Temperature effects on three downy brome (Bromus tectorum) seed collections inoculated with the fungal pathogen Pyrenophora semeniperda

2019 ◽  
Vol 12 (02) ◽  
pp. 150-154
Author(s):  
Krista A. Ehlert ◽  
Zachariah Miller ◽  
Jane M. Mangold ◽  
Fabian Menalled ◽  
Alexandra Thornton
Keyword(s):  
Fungal Pathogen ◽  
Bromus Tectorum ◽  
Propagule Pressure ◽  
Downy Brome ◽  
Infection Rates ◽  
Temperature Dependent ◽  
Susceptibility To Infection ◽  
Winter Annual ◽  
Effects Of Temperature ◽  
Seed Collections

AbstractDowny brome (Bromus tectorum L., syn. cheatgrass) is a winter annual grass that invades North American cropping, forage, and rangeland systems. Control is often difficult to achieve, because B. tectorum has a large seedbank, which results in continuous propagule pressure. Pyrenophora semeniperda (Brittlebank and Adam) Shoemaker, a soilborne fungal pathogen, has been investigated as a biological control for B. tectorum, because it can kill seeds that remain in the seedbank, thereby reducing propagule pressure. Temperature influences P. semeniperda and has not been investigated in the context of seeds collected from different B. tectorum locations, that may vary in susceptibility to infection. We compared the effects of temperature (13, 17, 21, 25 C) and B. tectorum seed locations (range, crop, subalpine) with different mean seed weights on infection rates of P. semeniperda using a temperature-gradient table. Infection differed by seed location (P < 0.001) and temperature (P < 0.001), with lighter-weight seeds (i.e., range and subalpine) more susceptible to P. semeniperda infection. Infection increased as temperature increased and was higher at 21 C (66.7 ± 6.7%) and 25 C (73.3 ± 6.0%). Germination was affected by seed location (P < 0.001) and temperature (P = 0.019). Germination was highest for the crop seed location (45.4 ± 4.2%) and overall decreased at higher temperatures (21 and 25 C). Our results suggest that B. tectorum seeds from a crop location are less affected by P. semeniperda than those from range and subalpine locations. Moreover, this demonstrates a temperature-dependent effect on all populations.

Is Pyrenophora semeniperda the Cause of Downy Brome (Bromus tectorum) Die-offs?

2013 ◽  
Vol 6 (1) ◽  
pp. 105-111 ◽  
Author(s):  
Owen W. Baughman ◽  
Susan E. Meyer
Keyword(s):  
Seed Bank ◽  
Fungal Pathogen ◽  
Bromus Tectorum ◽  
Seed Banks ◽  
Causal Agent ◽  
Western North America ◽  
Downy Brome ◽  
Winter Annual ◽  
Persistent Seed Bank ◽  
Semi Arid

AbstractDowny brome (cheatgrass) is a highly successful, exotic, winter annual invader in semi-arid western North America, forming near-monocultures across many landscapes. A frequent but poorly understood phenomenon in these heavily invaded areas is periodic ‘die-off’ or complete stand failure. The fungal pathogen Pyrenophora semeniperda is abundant in cheatgrass seed banks and causes high mortality. To determine whether this pathogen could be responsible for stand failure, we quantified late spring seed banks in die-off areas and adjacent cheatgrass stands at nine sites. Seed bank analysis showed that this pathogen was not a die-off causal agent at those sites. We determined that seed bank sampling and litter data could be used to estimate time since die-off. Seed bank patterns in our recent die-offs indicated that the die-off causal agent does not significantly impact seeds in the persistent seed bank.

