RESUMEN

Caladium (Caladium × hortulanum) is an ornamental plant popular for its variable and colorful foliage. In 2020, plants showing leaf spots and blight, typical of anthracnose, were found in a field trial at the University of Florida's Gulf Coast Research and Education Center (UF/GCREC) in Wimauma, FL, USA. Leaf samples consistently yielded a Colletotrichum-like species with curved conidia and abundant setae production in the acervuli. The internal transcribed spacer (ITS), partial sequences of the glyceraldehyde-3-phosphate dehydrogenase gene (gapdh), actin gene (act), chitin synthase 1 gene (chs-1), beta-tubulin gene (tub2), and histone3 gene (his3) were amplified and sequenced. Blastn searches in the NCBI GenBank database revealed similarities to species of the Colletotrichum truncatum species complex. Phylogenetic analyses using multi-locus sequence data supports a distinct species within this complex, with the closest related species being C. curcumae. Based on morphological and phylogenetic analyses, a new species of Colletotrichum, named C. caladii, is reported. Pathogenicity assays and subsequent isolation confirmed that this species was the causal agent of the disease.

RESUMEN

Blackberry (Rubus L. subgenus Rubus Watson) is a deciduous berry crop that is the fourth most economically important berry crop, and its production is expanding in the southeastern United States. However, since most commercially available cultivars were bred under temperate conditions, they are not always well adapted and could be threatened by new pathogen populations inhabiting subtropical areas. In 2017, plants showing purple or brown leaf spots and angular-to-irregular lesions on both leaf surfaces, with clusters of black conidiophores at the center, were observed in a field trial at the University of Florida's Gulf Coast Research and Education Center (UF/GCREC) in Wimauma, FL. A fungus resembling Cercospora/Pseudocercospora was isolated from the lesions. The ribosomal DNA internal transcribed spacers, the translation elongation factor 1-alpha, and the actin genes were amplified and sequenced. Based on the phylogenetic analysis, the closest related species was Pseudocercospora pancratii. Pathogenicity assays and subsequent reisolation confirmed that this species is the causal agent of the disease. Among eight cultivars screened, no complete resistance was found. However, 'Osage' was the least susceptible, and 'Kiowa' was the most susceptible. This study is the first report of P. pancratii causing leaf spots on blackberry worldwide, and it may help shape future research into disease epidemiology and management for a crop that is rapidly expanding but has very limited disease information currently available for Florida growers.

Asunto(s)

Ascomicetos , Rubus , Florida , Filogenia , Fitomejoramiento

RESUMEN

During the fall of 2020 and summer of 2021, symptoms of leaf rust were observed on blackberry plants of 'Kiowa', and breeding line 1734 (progeny of 'Natchez' and Arapaho') in a field trial at the University of Florida, Wimauma, FL. Symptoms consisted of small chlorotic spots (1 to 3 mm) on the upper side of the leaf, while the underside had yellow-orange pustules. Disease incidence was up to 100% on both 'Kiowa' and the breeding line 1734, and severity was up to 20% with most of the symptoms observed on older leaves. Two isolates were collected from 'Kiowa' and one from the breeding line 1734 for further investigation. Isolates were maintained and multiplied on healthy 'Kiowa' plants in growth chambers (25 ºC and 12-12 h photoperiod). Uredinia (n=30) were erumpent and ranged from 90 to 320 µm (Average=285 µm, SD=5.3 µm) in diameter. Urediniospores (n=50) were obovoid, yellow, and ranged from 24 to 36 µm long (Average=32 µm, SD=3.2 µm) and 22 to 30 µm wide (Average=28 µm, SD=2.5 µm). Based on morphology and literature, the pathogen was tentatively identified as Kuehneola uredinis (Link) Arth (Arthur 1906; Shands et al., 2018). Spores from a single uredinium of each isolate were collected with a needle and suspended in 50 µL of molecular biology-grade water yielding a final concentration of approximately 5 x 104 spores/mL. Two µL of each spore suspension was used for the PCR reactions. Two DNA fragments were amplified using the primers Rust2inv and LR6, and Rust18S-R and NS1 for the 5.8S-ITS2-28S gene region of rDNA (1,755 bp) and partial 18S gene region of rDNA (2,684 bp), respectively. The amplified products of the partial 28S gene region were sequenced with the primers LR3 and LR0R, and the 18S gene region with NS5, NS6, and NS4 (Aime 2006). DNA sequences were deposited in GenBank (accession nos. OK509845 - OK509848). BLASTn searches revealed that the isolates were 100% identical to K. uredinis reported causing leaf rust on blackberry in California (1044/1044bp, and 1540/1540bp for accession numbers MF158087, and MF158088, respectively). To test for pathogenicity, blackberry cultivars Kiowa, Natchez, Osage, Ouachita, Ponca, Prime-Ark® 45, Prime-Ark® Freedom, Prime-Ark® Traveler, and Prime-Ark® Horizon were inoculated. Five plants of each cultivar were inoculated with a mixture of spores of the three isolates, and two plants of each cultivar were used as controls. Spores were washed from leaves of 'Kiowa' exhibiting sporulation using a suspension of 1% Tween 20 in deionized water. The final concentration of the inoculum was adjusted to 104 spores/mL. Plants were inoculated in the greenhouse with a spray bottle until run-off and kept inside clear plastic boxes for 48 h. Controls were sprayed with sterile deionized water. Plants were watered by mists of 3 s every 10 min twice a week. Disease incidence and severity were evaluated weekly on five leaves per plant that had been tagged before inoculation. The experiment was repeated once. Symptoms identical to the original were only observed in 'Kiowa' and 'Prime-Ark® Freedom'. One week after inoculation, disease incidence was already 100% in both cultivars, with at least one pustule on all the inoculated leaves, and six weeks later disease severity was up to 50% (Average= 35%, SD=2.4%). To our knowledge, this is the first report of K. uredinis causing leaf rust on blackberry in Florida. This disease was reported on Rubus spp. in several U.S. states, and recently in California on Rubus ursinus (Farr and Rossman 2021; Shands et al. 2018). Blackberry is an emerging crop in Florida and efforts should be implemented to monitor the occurrence and spread of leaf rust considering that urediniospores disperse long distances by wind, especially if growers choose the susceptible cultivars 'Kiowa' and 'Prime-Ark Freedom'. The apparent resistance observed in other commercial cultivars such as 'Osage', 'Ouachita', and 'Ponca' may serve as valuable breeding parents for developing new blackberry cultivars with resistance to leaf rust.

