Seleção de progênies de feijão-macuco (Pachyrhizus spp.) para o controle de Ralstonia solanacearum

Abstract

The genetic improvement program of yam bean (Pachyrhizus spp.) at the National Institute of Amazonian Research selected nine progenies for the control of Sclerotium rolfsii. However, they were not evaluated for their seed productivity and their efficacy in controlling Ralstonia solanacearum (RS). Therefore, the aim of this study was to evaluate and select yam bean progenies with high seed productivity and high toxicity against RS phylotype II. The agronomic experiment was conducted in a completely randomized block design with nine treatments, four replicates, and four plants per plot, using 2 m long tutors. Toxicity tests were performed using three methods: cell counting in a Neubauer Chamber (NC), spectrophotometry (SP), and disk diffusion (DD). The results showed that the progenies did not present significant differences in seed productivity, ranging from 0.56 (P5) to 0.98 t/ha (P23). Cell counting in NC and SP showed that aqueous extracts of Pachyrhizus spp. seeds at 5%, after 24 hours, promoted the multiplication of RS phylotype II. However, cell counts in NC showed that extracts with a concentration of 0.5%, in general, reduced the multiplication of RS. In the DD count, the 5% extracts exhibited inhibitory halos ranging from 0.26 to 1.45 mm in 12 hours and stimulating halos of up to 8.08 mm in 48 hours. Progenies P23 and P14 proved promising for use as biopesticides at a concentration of 0.5% in RS control, with seed productivity of 0.98 and 0.83 t/ha, respectively.