Downy Brome (Bromus tectorum) Vernalization: Variation and Genetic Controls

Weed Science ◽  
2018 ◽  
Vol 66 (3) ◽  
pp. 310-316 ◽  
Author(s):  
Nevin C. Lawrence ◽  
Amber L. Hauvermale ◽  
Ian C. Burke
Keyword(s):  
North America ◽  
Bromus Tectorum ◽  
Brachypodium Distachyon ◽  
Western North America ◽  
Downy Brome ◽  
Annual Grass ◽  
Vernalization Gene ◽  
Greenhouse Experiments ◽  
Winter Annual

AbstractDowny brome (Bromus tectorumL.) is a widely distributed invasive winter annual grass across western North America.Bromus tectorumphenology can vary considerably among populations, and those differences are considered adaptively significant. A consensus hypothesis in the literature attributes the majority of observed differences inB. tectorumphenology to differing vernalization requirements among populations. A series of greenhouse experiments were conducted to identify differences inB. tectorumvernalization requirements and link vernalization to expression of annual false-brome [Brachypodium distachyon(L.) P. Beauv.]-derived vernalization gene homolog (BdVRN1). Results from this study indicate that variation in time to flowering is partially governed by differing vernalization requirements and that flowering is linked to the expression ofBdVRN1.

Interference of Annual Weeds in Seedling Alfalfa (Medicago sativa)

Weed Science ◽  
1988 ◽  
Vol 36 (5) ◽  
pp. 583-588 ◽  
Author(s):  
Albert J. Fischer ◽  
Jean H. Dawson ◽  
Arnold P. Appleby
Keyword(s):  
Medicago Sativa ◽  
Bromus Tectorum ◽  
Early Spring ◽  
Amaranthus Retroflexus ◽  
Downy Brome ◽  
Weed Interference ◽  
Alfalfa Hay ◽  
Winter Annual ◽  
Annual Weeds

Barnyardgrass [Echinochloa crus-galli(L.) Beauv. #4ECHCG] and pigweeds (mixture ofAmaranthus retroflexusL. # AMARE andA. powelliiS. Wats. # AMAPO) seeded separately with alfalfa (Medicago sativaL.) in mid-August suppressed alfalfa severely before frost killed them in October and November. Some alfalfa was killed, and yield of alfalfa forage was reduced in each of three harvests the following year. These weeds did not harm alfalfa seeded in mid-September. Downy brome (Bromus tectorumL. # BROTE) and tumble mustard (Sisymbrium altissimumL. # SSYAL) suppressed alfalfa seeded in August and September. They reduced alfalfa stands and reduced yield of alfalfa forage in each of three harvests the following year. Alfalfa seeded August 27 and allowed to compete with a mixture of these species for various periods was injured most by weeds that emerged with the alfalfa and remained uncontrolled until forage harvest in May. These weeds did not reduce alfalfa yields if removed by 36 days after alfalfa emergence. Thereafter, yield decreased as the period of weed interference increased. Interference was most damaging in early spring, when growth of winter annual weeds was rapid and vigorous. Weeds seeded 65 or more days after alfalfa emergence did not reduce alfalfa yields but sometimes produced enough biomass to reduce the quality of the first-cutting alfalfa hay.

Niche specialization in Bromus tectorum seed bank pathogens

2018 ◽  
Vol 28 (3) ◽  
pp. 215-221
Author(s):  
Susan E. Meyer ◽  
Julie Beckstead ◽  
Phil S. Allen
Keyword(s):  
Seed Bank ◽  
Bromus Tectorum ◽  
Hyphal Growth ◽  
Niche Overlap ◽  
Downy Brome ◽  
Niche Specialization ◽  
Seed Mortality ◽  
Radicle Emergence ◽  
Seed Rot ◽  
Winter Annual

