Dry matter content and post-harvest physiological deterioration as phenemarkers for characterization of improved clones of cassava

Abstract

Postharvest Physiological Deterioration (PPD) is a devastating stress of cassava with a positive but undesirable relationship with dry matter (DM) content. The present study evaluated PPD susceptibility and DM among thirty-six improved genotypes of cassava to gain knowledge of their status for possible PPD management. In addition, PPD and DM were assessed as phene markers for estimating genetic distances (GD) among the 36 genotypes for breeding objectives. PPD was quantified using visual streaking evaluation and DM was by oven drying to a constant weight. The results obtained showed a high effect of individual root and genotype on PPD susceptibility and DM content among the assessed cassava genotypes. A weak positive relationship was observed between PPD and DM content (P<0.0001, r = 0.32). Five and three phenetic groups were identified among the 36 cassava genotypes for PPD and DM, respectively. Genetic distances estimated ranged between 0.01 and 0.56 GD with an average of 0.17 GD and nine phenetic clusters were revealed among the 36 cassava genotypes. The factorial analysis employed revealed some useful demarcations among the PPD pheneticgroups while there was no clear cut demarcation for DM phenetic groups among the cassava genotypes. The information embedded in this study is useful in facilitating breeding for PPD with an attention to DM content. Furthermore, it would encourage the use of agronomic traits, in the absence of molecular tools, for genotypic characterization in plants.

Keywords: Cassava, Genetic distance, phenetic groups, Postharvest physiological deterioration, and Dry matter content