Metarhizium carneum Formulations: A Promising New Biological Control to Be Incorporated in the Integrated Management of Meloidogyne enterolobii on Tomato Plants.

The increase in the populations of root-knot nematode Meloidogyne enterolobii in various vegetables such as tomatoes grown under greenhouse conditions as well as increasing restrictions on the use of certain chemical nematicides have led to the search for new, effective management strategies, preferably ones that are sustainable biological alternatives. In this work, two formulations of the nematophagous fungus Metarhizium carneum, one concentrated suspension and one wettable powder, were evaluated under greenhouse conditions to reduce the M. enterolobii infestation in tomato plants. In addition, the effectiveness of the liquid formulation of M. carneum was compared with two biological and three chemical commercial nematicides. The results show that the two M. carneum formulations reduced the M. enterolobii population density by 78 and 66% in relation to the control treatment. In comparison, the liquid formulation of M. carneum and Purpureocillium lilacinum treatments reduced nematode population density by 72 and 43%, respectively, while for metam sodium preplanting applications followed by M. carneum applications during the tomato growth stage, the reduction was 96%. The alternate use of some chemical compounds plus the application of M. carneum as a biocontrol is a good starting strategy for managing M. enterolobii populations. These results confirm that M. carneum is a serious candidate for the short-term commercialization of an environmentally friendly biological nematicide.

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

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.

The Bacterial Microbiome of Meloidogyne-Based Disease Complex in Coffee and Tomato.

The Meloidogyne-based disease complexes (MDCs) are caused by the interaction of different root-knot nematode species and phytopathogenic fungi. These complexes are devastating several important crops worldwide including tomato and coffee. Despite their relevance, little is known about the role of the bacterial communities in the MDCs. In this study 16s rDNA gene sequencing was used to analyze the bacterial microbiome associated with healthy and infested roots, as well with females and eggs of Meloidogyne enterolobii and M. paranaensis, the causal agents of MDC in tomato and coffee, respectively. Each MDC pathosystems displayed a specific taxonomic diversity and relative abundances constituting a very complex system. The main bacterial drivers of the MDC infection process were identified for both crops at order level. While corky-root coffee samples presented an enrichment of Bacillales and Burkholderiales, the corcky-root tomato samples presented an enrichment on Saprospirales, Chthoniobacterales, Alteromonadales, and Xanthomonadales. At genus level, Nocardia was common to both systems, and it could be related to the development of tumor symptoms by altering both nematode and plant systems. Furthermore, we predicted the healthy metabolic profile of the roots microbiome and a shift that may result in an increment of activity of central metabolism and the presence of pathogenic genes in both crops.