Genetic diversity and farmers’ selection of cassava (Manihot esculenta Crantz) varieties on small-scale farms in Northern and Central Vietnam

Abstract: Cassava (Manihot esculenta Crantz) is a tropical root crop grown for its starchy tuberous roots. In Vietnam, cassava’s use as a raw product for the starch and ethanol industry led to its increasing importance. Also, Vietnam is one of the countries predicted to be most affected by climate change and cassava may be one important crop for securing agricultural production. These diverse needs highlight the necessity for a diverse gene pool for different breeding goals. The genetic diversity of cassava on farmers’ fields in Northern and Central Vietnam was explored by using an interdisciplinary approach combining farmer interviews and genetic marker analysis. The study also included eight Vietnamese accessions from the cassava Germplasm Bank at CIAT, Colombia. Cassava varieties on fifteen farms in Northern and Central Vietnam showed high genetic diversity among varieties. Vietnamese farmers cultivated clones of different varieties to a great extent, which they were able to distinguish based on different morphological traits. However, genetic variation was also detected in some cassava varieties grown in a single field. Farmers were able to conserve their varieties as clones over long periods of time. Local and improved varieties were grown in both regions. These two groups of cassava were genetically differentiated, showing the necessity of preserving local varieties for increasing the gene pool for breeding. Genetic diversity in the farmers’ fields was not covered by the CIAT accessions, suggesting that local varieties should be incorporated into the germplasm bank. This interdisciplinary study made it possible to detect the actual genetic structure and diversity within farmers’ fields and it enhances the importance of understanding the farmers’ influence on the genetic composition of cassava.