To learn about the phenological adaptation of Lactuca georgica Grossh., a wild relative of domesticated lettuce, we studied seed sampled accessions obtained from individual plants at 19 locations throughout six regions in Armenia, and from two natural populations in Dagestan (Russian Federation) collected as bulk samples.The effects of various vernalization treatments on time to bolting, flowering and seed production time were investigated during four successive years at different growth stages of L. georgica plants.We demonstrate that low temperatures play a major role in stimulating the reproduction process of L. georgica plants.Our results would suggest that for L. georgica:1) There is an obligatory (or nearly so) vernalization requirement; 2) Plant age, vernalization duration, and genotype of original sample have a role in bolting and flowering regulation; 3) Some plants behaved as typical annuals, responding to vernalization treatment at the seedling stage, but, most did not; 4) Four months of vernalization could be adequate to reach bolting in plants with a developed vegetative rosette, for most-but not all-samples; 5) In order to find the best solution for stimulating the reproductive process of multiple genotypes, it seems that further study should focus on about 4 -6 months of vernalization at 4˚C applied to plants of about 10 -22 months old vegetative rosettes, with controlled post-vernalization condition; 6) L. georgica germplasm could be used as a source for delayed bolting in breeding of domesticated lettuce varieties.

为了解引进大蒜资源遗传多样性和引进后的适应性,对国家无性繁殖及多年生蔬菜种质资源圃从34个国家引进的228份大蒜(,Allium sativumL.)资源进行了表型性状评价.结果 表明:13个数量性状的变异系数分布在18.94％～56.36％之间,质量性状中除叶形仅一种表现型,其他质量性状表型丰富;25个性状的多样性指数分布在0～2.03之间,遗传多样性指数高,类型丰富.通过聚类分析,将引进的大蒜资源分为3个类群,类群Ⅰ地上部分植株矮小、细弱,叶片短而细,鳞茎表现较差,为丰产性较差的类群;类群Ⅱ鳞茎横茎小,鳞芽数少,鳞茎形状为高圆型;类群Ⅲ植株高大开展,叶片长且宽,鳞茎重且鳞茎横茎大.主成分分析中,选取累积贡献率为69.94％的3个因子来评价该批资源.大蒜鳞茎部分性状的相关分析表明,鳞茎横径、鳞茎高、鳞芽高、鳞芽背宽均与单头鳞茎重存在极显著的正相关关系,在选育高产大蒜品种时,这些性状将作为主要的目标性状;引种前后的鳞茎相关性状对比分析表明,不同种质在引种后的适应性表现差异较大,部分资源种植后鳞茎高和鳞茎横茎较引种时明显增大,表现出了较好的适应性.相关结果将为大蒜种质资源的利用及品种选育等提供重要参考.

Rhizomania, caused by Beet necrotic yellow vein virus (BNYVV) and transmitted by Polymyxa betae , is considered the most important disease of sugar beet and has spread to almost all production areas of the world. The most efficient way to control this soil-borne disease is through the cultivation of rhizomania-resistant varieties, which has proven successful since the 1980s. In the 2002–2003 season, sugar beet fields in the Imperial Valley, California, planted with a resistant commercial variety were observed with severe rhizomania symptoms suggesting resistance conferred by the most widely deployed gene, Rz1 , was compromised. BNYVV isolates were identified to which all resistant check varieties became infected and tested positive for the virus (RB-BNYVV, Rz1 -resistance breaking strain of Beet necrotic yellow vein virus ). For continuing development of BNYVV and RB-BNYVV resistant germplasm, a highly important reservoir of resistance factors is the Beta vulgaris subsp. maritima (BVM) accession collection. We evaluated 404 BVM accessions under BNYVV and RB-BNYVV field and greenhouse conditions to identify and select rhizomania resistant accessions useful for sugar beet germplasm improvement. Accessions from Denmark, Ireland, and Portugal showed the highest level of rhizomania resistance as characterized by foliar yellowing due to rhizomania, rhizomania disease index, and percent resistant beets. The low bolting tendency of Denmark and Ireland accessions suggest these for pre-breeding donor material.

