Amplified fragment length polymorphism in Elymus elymoides, Elymus multisetus, and other Elymus taxa

The geographic and phylogenetic significance of amplified fragment length polymorphism within and among 22 Elymus elymoides (Raf.) Swezey subsp. elymoides, 24 E. elymoides subsp. brevifolius (J.G. Sm.) Barkworth, and 13 Elymus multisetus (J.G. Sm.) Burtt-Davy squirreltail accessions was assessed relative to six other North American and three Eurasian Elymus taxa. Elymus elymoides and E. multisetus, comprising Elymus sect. Sitanion (Raf.) Á. Löve, were both monophyletic and closely related compared with other congeners. The monophyly of subsp. elymoides was also supported; subsp. brevifolius, however, was paraphyletic and separated into four genetically distinct groups. Estimates of nucleotide divergence among the five E. elymoides groups range from 0.0194 to 0.0288, with approximately 0.0329 differences per site between E. elymoides and E. multisetus. Corresponding estimates of nucleotide divergence range from 0.0243 to 0.0387 among North American taxa and from 0.0337 to 0.0455 between North American and Eurasian taxa. DNA polymorphism among E. elymoides accessions was correlated with geographic provenance and previously reported quantitative traits. Distinct genetic groups of E. elymoides generally correspond to different geographic regions, whereas divergent E. multisetus and E. elymoides accessions are sympatric. Thus, taxonomic ranks of E. multisetus and E. elymoides were supported and geographic groups within E. elymoides were distinguished.Key words: AFLP, Elymus, nucleotide diversity, squirreltail.

Using hydrothermal time concepts to model seed germination response to temperature, dormancy loss, and priming effects in Elymus elymoides

Hydrothermal time (HTT) describes progress toward seed germination under various combinations of incubation water potential ( ) and temperature (T). To examine changes in HTT parameters during dormancy loss, seeds from two populations of the bunchgrass Elymus elymoides were incubated under seven temperature regimes following dry storage at 10, 20 and 30°C for intervals from 0 to 16 weeks. Fully after-ripened seeds were primed for 1 week at a range of s. Data on germination rate during priming were used to obtain a HTT equation for each seed population, while data obtained following transfer to water were used to calculate HTT accumulation during priming. HTT equations accurately predicted germination time course curves if mean base water potential, b(50), was allowed to vary with temperature. b(50) values increased linearly with temperature, explaining why germination rate does not increase with temperature in this species. b(50) showed a linear decrease as a function of thermal time in storage. Slopes for the T × b(50) relationship did not change during after-ripening. This thermal after-ripening time model was characterized by a single base temperature and a constant slope across temperatures for each collection. Because the difference between initial and final b(50)s was uniform across tempera-tures, the thermal after-ripening requirement was also a constant. When seeds were primed for 1 week at −4 to −20 MPa, accumulation of HTT was a uniform 20% of the total HTT requirement. When primed at 0 to −4 MPa, HTT accumulation decreased linearly with decreasing priming potential, and a hydrothermal priming time model using a constant minimum priming potential adequately described priming effects. Use of these simple HTT relationships will facilitate modelling of germination phenology in the field.

Influence of Simulated Burning of Soil-Litter From Low Sagebrush, Squirreltail, Cheatgrass, and Medusahead on Water-Soluble Anions and Cations

We evaluated the influence of temperature and heating time on water-soluble anions and cations of soil-litters of low sagebrush (Artemisia arbuscula ssp. longicaulis), squirreltail (Elymus elymoides), cheatgrass (Bromus tectorum), and medusahead (Taeniatherum caputmeduase ssp. asperum). Soil-litters were collected from volcanic tablelands north of Honey Lake, California. These high clay, montmorillonitic, soils have rarely experienced wildfires. Soil-litter samples, in a 50 mt crucible, were placed in a preheated muffle furnace using a time-temperature matrix of 150, 250, 350, and 450°C at 1, 5,and 15 min. High performance ion-exchange chromatography was used to quantify water-soluble cations and anions. For most measured solutes, there was either a significant (P less than or equal to 0.05) burn time × temperature or a significant burn time × temperature × soil-litter type interaction. As compared to pre-burn values, heating of soil generally increased the concentration of the water-soluble solutes measured; nitrate was the exception. Maximum solute values were generally obtained at a temperature of 350°C at 5 and 15 min heating time. A temperature of 450°C at 15 min heating time resulted in the significant reduction of solute concentration below the maximum values. Nitrate was significantly higher in squirreltail soil-litter than the other soil-litters when the burn time was 1 min. Heating, in general, fostered an increase in water-soluble ammonium. For most solutes, heat-induced increases were greatest for the low sagebrush soil-litter.