Nitrogen fertilization, fungicide application, and genetic resistance for the management of diseases on wheat

Effect of growth stage on the relationship between tan spot and spot blotch severity and yield in winter wheat

WILCOXSON, R. D. 1980. Effects of fertilizers on slow rusting in wheat. Phytopathology 70:930-932. In an NPK factorial experiment, Marquis wheat rusted rapidly with rust development in 1979, but did not affect rust development in other years Puccinia graminis f.sp. tritici (wheat stem rust pathogen) and P. recondita as indicated by area under the disease progress curve. P20 5 enhanced stem f.sp. tritici (wheat leaf rust pathogen), Lee rusted moderately rapidly with both rust development in 1977, but did not affect stem rust or leaf rust pathogens, and Thatcher rusted slowly with the stem rust pathogen and rapidly development in any of the other 5 yr of the study. K20 enhanced leaf rust with the leaf rust pathogen. The interaction ofcultivars with fertilizer treatments development in 1973 and stem rust development in 1979, but did not affect was not significant. NH4NO3 enhanced leaf rust development in 1975, and stem either rust in other years. Slow rusting in wheat infected with the stem or leaf rust rusts slowly with the stem rust pathogen and rapidly with the leaf pathogens has been demonstrated to be a highly heritable trait rust pathogen. (3,7), but its usefulness in the control of the rusts depends in large In 1973, 1974, and 1975 leaf rust caused by Puccinia recondita part on how stable it is when the slow rusting cultivars are grown f.sp. tritici developed in the plots from naturally occurring under various environmental conditions. Fertilizers constitute an inoculum. Races UN 2 and UN 17 were the most common races in environmental factor that varies greatly from field to field and the area. Stem rust was not evaluated because leaf rust was so influences the susceptibility of plants. In general, fertilization with severe that stem rust did not develop appreciably. nitrogen alone tends to increase the susceptibility of plants to the In 1976, 1977, and 1979 the plots were inoculated with P. rusts, whereas fertilization with phosphorus or potassium alone graminis f.sp. tritici and leaf rust was prevented from developing by tends to decrease susceptibility. When these elements are used in a spraying 2-wk-old plants and the ground around them with a balanced fertilization program, phosphorus and potassium tend to solution of triazbutil (4-butyl-4H-1,2,4-triazole) (Indar®, Rohm overcome the adverse effects of nitrogen. The effects of fertilization and Haas Co., Philadelphia, PA 19105) in water at the rate of 877 on stem and leaf rusts have been summarized by Stakman and ml per hectare. Infection with P. graminis f.sp. tritici was initiated Aamodt (8), Chester (2), and more recently by Kiraily (4) and by spraying freshly collected urediospores of race 15B2-TLM, a Capetti et al (1). The objectives of this study were to evaluate the race that commonly occurs in this part of Minnesota, suspended in slow rusting characteristics of three cultivars in an NPK factorial Soltrol® (Phillips 66, Bartlesville, OK 74003), uniformly over each experiment. plot. The plants were inoculated when in the early boot growth stage. The border plants around the field also were inoculated. MATERIALS AND METHODS Rust severity was evaluated once each week beginning about 1 wk before inoculation. After the disease appeared, rust seventies A field at Rosemount, MN, in which a factorial experiment with were evaluated for an additional 3-5 wk with the aid of the NH 4NO 3, P20 5, and K20 had been established in 1959 and modified Cobb scale (5). Rust severity data obtained in each plot continued annually, was used throughout. Corn, alfalfa, and oats were converted to area under the disease progress curve (AUDPC) have been grown on the field. During the 2 yr preceeding these with the aid of the computer program used by Skovmand et al (7). experiments, the field was not fertilized and was planted with oats. AUDPC, an indication of both the amount of rust present during The fertilized plots were 7.7 > 19 m and the treatments were the growing season and the rate at which it developed, was used to randomized with four replicates. Each year 363 kg of NHnNO 3, 312 indicate the slow rusting characteristic of the cultivars in the kg of P2 0 5 , and 335 kg of K2 0 per hectare were scattered by hand various fertilizer treatments. Analysis of variance was used to help on the appropriate plots before planting, and the field was disced. interpret the AUDPC values in the various treatments. When the Spring wheat (Triticum aestivum L.) cultivars Lee, Marquis, and analysis of variance indicated that the fertilizer treatments had a Thatcher each were planted in 2.4-in-wide strips across each significant effect on rust development, individual fertilizer effects fertilizer plot at the rate of 90 kg of seed per hectare. Planting was were studied by comparing the average AUDPC values from all done during the last week of April or the first week of May, the plots that received the fertilizer with values from all that did not. normal planting time for this area. Weeds were controlled with propachlor ( 2 -chloro-N-isopropylacetanilide) and 2,4-D (2,4RESULTS dichlorophenoxyacetic acid). The entire experimental field was surrounded with a 6. 1-in-wide border of Marquis wheat. There was no statistically significant fertilizer >K cultivar The wheat cultivars were chosen for study because they are interaction in any of the years of the test, which indicates that the susceptible to the races of Puccinia graminis Pers. f.sp. tritici and P. relative susceptibilities of the cultivars to the rusts were not changed recondita Rob. ex Desm. f.sp. tritici studied, but they differ in the by the fertilizer treatments. In 1973, 1974, and 1975 leaf rust developed rate at which they rust: Marquis rusts rapidly with both pathogens, about equally in Marquis and Thatcher, as indicated by the Lee rusts moderately rapidly with both pathogens, and Thatcher nonsignificant average values for AUDPC, but it was significantly less severe in Lee (Table 1). In 1976, 1977, and 1979 stem rust developed about as expected: for Thatcher the average value for _________________________________________ AUDPC was 321 or lower, for Lee it was 640 or lower, and for 0031 -949X/80/09093003/$03.00/0 Marquis it was 890 or lower (Table 1). These differences in the ©The American Phytopathological Society cultivars were statistically significant (P = 0.01l) each year.

