RESUMO
Bacterial wilt, caused by the Ralstonia solanacearum species complex (RSSC), is the most destructive potato disease in Kenya. Studies were conducted to (i) determine the molecular diversity of RSSC strains associated with bacterial wilt of potato in Kenya, (ii) generate an RSSC distribution map for epidemiological inference, and (iii) determine whether phylotype II sequevar 1 strains exhibit epidemic clonality. Surveys were conducted in 2018 and 2019, in which tubers from wilting potato plants and stem samples of potential alternative hosts were collected for pathogen isolation. The pathogen was phylotyped by multiplex PCR and 536 RSSC strains typed at a sequevar level. Two RSSC phylotypes were identified, phylotype II (98.4%, n = 506 [sequevar 1 (n = 505) and sequevar 2 (n = 1)]) and phylotype I (1.6%, n = 30 [sequevar 13 (n = 9) and a new sequevar (n = 21)]). The phylotype II sequevar 1 strains were haplotyped using multilocus tandem repeat sequence typing (TRST) schemes. The TRST scheme identified 51 TRST profiles within the phylotype II sequevar 1 strains with a modest diversity index (HGDI = 0.87), confirming the epidemic clonality of RSSC phylotype II sequevar 1 strains in Kenya. A minimum spanning tree and mapping of the TRST profiles revealed that TRST27 '8-5-12-7-5' is the primary founder of the clonal complex of RSSC phylotype II sequevar 1 and is widely distributed via latently infected seed tubers. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
Assuntos
Ralstonia solanacearum , Solanum tuberosum , Quênia/epidemiologia , Filogenia , Doenças das Plantas/microbiologia , Ralstonia , Ralstonia solanacearum/genética , Solanum tuberosum/microbiologiaRESUMO
The malaria parasite, Plasmodium falciparum, was introduced into Hispaniola and other regions of the Americas through the slave trade spanning the 16th through the 19th centuries. During this period, more than 12 million Africans were brought across the Atlantic to the Caribbean and other regions of the Americas. Since malaria is holoendemic in West Africa, a substantial percentage of these individuals carried the parasite. St. Domingue on Hispaniola, now modern-day Haiti, was a major port of disembarkation, and malaria is still actively transmitted there. We undertook a detailed study of the phylogenetics of the Haitian parasites and those from Colombia and Peru utilizing whole-genome sequencing. Principal-component and phylogenetic analyses, based upon single nucleotide polymorphisms (SNPs) in protein coding regions, indicate that, despite the potential for millions of introductions from Africa, the Haitian parasites share an ancestral relationship within a well-supported monophyletic clade with parasites from South America, while belonging to a distinct lineage. This result, in stark contrast to the historical record of parasite introductions, is best explained by a severe population bottleneck experienced by the parasites introduced into the Americas. Here, evidence is presented for targeted selection of rare African alleles in genes which are expressed in the mosquito stages of the parasite's life cycle. These genetic markers support the hypothesis that the severe population bottleneck was caused by the required adaptation of the parasite to transmission by new definitive hosts among the Anopheles (Nyssorhynchus) spp. found in the Caribbean and South America.IMPORTANCE Historical data suggest that millions of P. falciparum parasite lineages were introduced into the Americas during the trans-Atlantic slave trade, which would suggest a paraphyletic origin of the extant isolates in the Western Hemisphere. Our analyses of whole-genome variants show that the American parasites belong to a well-supported monophyletic clade. We hypothesize that the required adaptation to American vectors created a severe bottleneck, reducing the effective introduction to a few lineages. In support of this hypothesis, we discovered genes expressed in the mosquito stages of the life cycle that have alleles with multiple, high-frequency or fixed, nonsynonymous mutations in the American populations which are rarely found in African isolates. These alleles appear to be in gene products critical for transmission through the anopheline vector. Thus, these results may inform efforts to develop novel transmission-blocking vaccines by identifying parasite proteins functionally interacting with the vector that are important for successful transmission. Further, to the best of our knowledge, these are the first whole-genome data available from Haitian P. falciparum isolates. Defining the genome of these parasites provides genetic markers useful for mapping parasite populations and monitoring parasite movements/introductions.
