Resumen
- Understanding the inheritance of agronomically relevant traits in cassava is fundamental for an efficient genetic improvement of the crop. Basic principles of qualitative genetics were established with the pioneering work of Mendel more than a hundred years ago. Later many scientists contributed to the elaboration of the principles of quantitative genetics which basically split it into three major components: additive, dominant and epistatic effects (or variances). This chapter provides an initial introduction to the concepts of quantitative genetics and its connection to crop breeding strategies. This chapter will be followed by a second chapter where experimental results are provided. In the analysis of genetic variation the pioneering research by Mendel focused on traits that segregated in contrasting classes (i.e. tall versus dwarf, purple versus white flowers, etc.). In fact, it was the sharp and distinctive phenotypic classes observed in these traits that helped Mendel to reach his breakthrough discoveries. The inheritance of these traits, identified as qualitative, is easy to study and predict because of the large effect of different alleles on the phenotype, which results in distinctive phenotypic classes, and because of the negligible effect of the environment in their expression.