Molecular, biochemical and physiological characteristics associated with quality and tolerance to drought and low temperature in tea (Camellia sinensis (L) O. Kuntze)

Abstract

Tea cultivars that make high black tea quality and are drought or low temperature tolerant are needed for sustainable tea cultivation. However, there is still a lack of precise, time- and costeffective selection criteria for these desired traits in tea breeding programmes. The aim of this study was to identify molecular, physiological and biochemical characteristics associated with black tea quality and tolerance to drought or low temperature in order to establish objective selection criteria for these traits. Cultivars that were pre-classified for absence or presence of each trait were used in the study. Using the random amplified polymorphic DNA (RAPD) technique, six specific RAPD bands were identified that closely associated with black tea quality (three bands), tolerance to drought (two bands) and low temperature (one band). These RAPD bands can be used as markers that will facilitate identification of elite breeding stocks or genotypes at an early stage. In the study on drought tolerance, individual parameters could not clearly separate the tolerant and susceptible cultivars, although a trend suggesting differences between the two groups was observed. The univariate analysis probably failed to show significance between the two groups due to the relatively small sample sizes used. This was to some extent confirmed by multivariate analysis in which it was established that high relative water content (RWC) and antioxidant activity can jointly be useful indicators of drought tolerance in tea. Drought tolerant cultivars maintained high relative water content and antioxidant activity in order to optimize water use and reduce oxidative stress. The study on low temperature tolerance showed that shoot extension was faster and total polyphenol content (TPC) and antioxidant activity were higher in tolerant than in susceptible cultivars. The small sample size may also have affected the ability to identify individual characteristics that associate with the trait. In conclusion, RAPD bands that closely associate with high black tea quality and drought or low temperature tolerance, relative water content and antioxidant activity during drought and total polyphenol content and antioxidant activity under low temperature stress could be used in the selection of elite tea cultivars. The RAPD technique and measurements of relative water content, total polyphenols and antioxidant activity are easy and inexpensive and can easily be incorporated in routine selection to save costs and time, and to improve selection precision and success of breeding programmes. The limitations associated with RAPD should be taken into account when using the technique to ensure consistence and reproducibility of the identified markers.