Assuntos
Adaptação Fisiológica/genética , Anopheles/parasitologia , Variação Genética , Filogenia , Plasmodium falciparum/genética , Animais , Marcadores Genéticos , Haiti , Malária Falciparum/parasitologia , Mosquitos Vetores/parasitologia , Mutação , Plasmodium falciparum/classificação , Plasmodium falciparum/fisiologia , América do Sul , Estados Unidos , Sequenciamento Completo do GenomaRESUMO
An ongoing survey for novel phytoplasmas and viruses that affect palms (Arecaceae) and their potential vectors is being conducted in Costa Rica. During that survey, a new species of derbid planthopper (Hemiptera: Fulgoroidea) from the palm Astrocaryum alatum H.F. Loomis was found in Heredia State and is here described as Agoo dahliana sp. n. Omolicna dubia Caldwell and O. latens Fennah were also found on coconut palms (Cocos nucifera L.) and represent new country records. Sequence data for the cytochrome c oxidase subunit I (COI) were generated for 9 ingroup (Omolicna Fennah) and 1 outgroup (Neocenchrea Metcalf) taxa; and for 18S ribosomal RNA gene were generated for 8 ingroup plus 2 outgroup taxa (Neocenchrea, Cenchrea Westwood). These data were compiled with available data from GenBank and BOLD for maximum likelihood phylogenetic reconstruction for Omolicna. These results, plus morphological evidence, support changing the status of the genus-group name Agoo Bahder Bartlett from subgenus within Omolicna to full genus, resulting in the new combination of Agoo xavieri Bahder Bartlett. Based on the original description and illustration of the genitalia of Omolicna rubrimarginata Fennah (from Trinidad), we transfer this species to Agoo, creating the combination Agoo rubrimarginata (Fennah), and bringing the total number of species in this genus to three, with A. dahliana sp. n. and A. xavieri currently only known from Costa Rica. Based on both molecular and morphological evidence, O dubia is transferred to Anchimothon Fennah. A key to differentiate the species of Agoo is presented.
Assuntos
Hemípteros , Animais , Cocos , Costa Rica , FilogeniaRESUMO
An ongoing survey for novel phytoplasmas and viruses that affect palms (Arecaceae) is being conducted in Costa Rica along with potential vectors. During that survey, a new species of derbid planthopper (Hemiptera: Fulgoroidea) in the genus Omolicna Fennah was detected from Heredia and Limón State and is here described as Omolicna xavieri sp. n. This new taxon was first found on declining coconut palms (Cocos nucifera) and subsequently on healthy coconut palms in Tortuguero National Park. Also, two additional species of Omolicna, O. brunnea and O. triata, were collected on coconut in the same habitat and represent new country records. There are no previously published records of Omolicna from Costa Rica. Sequence data for the cytochrome c oxidase subunit I (COI) and the 18S ribosomal RNA gene were obtained. In addition, novel 18S primers specific to auchenorrhynchan insects were developed and presented. The molecular data show high pairwise distances between O. xavieri sp. n. and other Omolicna species (24% to 31% and 10% using COI and 18S, respectively). Based on both morphological and sequence data, we erect and briefly describe the new subgenus Agoo for the new species to reflect the observed differences. A checklist of Omolicna species is presented.
Assuntos
Arecaceae , Hemípteros , Animais , Cocos , Costa RicaRESUMO
Phytophthora capsici is an oomycete plant pathogen with a wide host range. Worldwide, P. capsici is known for causing the principal disease of chili pepper crops. Our goal was to expand the available genome resources for this diverse pathogen by generating whole-genome sequences for six isolates of P. capsici from Mexico.
Assuntos
Genoma de Protozoário , Phytophthora , Capsicum/parasitologia , Genoma de Protozoário/genética , México , Phytophthora/genética , Doenças das Plantas/parasitologiaRESUMO
In Mexico, Fusarium mexicanum has been reported causing mango malformation disease and big-leaf mahogany malformation disease. Our objective was to determine the genetic diversity of F. mexicanum isolates obtained from malformed big-leaf mahogany and mango trees, using an internal simple sequence repeat (ISSR) analysis. A total of 61 isolates of F. mexicanum, 32 from mango and 29 from big-leaf mahogany, were initially genotyped using fourteen ISSR primers. Data from five primers that produced the highest number of polymorphic bands were selected for further analysis. The primers generated 49 polymorphic bands (85.96%) from a total of 57 fragments ranging in size from 250 to 2800 bp, with an average of 11.4 bands per primer. An analysis of molecular variance (AMOVA) indicated that the variation within populations, isolates grouped by host and geographic origin, was significant (43%), followed by the variation between the big-leaf mahogany versus mango isolates (34%), while among populations the variation was the lowest (22%). The genetic fingerprints suggested that genetic variability of F. mexicanum populations are structured by the host of origin rather than the geographic region.
