Genotype x year interaction for agronomical traits and proximate composition in yam beans (Pachyrhizus spp., Fabaceae) in the Brazilian Amazon
The yam bean (Pachyrhizus spp.) is an underutilized leguminous tuber that is well adapted to the Amazonian climate. This bean has 5 to 20% protein in its tuberous roots (dry weight), though it is little known even in Brazil. No improved varieties have been recommended for the Amazon region. We examine the Genotype x Year (GxY) interaction in 20 selected yam bean stocks and selected genotypes based on their performance. These materials were obtained from among a selection of 64 genotypes with natural outcrossing of P. erosus x P. tuberosus. The experiments were carried out in the Central Amazon during a low water period, from April to September in 2017 and 2018, in a completely randomized block design with 20 genotypes, three replicates, and eight plants per plot, 1 x 0.5 m apart between and within rows. Pods and roots were harvested after having been cultivated for six months. Pod and root yield, as well as the latter’s proximate composition, were evaluated. We found no significant GxY interaction, for pod and root yield. However, the carbohydrate, protein, lipid, fiber, and ash content in roots showed significant GxY interaction. These results indicate that selection of genotypes with high pod and root yield can be carried out in a single year in the dry period for cultivation during that season. However, selection to increase its nutritional value must be carried out over several years. The selected genotypes for presenting high root yield (> 3 t ha-1) were P7, P11, P15, P19, P37 and P57. The genotypes selected for high protein content in the roots (> 10% dry weight) were P13, P14, P37 and P62.