Assessment of citrus diversity in Ghana

Abstract

Citrus is among the plant germplasm conserved at the CSIR - Plant Genetic Resources Research Institute (CSIR - PGRRI), Bunso in Ghana; however, due to lack of information on the specific traits of this germplasm at the Institute, the potential diversity within the collection is not yet fully exploited. The objective of this study was to evaluate the morphological diversity among the citrus accessions under conservation at the field genebank of the CSIR - PGRRI, Bunso, Eastern region of Ghana. The various accessions were raised on rough lemon rootstocks, planted using the augmented design. The citrus accessions evaluated include different citrus types suitable for different purposes, such as Flying Dragon for rootstock, Sweet Lime for medicine and Mediterranean Sweet for fruit drink. Late Valencia and Mediterranean Sweet were used as checks. Planting was done at 8 m by 8 m. Apart from watering immediately after planting, the plants grew under natural condition without irrigation. Variability was revealed by all the traits studied, including scion trunk surface, tree shape, tree growth habit and branch angle, based on IPGRI descriptors for citrus. The resulting phylogenic tree clustered the citrus accessions mainly based on known genetic relationships, using the clustering away of citrons from mandarins as an example. Although the morphological traits used in the characterisation were not sophisticated, they were useful in discriminating among the accessions. Based on this study, the citrus genebank at CSIR - PGRRI, Bunso, Eastern region of Ghana contains 44 morphologically distinct accessions. The information generated in this study is important for guiding conservation and utilisation decisions geared towards the improvement of the citrus sub-sector in the country.