Wilt, Crown, and Root Rot of Common Rose Mallow (Hibiscus moscheutos) Caused by a Novel Fusarium sp.

A new crown and root rot disease of landscape plantings of the malvaceous ornamental common rose mallow (Hibiscus moscheutos) was first detected in Washington State in 2012. The main objectives of this study were to complete Koch's postulates, document the disease symptoms photographically, and identify the causal agent using multilocus molecular phylogenetics. Results of the pathogenicity experiments demonstrated that the Fusarium sp. could induce vascular wilt and root and crown rot symptoms on H. moscheutos 'Luna Rose'. Maximum-likelihood and maximum-parsimony phylogenetic analyses of portions of translation elongation factor 1-α and DNA-directed RNA polymerase II largest and second-largest subunit indicated that the Hibiscus pathogen represents a novel, undescribed Fusarium sp. nested within the Fusarium buharicum species complex.

First Report of Onion Rust Caused by Puccinia allii on Allium pskemense and A. altaicum.

In June 2003, uredinial and telial pustules were seen on leaves of accession W6-12755 Allium pskemense B. Fedtsch. originating from Uzbekistan and grown for germplasm increase in Pullman, WA. W6-18947 A. altaicum Pall., originating from Mongolia, displayed similar symptoms in the same garden in June 2000. A. altaicum is a wild onion exploited for food in its native range and is ancestral to A. fistulosum L., bunching onion (2). A. pskemense is a wild perennial sometimes propagated under cultivation (2). Both species have been exploited for research in breeding and systematics of Allium and used to a lesser degree in screening for pest or disease resistance. Clustered, golden orange, amphigenous uredinia were approximately 1 × 0.5 mm and surrounded by stromatic, subepidermal, blackish telia of variable size. Urediniospores (thick-walled, pale orange, echinulate, (25-) 27 to 32 (-34) × (19-) 21 to 25 µm, with as many as 10 scattered, indistinct pores), teliospores (two-celled, smooth, golden brown, 42 to 65 × 18 to 26 µm), and mesospores (27 to 42 × 15 to 21 µm, and approximately 30% as frequent as teliospores) all approximated the description for P. allii Rudolphi (4), but were more strongly congruent with the description of Puccinia blasdalei Diet. & Holw. (1), now considered a synonym (4). Specimens are deposited with WSP, Washington State University, Pullman. P. allii or its synonyms have been recorded from over 30 species of Allium (1,3,4), but to our knowledge, this is the first report of this rust on A. pskemense or A. altaicum. References: (1) J. C. Arthur. Manual of the Rusts in United States and Canada, Hafner Publishing, N.Y., 1962. (2) J. L. Brewster. Onions and Other Vegetable Alliums. CABI, Wallingford, Oxon, U.K, 1994. (3) D. F. Farr et al. Fungal Databases, Systematic Botany and Mycology Laboratory, On-line publication. ARS, USDA, 2003. (4) G. F. Laundon and J. M. Waterston. Puccinia allii. No. 52 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, U.K., 1965.

First Report of Pink Seed of Pea Caused by Erwinia rhapontici in the United States.

In March 2001, the USDA Federal Grain Inspection Service sent for analysis to USDA-ARS, Pullman, WA, 12 discolored seeds of field pea (Pisum sativum L.) from northeastern Montana. Symptoms consisted of pale pinkish brown-to-bright pink discoloration throughout the seed coat. Unlike the pink coloration resulting from application of pink pesticidal seed treatments, the coloration was permanent and could not be removed by extended washing. Ten discolored seeds were disinfested in 0.5% NaOCl for 1 to 2 min and rinsed in sterile distilled water. Five seeds were placed on malt extract agar amended with streptomycin sulfate and tetracycline hydrochloride at 50 mg per liter each, and five seeds were placed on nutrient broth yeast extract agar (NBY) (3) and incubated under ambient lab conditions. No organisms were isolated from peas on the antibiotic agar, but pale pink bacterial colonies were recovered from each of the five peas on NBY. The pink colonies were streaked for selection of single colonies, stored at 4°C, and revived for growth in shaken (120 rpm) NBY broth to optical density (OD) = 0.1 at 640 nm (≈108 CFU/ml). Three pea plants and one control plant were grown in the greenhouse until pods were sufficiently developed to be syringe-inoculated at the suture with 100 µl of bacterial culture. The experiment was repeated using a second bacterial isolate. In each experiment, pods on inoculated plants, but not the control plant, exhibited pale pinkish areas and later produced seeds discolored in shades of pink matching those from the original sample. Some symptomatic seeds were shriveled or aborted as well as discolored. Discolored seeds from the two experiments were plated to NBY and pale pinkish colonies were recovered as before, but no such colonies were recovered from the controls. Two isolates from the original sample and two recovered from the experimental inoculations were tested for anaerobic and aerobic growth using API 50 CHE and API 20 NE tests (bio Mérieux Vitek, Inc., Hazlewood, MO). Known strains of Erwinia rhapontici and E. rubrifaciens from the collection of Dennis Gross (Texas A&M University) were identically analyzed for comparison. All four isolates from pea were gram-negative, facultatively anaerobic, motile rod-shaped bacteria that produced a diffusible pink pigment on NBY. Tests indicated that these strains were E. rhapontici, because the results agreed with previously published data (1,2). Results with the known strain of E. rhapontici were congruent with those from the pea strains. The strain of E. rubrifaciens also produced a pink pigment on NBY, but unlike the other strains, it grew well at 37°C and was negative for acetoin production, nitrate reduction, esculin hydrolysis, and maltose, rhamnose, inositol, and melibiose fermentation and did not assimilate citrate aerobically. Pink seed of pea has been previously reported from Alberta, Canada (2). References: (1) J. G. Holt et al. Bergey's Manual of Determinative Bacteriology, Williams & Wilkins, Baltimore, MD, 1994. (2) H. C. Huang et al. Can. J. Plant Pathol. 12:445, 1990. (3) A. K. Vidaver. Appl. Microbiol. 15:1523, 1967.

Filamentous fungi quiescent in seeds and culm nodes of weedy and forage grass species endemic to the Palouse Region of Washington and Idaho.

Asymptomatic seeds of forage and weedy grasses from germplasm accessions and from uncultivated sites in eastern Washington and western Idaho were assayed for the presence of quiescent filamentous fungi. Asymptomatic culm nodes of the same species were similarly assayed. The predominant taxa isolated were strains of dematiaceous hyphomycetes, principally strains of Alternaria and Cladosporium. A. infectoria was the species most frequently isolated from seed. A. tenuissima was common and A. alternata was rare. Aspergillus, Penicillium and Fusarium were very rare or absent in stored germplasm. Pathogenic coelomycetes were common in asymptomatic node samples, occasionally present in asymptomatic field seed, but were not detected in germplasm accessions. Previous reports of frequent occurrence of A. alternata in grass seed are probably the results of misidentification of various small-spored Alternarias, especially A. infectoria, as A. alternata.