Phenotypic Variation in Fitness Traits of a Managed Solitary Bee, Osmia ribifloris (Hymenoptera: Megachilidae).

We investigated fitness in natural populations of a managed solitary bee Osmia ribifloris Cockerell (Hymenoptera: Megachilidae) from sites separated from 400 to 2,700 km. Parental wild bees originated in central Texas (TX), central-northern Utah (UT), and central California (CA). They were then intercrossed and raised inside a mesh enclosure in southern Mississippi (MS). Females from all possible mated pairs of O. ribifloris produced F1 broods with 30-40% female cocoons and outcrossed progeny were 30% heavier. Mitochondrial (COI) genomes of the four populations revealed three distinct clades, a TX-CA clade, a UT clade, and an MS clade, the latter (MS) representing captive progeny of CA and UT bees. Although classified as separate subspecies, TX and CA populations from 30° N to 38° N latitude shared 98% similarity in COI genomes and the greatest brood biomass per nest straw (600- to 700-mg brood). Thus, TX and CA bees show greater adaptation for southern U.S. sites. In contrast, UT-sourced bees were more distantly related to TX and CA bees and also produced ∼50% fewer brood. These results, taken together, confirm that adult O. ribifloris from all trap-nest sites are genetically compatible, but some phenotypic variation exists that could affect this species performance as a commercial blueberry pollinator. Males, their sperm, or perhaps a substance in their sperm helped stabilize our captive bee population by promoting legitimate nesting over nest usurpation. Otherwise, without insemination, 50% fewer females nested (they nested 14 d late) and 20% usurped nests, killing 33-67% of brood in affected nests.

First Report of Aerial Blight of Ruth's Golden Aster (Pityopsis ruthii) Caused by Rhizoctonia solani in the United States.

Ruth's golden aster (Pityopsis ruthii (Small) Small: Asteraceae) is an endangered, herbaceous perennial that occurs only at a few sites along the Hiwassee and Ocoee rivers in Polk County, Tennessee. This species is drought, heat, and submergence tolerant and has ornamental potential as a fall flowering landscape plant. In 2012, we vegetatively propagated various genotypes and established plantings in a landscape at Poplarville, Mississippi. In June and July of 2013, during periods of hot and humid weather, several well-established plants exhibited black or brown necrotic aerial blight symptoms including desiccation of stems and leaves. Blighted leaf samples were surface sterilized (10% commercial bleach, active ingredient 8.25% sodium hypochlorite, 1 min), rinsed in sterile water, air-dried, and plated on 2% water agar amended with 3.45 mg fenpropathrin/liter (Danitol 2.4 EC, Valent Chemical, Walnut Creek, CA) and 10 mg/liter rifampicin (Sigma-Aldrich, St. Louis, MO). Rhizoctonia sp. was identified based on hyphal morphology and cultures were maintained on potato dextrose agar. Colonies were fast growing, consisting of light tan to brown mycelia and tufts of crystalline aerial hyphae. Within 10 days, brown exudates were present in cultures and there was no pigmented reverse to the agar. Hyphae were a mean of 5.2 µm wide (4.6 to 6.1 µm; n = 10) and each compartment contained three or more nuclei. Hyphae were constricted at septa with right angle branching and no clamp connections, which is typical for Rhizoctonia solani (1). Light- to medium-brown, oblong to irregularly shaped sclerotia measuring 1.2 mm long (0.7 to 2.1 mm) × 0.9 mm wide (0.5 to 1.2 mm; n = 20) were formed in cultures after 3 weeks of growth. Total genomic DNA was extracted from two different colonies grown in potato dextrose broth for 7 days, amplified with PCR using ITS1 and ITS4 primers for amplification of the 18S rDNA subunit (2), the products purified, and sequenced. A consensus sequence of 657 bp was deposited in GenBank (Accession Nos. KF843729 and KF843730) and was 96% identical to two R. solani Kühn ITS sequences in GenBank (HF678125 and HF678122). R. solani was grown on twice autoclaved oats for 2 weeks at 21°C and incorporated into Pro-Mix BX, low fertility soilless medium (Premier Horticulture, Rivière-du-Loup, Quebec, Canada) at 4% (w/w) to inoculate seven P. ruthii plants grown in 10 cm-diameter pots; seven additional plants were grown in the same medium amended with 4% (w/w) sterile oats. Plants were grown in a greenhouse and covered with a plastic dome to maintain high humidity. After 2 weeks, six of the seven inoculated plants exhibited the same aerial blight symptoms as did the original infected plants from the field; none of the control plants developed disease symptoms. Colony morphology and hyphal characteristics as well as the sequence for the ITS region of rDNA from the re-isolated fungus were identical to the original isolate. To our knowledge, this is the first report of R. solani infecting Ruth's golden aster. We are not aware of the disease occurring in wild populations of the plant, but may impact plants grown in the landscape or greenhouse. References: (1) B. Sneh et al. Identification of Rhizoctonia Species. The American Phytopathological Society, St Paul, MN, 1991. (2) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, CA, 1990.

