First Report of a Pythiogeton sp. Causing Root and Basal Stalk Rot of Wild Rice in California.

In the summer of 2012, an outbreak of a newly discovered root and basal stalk rot of wild rice (Zizania palustris L.) cv. Franklin was observed in a 16-ha field in Big Valley, Lassen County, California (GPS coordinates 41°08'41.93″ N 121°10'07.49″ W). Infected plants exhibiting rot and dieback of roots and stalks were in various stages of decline, including death. Symptomatic stem and root tissues from affected plants were surface disinfected in 1% NaOCl for 90 s and placed on PARP agar plates, which were then incubated at 25°C in the dark for 1 week. Hyphal tips were used to start and maintain the organism in pure cultures. Isolates were transferred into petri plates with water and sterilized blades of turfgrass for the production of hyphae and reproductive structures. Isolates had coenocytic hyphae and produced zoospores 20 to 30 µm in diameter outside of sporangia (75 to 160 × 46 to 110 µm) from a naked mass of protoplasm, unlike from a vesicle, which is characteristic of Pythium spp. (2). Based on these morphological features, the isolate was tentatively identified as a Pythiogeton sp. Total genomic DNA was extracted from mycelia using the DNeasy Plant Mini Kit (Qiagen Inc., Valencia, CA). The internal transcribed spacers (ITS) 1 and 2 flanking the 5.8S rRNA regions were amplified by PCR and sequenced using universal ITS5 and ITS4 primers. A BLAST search of the 855-bp sequences revealed 98% similarity with a sequence of P. ramosum isolate Pg-164 (GenBank Accession No. JQ610190.1). The 21 nucleotide differences suggest that the isolate from wild rice may be an unreported species. The sequences were submitted to GenBank (KF719169). To fulfill Koch's postulates and confirm pathogenicity, 100 wild rice seeds were surface disinfected in 1% NaOCl for 90 s and placed in a 500 ml sterile pot with 250 g of autoclaved sand. Three 5 mm-diameter disks from the margin of a 7-day-old culture growing on PARP were placed in each of five pots. As a control, three 5 mm-diameter disks from a non-inoculated PARP plate were placed in five different pots, and five pots with autoclaved sand were not inoculated. All pots were kept in a randomized complete block design at 25°C for 14 days under a 14-h photoperiod. The pathogenicity test was repeated three times. After 14 days, the inoculated plants in all tests developed root and basal stalk rot, consistent with the symptoms observed on diseased wild rice in the field. The Pythiogeton sp. was consistently re-isolated on PARP from symptomatic plants but not from control plants. The non-inoculated wild rice plants remained asymptomatic. DNA sequences of the ITS region of the re-isolated Pythiogeton sp. revealed 100% identity with the isolate from the field. There have been reports of P. zeae on corn in Korea and P. zizaniae on water bamboo in Taiwan (1,2,3). This is the first report of a Pythiogeton sp. on wild rice. References: (1) P. J. Ann et al. Mycologia 98:116, 2006. (2) J. Huang et al. Mycoscience 54:130, 2013. (3) H. J. Jee et al. Mycologia 92:522, 2000.

First Report of Powdery Mildew Caused by Golovinomyces biocellatus on Peppermint in California.

In August of 2009, powdery mildew was observed on peppermint (Mentha piperita L.) in several commercial fields in the Fall River Valley of eastern Shasta County, California. Plant growth was apparently reduced by the disease, but its impact on yield was unknown. White fungal growth was restricted to the adaxial surfaces, where colonies were thin and effused. Heavily infected leaves developed a reddish tint as growth prematurely ceased. Doliform conidia ([26.6-] 29.2 [-31.7] × [13.2-] 15.6 [-16.8] µm) were produced in chains of approximately six conidia. Foot cells were cylindrical ([41.3-] 55.2 [-75.0] × [11.2-] 12.0 [-12.8] µm). Immature chasmothecia were yellowish brown and approximately 100.0 µm in diameter with flexuous, mycelium-like appendages up to 200 µm long. All these features were consistent with those of Golovinomyces biocellatus. Asci were not observed. To confirm the identity of the fungus, nuclear rDNA internal transcribed spacer (ITS) regions were amplified by PCR with universal primers ITS4 and ITS5. The sequence (537 bp) was an exact match for several submissions of G. biocellatus in GenBank (e.g., Accession No. EU035602, a sequence of the fungus from mint in Australia [1]). Pathogenicity was confirmed by brushing spores from naturally infected leaves onto three rooted cuttings of M. piperita 'Black Mitchum'. After the plants were covered with a plastic bag for 36 h to maintain high humidity, they were kept on a greenhouse bench at 23 to 28°C. Three noninoculated plants, which served as controls, were placed in another greenhouse in similar conditions. The experiment was repeated once. All inoculated plants developed signs of powdery mildew within 7 days of inoculation whereas noninoculated plants remained disease free. The fungus on inoculated leaves was morphologically indistinguishable from the one used to inoculate the plants. To our knowledge, this is the first report of G. biocellatus on peppermint in California. References: (1) J. R. Liberato and J. H. Cunnington. Australas, Plant Dis. Notes 2:38, 2007.

First Report of Damping-Off of Wild Rice in California Caused by Pythium torulosum.

During 1994, damping-off of wild rice (Zizania palustris L.) in a single field in eastern Shasta County, CA resulted in near total stand failure. Since then, the disease was observed in at least 11 other fields with varying levels of stand loss. In all cases, the affected wild rice was grown as a volunteer crop following one or more years of wild rice production. Symptoms included a dark red discoloration and necrosis of the primary root followed by seedling death. When the red discoloration was limited to secondary roots, the plants often survived. Pythium torulosum, readily recovered from symptomatic roots by isolation on PARP media, was identified by morphological structures produced on grass blades in water (homothallic with smooth-walled oogonia, plerotic oospores, monoclinous antheridia, and inflated filamentous sporangia) and a 99.2% internal transcribed spacer sequence similarity of the rDNA (1). To complete Koch's postulates, inoculum of two isolates of P. torulosum grown on moistened cornmeal/sand (2%/98% [v/v]) for 3 weeks at 25°C were combined and mixed into sterilized sandy loam soil at a rate of 30 cm3 inoculum per liter of soil. Sterilized noninfested soil was used as a control treatment. Twenty wild rice seeds (cv. Franklin) were sown in each of four replicate 20-cm-diameter pots in each treatment. Plants were submerged in water and maintained in a greenhouse at 18 to 25°C. After 8 weeks, plants stands were reduced 50% in infested pots; dry weights of infected plants were reduced by 45% relative to the controls. The fungus was reisolated from symptomatic plants but not from the plants grown in noninfested soil. The experiment was repeated with similar results. To our knowledge, this is the first report of damping-off of wild rice caused by P. torulosum. Reference: (1) C. A. Levesque and W. A. M. DeCock. Mycol. Res. 108:1363, 2004.

Integrated systems: from library to campus and beyond.

Integrated library systems have not yet been created, although they have been emphasized for nearly two decades. Now and in the future, the task is even more complex because the principal issue is access to information itself, wherever it is located and in whatever form it may exist. The goal becomes more feasible because of changes in library practices achieved with technological innovation. Although individual elements of a campus-wide information system may already exist, the details for implementation are yet to be articulated.