AbstractNiche theory predicts that when two species exhibit major niche overlap, one will eventually be eliminated through competitive exclusion. Thus, some degree of niche specialization is required to facilitate coexistence. We examined whether two important seed bank pathogens on the invasive winter annual grass Bromus tectorum (cheatgrass, downy brome) exhibit niche specialization. These pathogens utilize seed resources in complementary ways. Pyrenophora semeniperda is specialized to attack dormant seeds. It penetrates directly through the seed coverings. Hyphae ramify first through the endosperm and then throughout the seed. Seed death results as the embryo is consumed. In contrast, the Fusarium seed rot pathogen (Fusarium sp.) is specialized to attack non-dormant seeds in the early stages of germination. It cannot penetrate seed coverings directly. Instead, it responds to a cue emanating from the radicle end with directional hyphal growth and subsequent penetration at the point of radicle emergence, causing seed death. Non-dormant seeds usually escape P. semeniperda through germination even if infected because it develops more slowly than Fusarium. When water stress slows non-dormant seed germination, both P. semeniperda and Fusarium can attack and cause seed mortality more effectively. The Fusarium seed rot pathogen can sometimes reach epidemic levels and may result in B. tectorum stand failure (‘die-off’). Stands usually re-establish from the persistent seed bank, but if P. semeniperda has also reached high levels and eliminated the seed bank, a die-off can persist indefinitely.

scholarly journals Behaviour of albino and melanic variants of Biomphalaria glabrata Say, 1818 (Mollusca: Planorbidae) following infection by Schistosoma mansoni Sambon, 1907

2009 ◽  
Vol 69 (1) ◽  
pp. 217-222 ◽  
Author(s):  
SM. Allegretti ◽  
JF. Carvalho ◽  
LA. Magalhães ◽  
EM. Zanotti-Magalhães
Keyword(s):  
Mortality Rate ◽  
Schistosoma Mansoni ◽  
Cross Sections ◽  
Biomphalaria Glabrata ◽  
Infection Rates ◽  
Susceptibility To Infection ◽  
Belo Horizonte

The behaviour of the albino and melanic variants of Biomphalaria glabrata of Belo Horizonte (MG. Brazil) was studied comparatively, in terms of their respective susceptibilities to infection by Schistosoma mansoni of the same origin, through observation of the elimination of cercariae for a three-month period and the calculation of mortality and infection rates, in control and in infected snails. The number of amoebocytes, granulocytes and hyalinocytes in the circulating hemolymph during different periods of infection was analyzed. The evolution of the infection in the tissues was observed by means of histological cross-sections. The melanic variant showed greater susceptibility to infection and a higher mortality rate. The albino variant showed a higher number of circulating amoebocytes, both granulocytes and hyalinocytes. A higher number of degenerated sporocysts were seen in the histological cross-sections of the albino variant. The results suggest that the melanic variant of B. glabrata was more susceptible to infection by S. mansoni than was the albino variant.

scholarly journals Global dynamics of a Huanglongbing model with a periodic latent period

2021 ◽  
Vol 0 (0) ◽  
pp. 0
Author(s):  
Yan Hong ◽  
Xiuxiang Liu ◽  
Xiao Yu
Keyword(s):  
Reproduction Number ◽  
Threshold Value ◽  
Transmission Model ◽  
Threshold Dynamics ◽  
Global Dynamics ◽  
Temperature Dependent ◽  
Candidatus Liberibacter ◽  
Effects Of Temperature ◽  
Disease Free ◽  
The Basic Reproduction Number

<p style='text-indent:20px;'>Huanglongbing (HLB) is a disease of citrus that caused by phloem-restricted bacteria of the Candidatus Liberibacter group. In this paper, we present a HLB transmission model to investigate the effects of temperature-dependent latent periods and seasonality on the spread of HLB. We first establish disease free dynamics in terms of a threshold value <inline-formula><tex-math id="M1">\begin{document}$ R^p_0 $\end{document}</tex-math></inline-formula>, and then introduce the basic reproduction number <inline-formula><tex-math id="M2">\begin{document}$ \mathcal{R}_0 $\end{document}</tex-math></inline-formula> and show the threshold dynamics of HLB with respect to <inline-formula><tex-math id="M3">\begin{document}$ R^p $\end{document}</tex-math></inline-formula> and <inline-formula><tex-math id="M4">\begin{document}$ \mathcal{R}_0 $\end{document}</tex-math></inline-formula>. Numerical simulations are further provided to illustrate our analytic results.</p>

Effects of Temperature and Charge Depletion on the Spin Density in Hydrogenated Amorphous Silicon