Assuntos
Fusariose/metabolismo , Fusarium/genética , Impressões Digitais de DNA/métodos , Fusariose/genética , Fusarium/metabolismo , Variação Genética/genética , Genética Populacional/métodos , Genótipo , Mangifera/microbiologia , Meliaceae/microbiologia , México , Repetições de Microssatélites/genética , Doenças das Plantas/genética , Doenças das Plantas/microbiologia , Folhas de Planta/genética , Análise de Sequência de DNA/métodos , Árvores/genéticaRESUMO
Myxia belinda gen. et sp. nov. is established for a new taxon of Cixiidae in the tribe Oecleini collected from palms in Costa Rica. The new taxon was discovered while surveying palms for potential phytoplasma vectors. Placement in a new genus is supported by a 1,383 bp sequence of 18S that differs by 2.77% from Haplaxius, 5.20% from Myndus taffini, and 2.80% from Nymphomyndus caribbea. Intrageneric variation for 18S was found to be approximately 0.5% to 0.6% within Haplaxius. Generic level differences within the Oecleini for COI ranged from 15% to 17% with the novel taxon differing by about 16% from other genera. The new genus is most similar in appearance to Haplaxius but possesses striking sexual dimorphism, and the aedeagus is only partially surrounded by the phallobase (versus entirely enveloped in Haplaxius). The discovery of a novel taxon of cixiid on palms that is similar to Haplaxius is important because of the role that Haplaxius crudus plays in phytoplasma transmission in palm agro- and natural ecosystems.
Assuntos
Hemípteros , Animais , Costa Rica , Ecossistema , Florestas , Los AngelesRESUMO
Globally destructive crop pathogens often emerge by migrating out of their native ranges. These pathogens are often diverse at their centre of origin and may exhibit adaptive variation in the invaded range via multiple introductions from different source populations. However, source populations are generally unidentified or poorly studied compared to invasive populations. Phytophthora infestans, the causal agent of late blight, is one of the most costly pathogens of potato and tomato worldwide. Mexico is the centre of origin and diversity of P. infestans and migration events out of Mexico have enormously impacted disease dynamics in North America and Europe. The debate over the origin of the pathogen, and population studies of P. infestans in Mexico, has focused on the Toluca Valley, whereas neighbouring regions have been little studied. We examined the population structure of P. infestans across central Mexico, including samples from Michoacán, Tlaxcala and Toluca. We found high levels of diversity consistent with sexual reproduction in Michoacán and Tlaxcala and population subdivision that was strongly associated with geographic region. We determined that population structure in central Mexico has contributed to diversity in introduced populations based on relatedness of U.S. clonal lineages to Mexican isolates from different regions. Our results suggest that P. infestans exists as a metapopulation in central Mexico, and this population structure could be contributing to the repeated re-emergence of P. infestans in the United States and elsewhere.
Assuntos
Genética Populacional , Phytophthora infestans/genética , Doenças das Plantas/microbiologia , Solanum tuberosum/microbiologia , MéxicoRESUMO
Phytophthora andina is a heterothallic plant pathogen of Andean solanaceous hosts and is an interspecific hybrid of P. infestans and an unknown Phytophthora species. The objective of this study was to estimate the nuclear DNA content of isolates in three clonal lineages of P. andina relative to P. infestans Twelve isolates of P. andina and six isolates of P. infestans were measured for nuclear DNA content by propidium iodide-stained flow cytometry. We found that the DNA content of P. andina was similar but slightly smaller, on average, than that of our sample of P. infestans isolates. This is consistent with P. andina being a homoploid hybrid rather than allopolyploid hybrid. Nuclear DNA content was more variable among a smaller sample of P. infestans isolates, including a putative triploid isolate from Mexico, but small differences in nuclear DNA content were also observed among P. andina isolates. Both species appear to be able to tolerate significant variation in genome size.
Assuntos
DNA/análise , Phytophthora/genética , Phytophthora/isolamento & purificação , Plantas/microbiologia , Citometria de Fluxo , MéxicoRESUMO
Phytophthora infestans is a destructive plant pathogen best known for causing the disease that triggered the Irish potato famine and remains the most costly potato pathogen to manage worldwide. Identification of P. infestan's elusive center of origin is critical to understanding the mechanisms of repeated global emergence of this pathogen. There are two competing theories, placing the origin in either South America or in central Mexico, both of which are centers of diversity of Solanum host plants. To test these competing hypotheses, we conducted detailed phylogeographic and approximate Bayesian computation analyses, which are suitable approaches to unraveling complex demographic histories. Our analyses used microsatellite markers and sequences of four nuclear genes sampled from populations in the Andes, Mexico, and elsewhere. To infer the ancestral state, we included the closest known relatives Phytophthora phaseoli, Phytophthora mirabilis, and Phytophthora ipomoeae, as well as the interspecific hybrid Phytophthora andina. We did not find support for an Andean origin of P. infestans; rather, the sequence data suggest a Mexican origin. Our findings support the hypothesis that populations found in the Andes are descendants of the Mexican populations and reconcile previous findings of ancestral variation in the Andes. Although centers of origin are well documented as centers of evolution and diversity for numerous crop plants, the number of plant pathogens with a known geographic origin are limited. This work has important implications for our understanding of the coevolution of hosts and pathogens, as well as the harnessing of plant disease resistance to manage late blight.