Resumen Los fitoplasmas (clase Mollicutes) son agentes causales de enfermedades de plantas que provocan pérdidas económicas o amenazan la biodiversidad local. Una recolecta de plantas de Catharanthus roseus que mostraban síntomas de posible infección con fitoplasmas se realizó en diferentes lugares de Costa Rica desde 2012 a 2016. Un total de 73 plantas fueron recolectadas con síntomas tales como viriscencia, filodia, brotación axilar múltiple, reducción foliar, deformación foliar, clorosis, y amarillamiento. Todas las muestras fueron evaluadas mediante PCR anidado usando los pares de imprimadores universales y específicos para fitoplasmas. Infección por fitoplasmas se detectó en 52 (71.2 %) de las muestras. Fitoplasmas de seis subgrupos dentro de los grupos 16Sr I, III, IX, XIII y XV fueron identificados basados en secuenciación del ADN y análisis de polimorfismos de restricción (RFLP) in silico. El grupo predominante encontrado en las muestras positivas (n = 30) fue el 16SrI (‘CandidatusPhytoplasma asteris’), éste mostró variedad de síntomas y amplia distribución desde el nivel del mar hasta casi los 1 400 m.s.n.m. en seis de las siete provincias de Costa Rica. El grupo 16SrIII fue el segundo más abundante (14 muestras); y los restantes tres grupos se encontraron en pocas muestras de C. roseus (8 muestras). Además, fitoplasmas del grupo 16SrXIII se detectaron por primera vez en el país. De acuerdo a nuestro conocimiento, este es el primer informe de infección natural de C. roseus con fitoplasmas de los subgrupos 16SrI-B, 16SrI-P, 16SrIII-F, 16SrIX-F, 16SrXIII-A y 16SrXV-B en Costa Rica y Centroamérica.

Abstract Phytoplasmas (class Mollicutes) are causal agents of plant diseases with an economic impact on crops or threatening local biodiversity. A survey was conducted from 2012 to 2016 on infected Catharanthus roseus plants that exhibited symptoms reminiscent of phytoplasma infection throughout Costa Rica. A total of 73 plants were collected exhibiting symptoms such as virescence, phyllody, axillary proliferation, little leaf, leaf malformation, chlorosis, or yellowing. All samples were tested by nested PCR using phytoplasma universal and specific primer pairs. Phytoplasma infection was detected in 52 (71.2 %) of the plants collected. Phytoplasmas of six subgroups belonging to 16Sr groups I, III, IX, XIII and XV were identified based on sequencing and in silico RFLP analyses. ‘Candidatus Phytoplasma asteris’ (16SrI) was the predominant group among the positive samples (n = 30) showing variety of symptoms and wide distribution from sea level to ca. 1 400 m.a.s.l. in six of the seven Costa Rican provinces. Group 16SrIII was the second most abundant (14 samples); and the remaining three groups were seldom found in C. roseus (8 samples). Moreover, group 16SrXIII phytoplasma was detected for the first time in the country. To the best of our knowledge, this is the first report of natural infection of C. roseus with phytoplasma subgroups 16SrI-B, 16SrI-P, 16SrIII-F, 16SrIX-F, 16SrXIII-A, and 16SrXV-B in Costa Rica and Central America.

Citrus leprosis (CL) is a serious threat to the citrus industry, especially for sweet oranges. For a long time, Citrus spp. were considered the only susceptible hosts. However, other plant species were also found either experimentally or naturally to be susceptible to Citrus leprosis virus C (CiLV-C). To assess the experimental host range of CiLV-C, a large number of plant species were inoculated with Brevipalpus phoenicis, viruliferous to CiLV-C, under experimental conditions. Out of the 140 tested species (43 families), 59 species (24 families) developed localized chlorotic and/or necrotic lesions upon inoculation of leaves with viruliferous mites, and 40 species (18 families) of them yielded positive results for CiLV-C detection in at least one of the following assays: ELISA, RT-PCR, transmission electron microscopy and immunfluorescence. For those that developed lesions and yielded negative results in CiLV-C detection assays, the results may be attributed to the small number of lesions and their necrotic state with very little viral material. The fact that a considerable number of plant species are susceptible to the virus after mite inoculation brings up implications for the epidemiology, quarantine and evolution of the citrus leprosis pathosystem.

Guacimo trees (Guazuma ulmifolia, Sterculiaceae) showing witches' broom symptoms (GWB), small leaves, short internodes, stunting and no flower and fruit production were observed on side roads and fences in different areas of Costa Rica. The occurrence of phytoplasma infection in GWB trees was evaluated by transmission electron microscopy (TEM), and by molecular analyses based on 16S rDNA: nested-PCR/RFLP, sequencing and phylogenetics. Phytoplasmas were observed only in the sieve cells of symptomatic trees by TEM. The infection was confirmed by nested-PCR; amplicons of about 1.2 kb were obtained from all DNA samples from symptomatic trees. The RFLP analysis generated patterns identical among GWB samples and showed a relationship of this phytoplasma to hibiscus witches' broom group (16SrXV). The 16S rDNA sequence (1460 nt), obtained from the P1A/16S-SR semi-nested-PCR products of two phytoplasma strains, shared 98.8% similarity with 'Candidatus Phytoplasma brasiliense' (GenBank accession: AF147708). The virtual RFLP pattern indicated a similarity coefficient of 0.95 with 16Sr group XV-A (AF147708), suggesting that the GWB phytoplasma may represent a new subgroup within this group. This is the first report of a phytoplasma infecting the neotropical tree species G. ulmifolia and the natural occurrence of a phytoplasma strain closely related to 'Ca. Phytoplasma brasiliense' in Costa Rica.

En varias zonas de Costa Rica se observaron árboles de guácimo (Guazuma ulmifolia, Sterculiaceae) con síntomas de escoba de bruja (GWB), hoja pequeña, acortamiento de entrenudos, dando al árbol un aspecto general de enanismo. La infección por fitoplasmas en los árboles de guácimo se evaluó mediante microscopia electrónica de transmisión (TEM), análisis moleculares del 16S rDNA mediante PCR anidado, RFLP´s, secuenciación y filogenia. En la TEM, los fitoplasmas se observaron sólo en las células del floema de los árboles sintomáticos. La infección se confirmó por PCR anidada, los productos amplificados de aproximadamente 1,2 kb se obtuvieron para todas las muestras sintomáticas evaluadas. El análisis de RFLP generó patrones idénticos entre las muestras con GWB y mostró relación de este fitoplasma con el de la "escoba de bruja del hibisco" (16SrXV). La secuencia de ADNr 16S (1460 nt) de los productos obtenidos por PCR semi-anidado (P1A/16S-SR) de dos muestras de GWB mostraron 98,8% de similitud con "Candidatus Phytoplasma brasiliense" (GenBank, registro AF147708). El patrón RFLP virtual reveló 95% de similitud con el grupo 16Sr XV-A (AF147708), lo que sugiere que el fitoplasma GWB puede representar un nuevo subgrupo dentro del 16Sr XV. Este es el primer informe de un fitoplasma infectando a la especie neotropical G. ulmifolia y de la ocurrencia natural de un fitoplasma estrechamente relacionado con "Ca. Phytoplasma brasiliense" en Costa Rica