Colletotrichum gloeosporioides is the common causal agent of anthracnose in papaya (Carica papaya L.) fruits, and infection by this fungal pathogen results in severe post-harvest losses. In the Yucatán peninsula (Mexico) a different Colletotrichum species was isolated from papaya fruits with atypical anthracnose lesions. The DNAs from a variety of Colletotrichum isolates producing typical and atypical lesions, respectively, were amplified by PCR with C.gloeosporioides-specific primers. All isolates from typical anthracnose lesions yielded a 450 bp PCR product, but DNAs from isolates with atypical lesions failed to produce an amplification product. For further characterization, the rDNA 5.8S-ITS region was amplified by PCR and processed for sequencing and RFLP analysis, respectively, to verify the identity of the papaya anthracnose pathogens. The results revealed unequivocally the existence of two Colletotrichum species causing anthracnose lesions on papaya fruits: C. gloeosporioides and C. capsici. PCR-RFLP using the restriction endonuclease MspI reliably reproduced restriction patterns specific for C. capsici or C. gloeosporioides. The generation of RFLP patterns by MspI (or AluI or RsaI) is a rapid, accurate, and unequivocal method for the detection and differentiation of these two Colletotrichum species.

The macroalgae consortium biomass in the Mexican Caribbean represents an emerging and promising biofuel feedstock. Its biological pretreatment and potential for energetic conversion to biomethane were investigated, since some macroalgae have hard cell walls that present an obstacle to efficient methane production when those substrates are used. It has been revealed by anaerobic digestion assays that pretreatment with a Bm-2 strain (Trametes hirsuta) isolated from decaying wood in Yucatan, Mexico was 104 L CH 4 •kg VS −1 ; In fact, the fungal pretreatment produced a 20% increase in methane yield, with important amounts of alkali metals Ca, K, Mg, Na of 78 g/L, ash 35.5% and lignin 15.6%. It is unlikely that high concentrations of ash and alkali metals will produce an ideal feedstock for combustion or pyrolysis, but they can be recommended for a biological process.

Anthracnose, caused by Colletotrichum truncatum (syn. C. capsici), has become a common disease of tropical crops, severely affecting the quantity and quality of fruit and seed and, therefore, reducing their market value. For years, chemical control has been extensively used for managing this disease. However, the appearance of isolates that are resistant to the most commonly employed fungicides is increasingly widespread. Twenty C. truncatum isolates from pepper, papaya, and physic nut were tested in vitro against four fungicides to determine their sensitivity. All evaluated isolates were resistant to azoxystrobin and thiabendazole and susceptible to cyprodinil + fludioxonil and mancozeb. To determine the molecular mechanism conferring thiabendazole resistance, the TUB-2 gene was characterized, revealing a glutamic acid to alanine substitution at position 198 in 6 of the 20 isolates that were tested. This work confirms the emergence of benzimidazole-based fungicide resistance in C. truncatum populations and highlights the need for monitoring fungicide sensitivity as an essential activity for the development of effective control schemes.

Colletotrichum capsici is an important fungal species that causes anthracnose in many genera of plants causing severe economic losses worldwide. A primer set was designed based on the sequences of the ribosomal internal transcribed spacer (ITS1 and ITS2) regions for use in a conventional PCR assay. The primer set (CcapF/CcapR) amplified a single product of 394 bp with DNA extracted from 20 Mexican isolates of C. capsici. The specificity of primers was confirmed by the absence of amplified product with DNA of four other Colletotrichum species and eleven different fungal genera. This primer set is capable of amplifying only C. capsici from different contaminated tissues or fungal structures, thereby facilitating rapid diagnoses as there is no need to isolate and cultivate the fungus in order to identify it. The sensitivity of detection with this PCR method was 10 pg of genomic DNA from the pathogen. This is the first report of a C. capsici-specific primer set. It allows rapid pathogen detection and provides growers with a powerful tool for a rational selection of fungicides to control anthracnose in different crops and in the post-harvest stage.

