Although vanilla originated from Mexico and an important pathogen for this plant is Fusarium oxysporum f. sp. vanilla , studies concerning their association are limited. Previous reports on agents that cause root and stem rot in vanilla clearly indicate that Fusarium species are associated with this disease. During 2009 and 2010 in Papantla, which is the greatest vanilla-producing region of Mexico, the fungus was isolated from vanilla roots and stems that showed symptoms of the disease. From 189 isolates of Fusarium, 11 morphologically different colonies were selected to verify the species of each colony by microscopic observation of their morphological characteristics when cultivated on SNA and PDA media and by amplifying and sequencing their ITS regions. The detected species corresponded to F. proliferatum , Fusarium sp., F. oxysporum f. sp. vanillae (which was the most numerous and most pathogenic to vanilla stems and leaves), an undetermined species of Fusarium , and F. proliferatum , which showed no evidence of producing disease symptoms.

BackgroundUpon exposure to unfavorable environmental conditions, plants need to respond quickly to maintain their homeostasis. For instance, physiological, biochemical and transcriptional changes occur during plant-pathogen interaction. In the case of Vanilla planifolia Jacks., a worldwide economically important crop, it is susceptible to Fusarium oxysporum f. sp. vanillae (Fov). This pathogen causes root and stem rot (RSR) in vanilla plants that lead to plant death. To investigate how vanilla plants, respond at the transcriptional level upon infection with Fov, here we employed the RNA-Seq approach to analyze the dynamics of whole-transcriptome changes during two-time frames of the infection.ResultsAnalysis of global gene expression profiles upon infection by Fov indicated that the major transcriptional change occurred at 2 days post-inoculation (dpi), in comparison to 10 dpi. Briefly, the RNA-Seq analysis carried out in roots found that 3420 and 839 differentially expressed genes (DEGs) were detected at 2 and 10 dpi, respectively, as compared to the control. In the case of DEGs at 2 dpi, 1563 genes were found to be up-regulated, whereas 1857 genes were down-regulated. Moreover, functional categorization of DEGs at 2 dpi indicated that up-regulated genes are mainly associated to translation, whereas down-regulated genes are involved in cell wall remodeling. Among the translational-related transcripts, ribosomal proteins (RPs) were found increased their expression exclusively at 2 dpi.ConclusionsThe screening of transcriptional changes of V. planifolia Jacks upon infection by Fov provides insights into the plant molecular response, particularly at early stages of infection. The accumulation of translational-related transcripts at early stages of infection potentially points to a transcriptional reprogramming coupled with a translational regulation in vanilla plants upon infection by Fov. Altogether, the results presented here highlight potential molecular players that might be further studied to improve Fov-induced resistance in vanilla plants.

In the 2013-2014 growing season, field surveys were conducted in native corn fields located in high altitude agricultural communities in the 'Sierra Norte de Puebla' in Mexico. Symptoms typical of maize bushy stunt (MBS) disease were observed and DNA extracted from symptomatic native corn plants was used as template to confirm the presence of phytoplasmas.Amplification and sequencing of 16S rRNA-encoding sequences and chaperonin 60 universal target (cpn60 UT) sequences followed by in vitro restriction fragment length polymorphism and phylogenetic analyses revealed that the phytoplasma detected belongs to the subgroup 16SrI-B, 'Candidatus Phytoplasma asteris'. Based on 16S rRNA-encoding gene sequence analysis and on a single nucleotide polymorphism within the cpn60 UT sequence, two MBS strains, MBS-Puebla and MBS-Veracruz, were identified. This is the first detection of MBS phytoplasma (MBSP) affecting native corn and the first molecular survey made in corn fields in Mexico to detect and characterize MBSP. We discuss these results in light of the potential evolutionary relationship between corn and MBSP.

Fusarium oxysporum f. sp. vanillae is considered the most important fungus affecting vanilla crops around the world, causing rot on vanilla roots and stems. Previous studies showed that the ability to infect vanilla plants is a polyphyletic trait among strains of the Fusarium oxysporum species complex (FOSC). The same studies proposed a single origin for F. oxysporum f. sp. vanillae isolates sampled from Mexico, the centre of origin and distribution of vanilla. The aim of this work was to test the hypothesis of the monophyletic origin of a wider sample of isolates of F. oxysporum f. sp. vanillae infecting Mexican vanilla and estimate nucleotide diversity of pathogen isolates from the main vanilla‐producing countries. Sequence data for the TEF1α gene from 106 isolates was assembled. The phylogenetic analyses suggest that some Mexican isolates of F. oxysporum f. sp. vanillae belong in two well‐supported clades, mixed with isolates from Madagascar, Indonesia, Réunion and Comoros. The phylogenetic position of other Indonesian and Mexican isolates is unresolved. Estimations of nucleotide diversity showed that the population from Mexico is genetically more diverse than the other three populations from Madagascar, Indonesia and Réunion. The results support a polyphyletic origin of vanilla‐infecting isolates of F. oxysporum worldwide, and also reject the proposition that Mexican isolates have a single origin. The phylogenetic optimizations over the strict consensus tree of the ability to infect vanilla plants suggest that pathogenic strains around the world are the product of multiple shifts of pathogenesis and dispersion events.

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