Domestication of Irvingia gabonensis: 2. The selection of multiple traits for potential cultivars from Cameroon and Nigeria

Abstract

Ten fruit and kernel traits were assessed in 24 fruits of each of 152Irvingia gabonensis trees in three distinct populations inwest and central Africa [2 populations of non-planted trees in Cameroon:Nko'ovos II (21 trees) and Elig-Nkouma (31 trees) and 1 population ofplanted trees in Nigeria: Ugwuaji (100 trees)]. Strong relationships were foundbetween fruit weight and other fruit traits (e.g. flesh weight[r 2 = 0.99: P < 0.001],fruit length [r 2 = 0.74–0.83:P < 0.001], fruit width[r 2 = 0.77–0.88: P< 0.001]). In contrast, relationships between kernel weight and otherkernel/nut traits (e.g. shell weight and nut weight) were found to be weak[r 2 = 0.009–0.37, P =0.058–0.001], with the exception of nut weight at Nko'ovos II(r 2 = 0.65, P < 0.001).Relations hips between fruit and kernel traits (fruit massv. kernel mass, fruit mass v. shellmass, flesh mass v. kernel mass, nut massv. fruit mass and flesh depth v.kernel mass) were found to be very weak. This indicates that domesticationthrough the selection and vegetative propagation of multiple-trait superiorphenotypes is unlikely to be able to combine good fruit characteristics and goodkernel characteristics within cultivars. Consequently, domestication activitiesshould independently focus on ideotypes representing: lsquofresh fruitrsquotraits, and lsquokernelrsquo traits, that combine high values of thedifferent fruit and kernel characteristics respectively. Evidence from thisstudy indicates that selection of the three trees closest to the fruit ideotypeper village as the mother plants for vegetative propagation and cultivardevelopment, should give village level gains of 1.3 – 2-fold in fruitmass, and up to 1.5-fold in taste. Similarly for the kernel ideotype, selectionof the three trees with the best fit would give potential gains in kernel massof 1.4 – 1.6-fold.