A Latent Period Duration Model for Wheat Stem Rust.

Wheat stem rust (WSR), caused by Puccinia graminis subsp. graminis Pers., is a highly destructive disease of wheat and several other small grains.

Evaluation of the Ryegrass Stem Rust Model STEMRUST_G and Its Implementation as a Decision Aid.

STEMRUST_G, a simulation model for epidemics of stem rust in perennial ryegrass grown to maturity as a seed crop, was validated for use as a heuristic tool and as a decision aid for disease management with fungicides. Multistage validation had been used in model creation by incorporating previously validated submodels for infection, latent period duration, sporulation, fungicide effects, and plant growth. Validation of the complete model was by comparison of model output with observed disease severities in 35 epidemics at nine location-years in the Pacific Northwest of the United States.

A simulation model for epidemics of stem rust in ryegrass seed crops.

A simulation model (STEMRUST_G, named for stem rust of grasses) was created for stem rust (caused by Puccinia graminis subsp. graminicola) in perennial ryegrass grown to maturity as a seed crop. The model has a daily time step and is driven by weather data and an initial input of disease severity from field observation.

Genome diversity in Brachypodium distachyon: deep sequencing of highly diverse inbred lines.

Brachypodium distachyon is small annual grass that has been adopted as a model for the grasses. Its small genome, high-quality reference genome, large germplasm collection, and selfing nature make it an excellent subject for studies of natural variation. We sequenced six divergent lines to identify a comprehensive set of polymorphisms and analyze their distribution and concordance with gene expression.

The use and role of predictive systems in disease management.

Disease predictive systems are intended to be management aids. With a few exceptions, these systems typically do not have direct sustained use by growers. Rather, their impact is mostly pedagogic and indirect, improving recommendations from farm advisers and shaping management concepts.

Infection of Brachypodium distachyon by formae speciales of Puccinia graminis: early infection events and host-pathogen incompatibility.

Puccinia graminis causes stem rust, a serious disease of cereals and forage grasses. Important formae speciales of P. graminis and their typical hosts are P.

Pathotype-specific QTL for stem rust resistance in Lolium perenne.

A genetic map populated with RAD and SSR markers was created from F1 progeny of a stem rust-susceptible and stem rust-resistant parent of perennial ryegrass (Lolium perenne). The map supplements a previous map of this population by having markers in common with several other Lolium spp. maps including EST-SSR anchor markers from a consensus map published by other researchers.

Effects of the Mycoparasite Sphaerellopsis filum on Overwintering Survival of Stem Rust in Perennial Ryegrass.

Sphaerellopsis filum is a mycoparasite of Puccinia graminis subsp. graminicola, a rust fungus that causes widespread crop damage on perennial ryegrass grown for seed. In observations taken over the winter months, S.

Sensitivity of Disease Management Decision Aids to Temperature Input Errors Associated with Sampling Interval and Out-of-Canopy Sensor Placement.

Many plant disease epidemic models, and the disease management decision aids developed from them, are created based on temperature or other weather conditions measured in or above the crop canopy at intervals of 15 or 30 min. Disease management decision aids, however, commonly are implemented based on hourly weather measurements made from sensors sited at a standard placement of 1.5 m above the ground or are estimated from off-site weather measurements.

Mapping with RAD (restriction-site associated DNA) markers to rapidly identify QTL for stem rust resistance in Lolium perenne.

A mapping population was created to detect quantitative trait loci (QTL) for resistance to stem rust caused by Puccinia graminis subsp. graminicola in Lolium perenne. A susceptible and a resistant plant were crossed to produce a pseudo-testcross population of 193 F(1) individuals.

Decision aids for multiple-decision disease management as affected by weather input errors.

Many disease management decision support systems (DSSs) rely, exclusively or in part, on weather inputs to calculate an indicator for disease hazard. Error in the weather inputs, typically due to forecasting, interpolation, or estimation from off-site sources, may affect model calculations and management decision recommendations. The extent to which errors in weather inputs affect the quality of the final management outcome depends on a number of aspects of the disease management context, including whether management consists of a single dichotomous decision, or of a multi-decision process extending over the cropping season(s).

Demonstration of pathotype specificity in stem rust of perennial ryegrass.

Rust diseases cause significant damage in forage and seed crops of perennial ryegrass (Lolium perenne), which is highly heterozygous and heterogeneous and thus presents difficulty in genetic analysis. There has been no definitive demonstration of the existence of pathotypes for stem rust or other rusts of perennial ryegrass, although experiments with crown rust (Puccinia coronata) of this host are strongly suggestive of pathotype specificity. We made single-pustule isolates of P.

Field assessment of a model for fungicide effects on intraplant spread of stem rust in perennial ryegrass seed crops.

Intraplant spread of stem rust (Puccinia graminis subsp. graminicola) in perennial ryegrass during tiller extension is a major determinant of epidemic severity and is dominated by stem extension dynamics. Simple equations for extension of inflorescence and internodes are presented and parameterized.

A damage function for stem rust of perennial ryegrass seed crops.

