Cryptic Diversity, Molecular Systematics, and Pathogenicity of Genus Pestalotiopsis and Allied Genera Causing Gray Blight Disease of Tea in Taiwan, With a Description of a New Pseudopestalotiopsis Species.

Camellia sinensis (L.) O. Kuntze, commonly known as tea, is widely cultivated around the world in tropical and subtropical areas. Tea is mainly manufactured using young shoots of tea plants. Therefore, it is essential to control foliar diseases. Gray blight disease is caused by pestalotiopsis-like taxa and is known as one of the most destructive tea diseases. Although several studies have provided the groundwork for the fungal diseases associated with C. sinensis in Taiwan, gray blight disease has not been characterized based on diversity, molecular systematics, or pathogenicity. The goal of this study was to identify and characterize the causative agents of tea gray blight disease. A total of 98 pestalotiopsis-like isolates associated with symptomatic leaves of C. sinensis from major tea fields in Taiwan were investigated. Based on phylogenies of single and concatenated DNA sequences (internal transcribed spacer, ß-tubulin, translation elongation factor 1-α) together with morphology, we resolved most of the pestalotiopsis-like species in this study. The study revealed seven well-classified taxa and seven tentative clades in three genera: Pestalotiopsis, Pseudopestalotiopsis, and Neopestalotiopsis. One novel species, Pseudopestalotiopsis annellata, was introduced. Five new records, Pseudopestalotiopsis chinensis, Pseudopestalotiopsis camelliae-sinensis, Pestalotiopsis camelliae, Pestalotiopsis yanglingensis, and Pestalotiopsis trachicarpicola, were introduced for the first time in Taiwan. Pseudopestalotiopsis chinensis was the taxon most frequently isolated from C. sinensis in this study. Furthermore, results of pathogenicity assessments exhibited that, with wound inoculation, all assayed isolates in this study were pathogenic on tea leaves. Pseudopestalotiopsis chinensis and Pseudopestalotiopsis camelliae-sinensis were identified as the major pathogens associated with gray blight disease of tea in Taiwan. To our knowledge, this is the first study of the diversity, pathogenicity, and characterization of pestalotiopsis-like fungi causing tea gray blight disease in Taiwan.

Development of STS and CAPS markers for variety identification and genetic diversity analysis of tea germplasm in Taiwan.

BACKGROUND: Tea (Camellia sinensis) is an important economic crop in Taiwan. Particularly, two major commercial types of tea (Paochong tea and Oolong tea) which are produced in Taiwan are famous around the world, and they must be manufactured with specific cultivars. Nevertheless, many elite cultivars have been illegally introduced to foreign countries. Because of the lower cost, large amount of "Taiwan-type tea" are produced and imported to Taiwan, causing a dramatic damage in the tea industry. It is very urgent to develop the stable, fast and reliable DNA markers for fingerprinting tea cultivars in Taiwan and protecting intellectual property rights for breeders. Furthermore, genetic diversity and phylogenetic relationship evaluations of tea germplasm in Taiwan are imperative for parental selection in the cross-breeding program and avoidance of genetic vulnerability. RESULTS: Two STS and 37 CAPS markers derived from cytoplasmic genome and ESTs of tea have been developed in this study providing a useful tool for distinguishing all investigated germplasm. For identifying 12 prevailing tea cultivars in Taiwan, five core markers, including each one of mitochondria and chloroplast, and three nuclear markers, were developed. Based on principal coordinate analysis and cluster analysis, 55 tea germplasm in Taiwan were divided into three groups: sinensis type (C. sinensis var. sinensis), assamica type (C. sinensis var. assamica) and Taiwan wild species (C. formosensis). The result of genetic diversity analysis revealed that both sinensis (0.44) and assamica (0.41) types had higher genetic diversity than wild species (0.25). The close genetic distance between the first (Chin-Shin-Oolong) and the third (Shy-Jih-Chuen) prevailing cultivars was found, and many recently released varieties are the descents of Chin-Shin-Oolong. This implies the potential risk of genetic vulnerability for tea cultivation in Taiwan. CONCLUSIONS: We have successfully developed a tool for tea germplasm discrimination and genetic diversity analysis, as well as a set of core markers for effective identification of prevailing cultivars in Taiwan. According to the results of phylogenetic analysis on prevailing tea cultivars, it is necessary to broaden genetic diversity from wild species or plant introduction in future breeding programs.