HETEROSIS AND HERITABILITY ESTIMATES OF PURINE ALKALOIDS AND POLYPHENOLS IN COCOA

Abstract

Cocoa ( Theobrama cacao L. ) is an important allogamous tropical tree crop, whose centre of diversity is considered to be in Central America. Dry cocoa beans from five cocoa clones, and their intercrossed hybrids were analysed based on the variation of alkaloids and polyphenolic compounds contents, in order to gain insights on the heterosis and broad-sense heritability. Polyphenols and alkaloids were analysed at 280 nm by HPLC, using a Photodiode Array Detector (PDA); while anthocyanins were separated with the SEP-PAK Vac 6cc 1000 mg (waters) column and measured at 520 nm with a PDA. Dry cocoa beans displayed high content of purine alkaloids (2.1 and 8.8 mg g-1 for caffein and theobromine, respectively), and polyphenols (25 and 2978 \ub5g g-1 for catechin and epicatechin, respectively). Among the five cocoa clones, SNK16 was the highest in purine alkaloid (caffein and theobromin) and flavanol (catechin and epicatechin); while T79/467 possessed the greatest quantity of cyanidin-3-galactoside and cyanidin-3-arabinoside. From all the parameters studied, anthocyanins (Cyanidin-3-galactoside and cyanidin-3-arabinoside) exhibited the highest level of heterosis. Parental genotypes SNK16 and T79/467 showed good aptitudes for the combination of characters because their reciprocal hybrids F5 and F9, distinguished themselves by better levels of mid-parent heterosis values. Besides, the heritability value in strict sense of this Cyanidin-3-galactoside was very high. Absence of significant difference between genotypes, coming from reciprocal crossbreeding for Cyanidin-3-galactoside, suggests that this character in cocoa would be nuclear contrary to purine alkaloids and flavan-3-ols, where their transmission to offsprings can be stated as cytoplasmic.Le cacaoyer ( Theobrama cacao L. ) est une importante plante tropicale allogame originaire d\u2019Am\ue9rique Centrale. Les teneurs en alcalo\uefdes et en polyph\ue9nols ont \ue9t\ue9 analys\ue9es sur des f\ue8ves de cinq clones de cacao et de leurs descendants issus des croisements r\ue9ciproques afin de d\ue9terminer l\u2019h\ue9t\ue9rosis et l\u2019h\ue9ritabilit\ue9 de ces m\ue9tabolites. Les alcalo\uefdes et les polyph\ue9nols ont \ue9t\ue9 analys\ue9s par HPLC \ue0 280nm utilisant un d\ue9tecteur \ue0 barrettes de photodiode (PDA) alors que les anthocyanines l\u2019ont \ue9t\ue9 sur une colonne SEP-PAK Vac 6cc 1000 mg \ue0 520nm utilisant le PDA. Ces f\ue8ves ont des teneurs \ue9lev\ue9es en alcalo\uefdes puriques (2,1 et 8,8 mg.g-1 de caf\ue9ine et de th\ue9obromine respectivement) et en polyph\ue9nols (25 \ub5g.g-1 de cat\ue9chine et 2978 \ub5g.g-1 d\u2019epicat\ue9chine). Des cinq clones utilis\ue9s, SNK16 s\u2019est distingu\ue9 par des teneurs les plus \ue9lev\ue9es en caf\ue9ine, th\ue9obromine, cat\ue9chine et \ue9picat\ue9chine. De tous les param\ue8tres analys\ue9s, les anthocyanines ont montr\ue9 un niveau d\u2019h\ue9t\ue9rosis \ue9lev\ue9. Les g\ue9notypes SNK16 et T79/467 ont pr\ue9sent\ue9 une meilleure aptitude \ue0 la combinaison et les hybrides issus de leur croisement r\ue9ciproque (F5 et F9) ont pr\ue9sent\ue9 une meilleure h\ue9t\ue9rosis par rapport au meilleur parent. L\u2019utilisation de ces deux clones dans un champ semencier serait tr\ue8s importante pour des industries pharmaceutiques car leur croisement g\ue9n\ue8re des hybrides \ue0 haut potentiel en alcalo\uefdes et en polyph\ue9nols. De plus, l\u2019absence d\u2019une diff\ue9rence significative de cyanidine-3-galactoside entre hybrides r\ue9ciproques sugg\ue8re que l\u2019h\ue9ritabilit\ue9 de ce caract\ue8re serait nucl\ue9aire contrairement aux alcalo\uefdes puriques et aux flavan-3-ols dont l\u2019h\ue9ritabilit\ue9 serait de nature cytoplasmique