Barbara C. Hellier

First report of Onion yellow dwarf virus, Leek yellow stripe virus, and Garlic common latent virus in garlic in Washington State.

Washington State ranks fourth in the country in garlic (Allium sativum) production (2). The impact of viruses on garlic production may be significant in Washington State, but little is known about the occurrence or identity of specific viruses (2). The USDA-ARS Western Regional Plant Introduction Station (WRPIS) collects, maintains, and distributes garlic accessions. As part of the regeneration process, accessions are grown in field conditions at the WRPIS farm in Pullman, WA. In June 2004, several WRPIS accessions developed symptoms indicative of viral infection, primarily chlorotic spots and yellow stripes on leaves and scapes. Cultivars Georgia Fire and Georgia Crystal showed more than 90% incidence of symptomatic plants. Some chlorotic spots appeared similar to those caused by Iris yellow spot virus on other Allium spp. such as A. cepa. However, enzyme-linked immunosorbent assay (ELISA), as well as polymerase chain reaction (PCR) with IYSV-specific primers (1) did not reveal the presence of IYSV. Degenerate, group-specific primers to potyviruses (3) and carlaviruses (courtesy of S. D. Wyatt) were used on total nucleic acids extracted from each symptomatic plant with reverse transcription (RT)-PCR. The samples (n = 26) gave an RT-PCR product of the expected size with the group-specific potyvirus RT-PCR test. One sample was positive with the carlavirus group RT-PCR test. RT-PCR products from both tests were cloned and sequenced. Comparisons with sequences in GenBank showed that all but one had Onion yellow dwarf virus (OYDV), whereas one sample had a mixed infection of OYDV and Leek yellow stripe virus. Sequence analysis showed that the carlavirus was Garlic common latent virus. Sequence identities ranged from 95 to 99% for each of the viruses when compared with those available in GenBank. All samples were then tested for each of these viruses with commercially available antisera. Results of ELISA confirmed the findings of RT-PCR. To our knowledge, this is the first report for each of these garlic viruses from Washington State. This finding prompts the need for evaluating all garlic accessions for the potential impact of these viruses on garlic germ plasm conservation and distribution. References: (1) L. J. du Toit et al. Plant Dis. 88:222, 2004. (2) R. M. Hannan and E. J. Sorensen. Crop Profile for Garlic in Washington. Washington State University Coop Extension and the U.S. Department of Agriculture, 2002. (3) S. S. Pappu et al. J. Virol. Methods 41:9, 1993.

First Report of Onion Rust Caused by Puccinia allii on Allium pskemense and A. altaicum

In June 2003, uredinial and telial pustules were seen on leaves of accession W6-12755 Allium pskemense B. Fedtsch. originating from Uzbekistan and grown for germplasm increase in Pullman, WA. W6-18947 A. altaicum Pall., originating from Mongolia, displayed similar symptoms in the same garden in June 2000. A. altaicum is a wild onion exploited for food in its native range and is ancestral to A. fistulosum L., bunching onion (2). A. pskemense is a wild perennial sometimes propagated under cultivation (2). Both species have been exploited for research in breeding and systematics of Allium and used to a lesser degree in screening for pest or disease resistance. Clustered, golden orange, amphigenous uredinia were approximately 1 × 0.5 mm and surrounded by stromatic, subepidermal, blackish telia of variable size. Urediniospores (thick-walled, pale orange, echinulate, (25-) 27 to 32 (-34) × (19-) 21 to 25 μm, with as many as 10 scattered, indistinct pores), teliospores (two-celled, smooth, golden brown, 42 to 65 × 18 to 26 μm), and mesospores (27 to 42 × 15 to 21 μm, and approximately 30% as frequent as teliospores) all approximated the description for P. allii Rudolphi (4), but were more strongly congruent with the description of Puccinia blasdalei Diet. & Holw. (1), now considered a synonym (4). Specimens are deposited with WSP, Washington State University, Pullman. P. allii or its synonyms have been recorded from over 30 species of Allium (1,3,4), but to our knowledge, this is the first report of this rust on A. pskemense or A. altaicum. References: (1) J. C. Arthur. Manual of the Rusts in United States and Canada, Hafner Publishing, N.Y., 1962. (2) J. L. Brewster. Onions and Other Vegetable Alliums. CABI, Wallingford, Oxon, U.K, 1994. (3) D. F. Farr et al. Fungal Databases, Systematic Botany and Mycology Laboratory, On-line publication. ARS, USDA, 2003. (4) G. F. Laundon and J. M. Waterston. Puccinia allii. No. 52 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, U.K., 1965.

