Growth habits and heritability estimates of shea hybrid populations

Shea is an undomesticated agroforestry tree found predominantly in West and some East African countries. Its butter is very important in the global food, cosmetic and pharmaceutical industries. The tree has a lengthy vegetative growth taking up to 12 years before flowering, making it undesirable for cultivation. The tree has also not seen any improvement of traits whether agronomic or yield related such as kernel and butter traits. The objective of this project was to evaluate our first developed shea populations from selected diverse parents in order to understand juvenile growth of shea, shedding light on inheritance of traits with the possibility of developing parklands and enriching old ones. Eight artificially developed populations were evaluated for early agronomic traits. Apart from providing understanding on the growth of shea crops, the population when matured will enhance knowledge on the inheritance and improvement of shea butter quality traits. Morphological growth after 4 years showed significant differences in all traits measured between the populations. Heritability estimates for key growth traits were high, with leaf width and number of primary branches being the highest heritable traits of 0.97, while plant height had the lowest heritability estimate of 0.81. Jorquette height and number displayed also high heritability, 0.83 and 0.92 respectively. Correlation studies further revealed significant positive correlation between petiole length and stem diameter (r = 0.82) and between total plant height and stem diameter (r = 0.95). There was also positive correlation between all leaf traits studied. Principal component analysis of the population revealed that the first two axes accounted for 79.45 % of the observed variations. To conclude, these first developed populations are showing improved vigour and growth, serving as a reference for future shea population development through hybridization.