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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. [ABSTRACT FROM AUTHOR]

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The bacteria that cause citrus huanglongbing (HLB), Candidatus Liberibacter spp., are obligate bacteria to the citrus phloem and to different systems of the vector insect, Diaphorina citri, therefore, the genomic approach has been useful to study its pathogenicity mechanisms. This approach has allowed the identification of a homologous copy of the gene coding for the enzyme ATP / ADP translocase, which has the ability to import ATP and nucleotides from the host, causing considerable energy parasitism. This enzyme has been related to the endoparasitic activity of animal and human pathogens more than to phytopathogens. The present work analyzed the evolutionary relationship between the amino acid sequence of ATP / ADP translocase between different species of Ca. Liberibacter and groups such as Ricketssia sp. and Chlamydia sp. Phylogenetic analyzes show that the variation in the sequence of the gene coding for the enzyme is delimited in clades corresponding to the species of Ca. Liberibacter, suggesting that the variation in the enzyme responds to a co-evolutionary process. Also, the phylogeny shows that the closest common ancestor to Ca. Liberibacter could be a non-pathogenic endosymbiont of the genus Ca. Midichloria. Amino acid sequence conservation analysis shows that there are several positions in the sequence that could be related to species variation. The present work offers the hypothesis that the evolutionary origin of the energy parasitism capacity of the causal agents of HLB is a nonpathogenic endosymbiont. [ABSTRACT FROM AUTHOR]