INHERITANCE OF CATECHIN AND CAFFEINE CONTENT IN KENYAN TEA (Camellia sinensis (L.) O. Kuntze)

Abstract

Diallel designs are used in many breeding programmes because of the important genetic information they offer to plant breeders. Eight biochemical traits were studied to estimate the general combining abilities (GCA), specific combining abilities (SCA), heterosis and stability of 16 F1 crosses arising from a 4 x 4 diallel cross of the 4 tea clones evaluated at Timbilil and Kangaita TRFK experimental stations. Data analysis was carried out using GLM procedure from SAS at each of the site. There were significant (p<0.05) differences between the genotypes for all the traits under study at both sites. At Timbilil, general combining ability (GCA) effects were significant (p<0.05) for GA, EGC, CAFF, ECG, EGCG and TC, while at Kangaita, all traits had significant (p<0.05) GCA effects except C, implying that these traits are governed by additive gene effects. EPK TN14-3 had the best general combining ability at both Timbilil and Kangaita for nearly all the assessed traits. Specific combining ability at Timbilil was significant (p<0.05) for EGC, CAFF, EC, EGCG, TC, while at Kangaita, significant (p<0.05) SCA effects was exhibited in all the traits except CAFF. Maternal effects were significant (p<0.05) for EGC, EGCG and TC at Timbilil. At Kangaita maternal effects were significant (p<0.05) for EC signifying importance of the choice of female parents in breeding programmes targeting these traits. Both GGE biplot and the AMMI stability methods revealed that cross TRFK 6/8 x EPK TN14-3 (476) was the most stable cross for TC, EGCG and caffeine. The study demonstrated that quantitative genetic parameters such as additive, non-additive gene and maternal effects have considerable influence on the inheritance of catechins and caffeine, and consequently on tea quality targeting high value diversified tea products as well as advanced tea breeding programmes.