Viewpoint: Selection for improved drought response in cool-season grasses

Water limits the establishment, growth, and production of cool-season grasses on semiarid rangelands, and plant improvement programs for these areas must be capable of screening breeding lines for response to drought. Although many techniques to evaluate various morphological and physiological characteristics have been proposed, few have been used successfully in plant breeding programs. Consequently, a need exists to identify and develop rapid, reliable screening techniques that can assess integrated plant response to drought in large plant populations. Improved seedling emergence has been achieved in Russian wildrye [Psathyrostachys juncea (Fischer) Nevski] by selecting for emergence from a deep seeding depth and long coleoptiles. Water uptake by roots is critical, and screening for enhanced seedling root growth in cool-season grasses offers considerable promise. In spite of the important role that stomatal control has in regulating plant water loss, limited success has been achieved in incorporating desirable stomatal characteristics into improved grass cultivars. Although osmotic adjustment appears beneficial in some crop species, more research is needed before cool-season grasses should be selected based on osmotic adjustment. Selection for improved water-use efficiency in cool-season grasses based on carbon isotope discrimination is a promising approach. Successful incorporation of these various traits into improved cool-season grass cultivars necessitates close cooperation between breeders and physiologists.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

Breeding CWG-R crested wheatgrass for reduced-maintenance turf

Using reduced-maintenance turfgrass as an alternative to current high-maintenance turfgrass species would conserve resources, labor, and potentially reduce pollutants in the environment. CWG-R is an experimental population of crested wheatgrass [Agropyron cristatum (L.) Gaertn.] from Iran that has shown potential as a low-maintenance turf. The objective of this research was to estimate the genetic variation for turf traits within the CWG-R population when evaluated under a reduced-maintenance regimen. Ninety CWG-R clonal lines were established in 1998 near Logan, UT, as spaced-plant plots in a RCB design with four replicates. Maintenance of 50% ET0 replacement, 97.74 kg of nitrogen ha1yr1, and mowing at 7.62 cm was approximately 40% lower than typical for high-input Kentucky bluegrass (Poa pratensis L.) turf. Critical turf traits, including spring regrowth, season-long (March–October) and mid-summer (June–July) turf quality, color, and rhizomatous spread were evaluated in 1999 and 2000. Significant genetic variation among clonal lines was evident with broad-sense heritabilities of 0.65, 0.76, 0.45, and 0.76 for spring regrowth, season-long turf quality, color, and rhizomatous spread, respectively. Several clonal lines remained green throughout the summer months and maintained acceptable turf quality and color ratings during the critical mid-summer period. The high broad-sense heritability estimates within this population indicate potential for successful improvement of critical turf traits by phenotypic selection. These results indicate that that CWG-R could be an important low-maintenance turf-type crested wheatgrass germplasm

Dramatic Change in Jupiter's Great Red Spot from Spacecraft Observations

Jupiter's Great Red Spot (GRS) is one of its most distinct and enduring features. Since the advent of modern telescopes, keen observers have noted its appearance and documented a change in shape from very oblong to oval, confirmed in measurements from spacecraft data. It currently spans the smallest latitude and longitude size ever recorded. Here we show that this change has been accompanied by an increase in cloud/haze reflectance as sensed in methane gas absorption bands, increased absorption at wavelengths shorter than 500 nanometers, and increased spectral slope between 500 and 630 nanometers. These changes occurred between 2012 and 2014, without a significant change in internal tangential wind speeds; the decreased size results in a 3.2 day horizontal cloud circulation period, shorter than previously observed. As the GRS has narrowed in latitude, it interacts less with the jets flanking its north and south edges, perhaps allowing for less cloud mixing and longer UV irradiation of cloud and aerosol particles. Given its long life and observational record, we expect that future modeling of the GRS's changes, in concert with laboratory flow experiments, will drive our understanding of vortex evolution and stability in a confined flow field crucial for comparison with other planetary atmospheres

Parent-progeny relationships and genotype X environment effects for factors associated with grass tetany and forage quality in Russian Wildrye

Grass tetany (hypomagnesemia) has caused severe economic losses in ruminant animals grazing cool-season grasses, including Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski]. The malady has been associated with deficiencies in Mg, Ca, and carbohydrates, and high levels of K. The K/(Ca + Mg) ratio (KRAT), expressed as moles of charge, is often used to express the grass tetany potential of forage. Development and use of new cultivars with an improved balance of the associated minerals would be an economical approach to reduce the incidence of grass tetany. Objectives of this study were to characterize the genetic variability, genotype by environment interactions, and intercharacter relationships for P, K, Ca, Mg, KRAT, crude protein (CP), neutral detergent fiber (NDF), and in vitro dry matter digestibility (IVDMD), among 21 clonal lines of Russian wildrye and their polycross progenies. Evaluations were made for 2 yr at three diverse locations in the USA and Canada. The clonal lines were derived from cultivars and plant introductions. Although the clone x location interaction was usually significant, differences among the clonal lines were significant for K, Ca, Mg, and KRAT, and three forage quality estimates of CP, NDF, and true IVDMD. Although the magnitude of the genetic variability among the progenies was substantially less than that found among the clonal lines, we conclude that the grass tetany potential, CP, NDF, IVDMD, and P concentration of this breeding population can be altered through breeding. Opportunities for genetic improvement in forage quality were particularly favorable for CP. Genetic correlations among the clonal lines suggested that selection for higher levels of CP would be accompanied by increased K, Ca, Mg, and IVDMD and reduced KR AT and NDF

