Abstract
Understanding the genetic diversity among accessions and germplasm is an important requirement for crop development as it allows for the selection of diverse parental combinations for enhancing genetic gain in varietal selection, advancement and release. The study aimed to characterize 183 provitamin A cassava (Manihot esculenta Crantz) accessions and five Sierra Leonean varieties using morphological traits, total carotenoid content and SNP markers to develop a collection for conservation and further use in the cassava breeding program. Both morphological parameters and 5634 SNP markers were used to assess the diversity among the provitamin-A cassava accessions and varieties. Significant differences were observed among the accessions for most of the traits measured. The first five PCs together accounted for 70.44% of the total phenotypic variation based on yield and yield components among the 183 provitamin-A cassava accessions and five Sierra Leonean varieties. The present study showed that provitamin-A cassava accessions in Sierra Leone have moderate to high diversity based on morphological and molecular assessment studies. The similarity index among the 187 and 185 cassava accessions grouped them into 6 and 9 distinct clusters based on morphological and molecular analyses, respectively. A significant positive, but low correlation (r = 0.104; p < 0.034), was observed between the two dendrograms. The results obtained will serve as a guide and basis of germplasm management and improvement for total carotenoid content, yield and African cassava mosaic disease resistance in Sierra Leone.
Highlights
Genetic diversity provides species with the ability to adapt to changing environments
The present study showed that provitamin-A cassava accessions in Sierra Leone have moderate to high diversity based on morphological and molecular assessment studies
The plant materials used in the study consisted of 183 provitamin-A cassava accessions known for their varying levels of provitamin- A properties, obtained from the International Institute of Tropical Agriculture (IITA, Ibadan, Nigeria) and established at the Taiama experimental site in Sierra Leone, in 2014 (Table 1) and five Sierra Leonean cassava varieties
Summary
Genetic diversity provides species with the ability to adapt to changing environments. Several studies have been reported on the use of morphological descriptors to determine the genetic diversity among cassava genotypes (Rimoldi et al 2010; Asare et al 2011; Thompson 2013). Previous studies in plant genetic diversity used DNA molecular markers for beta carotene improvement in cassava (Ferreira et al 2008; Rimoldi et al 2010), and included amplified fragment length polymorphism (Benesi et al 2010), simple sequence repeats (Alves et al 2011; Parkes 2009; Oliveria et al 2012; Costa et al 2013) and single nucleotide polymorphism (Kizito et al 2005; Tangphatsornruang et al 2008; Ferguson et al 2011; Thompson 2013; Rabbi et al 2015). With recent advances in high throughput genotyping technologies, single nucleotide polymorphism markers (SNPs) are increasingly becoming markers of preference for plant genetic studies and breeding
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