Argentinean Wheat Research Articles

Effect of tolerance to Septoria tritici blotch on grain yield, yield components and grain quality in Argentinean wheat cultivars

Septoria tritici blotch (STB) caused by Zymoseptoria tritici (Mycosphaerella graminicola) is a major disease of wheat worldwide due to significant losses in grain yield and quality. Disease tolerance is the ability to maintain yield performance in the presence of disease symptoms. Therefore, it could be a useful tool in the management of the disease. Although it is known, that there is disease tolerance to STB in some wheat cultivars, this aspect has not been studied among Argentinean cultivars. The aims of this study were to evaluate genotypic differences in tolerance to STB among Argentinean cultivars, considering the relationship between the area under disease progress curve or the green leaf area or the non-green leaf area duration with the grain yield. In addition the effect of the disease on yield, yield components, test weight, grain protein concentration, wet and dry gluten concentration and the influence of tolerance on these traits was investigated. Field experiments were carried out with ten cultivars in a split-split-plot design during 2010 and 2011. Inoculation treatments were the main plots and cultivars, the subplots. STB significantly reduced grain yield, their components, test weight and increase grain protein and gluten concentration. Cultivar Baguette 10 showed major tolerance to STB, indicated by a consistent low regression slope between the green area duration and yield, while Klein Chaja was non-tolerant due to a high regression slope. However, many cultivars such as Buck Brasil, Buck 75 Aniversario, Klein Escorpion and Klein Flecha had considerably similar regression slopes to Baguette 10, provided good levels of tolerance. Other cultivars presented no significant differences. The correlation coefficient between tolerance and grain yield potential was not significant, suggesting that tolerant high-yielding cultivars can be obtained. No relationship was found between quality group or tolerance with the increase in protein and gluten concentration due to STB either.

The uneven and combined development of class forces: migration as combined development

One of the more interesting and potentially powerful developments within Marxist approaches to the field of international relations has been the recent revival of Trotsky’s concept of uneven and combined development (UCD). However, it appears that there have been very few attempts within this literature to specify in concrete terms what is meant by mechanisms of ‘combination’. Failing this, UCD runs the risk of falling into triviality. To this end, this article suggests that migration has historically functioned as a crucial element of combined development, contributing to the uneven incorporation of non-capitalist societies into the remit of a developing world capitalist market. As illustration, I take settler-colonial development and the Great Atlantic Migrations as my focal point, drawing out a comparative study of Argentine and Canadian wheat production in the late nineteenth century. In positing these migrations as mechanisms of combined development I suggest that such were the means by which both European capitalism developed extensively and intensively and New World societies were subjected to the ‘pressures of backwardness’, compelled to transform their own social relations of production.

New sources of resistance to Septoria tritici blotch in wheat seedlings

The resistance of a set of Argentine wheat cultivars, differentials, and foreign lines with known genes of resistance to Zymoseptoria tritici was assessed at the seedling stage against a set of molecularly characterized Argentine fungal isolates under three experimental conditions. The experimental design was a split-split-plot with two replications. The environment conditions were the main plots, the fungal isolates were the subplots and the wheat lines with known resistance genes or used as differential lines or the Argentine commercial cultivars were the sub-subplots. Sixteen fungal isolates were inoculated on 23 wheat accessions including 12 foreign lines with known resistance genes, two differential lines, and nine Argentine cultivars that were selected on the basis of their moderate resistance to natural infection, to identify isolate-specific and partial resistances. The genotypes TE 9111 and Oasis among the foreign lines along with the Argentine cultivars Pro INTA Puntal, Klein Volcan and Buck 75 Aniversario expressed the highest number of specific-resistance interactions. Flame, Tadinia and Kavkaz among the foreign lines showed partial resistances to a higher number of fungal isolates; a comparable resistance pattern was also obtained in the Argentine cultivars Klein Sagitario, Klein Dragon, Don Ernesto and Buck Arriero. Our study demonstrated that the presence of resistance genes in several foreign lines against Septoria tritici blotch is effective against some of the Argentine fungal isolates. In addition, the Argentinean wheat cultivars that showed isolate-specific and nonspecific resistances probably carry novel resistance genes against the pathogen.