Analysis of genetic diversity in flowering dogwood natural stands using microsatellites: the effects of dogwood anthracnose.

Flowering dogwood (Cornus florida L.) populations recently have experienced severe declines caused by dogwood anthracnose. Mortality has ranged from 48 to 98%, raising the concern that genetic diversity has been reduced significantly. Microsatellite data were used to evaluate the level and distribution of genetic variation throughout much of the native range of the tree. Genetic variation in areas affected by anthracnose was as high as or higher than areas without die-offs. We found evidence of four widespread, spatially contiguous genetic clusters. However, there was little relationship between geographic distance and genetic difference. These observations suggest that high dispersal rates and large effective population sizes have so far prevented rapid loss of genetic diversity. The effects of anthracnose on demography and community structure are likely to be far more consequential than short-term genetic effects.

Genetic Analysis of Fungicide-Resistant Sclerotinia homoeocarpa Isolates from Tennessee and Northern Mississippi.

Sclerotinia homoeocarpa is the causal agent of dollar spot disease that reduces the uniformity and aesthetic value of golf putting greens. Fungicide-resistant isolates of S. homoeocarpa were collected from putting greens at 10 locations across Tennessee and northern Mississippi. Genetic diversity among the 60 isolates was investigated using vegetative compatibility, conserved gene sequences, and amplified fragment length polymorphism (AFLP). Six tester strains were paired with Tennessee and northern Mississippi isolates on potato dextrose agar. Some of the 60 isolates were delineated into vegetative compatibility groups, but fungicide resistance could not be associated with a particular vegetative compatibility group. Genetic similarities of isolates at the vegetative compatibility level could be attributed to founder effects. Sequencing the regions of CAD, EF1-α, ß-tubulin, and internal transcribed spacers revealed 100% homology among isolates. Capillary gel electrophoresis and analysis of AFLP fragments indicated 86 to 100% similarity between the isolates. Vegetative compatibility and molecular data indicate that the populations of the pathogen are clonal. Isolates did not cluster according to fungicide resistance during unweighted pair group with arithmetic means analysis, but did appear to cluster according to vegetative compatibility group and location. Although associations could not be made between molecular markers and fungicide resistance, links between vegetative compatibility and AFLP markers may provide a foundation from which other studies could be performed.

Genetic Characterization of Binucleate Rhizoctonia Species Causing Web Blight on Azalea in Mississippi and Alabama.

Web blight on containerized azalea is an annual problem for commercial nurseries during summer months in the southern United States. Losses to web blight are associated with the cost of fungicide applications, delayed marketing of diseased plants, and plant death. Two hundred and eleven isolates of binucleate Rhizoctonia were recovered from azalea leaves with web blight symptoms from two nurseries in Mississippi and Alabama over 3 years. The internal transcribed spacer region (ITS) of the ribosomal DNA (rDNA) was sequenced from all isolates to determine genetic identity. A single anastomosis group (AG) of binucleate Rhizoctonia represented 92% of the samples collected from infected leaves. Genetic data and hyphal fusion experiments confirmed that these isolates belong to AG-U, which was recently identified from root and stem infections on miniature rose in Japan. Isolates of binucleate Rhizoctonia belonging to anastomosis groups AG-R, CAG-7 (=AG-S), and AG-G were also identified in the sample in low frequency. This is the first report of the occurrence of binucleate Rhizoctonia AG-U in the United States.