Path and Ridge Regression Analysis of Seed Yield and Seed Yield Components of Russian Wildrye (Psathyrostachys juncea Nevski) under Field Conditions

The correlations among seed yield components, and their direct and indirect effects on the seed yield (Z) of Russina wildrye (Psathyrostachys juncea Nevski) were investigated. The seed yield components: fertile tillers m-2 (Y1), spikelets per fertile tillers (Y2), florets per spikelet- (Y3), seed numbers per spikelet (Y4) and seed weight (Y5) were counted and the Z were determined in field experiments from 2003 to 2006 via big sample size. Y1 was the most important seed yield component describing the Z and Y2 was the least. The total direct effects of the Y1, Y3 and Y5 to the Z were positive while Y4 and Y2 were weakly negative. The total effects (directs plus indirects) of the components were positively contributed to the Z by path analyses. The seed yield components Y1, Y2, Y4 and Y5 were significantly (P<0.001) correlated with the Z for 4 years totally, while in the individual years, Y2 were not significant correlated with Y3, Y4 and Y5 by Peason correlation analyses in the five components in the plant seed production. Therefore, selection for high seed yield through direct selection for large Y1, Y2 and Y3 would be effective for breeding programs in grasses. Furthermore, it is the most important that, via ridge regression, a steady algorithm model between Z and the five yield components was founded, which can be closely estimated the seed yield via the components

Results of the third Marine Ice Sheet Model Intercomparison Project (MISMIP+)

We present the result of the third Marine Ice Sheet Model Intercomparison Project, MISMIP+. MISMIP+ is intended to be a benchmark for ice-flow models which include fast sliding marine ice streams and floating ice shelves and in particular a treatment of viscous stress that is sufficient to model buttressing, where upstream ice flow is restrained by a downstream ice shelf. A set of idealized experiments first tests that models are able to maintain a steady state with the grounding line located on a retrograde slope due to buttressing and then explore scenarios where a reduction in that buttressing causes ice stream acceleration, thinning, and grounding line retreat. The majority of participating models passed the first test and then produced similar responses to the loss of buttressing. We find that the most important distinction between models in this particular type of simulation is in the treatment of sliding at the bed, with other distinctions - notably the difference between the simpler and more complete treatments of englacial stress but also the differences between numerical methods - taking a secondary role. © 2020 Wolters Kluwer Medknow Publications. All rights reserved

Results of the third Marine Ice Sheet Model Intercomparison Project (MISMIP+)

We present the result of the third Marine Ice Sheet Model Intercomparison Project, MISMIP+. MISMIP+ is intended to be a benchmark for ice-flow models which include fast sliding marine ice streams and floating ice shelves and in particular a treatment of viscous stress that is sufficient to model buttressing, where upstream ice flow is restrained by a downstream ice shelf. A set of idealized experiments first tests that models are able to maintain a steady state with the grounding line located on a retrograde slope due to buttressing and then explore scenarios where a reduction in that buttressing causes ice stream acceleration, thinning, and grounding line retreat. The majority of participating models passed the first test and then produced similar responses to the loss of buttressing. We find that the most important distinction between models in this particular type of simulation is in the treatment of sliding at the bed, with other distinctions – notably the difference between the simpler and more complete treatments of englacial stress but also the differences between numerical methods – taking a secondary role

Homoleptic Low-Valent Polyazides of Group 14 Elements

First examples of coordinatively unsaturated, homoleptic azido complexes of low-valent group 14 elements are reported. A simple strategy uses low-valent precursors, ionic azide transfer reagents and bulky cations to obtain salt-like compounds containing E(N3)3- of Ge(II)/Sn(II) which are fully characterised, including XRD. Remarkably, these compounds are kinetically stable at r.t. and isolable in sub-gram quantities

MHD Modeling of Conductors at Ultra-High Current Density

In conjunction with ongoing high-current experiments on Sandia National Laboratories' Z accelerator, the authors have revisited a problem first described in detail by Heinz Knoepfel. Unlike the 1-Tesla MITLs of pulsed power accelerators used to produce intense particle beams, Z's disc transmission line (downstream of the current addition) is in a 100--1,200 Tesla regime, so its conductors cannot be modeled simply as static infinite conductivity boundaries. Using the MHD code MACH2 they have been investigating the conductor hydrodynamics, characterizing the joule heating, magnetic field diffusion, and material deformation, pressure, and velocity over a range of current densities, current rise-times, and conductor materials. Three purposes of this work are (1) to quantify power flow losses owing to ultra-high magnetic fields, (2) to model the response of VISAR diagnostic samples in various configurations on Z, and (3) to incorporate the most appropriate equation of state and conductivity models into the MHD computations. Certain features are strongly dependent on the details of the conductivity model