Genotypic and environmental effects on starch properties of Argentinean wheat flours

The aim of this study was to determine the influence of different environments and genotypes on starch characteristics and properties of Argentinean wheat flours. Amylose content, starch granule size distribution, thermal characteristics, and pasting properties of flours were determinate on 24 wheat genotypes from six environments. There were significant differences for all parameters analyzed among genotypes and environments (p < 0.05). The environment was the main factor responsible for the increase of variability observed in amylose content. According to variance ratios, environmental conditions have a greater influence on the characteristics of A granules, while genotype influenced mostly B granules diameter and volume percentage. Balcarce‐2010 and Reconquista‐2010, environments which showed drought during grain filling, were the environments that presented the highest volume percent of B granules and the lowest percent of A granule. Genotype was the greatest source of variation, according to variance relationship, for DSC parameters. ΔH values were the highest on MarcosJuarez‐2009 and Reconquista‐2010 where high temperatures during grain filling period were recorded. Besides, these two environments also presented high pasting temperature values. Environment had a noticeable greater impact on starch properties of wheat than genotype for all pasting properties parameters except for pasting temperature. Both genetic and environmental factors control physicochemical characteristics of starch and the size distribution of starch granules in wheat grains at different degrees.

Selection and characterization of Argentine isolates of Trichoderma harzianum for effective biocontrol of Septoria leaf blotch of wheat.

Species of the genus Trichoderma are economically important as biocontrol agents, serving as a potential alternative to chemical control. The applicability of Trichoderma isolates to different ecozones will depend on the behavior of the strains selected from each zone. The present study was undertaken to isolate biocontrol populations of Trichoderma spp. from the Argentine wheat regions and to select and characterize the best strains of Trichoderma harzianum by means of molecular techniques. A total of 84 out of the 240 strains of Trichoderma were able to reduce the disease severity of the leaf blotch of wheat. Thirty-seven strains were selected for the reduction equal to or greater than 50% of the severity, compared with the control. The percentage values of reduction of the pycnidial coverage ranged between 45 and 80%. The same last strains were confirmed as T. harzianum by polymerase chain reaction amplification of internal transcribed spacers, followed by sequencing. Inter-simple sequence repeat was used to examine the genetic variability among isolates. This resulted in a total of 132 bands. Further numerical analysis revealed 19 haplotypes, grouped in three clusters (I, II, III). Shared strains, with different geographical origins and isolated in different years, were observed within each cluster. The origin of the isolates and the genetic group were partially related. All isolates from Paraná were in cluster I, all isolates from Lobería were in cluster II, and all isolates from Pergamino and Santa Fe were in cluster III. Our results suggest that the 37 native strains of T. harzianum are important in biocontrol programs and could be advantageous for the preparation of biopesticides adapted to the agroecological conditions of wheat culture.

Aparición de un aislado estrechamente relacionado con el Maize yellow striate virus en plantas de trigo

En la Argentina, desde 2007 se han observado síntomas similares a virus en campos de trigo, tales como rayas cloróticas, enanismo y amarillamiento. Se tomaron muestras de plantas y hojas sintomáticas de Marcos Juárez (2007) y de Río Cuarto (2008 y 2013), ambas localidades de la provincia de Córdoba. El virus fue transmitido experimentalmente a partir de plantas de trigo sintomáticas a los cultivares Baguette 10 y BIOINTA 3005, utilizando el vector Delphacodes kuscheli Fennah (Delphacidae); los síntomas de rayas cloróticas, enanismo y amarillamiento en los cereales inoculados se reprodujeron a los 10-15 días posinoculación. La presencia de virus se confirmó por microscopía electrónica y RT-PCR usando cebadores degenerados, que amplifican una región conservada del gen de la polimerasa (L) de los rhabdovirus de plantas. La comparación de secuencias mostró 98% de identidad de nucleótidos con el Maize yellow striate virus C. Caroya (JQ715419) aislado de maíz en Argentina. Hasta el momento, este es el primer reporte de la presencia del Maize yellow striate virus en trigo en la Argentina.

Molecular and mycotoxin characterization of Fusarium graminearum isolates obtained from wheat at a single field in Argentina

Fusarium graminearum is the primary causal agent of Fusarium head blight of wheat in Argentina. This disease affects yield losses and quality of grains, reducing the wheat end-use, also causing mycotoxin contamination. In this study, the genetic variability and deoxynivalenol (DON) potential/production of F. graminearum sensu stricto (s.s.) isolates obtained from wheat samples of the 2009, 2010, and 2011 growing seasons from a single location in Argentina were evaluated. The genetic variability detected using inter-simple sequence repeat (ISSR) was analyzed in relation to the in vitro deoxynivalenol production, the main monitored and quantified mycotoxin according to the current regulations for the international marketing of cereals. Of the 68 F. graminearum s.s. isolates obtained in this study, 95 % showed a different banding pattern with ISSR molecular markers and a high variability was detected within the population. However, no clustering was found in relation with year or DON production. All isolates amplify for the DON-related gene and a high variability in DON production was observed among the isolates, with production values between non-producers and 1741 μg/g. The results suggest that the F. graminearum s.s. population varies significantly in both genetic structure and toxin production in a limited sampled area.