SINE extinction preceded LINE extinction in sigmodontine rodents: implications for retrotranspositional dynamics and mechanisms.

Short Interspersed Nuclear Elements, or SINEs, retrotranspose despite lacking protein-coding capability. It has been proposed that SINEs utilize enzymes produced in trans by Long Interspersed Nuclear Elements, or LINEs. Strong support for this hypothesis is found in LINE and SINE pairs that share sequence homology; however, LINEs and SINEs in primates and rodents are only linked by an insertion site motif. We have now profiled L1 LINE and B1 SINE activity in 24 rodent species including candidate taxa for the first documented L1 extinction. As expected, there was no evidence for recent activity of B1s in species that also lack L1 activity. However, B1 silencing appears to have preceded L1 extinction, since B1 activity is also lacking in the genus most closely related to those lacking active L1s despite the presence of active L1s in this genus. A second genus with active L1s but inactive B1s was also identified.

Extinction of LINE-1 activity coincident with a major mammalian radiation in rodents.

LINE-1 transposable elements (L1s) are ubiquitous in mammals and are thought to have remained active since before the mammalian radiation. Only one L1 extinction event, in South American rodents in the genus Oryzomys, has been convincingly demonstrated. Here we examine the phylogenetic limits and evolutionary tempo of that extinction event by characterizing L1s in related rodents. Fourteen genera from five tribes within the Sigmodontinae subfamily were examined. Only the Sigmodontini, the most basal tribe in this group, demonstrate recent L1 activity. The Oryzomyini, Akodontini, Phyllotini, and Thomasomyini contain only L1s that appear to have inserted long ago; their L1s lack open reading frames, have mutations at conserved amino acid residues, and show numerous private mutations. They also lack restriction site-defined L1 subfamilies specific to any species, genus or tribe examined, and fail to form monophyletic species, genus or tribal L1 clusters. We determine here that this L1 extinction event occurred roughly 8.8 million years ago, near the divergence of Sigmodon from the remaining Sigmodontinae species. These species appear to be ideal model organisms for studying the impact of L1 inactivity on mammalian genomes.

Permanent Genetic Resources added to the Molecular Ecology Resources Database 1 February 2010-31 March 2010.

This article documents the addition of 228 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Anser cygnoides, Apodemus flavicollis, Athene noctua, Cercis canadensis, Glis glis, Gubernatrix cristata, Haliotis tuberculata, Helianthus maximiliani, Laricobius nigrinus, Laricobius rubidus, Neoheligmonella granjoni, Nephrops norvegicus, Oenanthe javanica, Paramuricea clavata, Pyrrhura orcesi and Samanea saman. These loci were cross-tested on the following species: Apodemus sylvaticus, Laricobius laticollis and Laricobius osakensis (a proposed new species currently being described).

Jones matrix analysis of magnetooptical media and read-back systems.

A Jones matrix approach is used to study a magnetooptic read-back system which uses a wave plate for maximizing the signal. The effects and interactions of Kerr rotation, Kerr ellipticity, birefringence in the substrate and in the optical system, and misalignment of the optical components are considered. Several criteria are developed for maximizing the signal and minimizing the noise.

Comparative analysis of non-random DNA repair following Ac transposon excision in maize and Arabidopsis.

Ac/Ds transposable elements often leave short DNA rearrangements, or 'footprints,' at the sites where they excise. Previous studies at the maize waxy (wx) gene suggest that the DNA repair that forms transposon footprints is not random. Each excision site consistently displays a different, predominant repair product suggesting flanking DNA may influence footprint formation. We have expanded these studies to show that predominant end-joining products also form in association with Ac/Ds excision in Arabidopsis and that chromosomal location of the Ac-containing construct does not appear to influence this repair. The predominant repair product is identical in both maize and Arabidopsis for Ac elements with the same adjacent DNA sequences. However, a broader range of minor footprint types is observed in Arabidopsis, including footprints that are rare in maize, suggesting potential differences in the host proteins involved in either transposition, repair or both. The data also suggest that the sequences influencing footprint formation are within 39 bp 5' and 18 bp 3' of the transposon. These studies demonstrate that transgenic Ac/Ds-containing plants will be useful tools in dissecting plant DNA repair processes.