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This paper presents the geographical distribution, biology and life cycle, symptoms of damage, pathotypes, races or biotypes, survival and spread, economic importance, and management measures (chemical, cultural and biological control methods, and pest resistance) of the parasitic nematodes of coffee and cocoa, with particular emphasis on Meloidogyne spp. and Pratylenchus spp.

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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 corckyroot 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.

This chapter describes the nematode parasites of coffee and cocoa. Information is given on their distribution, biology and life cycle, symptoms of damage, pathotypes (races or biotypes), survival and means of dissemination, environmental factors affecting parasitism, other hosts, disease complexes, economic importance, methods of diagnosis, and management measures, which include host resistance, cultural, chemical and biological control methods.

Background. In Mexico, coffee leaf rust (CLR) is the main disease that affects the Arabica coffee crop. In this study, the local response of two Mexican cultivars of Coffea arabica (Oro Azteca and Garnica) in the early stages of Hemileia vastatrix infection was evaluated. Methods. We quantified the development of fungal structures in locally-infected leaf disks from both cultivars, using qRT-PCR to measure the relative expression of two pathogenesis recognition genes (CaNDR1 and CaNBS-LRR) and three genes associated with the salicylic acid (SA)-related pathway (CaNPR1, CaPR1, and CaPR5). Results. Resistance of the cv. Oro Azteca was significantly higher than that of the cv. Garnica, with 8.2% and 53.3% haustorial detection, respectively. In addition, the nonrace specific disease resistance gene (CaNDR1), a key gene for the pathogen recognition, as well as the genes associated with SA, CaNPR1, CaPR1, and CaPR5, presented an increased expression in response to infection by H. vastatrix in cv. Oro Azteca if comparing with cv. Garnica. Our results suggest that Oro Azteca's defense mechanisms could involve early recognition of CLR by NDR1 and the subsequent activation of the SA signaling pathway.

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Root-knot nematodes (Meloidogyne spp.) threaten the livelihood of millions of farmers producing coffee worldwide. The use of resistant plants either as cultivars or rootstocks appears to be the single most effective method of control. A screening method was developed to evaluate large populations of plants for resistance to root-knot nematodes. Two coffee cultivars, one susceptible and the other resistant to Meloidogyne paranaensis, were grown under controlled conditions in two substrates: a commercial sieved potting compost and an inert substrate containing sand with a water-absorbent synthetic polymer. Plant growth and development and nematode multiplication were compared for two inoculation dates (2 and 8 weeks after planting) and two evaluation dates (eight and 13 weeks after inoculation). Root growth, but not nematode multiplication, was influenced by the choice of substrate. Evaluation of the differences in root weight and nematode numbers between the different cultivars, substrates and dates of inoculation suggested that an optimal condition could be defined. The best discrimination between susceptible and resistant plants was found in the experiment where inoculation occurred at 2 weeks after planting and evaluation occurred at 8 weeks after inoculation. Because the total duration of this experiment was only 3 months, highthroughput evaluation was possible, opening up new possibilities for screening large germplasm collections and studying the genetic control of root-knot nematode resistance in coffee.