COMPARISON OF FIELD PERFORMANCE BETWEEN DASHEEN MOSAIC VIRUS-FREE AND VIRUS-INFECTED IN VITRO PLANTS OF COCOYAM (XANTHOSOMA SPP.) IN NICARAGUA

Abstract

Cocoyam (Xanthosoma spp.) is the most important export crop of all the root and tuber crops grown in Nicaragua. Despite its importance, the total planted area and yield have significantly decreased during the past few years, a decrease that is mainly due to diseases that are disseminated through the planting material. In this study virus-free (NI) and virus-infected (I) in vitro plants from three genotypes were established in a non-traditional production area. The aim was to evaluate their agronomic performance, and to study the re-infection of dasheen mosaic virus (DsMV) and its effect on yield. Repeated measurements of morphological traits were made during the experimental period. The height of the plants, the diameter of the pseudo-stem and the leaf area increased continuously up to 217 days after planting after which the growth curves declined. The genotypes differed in all yield components, except in yield per plant. Regardless of genotype, the NI plants produced a larger number of cormels that were heavier and longer than the cormels produced by I plants. This resulted in a higher yield from NI plants (18.2 t ha⁻¹) compared with I plants (13.6 t ha⁻¹). Seven months after planting between 60 and 90 % of the NI plants, depending on genotype, were infected with DsMV. Aphis gossypii was the only aphid observed in the field trial and is therefore most probably the vector responsible for the transmission of the virus.