Net Blotch Severity Research Articles

Cultivar Mixtures as Part of Integrated Protection of Winter Barley from Leaf Diseases and Abiotic Stresses

Background: Currently, cultivar mixtures are being extensively used in agriculture worldwide. The current research study aimed to identify the optimal proportion of cultivars with different resistance to pathogens to reduce the severity of leaf diseases in mixed cultivars against net blotch and leaf rust of barley.Methods: Leaf rust severity was assessed using a modified Cobb scale, and net blotch severity with the E. E. Geshele scale. Disease severity was averaged from triplicate measurements on 25–30 plants. After harvest, 1000 seeds per plot were weighed. Differences were evaluated using the Fisher test (α = 0.05), and correlations via the Chaddock scale in Statistica 13.3.Results: A high degree of inverse correlation was established between the proportion of resistant cultivars and the severity by both diseases r= – 0.93/– 0.99. The optimal mixture combination of a resistant and susceptible cultivar against net blotch was recorded as 1S:4R, and leaf rust as 1S:3R and 1S:4R.Conclusion: In mixed barley crops, a strong inverse correlation was found between the proportion of resistant cultivars and disease severity (r = –0.93/–0.99). Disease severity correlated directly with humidity and temperature in spring, with an inverse correlation for net blotch in June. Using mixed cultivars enhances crop resistance to abiotic and biotic stresses, making it suitable for eco-friendly farming.Keywords: Abiotic factors; Barley; Mixture of cultivars; Puccinia hordei; Pyrenophora teres

Linear Discriminant Analysis for Predicting Net Blotch Severity in Spring Barley with Meteorological Data in Finland

Predictive information on plant diseases could help to reduce and optimize the usage of pesticides in agriculture. This research presents classification procedures with linear discriminant analysis to predict three possible severity levels of net blotch in spring barley in Finland. The weather data utilized for classification included mathematical transformations, namely features of outdoor temperature and air humidity with calculated dew point temperature values. Historical field observations of net blotch density were utilized as a target class for the identification of classifiers. The performance of classifiers was analyzed in sliding data windows of two weeks with selected, cumulative, summed feature values. According to classification results from 36 yearly data sets, the prediction of net blotch occurrence in spring barley in Finland can be considered as a linearly separable classification task. Furthermore, this can be achieved with linear discriminant analysis by combining the output probabilities of separate binary classifiers identified for each severity level of net blotch disease. In this case, perfect classification with a resolution of three different net blotch severity levels was achieved during the first 50 days from the beginning of the growing season. This strongly suggests that real-time classification based on a few weather variables measured on a daily basis can be applied to estimate the severity of net blotch in advance. This allows application of the principles of integrated pest management (IPM) and usage of pesticides only when there is a proven need.

The Combination of Low-Cost, Red-Green-Blue (RGB) Image Analysis and Machine Learning to Screen for Barley Plant Resistance to Net Blotch.

Challenges of climate change and growth population are exacerbated by noticeable environmental changes, which can increase the range of plant diseases, for instance, net blotch (NB), a foliar disease which significantly decreases barley (Hordeum vulgare L.) grain yield and quality. A resistant germplasm is usually identified through visual observation and the scoring of disease symptoms; however, this is subjective and time-consuming. Thus, automated, non-destructive, and low-cost disease-scoring approaches are highly relevant to barley breeding. This study presents a novel screening method for evaluating NB severity in barley. The proposed method uses an automated RGB imaging system, together with machine learning, to evaluate different symptoms and the severity of NB. The study was performed on three barley cultivars with distinct levels of resistance to NB (resistant, moderately resistant, and susceptible). The tested approach showed mean precision of 99% for various categories of NB severity (chlorotic, necrotic, and fungal lesions, along with leaf tip necrosis). The results demonstrate that the proposed method could be effective in assessing NB from barley leaves and specifying the level of NB severity; this type of information could be pivotal to precise selection for NB resistance in barley breeding.

Agronomic Performance of Heterogeneous Spring Barley Populations Compared with Mixtures of Their Parents and Homogeneous Varieties

Diversity within a crop of self-pollinating species can provide advantages in sustainable farming, including the ability to adapt to environments. However, few results proving the benefits in various species and climatic conditions are available. Our aim was to find the differences between heterogeneous and homogeneous materials and determine if crossing has advantage over mixing. We compared essential traits of twelve heterogeneous spring barley composite cross populations (CCPs) to those of seven mixtures representing similar genetic backgrounds and five homogeneous varieties in nine organic and three conventional environments over the course of three years. We found significant advantages for heterogeneous materials, particularly CCPs, for yield in organic and stress environments as well as yield stability, N utilisation efficiency, protein content, 1000-grain weight, and net blotch severity and observed positive trends for N uptake efficiency and weed competitiveness. CCPs’ advantages over mixtures were for protein content and 1000-grain weight, a nonsignificant yield gain in low-yield and stress environments, higher yield stability, and minor positive trends for net blotch, NUE, and weed competitiveness. We suggest heterogeneous populations as valuable alternatives to uniform varieties for organic and poor cultivation environments. Although multi-component mixtures could provide a performance similar to CCPs, considering the adaptation potential, populations would be more advantageous overall.

