Phenotypic Variation in a Panel of 149 varieties of Cassava (Manihot esculenta Crantz): A Pre-Breeding Investigation in Togo

Abstract

Evaluating the genetic diversity within a plant species is crucial for identifying genes that control important biological functions, facilitating the rationale for developing new varieties. The genetic diversity in a panel of 149 cassava varieties was explored to assess its nature, pattern, and differentiation. The experiment was conducted at the Breeding Station of Davié in the forest-savanna transition zone characterized by a bimodal rainfall pattern. One hundred and fourty nine varieties were planted in an augmented block design, with five improved and released varieties as check genotypes. Data on sixteen phenotypic traits were collected based on cassava traits ontology. A high diversity coefficient of 0.78 was observed among varieties. Multivariate analysis revealed all assessed traits as discriminative for cassava varieties. Principal Component Analysis identified traits such as fresh root yield, plant vigour, number of roots per plant, Cassava Mosaic Disease (CMD) severity, aboveground biomass, leaf lobe dimensions, Cassava Bacterial Blight (CBB) severity, plant height, height to first branching, petiole length, harvest index as major contributors to the variability of the germplasm. Cluster and canonical analyses delineated seven significant groups, characterized by traits like CMD and CBB resistance, vigorous growth, high canopy and fresh root yield, high harvest index and root dry matter content.The findings provide a foundation for informed selection of parental lines in developing new high-yielding and CMD-resistant cassava varieties.