RESUMEN

Bemisia tabaci (Gennadius) biotype B transmits Tomato yellow leaf curl virus (TYLCV), which affects tomato production globally. Prompt destruction of virus reservoirs is a key component of virus management. Identification of weed hosts of TYLCV will be useful for reducing such reservoirs. The status of weeds as alternate hosts of TYLCV in Florida remains unclear. In greenhouse studies, B. tabaci adults from a colony reared on TYLCV-infected tomato were established in cages containing one of four weeds common to horticultural fields in central and south Florida. Cages containing tomato and cotton were also infested with viruliferous whiteflies as a positive control and negative control, respectively. Whitefly adults and plant tissue were tested periodically over 10 wk for the presence of TYLCV using PCR. After 10 wk, virus-susceptible tomato plants were placed in each cage to determine if whiteflies descended from the original adults were still infective. Results indicate that Bidens alba, Emilia fosbergii, and Raphanus raphanistrum are not hosts of TYLCV, and that Amaranthus retroflexus is a host.

Asunto(s)

Begomovirus/fisiología , Hemípteros/virología , Enfermedades de las Plantas/virología , Malezas/virología , Solanum lycopersicum/virología , Amaranthus/virología , Animales , Florida

RESUMEN

Thrips-transmitted Iris yellow spot virus (IYSV) is an important economic constraint to the production of bulb and seed onion crops in the United States and many other parts of the world. Because the virus is exclusively spread by thrips, the ability to rapidly detect the virus in thrips vectors would facilitate studies on the role of thrips in virus epidemiology, and thus formulation of better vector management strategies. Using a polyclonal antiserum produced against the recombinant, Escherichia coli-expressed nonstructural protein coded by the small (S) RNA of IYSV, an enzyme linked immunosorbent assay was developed for detecting IYSV in individual as well as groups of adult thrips. The approach enabled estimating the proportion of potential thrips transmitters in a large number of field-collected thrips collected from field-grown onion plants. Availability of a practical and inexpensive test to identify viruliferous thrips would be useful in epidemiological studies to better understand the role of thrips vectors in outbreaks of this economically important virus of onion.

Asunto(s)

Bunyaviridae/aislamiento & purificación , Insectos Vectores/virología , Thysanoptera/virología , Animales , Bunyaviridae/inmunología , Ensayo de Inmunoadsorción Enzimática , Cebollas/virología , Proteínas Virales/inmunología

RESUMEN

The complete nucleotide sequence and genome organization of a peach virus isolate from a naturally infected peach tree showing typical peach wart-like symptoms on the fruit surface was determined and compared to sequences of members of the family Betaflexiviridae. The genome consists of 7,987 nucleotides, excluding the poly-A tail, and has four open reading frames (ORFs). Analysis of the whole genome and putative proteins encoded by each ORF revealed greatest sequence similarity to a cherry isolate of cherry mottle leaf virus (CMLV). The two isolates have similar genome organizations and share 88 and 93 % homology in their corresponding products of the replicase and coat protein genes, respectively. CMLV has been reported from several Prunus spp. and may be associated with peach wart-like disease symptoms on peach fruit.