Characterization of wild Beta populations in and adjacent to sugar beet fields in the Imperial Valley, California

Populations of wild Beta L. species exist as weeds in commercial sugar beet (Beta vulgaris L. subspecies vulgaris) fields in the Imperial Valley, California. Significant losses to sugar yield and quality result if these wild plants are not removed. In cases of extreme infestation, fields are abandoned without harvest. No selective chemicals are available to differentiate conventional sugar beet from wild relatives and hand removal is labor intensive and expensive. Planting sugar beet varieties with tolerance to glyphosate is a potential solution for infested fields, but risk of gene flow to adjacent wild relatives must be determined. Previous research identified these populations as either Beta vulgaris L. subspecies maritima (L.) Arcang. or Beta macrocarpa Guss. This distinction is critical because B. v. subsp. maritima will readily cross hybridize with cultivated sugar beet while B. macrocarpa rarely will. In April 2011, we collected herbarium samples, mature seed, and leaf tissue from wild Beta populations in 25 infested sugar beet fields throughout the Imperial Valley. Bolting cultivated beets were identified at two locations. Taxonomy of whole plant herbarium samples was unclear due to wild beet stem elongation when under competition with sugar beet plants for canopy light. Morphology of plants from collected seed grown in non-competitive conditions assigned taxonomy of these populations to B. macrocarpa. We used molecular tools to determine the genetic structure of wild Beta populations throughout the Imperial Valley. Extracted DNA was genotyped with 22 simple sequence repeat molecular markers and evaluated for population structure. The bolting beet samples were clearly separated from the majority of B. macrocarpa samples, except for two. The remaining wild populations were further divided into two subgroups suggesting exchange of genetic information or a common ancestor.

Genetic relationships and structured diversity of Lactuca georgica germplasm from Armenia and the Russian Federation among other members of Lactuca L., subsection Lactuca L., assessed by TRAP markers

We studied the genetic relationships of Lactuca georgica samples originating in Armenia and the Russian Federation with samples representing four other predominantly self-pollinating wild Lactuca species (L. serriola, L. aculeata, L. saligna, and L. virosa) originating in various countries, as well as with samples representing cultivated lettuce, L. sativa by using 48 TRAP markers. We also visualized their genetic diversity and structure. The present study is likely the first molecular phylogenetic evaluation of a detailed screening of L. georgica germplasm. Data analysis of the three major wild species in this study, L. georgica (134 samples), L. virosa (57 samples), and L. serriola (40 samples) showed that allele frequencies of all 47 polymorphic loci varied significantly among the species. A total of 11, 9, and 10 alleles were unique to L. georgica, L. serriola, and L. virosa, respectively; 71% of TRAP marker diversity was between species. The Neighbor-Joining tree clearly clustered the whole set of 238 samples according to their taxonomic determination. It also reflects the gene diversity as well as the genetic distance values among samples representing the between and within variance of the various species. The L. georgica samples clustered most distantly from the L. sativa samples. The interspecies comparisons between samples belonging to L. georgica with those belonging to L. sativa displayed a high distance, lower only from the interspecies comparisons between samples belonging to L. virosa (in the tertiary gene pool of cultivated lettuce) with those belonging to L. sativa. Thus, additional molecular data with more hybridization experiments are necessary to reconsider if L. georgica is indeed a constituent of the primary gene pool of cultivated lettuce. The L. georgica samples were divided into two sub-clusters, with samples collected in southeast and central Armenia grouping together while all those collected in the north and Dagestan grouped together.

WILD/WEED BETA POPULATIONS IN THE IMPERIAL VALLEY, CALIFORNIA

In North America, wild populations of Beta vulgaris subsp. maritima, Beta macrocarpa, and respective hybrids with cultivated beet are found in California. These likely originated from contaminated seed imported from Europe (Biancardi et al., 2012). Section Beta includes the wild species B. macrocarpa, and B. v. ssp. maritima, and the cultivated sugar beet, Beta vulgaris subsp. vulgaris (Frese, 2010). Successful hybridization amongst species of section Beta varies. Sugar beet will readily crossfertilize with B. v. ssp. maritima, but there is conflicting evidence for successful hybridization between sugar beet and B. macrocarpa (de Bock, 1986; Bartsch and Ellstrand, 1999; Jung et al., 1993; Frese, 2010). The relationships among the three species of section Beta have been investigated with PCR-based marker and DNA sequencing techniques. Previous research suggests a close relationship between B. v. ssp. vulgaris and B. v. ssp. maritima with a more distant position of B. macrocarpa in the phylogenetic tree (Letschert, 1993; Shen et al., 1998; Villain, 2007). When commercial production areas are adjacent to wild beet populations, gene flow from cultivated beets has the potential to alter the genetic composition of the nearby wild populations (Bartsch and Ellstrand, 1999). Carsner reported populations of B. v. ssp. maritima, B. macrocarpa, and respective hybrids with cultivated beet in the Imperial Valley, California in 1938 and they continue to be identified in California. Plant and root characteristics of Imperial Valley wild beets were compared with collections of B. v. ssp. maritima and B. macrocarpa from European coastlines. The wild beets found in the Imperial Valley differ from typical B. v. ssp. maritima and other wild beets found in California and are most similar to B. macrocarpa (McFarlane, 1975). In 2011, plants were collected from wild Beta populations adjacent to commercial sugar beet fields and while many samples had clear morphological characteristics of B. macrocarpa, several showed B. v. ssp. maritima-like characteristics. This distinction is critical because B. v. ssp. maritima will readily cross hybridize with cultivated sugar beet while B. macrocarpa hybrids occur less frequently and often result in infertile progeny. Further research is needed to evaluate wild beets in the Imperial Valley to understand the origin of populations, determine the species, and explore whether or not gene flow occurs between these wild beets and cultivated beet. Herbarium samples, leaf tissue and seed of weed beet in and around commercial sugar beet fields were collected with the objectives of assigning taxonomy based on morphology and determining genetic variation by genotyping.