Evaluation and Association Mapping of Resistance to Tan Spot and Stagonospora Nodorum Blotch in Adapted Winter Wheat Germplasm

Tan spot and Stagonospora nodorum blotch (SNB), often occurring together, are two economically significant diseases of wheat in the Northern Great Plains of the United States. They are caused by the fungi Pyrenophora tritici-repentis and Parastagonospora nodorum, respectively, both of which produce multiple necrotrophic effectors (NE) to cause disease. In this work, 120 hard red winter wheat (HRWW) cultivars or elite lines, mostly from the United States, were evaluated in the greenhouse for their reactions to the two diseases as well as NE produced by the two pathogens. One P. nodorum isolate (Sn4) and four Pyrenophora tritici-repentis isolates (Pti2, 331-9, DW5, and AR CrossB10) were used separately in the disease evaluations. NE sensitivity evaluation included ToxA, Ptr ToxB, SnTox1, and SnTox3. The numbers of lines that were rated highly resistant to individual isolates ranged from 11 (9%) to 30 (25%) but only six lines (5%) were highly resistant to all isolates, indicating limited sources of resistance to both diseases in the U.S. adapted HRWW germplasm. Sensitivity to ToxA was identified in 83 (69%) of the lines and significantly correlated with disease caused by Sn4 and Pti2, whereas sensitivity to other NE was present at much lower frequency and had no significant association with disease. As expected, association mapping located ToxA and SnTox3 sensitivity to chromosome arm 5BL and 5BS, respectively. A total of 24 potential quantitative trait loci was identified with −log (P value) \u3e 3.0 on 12 chromosomes, some of which are novel. This work provides valuable information and tools for HRWW production and breeding in the Northern Great Plains

Meta-analysis of yield response of foliar fungicide-treated hybrid corn in the United States and Ontario, Canada

Background Foliar fungicide applications to corn (Zea mays L.) occur at one or more application timings ranging from early vegetative growth stages to mid-reproductive stages. Previous studies indicated that fungicide applications are profitable under high disease pressure when applied during the tasseling to silking growth stages. Few comprehensive studies in corn have examined the impact of fungicide applications at an early vegetative growth stage (V6) compared to late application timings (VT) for yield response and return on fungicide investment (ROI) across multiple locations. Objective Compare yield response of fungicide application timing across multiple fungicide classes and calculate the probability of positive ROI. Methods Data were collected specifically for this analysis using a uniform protocol conducted in 13 states in the United States and one province in Canada from 2014–2015. Data were subjected to a primary mixed-model analysis of variance. Subsequent univariate meta-analyses, with and without moderator variables, were performed using standard meta-analytic procedures. Follow-up power and prediction analyses were performed to aid interpretation and development of management recommendations. Results Fungicide application resulted in a range of yield responses from -2,683.0 to 3,230.9 kg/ha relative to the non-treated control, with 68.2% of these responses being positive. Evidence suggests that all three moderator variables tested (application timing, fungicide class, and disease base level), had some effect (α = 0.05) on the absolute difference in yield between fungicide treated and non-treated plots (). Application timing influenced , with V6 + VT and the VT application timings resulting in greater yield responses than the V6 application timing alone. Fungicide formulations that combined demethylation inhibitor and quinone outside inhibitor fungicides significantly increased yield response. Conclusion Foliar fungicide applications can increase corn grain yield. To ensure the likelihood of a positive ROI, farmers should focus on applications at VT and use fungicides that include a mix of demethylation inhibitor and quinone outside inhibitor active ingredients

Meta-analysis of yield response of foliar fungicide-treated hybrid corn in the United States and Ontario, Canada

Foliar fungicide applications to corn (Zea mays L.) occur at one or more application timings ranging from early vegetative growth stages to mid-reproductive stages. Previous studies indicated that fungicide applications are profitable under high disease pressure when applied during the tasseling to silking growth stages. Few comprehensive studies in corn have examined the impact of fungicide applications at an early vegetative growth stage (V6) compared to late application timings (VT) for yield response and return on fungicide investment (ROI) across multiple locations

