Heritability and Genetic Advance Estimates of Key Shea Fruit Traits
Date
2023
Journal Title
Journal ISSN
Volume Title
Publisher
Agronomy
Abstract
Genetic erosion of shea trees, which has been on-going at an alarming rate, has necessitated
urgent conservation attentions. Owing to the vast geographical distribution of the species across
Ghana, in situ germplasms conservation was established by tagging and monitoring selected trees
annually. Technologies have been developed that enable shea germplasms to be grafted, allowing for
the development of germplasm banks at the research station of the Cocoa Research Institute of Ghana,
Bole. However, before these materials could be used in crop improvement programs, there is a need
to evaluate them for key fruit traits relevant to the global shea business. This experiment was carried
out to evaluate the tagged in situ shea trees for fruit and nut traits. Freshly harvested shea fruits
were evaluated for their brix, pulp yield and kernel size properties to see if there was the needed
diversity for crop improvement gains. Eight key traits were studied, with all showing significant
difference, with high broad sense heritability and genetic advance for all the traits, indicating the
potential for genetic gains in breeding programs. Qualitative analysis classified the fruits into five
shapes, ellipsoid fruit shape was the most frequent observation (69.5%), while oblong was the least
represented (1%). Fruit surface pubescence indicated that the surfaces without hairs (smooth) were
slightly higher in number (52.6%) than the surface with hairs (rough), which were 47.4%. Pearson
correlation studies showed a positive significant relationship between kernel weight and fruit weight
(0.68), fruit length (0.48), fruit width (0.51), pulp weight (0.5) and shell weight (0.77). Key components
responsible for total variations observed were decomposed from the first two principal components
(PC), which cumulatively explained 78.4% of the total observed variation within the materials. PC1
alone contributed 46.4%, while PC2 contributed 32%. Fruit weight, fruit length, fruit width, pulp
weight, nut weight, shell weight and kernel weight were contributing traits to variations observed in
PC1, while brix and percent pulp contributed to the variations observed in PC2. Percent kernel to
nut ratio contributed to the variations observed in PC3. Clustering of the germplasms showed no
regular pattern based on location or any particular trait, indicating a high level of diversity at 58% of
the Pearson dissimilarity index.
Description
Research Article
Keywords
heritability, genetic advance, shea