly defined, but it is generally accepted that they contribute to ameliorating stress in plants. [13][14][15] Most of the stress-related organic compounds are secondary plant metabolites and incidentally, tea contains large amounts of polyphenols, particularly of the flavonol class. Some polyphenol derivatives have been used in quality determination in black tea 16) and in fruits, 17) but the role of polyphenols in drought stress and their suitability as indicators of desiccation tolerance in tea have not be...

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“…There is however no explanation as to why PC168 did not drop in TPC as this particular cultivar has been classified as tolerant from field studies over several years (Mphangwe et al, 2013). Although these studies serve to further confirm that TPC can be used as an indicator for drought tolerance in C. sinensis (Cheruiyot et al, 2007), it must be noted that TPC cannot be used to classify tea cultivars for drought tolerance when the plants are grown under shade, as shade has been documented to influence flavonoid biosynthesis. Thus, TPC is considered unreliable because we need to assess new cultivars at an early stage, while they are growing in the nursery, under shade.…”

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Shoot Epicatechin and Epigallocatechin Contents Respond to Water Stress in Tea [Camellia sinensis(L.) O. Kuntze]

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