Developing Management Tools for Sunflower Rust (Puccinia Helianthi)

Sunflower rust, caused by Puccinia helianthi (Schwein), is an economically important disease in North Dakota. Since 2008, sunflower rust incidence and severity have increased. Therefore, a four year study was initiated to examine the management strategies for the disease. A total of 19 fungicide efficacy and timing trials were conducted from 2008-2011. Results indicated that DMI and QoI chemistries can be used effectively to manage the disease. Timing trials indicated that disease control was highest when fungicide applications were made at R5.0-R5.8. Results indicate a fungicide application is warranted when rust severities at approximately 1% are found on the upper-four leaves at R5. To observe phenotype variability in the pathogen, a P. helianthi survey was completed in 2011 and 2012. Single-pustule isolates were obtained and virulence phenotypes were evaluated on a set of nine differentials. Race characterization was assigned based on virulence phenotypes. In 2011, the most commonly detected races were 300 and 304, while the most virulent was 776. In 2012, races 304 and 324 were the most commonly detected and the most virulent was 777. To identify new sources of rust resistance, the core-set of Helianthus annuus germplasm was obtained from the USDA-North Central Regional Plant Introduction Station. The accession lines were screened both in the greenhouse and the field. The accessions were screened in the greenhouse individually to races 300, 304, 336, 337, and 777. Lines were screened in the field to a mixture of P. helianthi isolates coding to 300, 304, 336, and 337. The majority of lines were susceptible in both the field and greenhouse. At both field locations, PI 431538, PI 432512, and PI 650362 had year-end severities under 1%. Similarly, PI lines 432512 and 650362 had resistant infection types across all five races. The results of these studies provide information and tools that are being used currently to manage rust and will contribute to management in the future.National Sunflower AssociationNorth Dakota Department of Agricultur

Downy Mildew of Sunflower

PP-140

Disease Management and Estimated Effects on DON (Deoxynivalenol) Contamination in \u3ci\u3eFusarium\u3c/i\u3e Infested Barley

Fusarium head blight (FHB or scab) economically devastates barley production. FHB is predominantly caused by Fusarium graminearum and has resulted in major reductions in the quality of barley in the United States. The most common source of economic loss is through development of potent mycotoxins in the grain, the most prominent of which, in the United States, is deoxynivalenol (DON). DON levels can be managed through a variety of techniques. This study presents the estimate of the statistical relationship among DON contamination in barley, FHB incidence and severity, and a variety of disease management techniques. Data from 22 field studies and a survey of barley producers are used to estimate the relationship. Fungicide applications reduce DON in barley in general and via complementary interactions with the barley cultivar. Genetic FHB resistance in barley varieties is an important determinant of DON levels, as well as previous crop and factors related to time and location. Taking care to avoid rotations with FHB host crops immediately prior to barley is also important to reduce DON levels in barley. These become key inputs into barley producer decisions for evaluating the economic value of adopting FHB management techniques

Phenotypic Diversity of \u3ci\u3ePuccinia helianthi\u3c/i\u3e (Sunflower Rust) in the United States from 2011 and 2012

Puccinia helianthi, causal agent of sunflower rust, is a macrocyclic and autoecious pathogen. Widespread sexual reproduction of P. helianthi was documented in North Dakota and Nebraska for the first time in 2008 and has since frequently occurred. Concurrently, an increase in sunflower rust incidence, severity, and subsequent yield loss on sunflower has occurred since 2008. Rust can be managed with resistance genes but determination of virulence phenotypes is important for effective gene deployment and hybrid selection. However, the only P. helianthi virulence data available in the United States was generated prior to 2009 and consisted of aggregate virulence phenotypes determined on bulk field collections. The objective of this study was to determine the phenotypic diversity of P. helianthi in the United States. P. helianthi collections were made from cultivated, volunteer, and wild Helianthus spp. at 104 locations across seven U.S. states and one Canadian province in 2011 and 2012. Virulence phenotypes of 238 single-pustule isolates were determined on the internationally accepted differential set. In total, 29 races were identified, with races 300 and 304 occurring most frequently in 2011 and races 304 and 324 occurring most frequently in 2012. Differences in race prevalence occurred between survey years and across geography but were similar among host types. Four isolates virulent to all genes in the differential set (race 777) were identified. The resistance genes found in differential lines HA-R3 (R4b), MC29 (R2 and R10), and HA-R2 (R5) conferred resistance to 96.6, 83.6, and 78.6% of the isolates tested, respectively