Asunto(s)

Enfermedades de las Plantas/virología , Virus de Plantas/genética , Prunus/virología , Genoma Viral , Datos de Secuencia Molecular , Virus de Plantas/aislamiento & purificación

RESUMEN

A DNase released from the fungal pathogen of bean, Fusarium solani f. sp. phaseoli (Fsph), was previously shown to signal the activation of total disease resistance and activate pathogenesis-related (PR) genes in pea. Data in the current study which used the pea-endocarp model to research non-host resistance, indicated that DNase released by Verticillium dahliae (Vd), pathogenic on potato also has non-host resistance-inducing capabilities in peas. Other strains of Vd that release DNase are pathogenic on other plant species. DNase catalytic activity was also released from representative genera of other pathogenic fungi. Purified VdDNase induced pisatin and pea gene DRR49 (PR-10 gene) in pea endocarp tissue. VdDNase reduced the in vitro growth of Vd but completely inhibited that of F. solani f. sp. pisi (Fspi) and a Colletotrichum pathogen of potato. VdDNase (2 units) applied to pea endocarp tissue both broke resistance to Fsph and increased resistance to Fspi. Pea DNA damage generated both by the VdDNase enzyme and the intact Vd spores indicated that the host DNA alteration is a component of the non-host resistance response (innate immunity). These data support the previously reported inductive potential of fungal DNase and further implicate fungal DNases as signals in activating non-host resistance responses.

Asunto(s)

Desoxirribonucleasas/metabolismo , Genes de Plantas , Pisum sativum/microbiología , Inmunidad de la Planta , Verticillium/enzimología , Antifúngicos/aislamiento & purificación , Antifúngicos/metabolismo , Antifúngicos/farmacología , Daño del ADN , Desoxirribonucleasas/aislamiento & purificación , Desoxirribonucleasas/farmacología , Resistencia a la Enfermedad , Activación Enzimática , Pruebas de Enzimas , Proteínas Fúngicas/metabolismo , Proteínas Fúngicas/farmacología , Fusarium/efectos de los fármacos , Fusarium/crecimiento & desarrollo , Interacciones Huésped-Patógeno , Pisum sativum/genética , Pisum sativum/inmunología , Enfermedades de las Plantas/inmunología , Enfermedades de las Plantas/microbiología , Pterocarpanos/genética , Pterocarpanos/metabolismo , Semillas/citología , Semillas/enzimología , Esporas Fúngicas/metabolismo , Activación Transcripcional , Verticillium/inmunología

RESUMEN

The complete genomic sequence of American hop latent virus (AHLV; genus Carlavirus) was determined. The genome consists of 8,601 nucleotides plus a 3'-polyadenylate tail. The genome encompasses six potential open reading frames (ORF) in the positive sense, and their organization is typical of other carlaviruses. Analysis of the coat protein coding sequence at both the nucleic acid level and the amino acid level indicates that AHLV is only remotely related to the other carlaviruses known to infect common hop. Polyclonal antibodies were produced against the bacterially expressed coat protein of AHLV. These antibodies differentiated between AHLV and other carlaviruses of hop.

Asunto(s)

Carlavirus/genética , ARN Viral/genética , Secuencia de Aminoácidos , Animales , Anticuerpos Antivirales/biosíntesis , Secuencia de Bases , Proteínas de la Cápside/química , Proteínas de la Cápside/genética , Proteínas de la Cápside/inmunología , Carlavirus/clasificación , Chenopodium quinoa/virología , Regulación Viral de la Expresión Génica/fisiología , Genoma Viral , Humulus/virología , Funciones de Verosimilitud , Datos de Secuencia Molecular , Sistemas de Lectura Abierta , Filogenia , Conejos

RESUMEN

The complete nucleotide sequence of cherry leaf roll virus (CLRV, genus Nepovirus) from a naturally infected cherry tree (Prunus avium cv. Bing) in North America was determined. RNA1 and RNA2 consist of 7,893 and 6,492 nucleotides, respectively, plus a poly-(A) tail. Each RNA encodes a single potential open reading frame. The first 657 nucleotides of RNA1 and RNA2 are 99% identical and include the 5'-UTR and the first 214 deduced amino acids of the polyproteins following the first of two in-frame start codons. Phylogenetic analysis reveals close relationships between CLRV and members of subgroup C of the genus Nepovirus.

