Molecular and Environmental Triggering Factors of Pathogenicity of Fusarium oxysporum and F. solani Isolates Involved in the Coffee Corky-Root Disease.

Roberto Gamboa-Becerra,Luc Villain,Daniel López-Lima,Gloria Carrión,Damaris Desgarennes,Jean-Christophe Breitler

doi:10.3390/jof7040253

Abstract

Coffee corky-root disease causes serious damages to coffee crop and is linked to combined infection of Fusarium spp. and root-knot nematodes Meloidogyne spp. In this study, 70 Fusarium isolates were collected from both roots of healthy coffee plants and with corky-root disease symptoms. A phylogenetic analysis, and the detection of pathogenicity SIX genes and toxigenicity Fum genes was performed for 59 F. oxysporum and 11 F. solani isolates. Based on the molecular characterization, seven F. oxysporum and three F. solani isolates were assessed for their pathogenicity on coffee seedlings under optimal watering and water stress miming root-knot nematode effect on plants. Our results revealed that a drastic increment of plant colonization capacity and pathogenicity on coffee plants of some Fusarium isolates was caused by water stress. The pathogenicity on coffee of F. solani linked to coffee corky-root disease and the presence of SIX genes in this species were demonstrated for the first time. Our study provides evidence for understanding the pathogenic basis of F. oxysporum and F. solani isolates on coffee and revealed the presence of SIX and Fum genes as one of their pathogenicity-related mechanisms. We also highlight the relevance of chlorophyll, a fluorescence as an early and high-throughput phenotyping tool in Fusarium pathogenicity studies on coffee.

Highlights

The Meloidogyne-based disease complexes (MDCs) involve the interaction of different root-knot nematodes (RKN) Meloidogyne spp. and phytopathogenic fungi, especially Fusarium spp. which causes severe damage to several important crops worldwide including coffee [1,2,3,4]
Our investigation provides evidence: (i) about the association between the presence of Secreted In Xylem (SIX) and Fum genes and the pathogenicity of Fusarium isolates linked to coffee corky-root disease
Future studies should be addressed to study the SIX genes transference intra- and inter-species. (ii) That some pathogenicity SIX genes and toxigenicity Fum genes seem to play a primordial role in the basic determinism of pathogenicity potential of Fusarium isolates on coffee, in a complex and varied way for each of them depending on the isolate and independently of the species considered (F. oxysporum vs. F. solani)

Summary

Introduction

The Meloidogyne-based disease complexes (MDCs) involve the interaction of different root-knot nematodes (RKN) Meloidogyne spp. and phytopathogenic fungi, especially Fusarium spp. which causes severe damage to several important crops worldwide including coffee [1,2,3,4]. The MDCs cause severe symptoms known as corky-root disease, which lead to necrosis and atrophy of the root system. This is the case with M. arabicida in Costa Rica, M. incognita mainly in Brazil or M. paranaensis in Brazil, Guatemala, Hawai, and Mexico [1,2,4,6,7,8]. As described by these authors, the inefficient functioning of roots with reduced uptake of water and nutrients (like drought symptoms in the plant canopy) is due to diverting water and nutrients to the growing female nematodes in infected roots. Hua et al (2019) [9] reported that the inoculation of M. incognita together with F. oxysporum f. sp. niveum enhanced the susceptibility of several watermelon genotypes to Fusarium wilt (including genotypes resistant to F. oxysporum f. sp. niveum) and led to an early development of wilt symptoms and increased disease damage

Objectives

Methods

Results

Discussion

Conclusion