1991 ◽  
Vol 219 ◽  
Author(s):  
J.-K. Lee ◽  
E. A. Schiff
Keyword(s):  
Spin Density ◽  
Negative Charge ◽  
Temperature Dependent ◽  
Defect Model ◽  
Depletion Width ◽  
Initial Charge ◽  
Effects Of Temperature ◽  
Hydrogenated Amorphous ◽  
Spin Densities ◽  
Charge Depletion

ABSTRACTThe dependence of the spin density upon temperature and charge depletion is calculated based on the standard defect model in a-Si:H of a D-center with positive, neutral, and negative charge states. The results are compared with recent measurements of depletion width modulated spin densities and temperature-dependent spin densities. It is shown that the initial charge density assumed for the defect system substantially affects conclusions regarding electronic correlation energies drawn from the measurements.

scholarly journals Emission Characteristics of Fluorescent Labels with Respect to Temperature Changes and Subsequent Effects on DNA Microchip Studies

2005 ◽  
Vol 71 (10) ◽  
pp. 6453-6457 ◽  
Author(s):  
Wen-Tso Liu ◽  
Jer-Horng Wu ◽  
Emily Sze-Ying Li ◽  
Ezrein Shah Selamat
Keyword(s):  
Melting Curve ◽  
Melting Curve Analysis ◽  
Emission Characteristics ◽  
Fluorescent Labels ◽  
Temperature Dependent ◽  
Temperature Changes ◽  
Formamide Concentration ◽  
Effects Of Temperature ◽  
Microarray Studies ◽  
Texas Red

ABSTRACT The effects of temperature, salt concentration, and formamide concentration on the emission characteristics of commonly used fluorescent labels were evaluated on DNA microchips. The emission intensities of different fluorophores without hybridization were observed to vary, each to a different extent, to mainly temperature changes. Rhodamine red, TAMRA (tetramethylrhodamine), and dyes from the carbocyanide group exhibited the largest variations, and Texas Red and Oregon Green exhibited the smallest variations. This temperature dependency was shown to affect results obtained during melting curve analysis in DNA microarray studies. To minimize the bias associated with the temperature-dependent emission of different fluorescent labels, a normalization step was proposed.

Temperature and parasite life-history are important modulators of the outcome of Trypanosoma rangeli–Rhodnius prolixus interactions

Parasitology ◽  
2016 ◽  
Vol 143 (11) ◽  
pp. 1459-1468 ◽  
Author(s):  
JULIANA DE O. RODRIGUES ◽  
MARCELO G. LORENZO ◽  
OLINDO A. MARTINS-FILHO ◽  
SIMON L. ELLIOT ◽  
ALESSANDRA A. GUARNERI
Keyword(s):  
Life Histories ◽  
Protozoan Parasite ◽  
Infection Rates ◽  
Trypanosoma Rangeli ◽  
Negative Effects ◽  
Temperature Dependent ◽  
Liver Infusion Tryptose ◽  
Insect Fitness ◽  
Different Levels

SUMMARYTrypanosoma rangeli is a protozoan parasite, which does not cause disease in humans, although it can produce different levels of pathogenicity to triatomines, their invertebrate hosts. We tested whether infection imposed a temperature-dependent cost on triatomine fitness using T. rangeli with different life histories. Parasites cultured only in liver infusion tryptose medium (cultured) and parasites exposed to cyclical passages through mice and triatomines (passaged) were used. We held infected insects at four temperatures between 21 and 30 °C and measured T. rangeli growth in vitro at the same temperatures in parallel. Overall, T. rangeli infection induced negative effects on insect fitness. In the case of cultured infection, parasite effects were temperature-dependent. Intermoult period, mortality rates and ecdysis success were affected in those insects exposed to lower temperatures (21 and 24 °C). For passaged-infected insects, the effects were independent of temperature, intermoult period being prolonged in all infected groups. Trypanosoma rangeli seem to be less tolerant to higher temperatures since cultured-infected insects showed a reduction in the infection rates and passaged-infected insects decreased the salivary gland infection rates in those insects submitted to 30 °C. In vitro growth of T. rangeli was consistent with these results.

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