In 2004, bacterial galls were found on the roots of carrots in Shizuoka Prefecture, Japan. Galls were about 0.1-2 cm in diameter, light brown in color and had rough surfaces. In 2005, similar galls were found on the roots of three weeds: henbit (Lamium amplexicaule L.), Persian speedwell (Veronica persica Poir.) and leaf mustard (Brassica juncea L.). A bacterium that forms white, rough colonies was isolated from the carrot and weeds galls. The bacterial isolates had properties identical with Rhizobacter dauci Goto and Kuwata. Phylogenetic analysis based on 16S rDNA sequences showed that the carrot isolate had the highest homology (similarity of 100%) with that of the type strain of R. dauci. Rep-PCR genomic fingerprinting using BOX A1R primer showed that the carrot and weeds isolates were nearly identical. Pathogenicity of the isolates was confirmed by inoculating the roots of carrots and the weeds. After 2-5 weeks, they formed galls on the roots of the original host species and on other plant species tested. The galls were indistinguishable from those formed naturally, and the inoculated bacterium was reisolated. Thus, the causal bacterium of carrot and weeds gall was identified as R. dauci, and the bacterium was found to have a wider host range than previously known. These weed hosts may serve as inoculum sources for carrot bacterial gall disease.

(2012). Isolation and plant host range of Rhizobacter dauci, causal agent of carrot bacterial gall. Jpn. J. Phytopathol.78: 293-300.Bacterial galls were found on roots of tomato (Solanum lycopersicum), cabbage (Brassica oleracea), shepherd's purse (Capsella bursapastoris var. pinnata), bog yellowcress (Rorippa palustris), purple deadnettle (Lamium purpureum) and corn speedwell (Veronica arvensis) in Shizuoka Prefecture from December 2007 to July 2008. Galls had formed on the main or secondary roots, and bacterial aggregates were often observed on the surface of the galls. Bacterial isolates from the plant galls formed white, rough colonies and had properties identical to those of Rhizobacter dauci. Phylogenetic analysis based on 16S rDNA sequence showed that the isolates had the highest homology (similarity of 100%) with that of the type strain of R. dauci. Pathogenicity of the isolates was confirmed by inoculating the roots of carrots and the original host species. After 4 weeks, galls had formed on the roots of the plants, and the bacterium was reisolated. This report is the first of bacterial galls caused by R. dauci on tomato, cabbage, shepherd's purse, bog yellowcress, purple deadnettle and corn speedwell. To investigate the host range of R. dauci, 20 vegetable crop species of seven families were planted in a field infested with the bacterium. After 1.5 months, galls had formed on the roots of nine vegetables representing four families, and a bacterium that forms white, rough colonies was isolated from the infested plants. Pathogenicity of the isolates was confirmed by inoculating the roots of carrots; galls formed on the roots, and the bacterium was reisolated. After direct inoculation of 77 plant species from 24 families with the carrot isolate R. dauci O1, galls formed on the roots, stems or tubers of 46 plant species of 20 families, and the inoculated bacterium was reisolated. These results suggested that R. dauci has an extremely wide host range. It may commonly inhabit the roots of various plants in the field.

A new leaf rot disease was found on the leaves of figmarigold (Lampranthus spectabile). The causal organism, identified as Pythium aphanidermatum was found to cause the same symptoms after artificial inoculation and was then reisolated from the inoculated plants. We propose to name the disease Pythium rot of figmarigold. Keywords Figmarigold Á Pythium aphanidermatumFigmarigold (Lampranthus spectabile) is a popular ornamental plant with thick, fleshy leaves and brilliant flowers. Frequently, it is planted as a groundcover at the edge of gardens, crop fields and roads. In June 2004, a leaf rot disease was observed on figmarigold grown as an edging plant at the border of vegetable fields in Izunokuni City, Shizuoka Prefecture. The disease occurred mostly during the rainy season at high temperature and humidity. The disease was characterized by the conspicuous water-soaked appearance of the infected leaves, and soft rot and rapid collapse of the fleshy tissues followed (Fig. 1a-c). These leaves finally dried out to look like thin whitish, paper. Aerial mycelia were sometimes visible on the surface of lesions (Fig. 1c). With a light microscope, aseptate hyphae in the water-soaked lesions and oospores in old lesions were observed (Fig. 1d).Leaf lesions were cut into about 5 mm long pieces, surface-sterilized with 70% ethanol and 1% sodium hypochlorite solution, washed three times in sterilized water, air-dried on sterilized filter paper, and placed on 1.5% water agar (WA) plate. Hyphae grew on the plate, forming white colonies with loose, aerial mycelia. A pure culture was obtained by single-hypha isolation and maintained on potato-dextrose agar (PDA) slant.For morphological characterization of the organism, isolate Mp-1 was used to inoculate a leaf piece of figmarigold that had been autoclaved at 121°C for 15 min and placed on WA. The plate was incubated at 25°C. After 2 days, aseptate mycelia grew on WA, and sporangia consisting of swollen hyphae formed. Vesicles were formed from the sporangia, which produced zoospores 3 days after inoculation. A large number of oogonia and antheridia also formed. The presence of sterilized leaf tissue on WA was requisite to induce this morphology in isolate Mp-1.The main hyphae were 6.4-10.0 lm (ave. 7.7 lm) wide. Sporangia consisted of complexes of swollen hyphal branches. Encysted zoospores were 9.6-14.0 lm (ave. 11.3 lm) in diameter. Oogonia were terminal, globose, smooth and 22.5-29.7 lm (ave. 26.1 lm) in diameter. Antheridia were mostly intercalary or terminal, one per oogonium, monoclinous or declinous, sac-shaped, 9.5-17.8 lm (ave. 13.0 lm) long and 9.5-14.2 lm (ave. 11.2 lm) in diameter. Oospores were globose, aplerotic, one per oogonium, and 17.8-23.7 lm (ave. 20.8 lm) in diameter. The thickness of oospore wall ranged from 1.3-2.0 lm (ave. 1.7 lm) wide. Cardinal temperatures for hyphal growth on PDA were 10°C minimum, 35°C optimum and 40°C maximum, respectively. The daily growth rate at 25°C was 31.9 mm.The morphological measurements and growth response to temperature of is...