Interaction of Fusarium oxysporum and root-knot nematodes (Meloidogyne incognita) on cotton growth under greenhouse conditions

Abstract

Fusarium oxysporum is a fungus that causes tremendous yield losses in cotton. In association with root-knot nematodes, these losses become even greater. The objective of the study was to assess the virulence of root-knot nematodes (Meloidogyne incognita) and different F. oxysporum densities on the growth of the OKP768 cotton variety under greenhouse conditions. A randomized complete bloc design was used, with twelve treatments of Fusarium densities and nematodes, each repeated six times. A combination of five inoculum densities of F. oxysporum conidia (D1: 2.10^6; D2: 4.10⁶; D3: 6.10⁶; D4: 8.10⁶ and D5: 1.10⁷/pot); one inoculum density of nematodes (1.500 juveniles/pot) and a control with neither nematodes nor fusarium were used as treatment. After cotton sowing, nematodes and F. oxysporum conidia were inoculated (one and two months, respectively) in a crown around the plant collar. During the trial, the temperature inside the greenhouse varied between 27.07°C and 36.80°C, while humidity varied between 37.75% and 83.00%. Treatments combining nematodes and 8.10⁶ ;1.10⁷ densities of Fusarium significantly reduced plant height, collar diameter and root biomass. With these treatments, the plants failed to produce floral buds and fruit branches. Nematodes only and combined to Fusarium densities treatments reduced growth parameter values, in particular height, leaf area, collar diameter and root biomass. Treatments combining nematodes with Fusarium applied at 8.10⁶ and 1.10⁷ per pot induced higher mean xylem discolouration than other treatments inducing plant growth to decrease with increasing xylem discolouration. It can therefore be concluded that treatments combining nematodes with Fusarium densities (D4Nem and D5Nem) negatively affect cotton growth and development, and that there is an interaction between M. incognita and F. oxysporum.