Project summary: A genomics approach to improvement of disease resistance in tea (Camellia sinensis)

Summary of the Research Problem
Tea is the most widely produced and consumed beverage in the world.  Sri Lanka, though relatively small in size, is the world’s third largest tea producer behind India and China, and the world’s largest tea exporter. The production of a range of fine quality tea varieties is essential in order for Sri Lanka to be competitive in the world market. Sri Lankan tea is famous for its unique character, towards which the composition of polyphenols contributes substantially. Not only the genotype with respect to the flavonoid pathway, but also different agroclimatic conditions in different tea growing regions, determine the chemical composition of tea. Unfortunately, the tea plant is susceptible to a number of devastating diseases, of which the fungus blister blight (Exobasidium vexans) is of major economic importance throughout the tea growing regions of Asia. E.vexans attacks only young and succulent leaves and stems and therefore the quantity and quality of the harvested leaf will be seriously affected. In the absence of any control measures direct crop loss could be as high as 43%.

Recent work from the Tea Research Institute of Sri Lanka (TRI) has indicated that tea polyphenols, specifically flavanol-derivatives, play an important role in resistance to E. vexans. Little is known of the genetic and biochemical factors that control the content and composition of tea polyphenols. This proposal establishes a collaboration between TRI and the Samuel Roberts Noble Foundation (NF), a world leader in the molecular biology of plant polyphenol biosynthesis. Funding is requested to enable the NF to host a young  scientist from Sri Lanka in the laboratory of Dr Rick Dixon, Director of NF’s Plant Biology Division. During the two year funding period, we will generate an extensive tea leaf/shoot EST collection, functionally characterize genes encoding two enzymes critical for defense-realted tea polyphenols, and generate EST-SSR markers to assist in tea disease resistance breeding programs. We will also establish an inducible cell culture system for the future application of integrated transcriptome and metabolome approaches for gene discovery in tea disease resistance pathways, The work plan will build upon the infrastructure generated under NSF-PGRP grant # 0109732 “An integrated approach to functional genomics and bioinformatics in a model legume”.

An understanding of the molecular genetics underlying the production of pre-formed and induced antimicrobial factors in the tea plant would help in the development of resistant varieties. These may also contain higher amounts of those specific flavonoids that are the most beneficial to tea quality and human health. Chemical, biochemical and molecular markers would assist the Sri Lankan tea breeding programs in the screening of lines for disease resistances at the early stages of the breeding program. We propose an integrated genomics approach to discover genes important for chemical-based disease resistance in tea, and for developing molecular markers to assist in breeding for resistance against fungal diseases such as blister blight.

• Dr  I. Sarath B. Abeysinghe, Biochemistry Division, The Tea Research Institute of Sri Lanka, Talawakelle, Sri Lanka.
• K. M. Mewan, Biochemistry Division, The Tea Research Institute of Sri Lanka, Talawakelle, Sri Lanka.

• National Science Foundation Plant Genome Developing Countries Collaboration.