Genetic diversity of Fusarium graminearum sensu lato isolates from wheat associated with Fusarium Head Blight in diverse geographic locations of Argentina

Fusarium Head Blight is an important wheat disease in the Argentine Pampas region, being Fusarium graminearum the predominant pathogen. DNA polymorphism of the isolates was analyzed by IGS-RFLP and ISSR. IGS-RFLP and ISSR profiling were carried out using six endonucleases and eight primers, respectively. IGS-RFLP yielded 41 bands, 30 of which were polymorphic while ISSR produced 87 bands with 47 polymorphic bands. Both markers showed genetic variability among the analyzed isolates; however, IGS-RFLP was more efficient than ISSR, showing a higher polymorphic average (59.91%) than the latter (44.11%). The averages of polymorphic information content (PIC) were 0.211 and 0.129, respectively. Twenty haplotypes were identified by IGS-RFLP and 15 haplotypes by ISSR. Genotype clustering within dendrograms was different for both types of markers. The genetic groups obtained by IGS-RFLP showed a partial association to geographic origin. This is the first report on genetic variability of F. graminearum isolates from wheat in Argentina using IGS-RFLP and ISSR markers.

Distribution of races and Tox genes in Pyrenophora tritici-repentis isolates from wheat in Argentina

Fil: Moreno, Maria Virginia. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Agronomia; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina

Two-dimensional environmental profiles of growth and fumonisin production by Fusarium proliferatum on a wheat-based substrate

The effect of water activity (aW; 0.995, 0.99, 0.98, 0.96, 0.94, 0.92, and 0.90), temperature (15, 25, and 30°C), incubation time (7, 14, 21 and 28days), and their interactions on mycelial growth and fumonisin production on wheat-based medium by three Fusarium proliferatum strains isolated from wheat in Argentina was evaluated. Maximum growth rates were obtained at the highest aW (0.995) and 30°C, with growth decreasing as the aW of the medium was reduced. Maximum amounts of total fumonisins (FB1, FB2 and FB3) were produced at 0.99 aW and 25°C after 21 and 28days of incubation for 2 strains, and at 15°C and 0.98 aW after 28days of incubation for the third strain. The fumonisin concentrations varied considerably depending on the aW and temperature interactions assayed. The studied strains had different fumonisin production profiles. F. proliferatum ITEM 15661 and ITEM 15664 produced FB1 and FB2 whereas F. proliferatum ITEM 15654 was able to produce FB1, FB2 and FB3. Interestingly, fumonisin production profiles for each particular strain were related to incubation temperatures. Fumonisins were produced from 15 to 30°C and at aW values of 0.92 to 0.995 after 21 to 28days of incubation. However at 7 and 14days of incubation small amounts of fumonisin were produced at aW lower than 0.94. Two-dimensional profiles of aW by temperature interactions were developed from these data to identify areas where conditions indicate a significant risk from fumonisin accumulation on wheat. Temperature and aW conditions that resulted in fumonisin production are those found during wheat grain development (especially milk and dough stages) in the field. This study provides useful base line data on conditions representing a high and a low risk for contamination of wheat by fumonisins which is becoming of greater concern because this cereal is destined mainly for human consumption.

Fine mapping of LrSV2, a race-specific adult plant leaf rust resistance gene on wheat chromosome 3BS

Fine mapping permits the precise positioning of genes within chromosomes, prerequisite for positional cloning that will allow its rational use and the study of the underlying molecular action mechanism. Three leaf rust resistance genes were identified in the durable leaf rust resistant Argentinean wheat variety Sinvalocho MA: the seedling resistance gene Lr3 on distal 6BL and two adult plant resistance genes, LrSV1 and LrSV2, on chromosomes 2DS and 3BS, respectively. To develop a high-resolution genetic map for LrSV2, 10 markers were genotyped on 343 F2 individuals from a cross between Sinvalocho MA and Gama6. The closest co-dominant markers on both sides of the gene (3 microsatellites and 2 STMs) were analyzed on 965 additional F2s from the same cross. Microsatellite marker cfb5010 cosegregated with LrSV2 whereas flanking markers were found at 1cM distal and at 0.3cM proximal to the gene. SSR markers designed from the sequences of cv Chinese Spring BAC clones spanning the LrSV2 genetic interval were tested on the recombinants, allowing the identification of microsatellite swm13 at 0.15cM distal to LrSV2. This delimited an interval of 0.45cM around the gene flanked by the SSR markers swm13 and gwm533 at the subtelomeric end of chromosome 3BS.