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.

Infection of bulbs of garlic (Allium sativum) by Fusarium proliferatum is increasingly documented worldwide and management of the pathogen is problematic. Garlic bulbs were harvested at the USDA-ARS Plant Introduction farm near Pullman, WA in fall 2015. From a sample of 18 bulbil-producing accessions whose bulbs were documented as infected by F. proliferatum, a mean of 64% of cloves from infected bulbs contained the pathogen. In umbels produced from infected bulbs, a mean of 11% were detected with the pathogen, with a mean infection rate of bulbils in infected umbels of 42%, resulting in a probability of bulbil infection of less than 5%. In bulbs harvested in fall 2016 from 15 accessions whose bulbs were previously documented as infected, a mean of 34% of cloves in infected bulbs contained the pathogen, but the pathogen was not detected in umbels or bulbils. Overall incidence of F. proliferatum in bulbs surveyed for infection in 2016 (99 accessions) at the same farm was assessed via a cumulative geometric distribution, and indicated occurrence in 87% of accessions, with probability of infection in a given bulb between 25 and 50%. In 2016, all but 0.01% of whole bulbs harvested for this survey of overall incidence were asymptomatic at harvest on the basis of firmness, but 77% of cloves were symptomatic (inclusive of all biological and abiotic causes) when peeled and plated to agar media 9–16 months after harvest. Bulbils take at least a year longer to mature into full size bulbs than do seed cloves, presenting a longer window for infection by several pathogens, but if planted to pathogen-free soil might represent a cost-effective means to strongly reduce infection of propagation material by F. proliferatum.

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.

Low temperatures can slow down emergence, decrease weed competitiveness, and lead to uneven crop maturity in direct-seeded crops such as baby leaf lettuce ( Lactuca sativa L.). In this study, seeds of 103 single-parent lineage, homozygous lettuce accessions (53 cos and 50 leaf type) from the USDA National Plant Germplasm System (NPGS) and six commercial standard lettuce cultivars (three cos and three leaf type) were evaluated in replications for percent germination after 7 and 10 days at 5 °C in a germination chamber. Cos and leaf types were selected for this study as they are most commonly used for baby leaf lettuce production. Differences were observed among entries in percent seeds germinated after both 7 and 10 days. Overall, an average of 68% of seeds germinated after 7 days and 94% germinated after 10 days. Although several NPGS accessions had higher percent germination than the commercial cultivars, the average percent germination was not statistically different between the two seed sources at 7 or 10 days. Percent germination also did not differ between entries of cos and leaf type after 7 or 10 days. Similarly, no difference in percent germination between entries of dark and white seed color was observed after 7 or 10 days. No relationship between 100 seed weight and percent germination was observed after 7 days ( r 2 = 0.07) or 10 days ( r 2 = 0.13). Thus, lettuce seed type, color, and 100 seed weight do not appear to be good predictors of germination under cold conditions in lettuce. The accessions with the highest percent germination after 7 days at 5 °C have the potential to be used for the development of new lettuce cultivars suitable for an extended, early season production in temperate climates when soil temperature is lower than optimal for lettuce germination. Further studies are needed to assess the ability of these accessions to germinate rapidly under cold field soil conditions.

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.

There is evidence from literature, state department of agriculture documents, and recent diagnoses that Sclerotium cepivorum, causal agent of white rot of garlic and onion, is spreading and/or becoming more established in the Pacific Northwest. Previously documented distributions are summarized and the fungus is reported for the first time from Latah Co., ID; Pend Oreille Co., WA; and Lake, Sanders, and Missoula counties, MT. Although known from a tightly quarantined prior occurrence in the Idaho portion of Treasure Valley (southwest Idaho), the pathogen has not been formally reported from that state nor from the state of Montana. Latah Co. has commercial production of seed garlic and borders adjacent Whitman Co., WA, where the National Plant Germplasm System (NPGS) maintains North America's largest non-commercial collection of garlic and wild/ornamental onion. Strict phytosanitary protocols have been implemented on the NPGS farm. Various areas within the Pacific Northwest have long been important for commercial Allium production, and a list of state departments of agriculture regulations addressing white rot is presented for Idaho, Oregon, and Washington. Accepted for publication 18 February 2013. Published 19 June 2013.