Asunto(s)

Orden Génico , Genoma Viral , Nepovirus/genética , Nepovirus/aislamiento & purificación , Enfermedades de las Plantas/virología , Prunus/virología , ARN Viral/genética , Regiones no Traducidas 5' , Análisis por Conglomerados , Datos de Secuencia Molecular , América del Norte , Sistemas de Lectura Abierta , Filogenia , Análisis de Secuencia de ADN , Homología de Secuencia de Ácido Nucleico

Asunto(s)

Carlavirus/clasificación , Genoma Viral , Virus del Mosaico/genética , Filogenia , Secuencia de Bases , Carlavirus/genética , Cicer/virología , Virus del Mosaico/clasificación , Sistemas de Lectura Abierta , Enfermedades de las Plantas/virología , ARN Viral/genética , Alineación de Secuencia , Análisis de Secuencia de ARN

RESUMEN

Viruses in certain genera in family Caulimoviridae were shown to integrate their genomic sequences into their host genomes and exist as endogenous pararetroviral sequences (EPRV). However, members of the genus Caulimovirus remained to be the exception and are known to exist only as episomal elements in the infected cell. We present evidence that the DNA genome of a new and distinct Caulimovirus species, associated with dahlia mosaic, is integrated into its host genome, dahlia (Dahlia variabilis). Using cloned viral genes as probes, Southern blot hybridization of total plant DNA from dahlia seedlings showed the presence of viral DNA in the host DNA. Fluorescent in situ hybridization using labeled DNA probes from the D10 genome localized the viral sequences in dahlia chromosomes. The natural integration of a Caulimovirus genome into its host and its existence as an EPRV suggests the co-evolution of this plant-virus pathosystem.

Asunto(s)

Caulimovirus/genética , Dahlia/genética , Cromosomas de las Plantas/genética , ADN de Plantas/genética , ADN Viral/genética , Dahlia/virología , Enfermedades de las Plantas/virología , Plantones/genética , Plantones/virología , Integración Viral

RESUMEN

ABSTRACT A strain of Bean common mosaic necrosis virus (BCMNV) from Idaho was identified by enzyme-linked immunosorbent assay using monoclonal antibodies and determined to be similar to the NL-3 D strain (of Drifjhout) by reaction of differential bean cultivars. However, this BCMNV strain (designated NL-3 K) caused earlier and more severe symptoms on bean plants representing host groups 0, 4, and 5. The nucleotide sequence encoding the predicted polyprotein of NL-3 K was 9,893 nucleotides (nt) in length, yielding a peptide with a molecular size of 362.1 kDa compared with a 9,626-nt, 350.9-kDa polyprotein for NL-3 D. Sequence analysis of the putative P1 protein suggests that the NL-3 K strain is a recombinant between NL-3 D and the Russian strain (RU1) of Bean common mosaic virus. The P1 protein of NL-3 K consisted of 415 amino acids compared with 317 for NL-3 D. The first 114 predicted amino acids of the NL-3 K P1 region were 98% identical with RU1. The remaining 301 amino acids of the protein shared only 34% identity with RU1 but were 98% identical with NL-3 D. Primers were designed that flanked the recombination point in the P1 coding sequence of NL-3 K. An amplicon of the expected size was produced by reverse-transcriptase polymerase chain reaction of total nucleic acid extracts of bean plants inoculated with NL-3 K, but not from those with NL-3 D or RU1. The increased symptom severity on selected common bean lines induced by NL-3 K suggests that the P1 gene may play a significant role in pathogenicity and virulence.

RESUMEN

During the 1999 to 2001 growing seasons, symptoms consisting of mosaic, stunting, yellowing, wilting, shortening of internodes, and phloem discoloration were observed in chickpea (Cicer arietinum) grown in the Department of Chuquisaca in southern Bolivia. In some fields, approximately 10% of the plants exhibited viruslike symptoms and suffered greatly reduced seed yields. Lentil (Lens culinaris) was also observed to be infected but not pea (Pisum sativum) or faba bean (Vicia faba) growing in nearby fields. Infected chickpea tissue reacted positively to the potyvirus group-specific monoclonal antibody (MAb), but there was no serological reaction with antisera to the potyviruses Bean yellow mosaic virus, Clover yellow vein virus, Cowpea aphid-borne mosaic virus, Pea seedborne mosaic virus, Bean common mosaic virus, or Bean common mosaic necrosis virus. Western blots of total protein extracts probed with the potyvirus MAb revealed a single band ca. 32 kDa. Comparative sequence analysis of cDNA clones generated from the putative coat protein gene consisted of 282 amino acids (31.9 kDa) and showed moderate identities of 67, 66, 63, 63, and 61% with the coat proteins of potyviruses Pepper severe mosaic virus, Pepper yellow mosaic virus, Potato virus Y, Plum pox virus, and Pepper mottle virus, respectively. Phylogenetic analysis of the coat protein amino acid sequence revealed that this virus is a unique member of the family Potyviridae and is phylogenetically most closely related to a group of Solanaceae-infecting potyviruses rather than to other legumeinfecting potyviruses. The proposed name for the new causal agent is Chickpea yellow mosaic virus.