Garibaldi A, Bertetti D, Pensa P, Poli A, Gullino M L
Center of Competence AGROINNOVA, University of Torino, Via Leonardo da Vinci, 44, 10095 Grugliasco, Italy.
Plant Dis. 2013 Aug;97(8):1119. doi: 10.1094/PDIS-02-13-0138-PDN.
Origanum vulgare L., common name oregano, family Labiatae, is grown for its aromatic and medicinal properties and as ornamental. In the fall of 2012, a blight was observed in a farm located near Albenga (northern Italy) on 6% of 30,000 50-day-old plants, grown in trays in a peat/perlite mix. Semicircular, water soaked lesions appeared on leaves and stems, starting from the basal ones. As the disease progressed, blighted leaves turned brown, withered, clung to the shoots, and matted on the surrounding foliage. Eventually, infected plants died. Leaf and stem fragments taken from the margin of the diseased tissues belonging to 10 plants were disinfected for 10 s in 1% NaOCl, rinsed with sterile water, and plated on potato dextrose agar (PDA). A fungus with the morphological characters of Rhizoctonia solani was consistently recovered. Three isolates of R. solani obtained from affected plants were successfully anastomosed with R. solani isolate AG 1 (ATCC 58946). Three pairings were made for each tester strain. The hyphal diameter at the point of anastomosis was reduced, the anastomosis point was obvious, and death of adjacent cells was observed. Results were consistent with other reports on anastomosis reactions (2). Isolates from oregano were paired with R. solani isolates AG 2, 3, 4, 6, 7, or 11 and examined microscopically. Anastomosis was not observed in any of the pairings. Tests were conducted twice. Mycelium of 10-day-old isolates from oregano appeared reddish brown, coarse, and radiate. Numerous dark brown sclerotia, 0.3 to 1.0 mm diameter (average 0.7) developed within 10 days after transfer of mycelia to PDA in 90 mm diameter petri dishes at 21 to 24°C. The descriptions of mycelium and sclerotia were typical for subgroup IB Type 1 (4). The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS1/ITS4 and sequenced. BLASTn analysis (1) of the 538 bp showed a 99% homology with the sequence of R. solani FJ746937, confirming the morphological identification of the species. The nucleotide sequence has been assigned the GenBank Accession KC493638. For pathogenicity tests, one of the isolates assigned to the anastomosis group AG-1-IB was tested by placing 9 mm diameter mycelial disks removed from PDA 10-day-old cultures of the fungus on leaves of 90-day-old oregano plants (n = 35). Thirty-five plants inoculated with non-inoculated PDA disks served as controls. Plants were covered with plastic bags and maintained in a growth chamber at 25 ± 1°C with 12 h light/dark. The first symptoms, similar to those observed in the farm, developed 3 days after inoculation. Nine days after the artificial inoculation, 50% of plants were dead. About 10 colonies of R. solani were reisolated from infected leaves of inoculated plants. Control plants remained healthy. The pathogenicity test was carried out twice with similar results. Symptoms caused by R. solani have been recently observed on O. vulgare in Greece (3). This is, to our knowledge, the first report of blight of O. vulgare caused by R. solani in Italy. References: (1) S. F. Altschul et al. Nucleic Acids Res., 25:3389, 1997. (2) D. E. Carling. Grouping in Rhizoctonia solani by hyphal anastomosis reactions. In: Rhizoctonia Species: Taxonomy, Molecular Biology, Ecology, Pathology and Disease control. Kluwer Academic Publishers, The Netherlands, pp. 37-47, 1996. (3) C. D. Holevas et al. Benaki Phytopathol. Inst., Kiphissia, Athens, 19:1-96, 2000. (4) R. T. Sherwood. Phytopathology 59:1924, 1969.
牛至（Origanum vulgare L.），俗名牛至草，属于唇形科，因其芳香特性、药用价值以及观赏性而被种植。2012年秋季，在阿尔本加（意大利北部）附近的一个农场里，人们发现一种疫病出现在30000株50日龄植株中的6%上，这些植株种植在泥炭/珍珠岩混合基质的育苗盘中。叶片和茎上出现半圆形、水渍状病斑，从基部开始。随着病情发展，染病叶片变为褐色、枯萎，附着在茎上，并与周围叶片交织在一起。最终，受感染植株死亡。从10株患病植株病组织边缘采集的叶和茎片段，在1%次氯酸钠中消毒10秒，用无菌水冲洗后，接种到马铃薯葡萄糖琼脂（PDA）培养基上。 consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. consistently recovered. 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