The choice of germplasm is critical for sustainable restoration, yet seed transfer guidelines are lacking for all but a few herbaceous species. Seed transfer zones based on genetic variability and climate were developed using tapertip onion (Allium acuminatum Hook.) collected in the Great Basin and surrounding areas in the United States. Bulbs from 53 locations were established at two common garden sites and morphological (such as leaf and scape dimensions), phenological (such as bolting date and flowering), and production traits (such as emergence and seeds per plant) were measured. Differences among source locations for plant traits within both common gardens were strong (P < 0.001), indicating genetic variation. Principal component 1 (PC 1) for phenological traits, with R 2 = 0.59, and PC 1 for production traits, with R 2 = 0.65, were consistently correlated with annual, maximum, minimum, and average temperature, annual precipitation, and frost-free days at source locations (P < 0.05). Regression of PC 1 phenology and PC 1 production scores with source location climates resulted in models with R 2 values of 0.73 and 0.52, respectively. Using a geographic information system, maps of these models were overlaid to develop proposed seed zones to guide the choice of germplasm for conservation and restoration of tapertip onion across the collection region.

Genetic diversity, population structure, and genome-wide marker-trait association analyses were conducted on a special collection of 298 homozygous lettuce (Lactuca sativa L.) lines. Each of these lines was derived from a single plant that had been genotyped with 384 SNP markers using LSGermOPA. They included 122 butterhead, 53 romaine, 63 crisphead, 53 leaf and 7 stem types. Genetic diversity among these plants was assessed by pairwise comparison based on 322 high-quality SNP markers selected from 384 SNPs. Only 258 unique genotypes were identified among the 298 lines because 26 pairs or small groups (a total of 66 lines) shared identical genotypes. The average genetic similarity coefficient (GS) among these unique genotypes was 63.9% with a range of 40.6% to 99.8%. A phylogenetic tree was constructed based on the genotypic data. The most likely number of populations was estimated to be two or six. Association analysis between the 322 SNP markers and 10 phenotypic traits using the 258 homozygous lines was performed by three different methods: single factor analysis, general linear model analysis, and mixed linear model analysis. Nine significant marker-trait associations (SMTAs) were detected at P<0.0001 with all three methods and also when considering kinship and/or population structure for this collection, with five SMTAs for seed coat color, one for leaf undulation, two for leaf anthocyanin, and one for stem anthocyanin. These markers will be useful in marker-assisted selection after further validation with segregating populations.

Multiple Allium accessions (garlic, and wild and ornamental Allium species) were screened for resistance using Penicillium allii and A. sativum (positive control). Single accessions of A. aflatunense, A. atroviolaceum, A. stipitatum, and Allium sp. remained asymptomatic. Single accessions of A. roseum and A. senescens, two accessions each of A. acuminatum and A. ampeloprasum and a single accession of A. moly displayed lesion expansion rates not exceeding 22%, 26%, 46%, 50%, 61%, 67% and 67%, respectively, of positive controls. Single accessions of A. sativum var. ophioscordon and A. scorodoprasum displayed rates not exceeding 68% and 55%, respectively, of positive controls with deep wounding, but did not consistently differ with shallow wounding. Accessions of A. canadense, A. sativum or A. longicuspis did not differ, differed inconsistently, or differed insubstantially from positive controls. Lesion expansion rates for A. acuminatum, A. ponticum and A. scorodoprasum were significantly less than in positive controls, but their small bulbs often rotted completely. Results document publicly available germplasm possessing significant resistance to P. allii.