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First Detection of Puccinia ballotiflora on Salvia greggii

Salvia greggii, autumn sage, is grown for its bright red to white flowers that bloom in late summer and fall. In February of 2008, a rust sample was sent to the CDFA plant pathology diagnostics laboratory in Sacramento from a nursery in Santa Barbara County, CA. Pustules were abundant on older leaves causing moderate defoliation of containerized stock. Only the varieties with entirely red or pink flowers were affected. S. greggii ‘Hotlips,’ a popular white/red bicolor, was unaffected. Amphigenous uredinia were cinnamon brown, round, powdery, and sometimes surrounded by yellow halos. Pustules were found primarily on the leaves, although a few were on the stems. Urediniospores were broadly obovoid, subglobose to broadly ellipsoid, echinulate, and 22 to 27 × 24 to 32 μm (24.9 × 26.9 μm average) with one apical pore and 2 to 3 equatorial pores. Urediniospore walls were cinnamon brown in color and measured 1.0 to 2.0 μm (1.5 μm average). No telia were observed. After the initial detection, this rust was found in additional nursery sites in Santa Cruz, Santa Clara, Santa Barbara, and Ventura counties in 2008 and 2009. In November of 2011, a sample from a landscape planting in Santa Barbara County of a similar rust with telia and teliospores was submitted. Urediniospores and teliospores were present in the same lesions. Lesions with teliospores were located primarily on the stems. Mature teliospores were two-celled, verrucose, chocolate brown, and 25 to 31 × 32 to 40 μm (28.6 × 35.3 μm average) with a pedicel ranging from 8 to 12 × 38 to 104 μm, sometimes attached obliquely. The rust matched the morphological characteristics of Puccinia ballotiflora (Syn = P. ballotaeflora Long) (2). To confirm pathogenicity, three 20-cm-tall plants of S. greggii ‘Navajo Red’ in 3.8-liter pots were spray inoculated with 10 ml of a 2.5 × 10³ urediniospores per ml suspension and incubated in a dew chamber at 23°C for 2 days in the dark. Plants were transferred to a growth chamber maintained at 22°C with a 12-h photoperiod. Three plants were sprayed with sterile distilled water as controls. Uredinial pustules (1 to 2 mm) appeared on the abaxial surface of the leaves after 3 weeks. The pathogenicity test was repeated with similar results. The internal transcribed spacer region of rDNA and a portion of the 28S rDNA were amplified with primer pairs ITS5 (5′-GGAAGTAAAAGTCGTAACAAGG-3′), Rust1 (5′-GCTTACTGCCTTCCTCAATC-3′), and Rust2inv (5′-GATGAAGAACACAGTGAAA-3′), LR6 (5′-CGCAGTTCTGCTTACC-3′) as described by Aime (1) and sequenced using the amplification primers, Rust2 (5′-TTTCACTGTGTTCTTCATC-3′) and Rust3 (5′-GAATCTTTGAACGCACCTTG-3′). BLAST query of the assembled sequence, GenBank KF381491, was 91% identical to P. acroptili, JN204194, its closest match of similar length. P. ballotiflora has been found in Colombia on S. cataractarum, S. petiolaris, and S. mayori (3), and in Texas and Mexico on S. ballotiflora (4). To the best of our knowledge, this is the first detection of P. ballotiflora on S. greggii worldwide. P. ballotiflora is already widespread in the nursery trade in California and frequent fungicide applications are necessary to keep plants marketable.

References: (1) M. C. Aime. Mycoscience 47:112, 2006. (2) J. W. Baxter and G. B. Cummins. Lloydia 14:201, 1951. (3) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Botany and Mycology Laboratory, Online publication http://nt.ars-grin.gov/fungaldatabases ARS, USDA, 2014 (4) F. D. Kern et al. Mycologia 25:448, 1933.