The screening for genetic resistance to fusarium head blight (FHB) in wheat has been challenged by the lack of efficacy of various artificial inoculation techniques in disease nurseries. In 2001-2003, we examined the influence of inoculum sources (conidial suspension, infested barley and corn kernels, or infested wheat debris) and inoculation frequency on the development of FHB and the deoxynivalenol (DON) content. The study was conducted on three spring wheat genotypes in a disease nursery of Ottawa, Ontario. The development of FHB was monitored by visually estimating disease severity on a scale of 0 to 9, six times during each growing season. Severity of FHB over time was summarized as the area under the disease-progress curve (AUDPC). Symptoms of FHB were also rated, at a critical developmental stage (soft dough), as critical-time disease severity (DS), percentage of infected spikelets (IS), and FHB index. The percentage of Fusarium-damaged kernels (FDK) and DON content in the wheat kernels were assessed after harvesting. All inoculation treatments had significantly greater AUDPC and DS in 2002, FHB index and IS in 2001 and 2002, and FDK in all three years than the noninoculated control. Regardless of inoculum source, two inoculations produced as much FHB, FDK, and DON as three inoculations. Among the inoculum sources, the conidial suspension or infested kernels yielded significantly greater AUDPC, DS, FHB index, IS, and DON content than the infested debris. Inoculation with conidial suspension resulted in greater FDK than inoculation with infested kernels or infested debris, between which there were no differences. The results of the present study confirm that conidial suspension and infested kernels are equally effective inoculants for FHB nurseries. Infested debris, though a natural source of inoculum, is less effective.