Correction to: Pyrenophora teres growth and severity of net blotch on barley under salt stress

Correction to: Pyrenophora teres growth and severity of net blotch on barley under salt stress

Gene expression and metabolite analysis in barley inoculated with net blotch fungus and plant growth-promoting rhizobacteria

Net blotch, caused by the ascomycete Drechslera teres, can compromise barley production. Beneficial bacteria strains are of substantial interest as biological agents for plant protection in agriculture. Belonging to the genus Paraburkholderia, a bacterium, referred to as strain B25, has been identified as protective for barley against net blotch. The strain Paraburkholderia phytofirmans (strain PsJN), which has no effect on the pathogen's growth, has been used as control. In this study, the expression of target genes involved in cell wall-related processes, defense responses, carbohydrate and phenylpropanoid pathways was studied under various conditions (with or without pathogen and/or with or without bacterial strains) at different time-points (0-6-12-48 h). The results show that specific genes were subjected to a circadian regulation and that the expression of most of them increased in barley infected with D. teres and/or bacterized with the strain PsJN. On the contrary, a decreased gene expression was observed in the presence of strain B25. To complement and enrich the gene expression analysis, untargeted metabolomics was carried out on the same samples. The data obtained show an increase in the production of lipid compounds in barley in the presence of the pathogen. In addition, the presence of strain B25 leads to a decrease in the production of defense compounds in this crop. The results contribute to advance the knowledge on the mechanisms occurring at the onset of D. teres infection and in the presence of a biocontrol agent limiting the severity of net blotch in barley.

Pyrenophora teres growth and severity of net blotch on barley under salt stress

Pyrenophora teres growth and severity of net blotch on barley under salt stress

Impact of protein hydrolysate biostimulants on growth of barley and wheat and their interaction with symbionts and pathogens

We compared the biostimulant effect of a novel chicken feather hydrolysate (FH) and a reference protein hydrolysate (RH) on barley and wheat in a pot experiment. Their interactions with arbuscular mycorrhizal fungi (AMF) and phosphorus (P) supply were also addressed. All experimental factors influenced barley growth. Shoot height and biomass of barley were increased by FH and reduced by RH. AMF decreased barley biomass at high P-supply. In wheat, the biomass was slightly reduced by AMF while other factors had no significant effect. In the parallel field experiment, RH but not FH increased yield and grain size of barley, while there was no significant effect of either hydrolysate on wheat. Application time had no effect on hydrolysate efficacy. Both hydrolysates promoted severity of net blotch (Pyrenophora teres maculata) on barley in the pot experiment, but reduced it in field. FH promoted wheat root colonisation by AMF under low-P supply. Our results show limited transferability of pot results to field conditions and manifest complex interactions between hydrolysates, soil phosphorus, and plant symbionts and pathogens.

Advanced Data Analysis as a Tool for Net Blotch Density Estimation in Spring Barley

A novel data analysis method for the evaluation of plant disease risk that utilizes weather information is presented in this paper. This research considers two different datasets: open weather data from the Finnish Meteorological Institute and long-term (1991–2017) plant disease severity observations in different hardiness zones in Finland. Historical net blotch severity data on spring barley were collected from official variety trials carried out by the Natural Resources Institute Finland (Luke) and the analysis was performed with existing data without additional measurements. Feature generation was used to combine different datasets and to enrich the information content of the data. The t-test was applied to validate features and select the most suitable one for the identification of datasets with high net blotch risk. Based on the analysis, the selected daily measured variables for the estimation of net blotch density were the average temperature, minimum temperature, and rainfall. The results strongly indicate that thorough data analysis and feature generation methods enable new tools for plant disease prediction. This is crucial when predicting the disease risk and optimizing the use of pesticides in modern agriculture. Here, the developed system resolves the correlation between weather measurements and net blotch observations in a novel way.