Observations of naturally occurring stem rust epidemics and seed yields in perennial ryegrass were taken in 19 field experiments conducted over the course of 9 years. Epidemic severity differed among years and also among experimental treatments (fungicide regimes) within years. In each experiment, attainable yield was represented by the nondiseased treatment, and yields of other treatments were expressed as relative yield (a proportion of the attainable yield).

Prediction of stem rust infection favorability, by means of degree-hour wetness duration, for perennial ryegrass seed crops.

ABSTRACT A weather-based infection model for stem rust of perennial ryegrass seed crops was developed and tested using data from inoculated bioassay plants in a field environment with monitored weather. The model describes favorability of daily weather as a proportion (0.0 to 1.

A temperature-based model for latent-period duration in stem rust of perennial ryegrass and tall fescue.

ABSTRACT A temperature-response curve for latent-period duration in stem rust (caused by Puccinia graminis subsp. graminicola) on perennial ryegrass and tall fescue was developed from constant-temperature experiments with inoculated plants and evaluated in field experiments. Under constant-temperature conditions, time from infection to 50% of pustules erupted for perennial ryegrass ranged from 54 days at 3.

Role of phenology in host susceptibility and within-plant spread of stem rust during reproductive development of perennial ryegrass.

ABSTRACT Perennial ryegrass (Lolium perenne) was inoculated with urediniospores of Puccinia graminis subsp. graminicola at four stages of reproductive tiller development. All developmental stages, from expansion of the penultimate leaf through anthesis, were equally susceptible to infection measured as number of pustules per total inoculated plant area.

New applications of statistical tools in plant pathology.

ABSTRACT The series of papers introduced by this one address a range of statistical applications in plant pathology, including survival analysis, nonparametric analysis of disease associations, multivariate analyses, neural networks, meta-analysis, and Bayesian statistics. Here we present an overview of additional applications of statistics in plant pathology. An analysis of variance based on the assumption of normally distributed responses with equal variances has been a standard approach in biology for decades.

Comparative analysis of multiple disease resistance in ryegrass and cereal crops.

Ryegrass (Lolium spp.) is among the most important forage crops in Europe and Australia and is also a popular turfgrass in North America. Previous genetic analysis based on a three-generation interspecific (L.

Interaction of Fungicide Physical Modes of Action and Plant Phenology in Control of Stem Rust of Perennial Ryegrass Grown for Seed.

Azoxystrobin provided protective and curative effects against stem rust (caused by Puccinia graminis subsp. graminicola) of inoculated perennial ryegrass under field conditions, significantly reducing disease severity compared with the nontreated check when applied as much as 15 days before infection or 14 days after infection. Propiconazole had a significant effect when applied 13, but not 15, days before infection or 7, but not 9, days after infection.

Regional Development of Orchardgrass Choke and Estimation of Seed Yield Loss.

A survey for choke, caused by Epichloë typhina, in orchardgrass seed-production fields in Oregon was conducted annually from 1998 to 2003. In all, 99 fields were inspected, 57 in more than 1 year, to produce a set of 217 observations on disease incidence. There was a significant increase in disease incidence in 38% of the revisited fields, and a significant reduction of incidence in 3%.

Effect of Autumn Planting Date and Stand Age on Severity of Stem Rust in Seed Crops of Perennial Ryegrass.

Perennial ryegrass (Lolium perenne) grown for seed is planted in autumn for July harvest (first-year seed crop), then kept in production for subsequent yearly harvests. Plots of first-year perennial ryegrass planted in early November had only 3% as much stem rust in June as plots planted in mid-September. In other plots where fungicides were used to prevent rust development, seed yield from the November-planted plots was reduced by 23% compared with September-planted plots.

Evaluation of Postharvest Burning and Fungicides to Reduce the Polyetic Rate of Increase of Choke Disease in Orchardgrass Seed Production.

Epichloë typhina, causal agent of choke disease, is detrimental to orchardgrass seed production. The fungus grows systemically, persists indefinitely as an endophyte within the perennial host, and produces a stroma bearing conidia and ascospores at the time of host flowering. The ascospores or conidia are thought to infect plants through the cut ends of tillers after swathing at harvest.

Host Range Differences Between Populations of Puccinia graminis subsp. graminicola Obtained from Perennial Ryegrass and Tall Fescue.

In the Pacific Northwest region of the United States, cool-season grasses grown for seed can be severely damaged by Puccinia graminis subsp. graminicola, causal agent of stem rust. Urediniospores of the pathogen, collected either from perennial ryegrass (Lolium perenne) or tall fescue (Festuca arundinacea), were tested for host range among selected grasses and cereals.

Freezing Temperature Effect on Survival of Puccinia graminis subsp. graminicola in Festuca arundinacea and Lolium perenne.

The Willamette Valley in Oregon is a major seed production area for cool-season grasses. Puccinia graminis subsp. graminicola survives over winter on its hosts as uredinial infections and causes epidemics of stem rust, the area's major disease on perennial ryegrass and tall fescue.