Kernel morphometric characteristics and oil content among Shea tree genotypes in Uganda

Abstract

Shea tree (Vitellaria paradoxa subsp. nilotica) is an important commercial tree for domestic oil and industrial products of cosmetics, chocolate and other confectionaries traded grown worldwide. We studied seed morphometric characteristics and crude oil content of Shea nuts in Uganda. Five populations, comprising of 16 ethnovarieties, were selected from Eastern, Northern and West Nile Sub-regions of Uganda, based on their attributes as judged by the farmers. Fresh kernel weight ranged from 2 to 18.85 mg per seed. Kernel weight increased with Shea fruit weight (y = 0.1499x + 6.1887, R² = 0.306). Moyo district had the highest oil content (54.37 ± 0.32%); while Amuru district had the lowest oil content (50.5 ± 1.32%). Oil content decreased with increasing kernel size (y = -0.4541x + 57.303, R² = 0.2116) and dry matter content (y = 0.635x - 9.863, R²= 0.011); and varied between ethnovarieties and Shea tree populations, p = 0.003 and P< 0.001, respectively. Tinny seeded (45.7 - 65.49%), Round fruited (45.41 - 65.91%), Dwarf tree (45.19 - 64.19%), Elliptical fruited (45.32 - 64.19%) and Soft pulped (42.16 - 69.77%) ethnovarieties had the highest oil content. Narrow sense heritability (h2) for oil yield was 1.72; while response to selection (R) was 16.48 with genetic gain (Gs) of 2.21%, given 10% top selection intensity.