Geographic variation in shea (Vitellaria paradoxa subsp. paradoxa) floral phenology and morphology in the Guinea savanna zone of Ghana

Abstract

Vitellaria paradoxa is a multipurpose tree endemic to the Sudano-Sahelian zone of Africa. The edible fat extracted from shea kernel is of cultural, nutritional and industrial significance.  Floral phenology and morphology do not only influence pollinator attraction but also serve as indicators of genetic diversity in tree improvement programmes. Understanding shea floral phenology is essential to unveiling phenological responses to climate change. The study investigated  the relationship between floral phenology and climatic variables,  and examined spatial variation in floral traits across  six  sites in  three regions (Upper West, Upper East, and Northeast) of Ghana. Twenty focal trees were tagged for observation of phenological parameters and measurement of floral traits in each site. We found a variation in the date of flowering onset between regions. Flowering commenced in Upper West over a month earlier than Upper East and Northeast regions. The weekly number of trees commencing flowering was found to be significantly associated with soil moisture and soil temperature. Shea floral traits (pedicel diameter, pedicel length, petal length, filament length and style length) also differed significantly between regions.  Although the study recommends multiple years of phenological observations on the impact of climatic conditions, the geographic variation in floral morphology should be considered in germplasm collection for tree improvement and domestication.

 Key Words:  Flowers; floral phenology; floral traits; climatic factors; shea parkland; Vitellaria paradoxa