Effect of Vrn-1, Ppd-1 genes and earliness per se on heading time in Argentinean bread wheat cultivars

Predicting phenology, in particular heading time, is crucial to avoid and/or minimize risk of damage of frost, drought and high temperatures during grain filling. Although some of the major genes controlling development, associated with photoperiod and vernalization responses, were identified, the association between the molecular characterization of those genes and photoperiod sensitivity, vernalization responses and earliness per se has been poorly studied. The present study was conducted to determine the effects of photoperiod and vernalization genes (and their allelic combination characterized by molecular approach) on heading time and its correlation with the phenological parameters determined by field experiments in a wide range of Argentine bread wheat commercial cultivars. Additionally, the association between photoperiod and vernalization responses with earliness per se was analyzed. Molecular characterization showed that most of the commercial Argentine wheat cultivars available in the market correspond to spring growth habit with dominant insensitive photoperiod alleles (SI) followed by spring habit sensitive to photoperiod (SS), while winter insensitive (WI) habit represented a minority group. All genotypes included in the present study (even those classified as SI and WI) were photoperiod sensitive when that trait was quantified from a physiological analysis as the slope of the relationship between duration of a particular phase and mean photoperiod sensed during the period between emergence and heading. SI showed lower photoperiod sensitivity than SS and WI, without clear differences between both later groups. In all cases, photoperiod sensitivity was the main attribute that determined the differences in time to heading even when vernalization requirements were not completely fulfilled in the WI. The genotypes with different photoperiod and vernalization allele combinations showed a wide range of duration of earliness per se. However, differences in earliness per se did not show any particular association with the groups classified by molecular markers for photoperiod and vernalization. The information included in the present study can be used to build a gene-based model for predicting phenology. However, the variations in photoperiod and/or vernalization sensitivity within the same allelic combination could still determine mismatching in the prediction of the models based on Ppd-1 and Vrn-1 genes.

Temperature and water stress impacts on growth and production of altertoxin-II by strains ofAlternaria tenuissima from Argentinean wheat

Alternaria tenuissima is commonly isolated from wheat in Argentina. The objective of this study was to examine the effects of temperature (15-34 °C) and water activity (0.98, 0.95 aw) on growth and temporal altertoxin II (ALTX-II) production by two strains over 14-21 days on a milled wheat agar. It was shown that growth occurred over the whole temperature range tested and was optimum at 25-30 °C and 0.98 aw, and 30 °C at 0.95 aw. The incubation time did not show any significant effect on ALTX-II accumulation. The optimum conditions for ALTX-II production were 0.98 aw and 30 °C for both strains. The strains also accumulated significant amounts of this toxin at 34 °C. This is the first study to evaluate the ecology of growth and production of ALTX-II by strains ofA. tenuissima.

Elemental and Isotopic Fingerprint of Argentinean Wheat. Matching Soil, Water, and Crop Composition to Differentiate Provenance

The aim of this study was to investigate if elemental and isotopic signatures of Argentinean wheat can be used to develop a reliable fingerprint to assess its geographical provenance. For this pilot study we used wheat cultivated at three different regions (Buenos Aires, Córdoba, and Entre Ríos), together with matching soil and water. Elemental composition was determined by ICP-MS. δ(13)C and δ(15)N were measured by isotopic ratio mass spectrometry, while (87)Sr/(86)Sr ratio was determined using thermal ionization mass spectrometry. Wheat samples from three sampling sites were differentiated by the combination of 11 key variables (K/Rb, Ca/Sr, Ba, (87)Sr/(86)Sr, Co, Mo, Zn, Mn, Eu, δ(13)C, and Na), demonstrating differences among the three studied regions. The application of generalized Procrustes analysis showed 99.2% consensus between cultivation soil, irrigation water, and wheat samples, in addition to clear differences between studied areas. Furthermore, canonical correlation analysis showed significant correlation between the elemental and isotopic profiles of wheat and those corresponding to both soil and water (r(2) = 0.97, p < 0.001 and r(2) = 0.96, p < 0.001, respectively). To our knowledge, this is the first report demonstrating the correspondence between soil, water, and wheat samples using different statistical methods, showing that wheat elemental and isotopic compositions are mainly related to soil and irrigation water characteristics of the site of growth.