Disease Management and Estimated Effects on DON (Deoxynivalenol) Contamination in Fusarium Infested Barley

Fusarium head blight (FHB or scab) economically devastates barley production. FHB is predominantly caused by Fusarium graminearum and has resulted in major reductions in the quality of barley in the United States. The most common source of economic loss is through development of potent mycotoxins in the grain, the most prominent of which, in the United States, is deoxynivalenol (DON). DON levels can be managed through a variety of techniques. This study presents the estimate of the statistical relationship among DON contamination in barley, FHB incidence and severity, and a variety of disease management techniques. Data from 22 field studies and a survey of barley producers are used to estimate the relationship. Fungicide applications reduce DON in barley in general and via complementary interactions with the barley cultivar. Genetic FHB resistance in barley varieties is an important determinant of DON levels, as well as previous crop and factors related to time and location. Taking care to avoid rotations with FHB host crops immediately prior to barley is also important to reduce DON levels in barley. These become key inputs into barley producer decisions for evaluating the economic value of adopting FHB management techniques

Meta-analysis of yield response of foliar fungicide-treated hybrid corn in the United States and Ontario, Canada

Background Foliar fungicide applications to corn (Zea mays L.) occur at one or more application timings ranging from early vegetative growth stages to mid-reproductive stages. Previous studies indicated that fungicide applications are profitable under high disease pressure when applied during the tasseling to silking growth stages. Few comprehensive studies in corn have examined the impact of fungicide applications at an early vegetative growth stage (V6) compared to late application timings (VT) for yield response and return on fungicide investment (ROI) across multiple locations. Objective Compare yield response of fungicide application timing across multiple fungicide classes and calculate the probability of positive ROI. Methods Data were collected specifically for this analysis using a uniform protocol conducted in 13 states in the United States and one province in Canada from 2014–2015. Data were subjected to a primary mixed-model analysis of variance. Subsequent univariate meta-analyses, with and without moderator variables, were performed using standard meta-analytic procedures. Follow-up power and prediction analyses were performed to aid interpretation and development of management recommendations. Results Fungicide application resulted in a range of yield responses from -2,683.0 to 3,230.9 kg/ha relative to the non-treated control, with 68.2% of these responses being positive. Evidence suggests that all three moderator variables tested (application timing, fungicide class, and disease base level), had some effect (α = 0.05) on the absolute difference in yield between fungicide treated and non-treated plots (). Application timing influenced , with V6 + VT and the VT application timings resulting in greater yield responses than the V6 application timing alone. Fungicide formulations that combined demethylation inhibitor and quinone outside inhibitor fungicides significantly increased yield response. Conclusion Foliar fungicide applications can increase corn grain yield. To ensure the likelihood of a positive ROI, farmers should focus on applications at VT and use fungicides that include a mix of demethylation inhibitor and quinone outside inhibitor active ingredients.This article is published as Wise, Kiersten A., Damon Smith, Anna Freije, Daren S. Mueller, Yuba Kandel, Tom Allen, Carl A. Bradley et al. "Meta-analysis of yield response of foliar fungicide-treated hybrid corn in the United States and Ontario, Canada." PLOS ONE 14, no. 6 (2019): e0217510. doi: 10.1371/journal.pone.0217510.</p