Fusarium head blight (FHB) remains a devastating disease in bread wheat (Triticum aestivum L.). Genetic resistance to FHB is complex; aside from active physiological resistance, plant developmental and morphological traits indirectly affect disease progression and provide a passive resistance mechanism. Here, the relationship between FHB Type II resistance and spike architecture traits was evaluated in a recombinant inbred line (RIL) population of bread wheat in field experiments during two crop seasons under a completely randomized block design with two replications. Point inoculation was carried out at anthesis of each RIL. Disease severity at 21 days post inoculation (dpi), area under the disease progress curve (AUDPC) comprising severity measurements at 12, 17 and 21 dpi, rachis length, spike density, number of spikelets per spike, number of florets per spike and number of florets per spikelet were determined. The population showed significant variation for all traits. Heritability was moderate-high for FHB severity (0.69) and AUDPC (0.63) and high for spike architecture traits (0.74–0.92). FHB severity at 21 dpi and AUDPC were significantly associated with number of florets per spike [r = 0.38 (P < 0.001) and r = 0.31 (P < 0.01) respectively] and with the number of florets per spikelet [r = 0.28 (P < 0.01) and r = 0.27 (P < 0.05) respectively], reflecting a greater spread of the fungus in spikes with higher floret number. These results suggest that the number of florets per spike and per spikelet should be considered in FHB resistance breeding efforts, because selection of lines with higher number of florets could lead to a correlated selection response towards increased FHB levels under field conditions.

Fusarium head blight (FHB) is a fungal disease of wheat (Triticum aestivum.L) that causes yield losses and produces mycotoxins which could easily exceed the limits of the EU regulations. Resistance to FHB has a complex genetic architecture and accurate evaluation in breeding programs is key to selecting resistant varieties. The Area Under the Disease Progress Curve (AUDPC) is one of the commonly metric used as a standard methodology to score FHB. Although efficient, AUDPC requires significant costs in phenotyping to cover the entire disease development pattern. Here, we show that there are more efficient alternatives to AUDPC (angle, growing degree days to reach 50% FHB severity, and FHB maximum variance) that reduce the number of field assessments required and allow for fair comparisons between unbalanced evaluations across trials. Furthermore, we found that the evaluation method that captures the maximum variance in FHB severity across plots is the most optimal approach for scoring FHB. In addition, results obtained on experimental data were validated on a simulated experiment where the disease progress curve was modeled as a sigmoid curve with known parameters and assessment protocols were fully controlled. Results show that alternative metrics tested in this study captured key components of quantitative plant resistance. Moreover, the new metrics could be a starting point for more accurate methods for measuring FHB in the field. For example, the optimal interval for FHB evaluation could be predicted using prior knowledge from historical weather data and FHB scores from previous trials. Finally, the evaluation methods presented in this study can reduce the FHB phenotyping burden in plant breeding with minimal losses on signal detection, resulting in a response variable available to use in data-driven analysis such as genome-wide association studies or genomic selection.

Tan spot (TS), known in Australia as yellow leaf spot, is caused by the fungal pathogen Pyrenophora tritici-repentis, a major foliar disease of wheat. Four experiments were conducted between 2016 and 2017 in two different climatic zones of southeastern Australia to determine the impact of TS on grain yield and quality in six wheat cultivars with different resistance ratings. In each experiment, high and low TS disease scenarios were applied to each cultivar. Disease severity was assessed as either whole-plot percentage leaf area affected (%LAA) or top three leaf (flag to flag-2) %LAA. Whole-plot %LAA was analyzed using both repeated measurements and area under the disease progress curve (AUDPC). For whole-plot %LAA, the repeated measurements identified differences in epidemic progression at key growth stages not identified through AUDPC. Both AUDPC and end-of-season flag to flag-2 %LAA were negatively correlated with grain yield and screenings. Increased rainfall impacting disease development and number of rain days above 5 mm increased TS severity across both climatic zones. Cultivar resistance ratings influenced grain yield loss, with moderately resistant, moderately susceptible, and susceptible cultivars losing up to 6, 18, and 24% grain yield, respectively. High disease significantly increased screenings by up to 1, 3, and 5% for moderately resistant, moderately susceptible, and susceptible cultivars, respectively. This study demonstrated that TS can cause significant grain yield losses in southeastern Australia, and a minimum cultivar rating of moderate resistance to moderate susceptibility was required to prevent severe TS and associated grain yield and quality losses. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Host resistance and fungicide control of leaf rust ( Puccinia hordei) in barley ( Hordeum vulgare) and effects on grain yield and yield components

