The Effect of Boxwood Leaf Volatiles on Conidial Germination of Calonectria pseudonaviculata, the Causal Agent of Boxwood Blight.

The fungal pathogen Calonectria pseudonaviculata causes boxwood blight and is a significant threat to the boxwood industry, as well as historic boxwood gardens. The pathogen produces conidia in sticky masses that are splash dispersed, which germinate and infect through stomata on the leaves or stems, causing leaf spots and stem lesions. Despite its ability to cause severe infections on boxwood plants, the pathogen often has a low germination rate on artificial media under lab conditions. To identify cues that stimulate germination, we explored whether host factors could induce high germination rates. In this study, we demonstrate that C. pseudonaviculata spores achieve high germination rates when they are placed on detached leaves of boxwood and other known hosts, compared to potato dextrose agar and glass coverslips. We also demonstrate that germination is induced by volatiles from detached leaves of boxwood, as well as the nonhost Berberis thunbergii. When C. pseudonaviculata spores were exposed to volatiles from boxwood leaves in the presence of ethylene scrubber packs that contained potassium permanganate, the stimulatory effect on spore germination was reduced. However, ethylene, a regulator of leaf senescence, did not stimulate germination of C. pseudonaviculata spores. This suggests that the pathogen may have evolved to recognize one or more host volatiles, other than ethylene to induce germination, thus limiting its growth until it senses the presence of a host plant.

Vaccines to Prevent Coccidioidomycosis: A Gene-Deletion Mutant of Coccidioides Posadasii as a Viable Candidate for Human Trials.

Coccidioidomycosis is an endemic fungal infection that is reported in up to 20,000 persons per year and has an economic impact close to $1.5 billion. Natural infection virtually always confers protection from future exposure, and this suggests that a preventative vaccine strategy is likely to succeed. We here review progress toward that objective. There has been ongoing research to discover a coccidioidal vaccine over the past seven decades, including one phase III clinical trial, but for reasons of either efficacy or feasibility, a safe and effective vaccine has not yet been developed. This review first summarizes the past research to develop a coccidioidal vaccine. It then details the evidence that supports a live, gene-deletion vaccine candidate as suitable for further development as both a veterinary and a human clinical product. Finally, a plausible vaccine development plan is described which would be applicable to this vaccine candidate and also useful to other future candidates. The public health and economic impact of coccidioidomycosis fully justifies a public private partnership for vaccine development, and the development of a vaccine for this orphan disease will likely require some degree of public funding.

Cool Temperatures Favor Growth of Oregon Isolates of Calonectria pseudonaviculata and Increase Severity of Boxwood Blight on Two Buxus Cultivars.

Controlled environment experiments were conducted to evaluate the effects of temperature on Calonectria pseudonaviculata mycelial growth and the effects of temperature and infection period on boxwood blight severity. In experiment 1, 15 Oregon isolates (representing five genotypes) were grown on potato dextrose agar (PDA) and malt extract agar (MEA) at six temperatures from 5 to 30°C. Growth (culture diameter) was measured after 2 weeks. Optimal growth occurred at 25°C on PDA and 20°C on MEA. Isolates of genotype G1 also grew faster than genotype G2, but only on MEA at 25°C. In experiment 2, Buxus cultivars Green Velvet (GV, more susceptible) and Winter Gem (WG, more resistant) were inoculated and incubated in moist chambers for 9 or 24 h at 22°C (infection period), then moved into growth chambers at 15 or 25°C. After 4 weeks, chamber temperatures were switched, and plants were incubated for 4 more weeks. Disease severity was evaluated weekly. During the first 4 weeks, disease was generally more severe on GV than WG, on plants with a 24-h versus a 9-h infection period, and on plants incubated at 15°C versus 25°C. However, disease was just as severe on WG as GV when the 24-h infection period was followed by incubation at 15°C. After the temperatures were switched, disease increased only on WG that were cooled from 25 to 15°C. Results show that Oregon isolates of C. pseudonaviculata are capable of growing faster and causing more severe disease at temperatures cooler than those reported previously.

Coccidioides posadasii in a Dog With Cervical Dissemination Complicated by Esophageal Fistula.

A 5-year-old male, neutered mixed breed dog with a history of a mass with an associated draining tract on the ventral cervical region was diagnosed with an esophageal fistula. The dog exhibited serosanguinous discharge from the draining tract, with enlarged left superficial cervical and mandibular lymph nodes, and was reported to have difficulty with deglutition of solid foods. Computed tomography revealed a communication of the draining tract with the esophagus along with enlargement of the left lateral retropharyngeal, left medial retropharyngeal, and mandibular lymph nodes. This prompted surgical exploration and debridement of the site, with closure of the esophageal fistula. Histopathology of thyroid gland, skeletal muscle, and adipose tissue obtained during surgical exploration showed spherules consistent with Coccidioides spp. infection. Antibody titers performed post-operatively were consistent with an active Coccidioides spp. Infection. By fungal culture and subsequent PCR and DNA sequencing, C. posadasii was identified as the species infecting the dog. Over the course of 85 days of antifungal therapy, discharge from the draining tract, lymphadenomegaly, and cutaneous and subcutaneous nodules resolved. In conclusion, this is the first reported case of disseminated coccidioidomycosis to the cervical region of a dog with involvement of the thyroid gland, skeletal muscle, adipose tissue, connective tissue, and secondary esophageal fistula. Coccidioides spp. infections should be considered a differential diagnosis in unusual cases for dogs that live in or have traveled to endemic areas.

