Quantitative genetic parameters in tea ( Camellia sinensis (L.) O. Kuntze): I. combining abilities for yield, drought tolerance and quality traits

Abstract

The combining abilities for yield, drought tolerance and quality related traits in Camellia sinensis were estimated using a 4 x 4 full diallel mating design. There was significant phenotypic variation for the nine traits measured among the progeny and their parents. Generally, parents with good combining ability produced progeny with above average performance for all the traits evaluated. The general combining ability (GCA) effects were significant for all but one black tea quality trait, TF:TR, while specific combining ability (SCA) effects were significant for fermentability, pubescence and bud weight. All the traits but TF:TR however were predominantly governed by additive gene effects. Strong maternal influence for all traits was evident except for thearubigins and bud weight signifying the importance of the choice of female parents in tea breeding programmes targeting yield, abiotic stress related traits and processing of black tea and special tea products like the silvery tips. Significant non-additive effects were demonstrated by all traits apart from yield, TF:TR and bud weight. However, only drought tolerance, TF and pubescence exhibited unidirectional dominance effects. The results show that the assessed traits are highly heritable and guided breeding and judicious clonal selection would lead to further tea improvement. Although no trait can be treated singly, utilization of open pollinated seed targeted towards improvement of yield and black tea quality traits particularly high levels of total polyphenols and pubescence aimed at developing a designer clone for specialty tea product would suffice given judicious choice and inclusion of suitable progenitors in seed orchards. It is inferred that the basic information about combining abilities is valuable for breeding of elite cultivars.