Huanglongbing (HLB) is a vascular disease of Citrus caused by three species of the α-proteobacteria “Candidatus Liberibacter”, with “Candidatus Liberibacter asiaticus” (CLas) being the most widespread and the one causing significant economic losses in citrus-producing regions worldwide. However, Persian lime (Citrus latifolia Tanaka) has shown tolerance to the disease. To understand the molecular mechanisms of this tolerance, transcriptomic analysis of HLB was performed using asymptomatic and symptomatic leaves. RNA-Seq analysis revealed 652 differentially expressed genes (DEGs) in response to CLas infection, of which 457 were upregulated and 195 were downregulated. KEGG analysis revealed that after CLas infection, some DEGs were present in the plant–pathogen interaction and in the starch and sucrose metabolism pathways. DEGs present in the plant–pathogen interaction pathway suggests that tolerance against HLB in Persian lime could be mediated, at least partly, by the ClRSP2 and ClHSP90 genes. Previous reports documented that RSP2 and HSP90 showed low expression in susceptible citrus genotypes. Regarding the starch and sucrose metabolism pathways, some genes were identified as being related to the imbalance of starch accumulation. On the other hand, eight biotic stress-related genes were selected for further RT-qPCR analysis to validate our results. RT-qPCR results confirmed that symptomatic HLB leaves had high relative expression levels of the ClPR1, ClNFP, ClDR27, and ClSRK genes, whereas the ClHSL1, ClRPP13, ClPDR1, and ClNAC genes were expressed at lower levels than those from HLB asymptomatic leaves. Taken together, the present transcriptomic analysis contributes to the understanding of the CLas-Persian lime interaction in its natural environment and may set the basis for developing strategies for the integrated management of this important Citrus disease through the identification of blanks for genetic improvement.

Mexico ranks second in the world for Persian lime (Citrus latifolia) exports, making it the principal citrus exporter within the national citrus industry, exporting over 600,000 tons per year. However, diseases are the main factor reducing production, resulting in significant economic losses. Among these diseases, fungal diseases like dieback, caused by species of Lasiodiplodia, are an emerging issue in Persian lime. Symptoms include gummosis, twig and branch dieback, cankers, the necrosis of bark and wood, fruit mummification, and tree decline. The aim of this study was to investigate the occurrence and pathogenicity of the fungal species associated with twig and branch dieback, cankers, and decline of Persian lime trees in southern Mexico, and to elucidate the current status of the Lasiodiplodia species causing the disease in Mexico. During June, July, and August of 2023, a total of the 9229 Persian lime trees were inspected across 230 hectares of Persian lime orchards in southern Mexico, and symptoms of the disease were detected in 48.78% of the trees. Branches from 30 of these Persian lime trees were collected. Fungal isolates were obtained, resulting in a collection of 40 strains. The isolates were characterized molecularly and phylogenetically through the partial regions of four loci: the internal transcribed spacer region (ITS), the β-tubulin gene (tub2), the translation elongation factor 1-alpha gene (tef1-α), and the DNA-directed RNA polymerase II second largest subunit (rpb2). Additionally, pathogenicity was assessed, successfully completing Koch’s postulates on both detached Persian lime branches and certified 18-month-old Persian lime plants. Through multilocus molecular phylogenetic identification, pathogenicity, and virulence tests, five species were identified as causal agents: L. iraniensis, L. lignicola, L. mexicanensis, L. pseudotheobromae, and L. theobromae. This study demonstrates that in southern Mexico, at least five species of the genus Lasiodiplodia are responsible for dieback in Persian lime. Additionally, this is the first report of L. lignicola and L. mexicanensis as causal agents of the disease in citrus, indicating novel host interactions between species of Lasiodiplodia and C. latifolia.

The objective of this research was to evaluate the conceptual fertilization model to generate nitrogen doses in maize in the humid tropics of Mexico. This method consisted of evaluating the balance between crop nitrogen demand (P1) minus soil nitrogen supply (P2) and fertilizer efficiency (P3). Four treatments with two varieties (VS-536 and V-537 C with and without fertilizer) were used in three locations in the central zone of Veracruz, Mexico, in the locations of Jamapa, Paso Real and El Rincón. The results showed that P1 was statistically superior to the unfertilized, in P2 there was no significant statistical difference and P3 was less than 50% in the three locations. The nitrogen doses estimated with the conceptual model were different in the three locations (Jamapa 85, Rincón 55, and Paso Real, 72 kg N ha-1) compared to the applied dose (150 kg N ha-1), representing an overfertilization of 44%, 64% and 52%, respectively. It was concluded that this model allowed generating adequate doses of nitrogen in less time and with less investment.