Comparative Genomics of Aspergillus flavus S and L Morphotypes Yield Insights into Niche Adaptation.

Aspergillus flavus, the primary causal agent for aflatoxin contamination on crops, consists of isolates with two distinct morphologies: isolates of the S morphotype produce numerous small sclerotia and lower numbers of conidia while isolates of the L morphotype produce fewer large sclerotia and abundant conidia. The morphotypes also differ in aflatoxin production with S isolates consistently producing high concentrations of aflatoxin, whereas L isolates range from atoxigenic to highly toxigenic. The production of abundant sclerotia by the S morphotype suggests adaptation for long-term survival in the soil, whereas the production of abundant conidia by the L morphotype suggests adaptation for aerial dispersal to the phyllosphere. To identify genomic changes that support differential niche adaption, the sequences of three S and three L morphotype isolates were compared. Differences in genome structure and gene content were identified between the morphotypes. A >530 kb inversion between the morphotypes affect a secondary metabolite gene cluster and a cutinase gene. The morphotypes also differed in proteins predicted to be involved in carbon/nitrogen metabolism, iron acquisition, antimicrobial defense, and evasion of host immunity. The S morphotype genomes contained more intact secondary metabolite clusters indicating there is higher selection pressure to maintain secondary metabolism in the soil and that it is not limited to aflatoxin production. The L morphotype genomes were enriched in amino acid transporters, suggesting efficient nitrogen transport may be critical in the nutrient limited phyllosphere. These findings indicate the genomes of the two morphotypes differ beyond developmental genes and have diverged as they adapted to their respective niches.

Genome Sequence of Ophidiomyces ophiodiicola, an Emerging Fungal Pathogen of Snakes.

Ophidiomyces ophiodiicola, which belongs to the order Onygenales, is an emerging fungal pathogen of snakes in the United States. This study reports the 21.9-Mb genome sequence of an isolate of this reptilian pathogen obtained from a black racer snake in Pennsylvania.

Environmental Growth Conditions of Trichoderma spp. Affects Indole Acetic Acid Derivatives, Volatile Organic Compounds, and Plant Growth Promotion.

Trichoderma species are soil-borne filamentous fungi widely utilized for their many plant health benefits, such as conferring improved growth, disease resistance and abiotic stress tolerance to their hosts. Many Trichoderma species are able to produce the auxin phytohormone indole-3-acetic acid (IAA), and its production has been suggested to promote root growth. Here we show that the production of IAA is strain dependent and diverse external stimuli are associated with its production. In in vitro assays, Arabidopsis primary root length was negatively affected by the interaction with some Trichoderma strains. In soil experiments, a continuum effect on plant growth was shown and this was also strain dependent. In plate assays, some strains of Trichoderma spp. inhibited the expression of the auxin reporter gene DR5 in Arabidopsis primary roots but not secondary roots. When Trichoderma spp. and A. thaliana were physically separated, enhancement of both shoot and root biomass, increased root production and chlorophyll content were observed, which strongly suggested that volatile production by the fungus influenced the parameters analyzed. Trichoderma strains T. virens Gv29.8, T. atroviride IMI206040, T. sp. "atroviride B" LU132, and T. asperellum LU1370 were demonstrated to promote plant growth through volatile production. However, contrasting differences were observed with LU1370 which had a negative effect on plant growth in soil but a positive effect in plate assays. Altogether our results suggest that the mechanisms and molecules involved in plant growth promotion by Trichoderma spp. are multivariable and are affected by the environmental conditions.

OPHIDIOMYCES OPHIODIICOLA ON A CAPTIVE BLACK RACER (COLUBER CONSTRICTOR) AND A GARTER SNAKE (THAMNOPHIS SIRTALIS) IN PENNSYLVANIA.

Two snakes were presented to the Pennsylvania State University Animal Diagnostic Laboratory with one suffering from external lesions where the scales were raised and discolored, and the other with oral lesions and swelling extending to the left eye, which was opaque. Histopathological analysis revealed multifocal granulomas containing fungal hyphae. Morphological and DNA sequence analyses revealed both suffered from infection by Ophidiomyces ophiodiicola, an emerging pathogen of snakes. This is the first report of this disease in Pennsylvania.

Diversity and Aggressiveness of Rhizoctonia solani and Rhizoctonia-like Fungi on Vegetables in New York.

Vegetable growers in New York, especially those growing table beets, have recently observed that the corn rotation is no longer effective in suppressing diseases caused by Rhizoctonia solani and Rhizoctonia-like fungi. To investigate this problem, 68 isolates of Rhizoctonia solani and Rhizoctonia-like fungi infecting vegetables in New York were isolated, characterized, and their pathogenicity on corn determined. Sequence analysis of the rDNA internal transcribed spacer region inferred 26 isolates to belong to R. solani anastomosis group (AG) 2-2 and 19 isolates to belong to AG 4. Remaining isolates belonged to AG 1, AG 2-1, AG 5, AG 11, Ceratobasidium AG (CAG) 2, CAG 6, and Waitea circinata var. zeae. This is a first report of AG 11 and W. circinata var. zeae recovered from naturally infected vegetables in New York. Pathogenicity tests on corn showed that the majority of isolates are pathogenic on corn, and isolates belonging to AG 2-2, AG 5, and AG 11 exhibited high aggressiveness. These results suggest that certain strains of R. solani and Rhizoctonia-like fungi infecting vegetables in New York have acquired the ability to infect corn. In addition, snap bean was inoculated with seven isolates exhibiting low to high aggressiveness on corn, and a correlation between aggressiveness on corn and snap bean was observed.