First Report of Ergot (Claviceps purpurea) on Drunken Horse Grass (Achnatherum inebrians) in China.

Drunken horse grass (Achnatherum inebrians) belongs to the family Poaceae: it is mainly distributed in the natural grasslands of northern and northwestern in China. Ergot is a disease that can not only affect the growth of the grass, but also cause livestock poisoning (Coufal-Majewski et al. 2016). In September 2018, ergot was observed in a large area (about 15 ha) in Xinghai county, Qinghai province, China (35° 47' N, 99° 53' E, Altitude 3559 m). Around 65% of the plants of Achnatherum inebrians were affected. Symptoms initially showed drop-like honeydew on the ears of drunken horse grass, and later brown to dark brown sclerotia were observed. These were straight to slightly curved, measured 6.7 to 13.5 × 1.5 to 2.1 mm, which was approximately 1 to 4 times the size of healthy seeds. Sixteen spikes with typical symptoms were collected from eight different fields. Sclerotia were disinfested by immersion in 75% ethanol for 30 s and 1% NaClO for 90 s, rinsed three times in sterilized water, plated on potato dextrose agar (PDA) medium, incubated at 24°C in the dark and isolates purified by culturing from single spores. Finally, 16 single-spore cultures with similar phenotypes were obtained from these sclerotia. Colonies produced on PDA for 15 days at 24 ℃ were grayish white with fluffy aerial mycelium, about 60 mm in diameter. Conidia were hyaline, ovoid to cylindrical, 5.42 to 7.69 × 2.85 to 3.75 μm (avg. 5.67 × 3.2; n = 50). These morphological characteristics were consistent with the descriptions of Claviceps species in general (PíchovÁ et al. 2018). To further identify the Claviceps spp., isolate NSZJ (=MHLZU-AI20201012) was selected as a representative for molecular characterization. Two nuclear protein-coding genes TUB2 and MCM7 were amplified by T2/T12 (O'Donnell and Cigelnik 1997) and CARCA-F/M456-5R (Rehner and Buckley 2005), respectively, and sequenced. Sequences were deposited in GenBank (accession nos. MW115640 for TUB2 and MW115641 for MCM7). A BLAST analysis of these two segments showed >99% identity with those sequences of isolate W3 of C. purpurea (Pazoutová et al. 2014). To confirm the pathogenicity on drunken horse grass, 20 healthy plants (2-year-old) grown in an experimental field at the College of Pasture Agriculture Science and Technology, Yuzhong Campus of Lanzhou University in China (104° 39' E, 35° 89' N, altitude1653m) were spray-inoculated with conidial suspension (1 × 106 conidia/ml) during the flowering period. Another 20 plants in the field were sprayed with sterilized distilled water as controls. All plants were individually covered with transparent polyethylene bags for 24 h to maintain high relative humidity. After 7 to 10 days, small yellowish-white drops of honeydew were observed in some florets. At 22 days post inoculation, all the inoculated panicles developed three to six sclerotia per head, ranging in size from 6.7 to 13.5 mm, while control plants remained healthy. The same pathogen was consistently re-isolated from inoculated spikes and confirmed by morphological and molecular characterization as described above. Claviceps purpurea was reported to be associated with ergot in A. lemmonii in Idaho and A. robustum in Montana (Alderman et al. 2004). To our knowledge, this is the first report of C. purpurea causing ergot in A. inebrians in China.

Citation

Haijuan Zhang, Taixiang Chen, Yali He, Chunjie Li. First Report of Ergot (Claviceps purpurea) on Drunken Horse Grass (Achnatherum inebrians) in China. Plant disease. 2021 Jan 28

PMID: 33507095

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