At present, the environmental impact of fossil fuels has generated the search for alternative sources of energy such as biomass from sugar cane and fodder pastures. In order to generate alternatives for the production of fiber and cellulose similar to that obtained with sugarcane bagasse, six varieties of Pennisetum purpureum Schumach were evaluated at the laboratory level (OM-22, Cameroon, Maralfalfa, CT-115, Roxo and Urockowona) at 120, 150 and 200 days after sowing (das). The varieties were sown in tip and tail in double cordon in strips of 5 furrows of 1.2 meters between rows and 20 meters in length. The soil was of a vertisol soil type with a pH of 5.4, clayey texture and 2.6% OM. It was found that OM-22, Cameroon, Maralfalfa, Roxo and Urockowona presented good potential for the production of fiber and cellulose at 150 das, discarding the variety CT-115. The Urockowona variety, presented the highest content of Suitable and Dry Fiber (SDF) in the three cut-off dates, excelling at 150 das with 34.4%; while the rest did not exceed 25% in the three evaluated dates. The total biomass yield was similar in the six varieties evaluated in their first cut, exceeding 80 t ha-1 in green from 150 das. It is concluded that the Urockowona, Camerun and Maralfalfa varieties are the ones with the greatest potential for the production of fiber and cellulose to make paper.

Vanilla is a highly valuable spice in multiple industries worldwide. However, it faces a serious problem due to a disease known as root and stem rot, caused by the fungus Fusarium oxysporum f. sp. vanillae. Little is known about the pathogenicity mechanisms this fungus employs to establish the disease, making it imperative to elucidate mechanisms such as the presence of pathogenicity effectors in its genome. The aim of the present study was to determine the presence of the SIX gene family in the genome of three strains of F. oxysporum associated with root rot: two pathogenic strains and one non-pathogenic endophyte strain. Additionally, the complete effectorome of these strains was predicted and compared to exclude effectors present in the endophytic strain. Our results show that only the SIX9 gene is present in the strains associated with the disease, regardless of their pathogenic nature. Furthermore, no variation was observed in the SIX9 gene among these strains, suggesting that SIX9 is not involved in pathogenicity. Instead, we identified 339 shared effectors among the three strains, including the non-pathogenic strain, strongly suggesting that these genes are not relevant for establishing root rot but may play a role in endophytic colonization. The highly virulent strain IXF41 exhibited eight exclusive pathogenicity effectors, while the moderately virulent strain IXF50 had four. Additionally, one effector was identified as shared between these two strains but absent in the endophytic strain. These effectors and their promoters were characterized, revealing the presence of several cis-regulatory elements responsive to plant hormones. Overall, our findings provide novel insights into the genomic determinants of virulence in F. oxysporum f. sp. vanillae, offering a foundation for future functional studies and the development of targeted disease management strategies.

Persian lime is one of the most important citrus fruits in Mexico. This species suffers from a physiopathy called Wood Pocket (WP), which is characterized by chlorosis in leaves and fruits, necrosis in the trunk, and the eventual death of the tree. The actual scientific knowledge about WP is very little; however, the producers, researchers, and technicians associate it with abiotic stress. In the present study, we observed that Persian limes exposed to temperatures over 45 °C for five months developed WP symptoms, while those kept at 25 °C during the same time did not. Both groups were then physiologically characterized. Our results show that WP strongly affects most fluorescence and gas exchange parameters. Specially, we observe that stomatal fluxes were negative in WP leaves. Our results suggest that WP in Persian lime plants might be a physiological affectation caused by the prolonged exposure to high temperatures. It might be possible that the physiological affectation (gas exchange and water use efficiency) could be associated with a high-temperature-induced abscisic acid accumulation, which, in turn, might have caused stomatal closure in WP-affected plants. However, this hypothesis must be corroborated experimentally.