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BackgroundC. gloeosporioides sensu lato is one of the most economically important post-harvest diseases affecting papaya production worldwide. There is currently no information concerning the genetic structure or demographic history of this pathogen in any of the affected countries. Knowledge of molecular demographic parameters for different populations will improve our understanding of the biogeographic history as well as the evolutionary and adaptive potential of these pathogens. In this study, sequence data for ACT, GPDH, β-TUB and ITS gene regions were analyzed for C. gloeosporioides sensu lato and C. truncatum isolates infecting papaya in Trinidad and Mexico in order to determine the genetic structure and demographic history of these populations.ResultsThe data indicated that Mexico is the ancestral C. gloeosporioides sensu lato population with asymmetrical migration to Trinidad. Mexico also had the larger effective population size but, both Mexico and Trinidad populations exhibited population expansion. Mexico also had greater nucleotide diversity and high levels of diversity for each gene. There was significant sub-division of the Trinidad and Mexico populations and low levels of genetic divergence among populations for three of the four gene regions; β-TUB was shown to be under positive selection. There were also dissimilar haplotype characteristics for both populations. Mutation may play a role in shaping the population structure of C. gloeosporioides sensu lato isolates from Trinidad and from Mexico, especially with respect to the ACT and GPDH gene regions. There was no evidence of gene flow between the C. truncatum populations and it is possible that the Mexico and Trinidad populations emerged independently of each other.ConclusionsThe study revealed relevant information based on the genetic structure as well as the demographic history of two fungal pathogens infecting papaya, C. gloeosporioides sensu lato and C. truncatum, in Trinidad and Mexico. Understanding the genetic structure of pathogen populations will assist in determining the evolutionary potential of the pathogen and in identifying which evolutionary forces may have the greatest impact on durability of resistance. Intervention strategies that target these evolutionary forces would prove to be the most practical.

Looking for a biotechnical potential, aqueous extracts of leaves of 12 native species used in the Mayan traditional medicine of the coastal dune and mangrove of Yucatan (Mexico) were selected to evaluate their biological activities. Rhizophora mangle and Manilkara zapota showed the highest free radical scavenging activity (3.94 ± 0.19 and 6.42 ± 0.32 μg/mL, respectively), and the highest antihypertensive activity was obtained from Solanum donianum (0.38 μg/mL). The anti-hyperglycemic activity of these species was also tested; the highest activities were registered with R . mangle . The antimicrobial activity of Malvaviscus arboreus , S . donianum , M . zapota , and R . mangle at 10% (w/v) was positive against six human pathogenic bacteria and Bonellia macrocarpa against one pathogenic fungus. Solanum donianum , M . zapota , B . macrocarpa , and R . mangle were positive against two pathogenic plant fungi. These results show that the aqueous extracts of five native plants of the Yucatan coast have potential as antioxidants, ACE inhibitors, α-amylase and α-glucosidase inhibitors, and as antimicrobials, which make their exploration for utilization in the agricultural and pharmaceutical industries a possibility.

Papaya meleira virus (PMeV), causal agent of meleira or sticky disease, is a double-stranded RNA (dsRNA) virus which has been previously reported only in Brazil. A study was carried out in order to verify the presence and occurrence of PMeV in Mexico. Latex samples from symptomatic and asymptomatic papaya fruits were collected in Quintana Roo state papaya orchards, where the first symptoms of PMeV were observed, and from 29 different municipalities located in ten papaya producer states in Mexico. A molecular protocol based on nucleic acid extraction was used for the diagnosis and a virus 12 Kb dsRNA distinctive band was observed in all PMeV infected plants. Around 46% of the evaluated plants were positive for this pathogen. Presence of the virus had been confirmed in seven states indicating the potential damage that PMeV could cause in the papaya crop in Mexico. The molecular analysis used allowed the diagnosis of infected plants without symptoms and facilitated the diagnosis in flowers and small papaya fruits also. The early diagnosis of PMeV will allow papaya producers to take appropriate and timely control measures. This is the first report of Papaya meleira virus in Mexico.