Identification of novel QTL for black tea quality traits and drought tolerance in tea plants (Camellia sinensis)

Abstract

Tea (Camellia sinensis) contain polyphenols and caffeine which have been found to be of popular interest in tea quality. Tea production relies on well distributed rainfall which influence tea quality. Phenotypic data for two segregating tea populations TRFK St 504 and TRFK St 524, were collected and used to identify the quantitative trait loci (QTL) influencing tea biochemical and drought stress traits based on a consensus genetic map constructed using the DArTseq platform. The populations comprised 261 F1 clonal progeny. The map consisted of 15 linkage groups which corresponds to chromosome haploid number of tea plant (2n = 2x = 30) and spanned 1260.1 cM with a mean interval of 1.1 cM between markers. A total of 16 phenotypic traits were assessed in the two populations. Both interval and multiple QTL mapping revealed a total of 47 putative QTL in the 15 LGs associated with tea quality and percent relative water content at a significant genomewide threshold of 5%. In total, six caffeine QTL, 25 catechins QTL, three theaflavins QTL, nine QTL for tea taster score and three QTL for percent relative water contents were detected. Out of these 47 QTL, 19 QTL were identified for ten traits in three main regions on LG01, LG02, LG04, LG12, LG13 and LG14. The QTL associated with caffeine, individual catechins, and theaflavins were clustered mostly in LG02 and LG04 but in different regions on the map. The explained variance by each QTL in the population ranged from 5.5 to 56.6%, with an average of 9.9%. Identification of QTL that are tightly linked to markers associated with black tea quality coupled with UPLC assay may greatly accelerate development of novel tea cultivars owing to its amenability at seedling stage. In addition, validated molecular markers will contribute greatly to adoption of marker-assisted selection (MAS) for drought tolerance and tea quality improvement.

Combined linkage and association mapping of putative QTLs controlling black tea quality and drought tolerance traits

“…A wide range of variation in individual catechins, theaflavins, and caffeine contents was observed in the two parents and F 1 progeny for all 16 phenotypic traits as described previously by Koech et al (2018).…”

“…Two pseudo-testcross populations used in this current study consisted of 109 F 1 progeny from TRFK St. 504 (TRFK 303/577 × GW Ejulu) and 152 F 1 progeny from TRFK St. 524 (GW Ejulu × TRFK 303/577) as described previously (Koech et al 2018). In brief, the two parental clones, TRFK 303/577 and GW Ejulu, are of Assamica and China varieties, respectively.…”

“…A total of 16 phenotypic traits as described in the previous work by Koech et al (2018) were used in this study. In brief, all the 16 phenotypic traits were assessed for a normal distribution.…”

“…One thousand four hundred and twenty-one DArTseq markers derived from C. sinensis genomic DNA of the two parents and 261 F 1 progeny were subjected to linkage mapping analyses using JoinMap 4.0 (Van Ooijen 2006) and QTL mapping analyses using MapQTL 6.0 software (Van Ooijen et al , 2000) as described previously (Koech et al 2018; Koech et al, 2019).…”

Genome-enabled prediction models for black tea (Camellia sisnesnsis) quality and drought tolerance traits

“…The selected eight phenotypic traits used were, %RWC, caffeine, catechin and tea tasters’ scores (aroma, astringency, brightness, briskness, and colour) which are associated with black tea quality and drought tolerance traits. All the individuals in both the discovery and validation populations were genotyped using 1 421 DArTseq markers (Koech et al , 2018; Koech et al , 2019).…”