Mycoflora study in a wheat flour mill of Argentina

The mycoflora of the environment: wheat conditioning, milling and screening, and filling zone, as well as, raw material -wheat-, intermediate product -grits- and end product -flour- on day 1, and after cleaning improvements -days 45 and 90- were studied in an Argentine wheat mill. Samples were incubated at 28°C for 5-7 days on Malt Extract Agar with chloramphenicol (100 mg L-1) and the results were expressed in colony forming units per cubic meter of air (CFU m-3) or per gram of sample (CFU g-1), respectively. Fungal genera and species were isolated and identified and the potential toxicogenic capacity of the Aspergillus flavus and Fusarium graminearum isolated was studied. Time-Place and Time-Product multifactorial ANOVA were carried out. After cleaning improvements, CFU m-3 of air decreased as a function of time. Cladosporium and Alternaria were abundant in every zone, Aspergillus predominated in the wheat conditioning zone and Penicillium and Eurotium decreased with time. Wheat was more contaminated than grits and flour; Aspergillus, Eurotium and Mucoraceae family were the most abundant. Deoxynivalenol was above the levels allowed in wheat, being acceptable in grits and flour. Aflatoxin and Zearalenone showed acceptable levels. When studied in vitro, 53% of Aspergillus flavus and 100% of Fusarium graminearum isolates, produced Total Aflatoxins, and Deoxynivalenol and Zearalenone, respectively.

Wheat Varietal Flours: Influence of Pectin and DATEM on Dough and Bread Quality

The effect of two additives, high methoxyl pectin (P) and the emulsifier diacetyl tartaric acid esters of monoglycerides commonly named DATEM (D) and their mixture (P+D) on dough properties and baking performance of two varietal Argentinean wheat flours (‘Buck Pronto’ [BP]; ‘Klein Escudo’ [KE] was analyzed. Rheological characterization of dough (alveogram, farinograms, texture profile analysis-TPA, and rheometric assays), with and without additives, was performed. SEM was used to evaluate the microstructure of dough. Baking performance was analysed by bread volume measurements, shape ratio of loaves (width/height), and the hardness of crumb and crust. Assays on dough showed differences in alveographic force (W) and in most of the texture profile analysis parameters. Assays on bread showed that BP specific volume was improved with the addition of P and P+D, but shape ratio was only improved with the mixture of P+D. Breads from KE flour with additives presented, in all cases, showed higher volumes and a better shape ratio than those obtained with the control sample. Hardness of KE crumb was diminished by all additives but BP crumb was softened only with the addition of P and P+D. All sensory parameters were improved for both types of bread, particularly with D and P+D.

Effects of the Gpc‐B1 locus on high grain protein content introgressed into Argentinean wheat germplasm

AbstractWheat grain protein content (GPC) is important for human nutrition and has a strong influence on the quality of pasta and bread. The objective of this study was to analyse the introduction of the Gpc‐B1 allele into two Argentinean bread wheat cultivars. Near‐isogenic lines were developed in ‘ProINTA Oasis’ and ‘ProINTA Granar’ using marker‐assisted selection. Gpc‐B1 lines showed a significant (P = 0.01) increase in GPC and a significant (P = 0.001) decrease in grain weight in comparison with control lines without Gpc‐B1. Differences in yield were not significant (P = 0.49) between lines. Gpc‐B1 lines significantly reduced (P = 0.02) straw nitrogen concentration at maturity and significantly increased (P = 0.02) the nitrogen harvest index. When data were analysed by genotype and environment, differences in some analysed parameters were found, indicating that Gpc‐B1 expression may be affected by different genetic backgrounds and environmental conditions. These results suggest that the introgression of the Gpc‐B1 allele into Argentinean wheat germplasm could be a valuable resource for improving GPC with no detrimental effect on grain yield.

