Abstract:
Tea is the most consumed non-alcoholic beverage in the world. China and India are the
biggest tea producing countries and accounted for 58% of the global tea production in
2016. These two countries are also vital as domestication centres of tea. Ancient tea
germplasm with over 1500 years old tea trees represents the most valuable tea germplasm
resource in the world. Related wild species also represent vital gene pools for further
genetic improvement. Yet, comprehensive studies on the population structure, genetic
relationships among wild and ancient tree tea types lacking. Therefore, in the current
study, we used 211 accessions including 78 wild tea plants representing 17 species (12
close wild relatives and 5 distantly related wild species) genotyped with 23 SSRs to
investigate the genetic diversity, relationships and wild species contributed to the
domestication of cultivated tea. SSR allelic polymorphisms revealed highest expected
heterozygosity/genetic diversity (He=0.812) and private allele percentages (74.3%) in
wild teas. Lowest expected heterozygosity (He=0.686) and second highest private allele
percentage (13.3%) was reported in Chinese Assam tea (CAS).
Conservation of related wild species and private allele rich CSA is of great importance.
PCoA analysis revealed 4 distinct non-overlapping groups. Similarly NJ tree and Structure
analysis also reported similar results. This indicates that cultivated tea possibly represent
three independent domestication events in China and India. Yet, multiple analysis revealed
that Chinese Assam type (CSA) and Indian Assam type tea (CSAIN) were more
genetically similar than China type tea (CT). Close wild relative Camellia taliensis was
found to be possibly contributed to the domestication of CSA in Yunnan, China. Chinese
Assam tea was found to be not cultivating in India. Additionally, Indian tea germplasm
reported being having a limited gene pool. Therefore, we recommend incorporating wild
teas and CSA into the tea breeding programmes in India.