Fusarium head blight (FHB) or scab of wheat (Triticum aestivum L.) and its associated mycotoxin deoxynivalenol (DON) can cause devastating economic losses. In North America, FHB of wheat is caused mainly by Fusarium graminearum Schwabe [sexual stage Gibberella zeae (Schwein.) Petch]. In this study, the chemotype of 73 single-spore isolates of F. graminearum obtained from wheat kernels collected from 2007 to 2010 from FHB-affected fields and grain elevators in Nebraska was determined to be 15-ADON. Eight selected isolates were evaluated for aggressiveness on spikes and DON production in grain using the FHB-susceptible spring wheat cultivar ‘Wheaton’. Aggressiveness was quantified as disease severity and area under the disease progress curve (AUDPC). Disease severity at 21 days after inoculation ranged from 40.9% to 99.5% and AUDPC ranged from 284%-days to 1279%-days. DON production in grain, measured by enzyme-linked immunosorbent assay (ELISA), ranged from 0.2 to 11.0 µg g−1. Aggressiveness as measured using AUDPC was positively and linearly related to DON production in grain (R2 = 0.98; P < 0.0001). Isolates that produced the most DON were also the most aggressive. These results confirmed previous findings that the predominant F. graminearum chemotype in North America is 15-ADON and suggest that in Nebraska, there are highly aggressive populations of F. graminearum with high DON production capacity that have potential to cause severe losses due to reduction in yield and grain quality. This information will enhance farmers’ preparedness and willingness to apply management measures in years with a high risk for FHB outbreaks and will help researchers better understand FHB.

Effect of helminthosporium leaf blight on performance of timely and late-seeded wheat under optimal and stressed levels of soil fertility and moisture

Effects of cultivar resistances and chemical seed treatments on fusarium head blight and bread wheat yield-related parameters under field condition in southern Ethiopia

Common wheat (Triticum aestivum L.) is the major crop cultivated in Xinjiang and Anhui provinces of China. The climate in these two provinces is favourable for wheat leaf rust (Puccinia triticina) (Pt) infection. Here, we demonstrate a detailed investigation on the leaf rust resistance of 60 major wheat cultivars cultivated in these two regions. A mixture of high virulent Pt races (THTT, THTS, THTQ and PHPS) were used to phenotype all the collected wheat cultivars at an adult plant stage. Phenotypic disease severity (FDS) and the area under the disease progress curve (AUDPC) for each of these wheat cultivars were calculated. Among all the tested wheat cultivars, three cultivars (Xindong20, Xindong 29 and 99AR142-1) with the lowest FDS and AUDPC may carry major resistance genes. Twenty-seven cultivars (45% of the total tested ones) showed a relatively lower resistance with an average of 12.52% FDS and 126.3 AUDPC. Minor resistance or slow rusting genes may be present in this group of cultivars. Molecular markers for leaf rust resistance genes Lr1, Lr9, Lr19, Lr24, Lr26 and Lr34 were further used for the genotypic screening. Lr1, Lr19, Lr26 and Lr34 were detected in 19 (31.7%), 1 (1.7%), 12 (20%) and 6 (10%) wheat cultivars, respectively. Neither Lr9 nor Lr24 could be detected in any of the tested cultivars. These results will greatly improve wheat molecular breeding for leaf rust resistance in these areas.

The inheritance of Fusarium head blight (FHB) resistance was investigated in eight western European wheat lines using a half-diallel of F1 crosses. The parents and F1 crosses were point-inoculated, with a highly aggressive isolate of Fusarium graminearum, in replicated field and glasshouse trials. Type II resistance was assessed by measuring the % FHB spread and % wilted tips. There was a good correlation between the two disease parameters, % FHB spread area under the disease progress curve (AUDPC) and % wilted tips AUDPC (r = 0.86, P < 0.01). Correlation coefficients between the field and glasshouse environments were r = 0.46 (P < 0.01) for % FHB spread AUDPC and r = 0.40 (P < 0.05) for % wilted tips AUDPC. Both general combining ability (GCA) and specific combining ability (SCA) effects influenced the inheritance of FHB resistance, suggesting that in this set of parents both additive and non-additive (dominance or epistatic) effects influence the inheritance of type II FHB resistance. Highly significant GCA-by-environment (P < 0.0001) and SCA-by-environment (P < 0.005) interactions were also observed. Specific combinations of western European wheat varieties were identified with type II FHB resistance at a level equal to or more resistant than the winter wheat variety ‘Arina’.