Genetic analysis and comparative virulence of isolates of Pyrenophora tritici-repentis from wheat in Argentina

Tan spot caused by the fungus Pyrenophora tritici-repentis, occurs in many wheat-growing regions worldwide and is considered among the major diseases of wheat in Argentina. In nature, this pathogen reproduces both sexually and asexually, but the extent of genetic variability in the P. tritici-repentis Argentinian population is unknown. The genetic structure of P. tritici-repentis populations was assessed with amplified polymorphic markers with sequence data from the internal transcribed spacer region of the ribosomal deoxyribonucleic acid (DNA) (ITS) analysis. Eighty-nine (89) P. tritici-repentis isolates were collected from 14 geographically distinct regions of the wheat-growing areas in Argentina. Clustered analysis of random amplified polymorphic DNAs (RAPDs) showed seven different groups of isolates at 43% similarity. Analyses of the ITS1 and ITS4 primers grouped the isolates in fifteen separated clusters and resulted in a sensible method by providing valuable information on the genotypic diversity detected in the populations. Additionally, diversity was assayed by analysis of severity and type of symptoms reaction indicating significant differences between cultivars and isolates. The utility of cleaved amplified polymorphic sequence analysis for molecular differentiation of pathotypes was demonstrated. It appears that the P. tritici-repentis population in Argentina is fairly diverse, and caution should be taken in any breeding strategy, since rare pathotypes may quickly become predominant if susceptible host genotypes are continuously grown. Key words: Tan spot, Pyrenophora tritici-repentis, wheat, genetic diversity, virulence.

Mycoflora study in a wheat flour mill of Argentina.

The mycoflora of the environment: wheat conditioning, milling and screening, and filling zone, as well as, raw material -wheat-, intermediate product -grits- and end product -flour- on day 1, and after cleaning improvements -days 45 and 90- were studied in an Argentine wheat mill. Samples were incubated at 28°C for 5–7 days on Malt Extract Agar with chloramphenicol (100 mg L-1) and the results were expressed in colony forming units per cubic meter of air (CFU m-3) or per gram of sample (CFU g-1), respectively. Fungal genera and species were isolated and identified and the potential toxicogenic capacity of the Aspergillus flavus and Fusarium graminearum isolated was studied. Time-Place and Time-Product multifactorial ANOVA were carried out. After cleaning improvements, CFU m-3 of air decreased as a function of time. Cladosporium and Alternaria were abundant in every zone, Aspergillus predominated in the wheat conditioning zone and Penicillium and Eurotium decreased with time. Wheat was more contaminated than grits and flour; Aspergillus, Eurotium and Mucoraceae family were the most abundant. Deoxynivalenol was above the levels allowed in wheat, being acceptable in grits and flour. Aflatoxin and Zearalenone showed acceptable levels. When studied in vitro, 53% of Aspergillus flavus and 100% of Fusarium graminearum isolates, produced Total Aflatoxins, and Deoxynivalenol and Zearalenone, respectively.

Integrated Foliar Disease Management to Prevent Yield Loss in Argentinian Wheat Production

Zero tillage often leads to wheat (Triticum aestivum L.) yield losses from diseases caused by necrotrophic foliar pathogens. The aim of this work was to evaluate the combined effect of tillage, N fertilization, fungicides, and resistant cultivars in reducing foliar disease severity to prevent significant yield losses. A 2‐yr study including combinations of (i) conventional and zero tillage; (ii) N fertilization rates 0, 80, or 160 kg ha−1 N; (iii) two fungicide treatments (with and without a fungicide (1 L of metconazole, 9%) at growth stages (GS) 32 and 39; and (iv) three wheat cultivars was conducted in the Rolling Pampas region in Argentina. The most common foliar disease in the trial was tan spot [Pyrenophora tritici‐repentis (Died.) Drechs.]. Conventional tillage reduced foliar disease severity at GS 23 by 46 and 56% and the area under disease progress curve (AUDPC) by 20 and 14% for each season, respectively compared with zero tillage. The cultivar Buck Bigua had significantly lower AUDPC values than the others. Fungicide and N application reduced disease severity at GS 23 by 35 and 34% respectively, on average over both years. Disease was less severe in zero tillage plots which received a fungicide compared to conventional tillage plots that were not treated with fungicide. In 2002 yields were greater in conventional tillage plots with 160 kg ha−1 N and fungicide application than in all other treatments. In 2003 yields were greatest in zero tillage plots with 160 kg ha−1 N and fungicide. The results of this study indicate that in spite of the increase of necrotrophic diseases, developing no‐till systems in wheat monoculture is possible without significant yield losses if effective disease management practices are applied.