Quantitative Trait Loci Mapping for Theobromine and Caffeine Contents in Tea Plant (Camellia sinensis)

Abstract

Understanding the genetic basis of theobromine and caffeine accumulation in the tea plant is important due to their contribution to tea flavor. Quantitative trait loci (QTL) analyses were carried out to identify genetic variants associated with theobromine and caffeine contents and ratio using a pseudo-testcross population derived from an intervarietal cross between two varieties of Camellia sinensis. A total of 10 QTL controlling caffeine content (CAF), theobromine content (TBR), sum of caffeine and theobromine (SCT), and caffeine-to-theobromine ratio (CTR) were identified over four measurement years. The major QTL controlling CAF, qCAF1, was mapped onto LG01 and validated across years, explaining an average of 20.1% of the phenotypic variance. The other QTL were detected in 1 or 2 years, and of them there were four, two, and three for TBR, SCT, and CTR, respectively. The present results provide valuable information for further fine mapping and cloning functional genes and for genetic improvement in tea plant.

Development of core-collections for Guizhou tea genetic resources and GWAS of leaf size using SNP developed by genotyping-by-sequencing

“…Camellia sinensis and related species are cross-pollinated species with a low selfpollination rate ranging from 2% to 6% (Chen, Yu & Tong, 2000;Ma et al, 2018a;Ma et al, 2018b;Ma et al, 2018c). Consistently, the heterozygosity rate of 73.5% were >20%.…”

“…Tea, coffee and cocoa are considered as the world's three best-known beverages and are also the most produced or consumed beverages worldwide (Wambulwa et al, 2016;Liu et al, 2017). To produce tea, people need to infuse processed tender shoots of the tea plant (Camellia sinensis) with connected species, all of which belong to Thea of genus Camellia in the family Theaceae (Ma et al, 2018a;Ma et al, 2018b;Ma et al, 2018c). Tea is a diploid (2n = 2x = 30) with a genome size of 3.02 Gb and is an endemic species in southwest China (Wei et al, 2018).…”

“…Germplasm preservation can be costly and time-consuming, therefore, developing 'core collections' with a minimal number of tea varieties that retain the genetic diversity is a cost-effective strategy (Frankel, 1984;Brown, 1989;Wang, Chen & Yang, 2011;Taniguchi, Kimura & Saba, 2014;Taniguchi, McCloskey & Ohno, 2014;Campoy et al, 2016;Ndjiondjop et al, 2017;Lassois et al, 2016). In addition, 'core-collections' are useful for genetic association analysis and the identification of genomic variation (Huggins et al, 2018;Zhang et al, 2018;Cunff et al, 2008;Heena et al, 2018;Ma et al, 2018a;Ma et al, 2018b;Ma et al, 2018c). Criteria based on the genetic distance between accessions have been proven sueful in evaluating and creating 'core collections' (Odong et al, 2013;Campoy et al, 2016;Ndjiondjop et al, 2017).…”

“…Previous studies on association mapping and core-collection development mainly focused on maize (Pace et al, 2015;Suwarno et al, 2015;Coan et al, 2018), sunflower (Heena et al, 2018, wheat (Muleta et al, 2017), pine (Bartholomé et al, 2017), sorghum (Bouchet et al, 2017), finger millet (Babu et al, 2018), melon (Hou et al, 2018), pea (Desgroux et al, 2017 and cotton (Ma et al, 2018a;Ma et al, 2018b;Ma et al, 2018c). By contrast, little has been done on tea germplasm with high density SNPs distributed on the whole genome.…”

Peer Review #2 of "Development of core-collections for Guizhou tea genetic resources and GWAS of leaf size using SNP developed by genotyping-by-sequencing (v0.1)"

“…The samples were planted in the city of Guiyang, China. The healthy tender shoots were harvested, snap-frozen in liquid N 2 , and kept at -80 °C until use (Jin et al, 2018).…”