Diversity of yam bean ( Pachyrhizus spp. Fabaceae) based on morphoagronomic traits in the Brazilian Amazon

Yam bean is a non-conventional horticultural crop adapted to the Amazon region. It presents edible roots, yet, its seeds contain cytotoxic components such as rotenone and pachyrhizin. The Instituto Nacional de Pesquisas da Amazonia has 64 yam bean genotypes in its germplasm bank, however, their diversity is unknown. The aim of this study was to assess the diversity of these genotypes using 10 morphoagronomic traits, plant height, number of secondary branches, shoot biomass, stem diameter, root biomass, number, length, diameter, length/diameter ratio (L/D), and shape. The accessions were planted on non-flooded land, Manaus, Amazonas (02[degrees] 59'48.2''S and 60[degrees] 01' 22.4''W) in completely randomized design with three replicates and three plants per plot spaced 0.5 x 1 m. The results showed significant diversity for all characters except for stem diameter and visual assessment of root shape. Biplot graphic explained 60% of the total variation, which identified that genotypes P44, P22 and P18 have high values for root yield (80-108 t ha super(-1)), number of secondary branches (15-31) and shoot biomass (0.5-0.8 kg plant super(-1)). Cluster analysis, considering 50% of relative Euclidean distance, revealed 15 major groups. We conclude that the genotypes assessed have wide diversity and some of them high root yield potential. This suggests that a yam bean breeding program can be successful for the yield of roots and seeds in the Amazonian region.Original Abstract: O feijao-macuco e uma hortalica nao convencional da Amazonia. Suas raizes sao comestiveis e suas sementes toxicas por conter rotenona e paquirizina. O Instituto Nacional de Pesquisas da Amazonia (INPA) tem conservado 64 genotipos de feijao-macuco em seu banco de germoplasma, mas a diversidade genetica destes e desconhecida. O objetivo deste trabalho foi avaliar estes acessos utilizando 10 descritores morfoagronomicos tais como: altura de planta, numero de ramas secundarias, massa da parte aerea, diametro de caule, massa, numero, comprimento, diametro, relacao comprimento/diametro e formato de raizes. O experimento foi conduzido em terra firme no municipio de Manaus (02[degrees] 59'48.2''LS e 60[degrees] 01' 22.4''LO), em delineamento de blocos ao acaso com tres repeticoes e tres plantas por parcela. Os resultados mostraram diversidade significativa para todos os caracteres, exceto para diametro do caule e avaliacao visual do formato da raiz. O Biplot explicou 60% da variacao total o qual mos