Thirteen Egyptian wheat cultivars were evaluated and characterized for adult plant resistance to yellow, leaf, and stem rusts. SSR markers linked to yellow, leaf and stem rust resistance genes were validated and subsequently used to identify wheat cultivars containing more than one rust resistance gene. Results of the molecular marker detection indicated that several genes, either alone or in different combinations, were present among the wheat cultivars, including Yr, Yr78 (stripe rust), Lr, Lr70 (leaf rust), Sr. Sr33, SrTA10187, Sr13, and Sr35 (stem rust), and Lr34/Yr18 and Lr49/Yr29 (leaf/stripe rust). The cultivar Sakha-95 was resistant to leaf and stem rusts, and partially resistant to stripe rust; however, this cultivar contained additional rust resistance genes (Lr, Sr and Lr/Yr). The area under the disease progress curve (AUDPC) type for the various wheat cultivars differed depending on the type of rust infection (yellow, leaf, or stem rust, indicated by Yr, Lr, and Sr). The cultivars Gem-12, Sids-14, Giza-171, and Giza-168 had AUDPC types of partial resistance and resistance. All six cultivars, however, contained additional rust resistance genes. Marker-assisted selection can be applied to improve wheat cultivars with efficient gene combinations that would directly support the development of durable resistance in Egypt. Once the expression of the resistance genes targeted in this study have been confirmed by phenotypic screening, the preferable cultivars can be used as donors by Egyptian wheat breeders. The results of this study will help breeders determine the extent of resistance under field conditions when breeding for rust resistance in bread wheat.

Determination of the Fusarium protein equivalent (FPE) levels in kernels for better characterisation of genotypes showing Fusarium head blight (FHB) resistance, and better detection of susceptibility to kernel infection among genotypes with slight symptom expression was carried out. Twelve wheat cultivars and eight hexaploid winter wheat lines derived from a cross of Triticum aestivum with related species T. macha, T. polonicum, and T. dicoccoides were evaluated for levels of spike and kernel infection, the content of the mycotoxin deoxynivalenol (DON) and FPE in kernels after artificial inoculation with the fungus Fusarium culmorum in the field in 2006–2007. The ELISA immunochemical method was employed for the quantitative analyses of DON and FPE. Three wheat lines had a significantly low infection of spikes and kernels compared to cvs Sumai 3 and Nobeoka Bozu, indicating the presence of specific resistance mechanisms to FHB. The significantly low AUDPC (area under the disease progress curve) and the high level of FPE and DON content in kernels indicated a lack of resistance in one wheat line (crossed with T. polonicum). The results showed highly significant correlations (P < 0.01) between FPE and DON content and between FPE and AUDPC. In addition, correlations between FPE and reductions in yield components were also highly significant. Quantification of Fusarium spp. in wheat kernels can be helpful for evaluating wheat genotypes for their levels of resistance to FHB.

Fusarium head blight (FHB) caused by Fusarium spp. is one of the most important fungal diseases of wheat (Triticum aestivum L.) in regions with wet climatic conditions. Improvement of the FHB resistance by developing new varieties requires sound knowledge on the inheritance of resistance. An 8 × 8 diallel analysis was performed to estimate general (GCA) and specific (SCA) combining ability of resistance to FHB. The F1s and parental lines were evaluated under artificial inoculation at the experimental field of IFA-Tulln, Austria during 2001 and 2002. Disease severity was evaluated by repeated scoring of the percentage of infected spikelets and calculating an area under the disease progress curve (AUDPC). The analysis of combining ability across two years showed highly significant GCA and non-significant SCA effects indicating the importance of additive genetic components in controlling FHB resistance. The significant GCA-by-year interaction presented the role of environmental factors in influencing the FHB reaction of wheat lines. The comparison of the crosses with low FHB infection and GCA effects of their parents showed that such crosses involved at least one parent with high or average negative GCA effect. The results revealed that it is feasible to use highly or moderately resistant genotypes and conventional breeding methods to achieve genetic improvement of FHB resistance in spring wheat.