Determinants of shea (Vitellaria paradoxa C.F. Gaertn.) fruit yield: A review of research approaches and current knowledge

Abstract

Vitellaria paradoxa (shea) has interannual variability in fruit yield patterns, which results in unpredictable export volumes. Research on factors accounting for this inconsistency is needed to manage tree stands for optimum yield, but existing studies on the topic have shown conflicting results. In order to synthesize research approaches used in examining determinants of shea reproductive success, and to identify research gaps, we reviewed the existing literature on the subject available in Scopus and Google Scholar from 2000 to 2021. Out of 119 primary research articles identified in our literature search, 40 articles met our predefined inclusion criteria. Geographically, most studies (75%) were conducted in West Africa, and six times as many studies used quantitative approaches compared with either qualitative or mixed method approaches. Fruiting emerged as the most studied aspect of shea reproductive biology (73% of studies), whereas less is known on floral biology and pollination. All studies that assessed the effect of agro-ecology, seasonality, pollination, and altitude reported significant effect of these factors on fruit yield. However, there were divergent outcomes on land use/management, dendrometry and parkland tree diversity on fruit yield. The majority of the studies examined single factor effects on yield for one flowering/fruiting season, which is a major weakness of the existing research. We recommended several strategies to improve the reliability of future studies on determinants of shea reproductive success, such as designing multi-factorial experiments to cater for extraneous variables, profiling land use history of the shea parkland and conducting experiments for multiple seasons.

Keywords

• Determinants
• Fruit yield
• Fructification
• Vitellaria paradoxa
• Reproductive biology