Effects of Net Blotch (<i>Pyrenophora teres</i>) on Malt Barley Yield and Grain Quality at Holeta, Central Ethiopia

arley (Hordeum vulgare L.) production is constrained by diseases such as net blotch caused by Pyrenophora teres Drechsl. The objectives of this study were to assess the effects of net blotch disease on malt barley yield and grain quality under natural infection. Four malt barley varieties (Beka, HB 120, HB 52 and Holker), three fungicide (propiconazole) spray intervals (at 7, 14 and 21 day) and no spray control were arranged in a randomized complete block design in four replications. The experiment was conducted at Holeta Agricultural Research Center, Ethiopia in the summer of 2005, on a plot of 12 m2 for each treatment. Disease incidence and severity, yield and grain quality parameters were measured and analyzed. The results indicated a significant (P< 0.05) difference in disease incidence and percentage severity index at 107 days after planting and for the Area under the Disease Progress Curve among spray intervals and the varieties. Variation in yield and yield components were indicated among the varieties. Relative yield losses of 7.711.5% occurred in Beka and 15.321.2% in HB 120. The hectoliter weight (HLW) for both the varieties and the spray intervals ranged from 63.5 to 66.8 kg and were significantly different among the spray intervals and the varieties. The varieties had thousand-kernel weight (TKW) in the range of 32.5 to 46.4 g. Net blotch severity reduced yield and TKW in Beka and HB 120. However, in other grain quality factors analyzed, significant variations were observed only mong the varieties. On slotted sieve screens (mm): 2.8, 2.5, 2.8 + 2.5, 2.2 and < 2.2 the % grain mass retained ranged from 30.647.3, 40.650.6, 74.792.3, 6.618.8 and 1.05.7, respectively. The grain protein content (GPC) of the varieties ranged from 8.49.5%. The germination- capacity varied from 99.1 to 99.8% and germination energy from 98.5 to 99.4%. The study showed that the grain plumpness, GPC and germination characteristics of the varieties meet the malt and brewery industry requirements. However, HB 120 and HB 52 appeared superior to Beka and Holker.

Interaction of net blotch and scald on barley

Net blotch caused by Pyrenophora teres f. sp. teres and scald caused by Rhynchosporium secalis are major foliar diseases of barley (Hordeum vulgare) and often occur together in the same fields in central Alberta, Canada. The differential development of these two diseases in relation to seeding date was investigated in five field trials in 2001 and 2003 under natural infection conditions. Significantly higher scald severity on barley was observed in all trials with early seeding (from early to mid May) as compared with late seeding (from late May to early June). Scald severity tended to be higher than net blotch severity in the early seeding date trials, whereas net blotch severity was generally higher than scald severity with late seeding. The differential development of disease severity between net blotch and scald was likely affected by temperature, host resistance, and natural inoculum. The interaction of the development of P. teres and R. secalis on barley ‘Harrington’ was investigated in artificially inoculated field plots in 1993 and 1995. In 1995, a mixture of both inocula induced a greater area under the disease progress curve (AUDPC) and caused a greater grain yield reduction than either inoculum alone in both seasons. No difference in grain yield was observed among plots in which P. teres or R. secalis were inoculated separately for either season. The disease progression and yield reductions observed in the present study indicate an additive effect as a result of the interaction between the two pathogens attacking the same plant. Early seeding of scald susceptible barley cultivars should be avoided in scald-infested fields in central Alberta. Scald susceptible cultivars may be seeded late for swath grazing of barley to escape scald infection.

Cultivar rotation as a strategy to reduce leaf diseases under barley monoculture

A 3-year experiment was established in 1998 to determine whether barley cultivar rotation could be used to reduce the impact of leaf diseases while maintaining crop productivity. Treatments consisted of various sequences of two cultivars with varying degrees of scald and net blotch resistance, 'Kasota', and 'AC Lacombe'; a previously scald-resistant cultivar 'CDC Earl'; a susceptible check, 'Harrington'; and a nonhost, triticale, cultivar 'Wapiti'. In 1998, significant differences in scald severity occurred among the barley cultivars tested. In 1999, significant rotation differences occurred for scald and net blotch severity as well as for PCR-based assay results for scald infection of grain. In general, disease severity was highest and yield was lowest when a barley cultivar was grown on its own residue, especially for cultivars other than 'Kasota'. Contrasts indicated that yield and kernel weight were lower, while scald and net blotch levels and PCR-based assay results were higher, for barley cultivar monoculture than for barley cultivar rotation. In 2000, when a barley cultivar was grown on its own residue, scald severity was usually higher compared with barley cultivar rotation. A similar trend was also observed for net blotch, except for the cultivars 'Kasota' and 'CDC Earl'. Poor stand establishment in some plots precluded the detection of yield differences among some treatments in 2000. Contrasts for 2000 indicated that higher levels of scald and net blotch, and decreased kernel and test weights, occurred for barley cultivar monoculture compared with barley cultivar rotation. In both 1999 and 2000, barley planted on triticale residue generally had higher yield, higher kernel weight and test weight, and lower disease levels compared with barley planted on barley residue. Barley cultivar rotation can be used as a short-term strategy to help reduce leaf disease levels and maintain crop productivity for Alberta barley producers, when rotational options are limited because of livestock feed requirements or market factors. However, long-term sustainable leaf disease management likely would require the introduction of rotations with alternative crops such as triticale, or the implementation of other methods of adding diversity, to cropping systems focused on the intensive production of livestock feed.

Effects of aldicarb and fungicides on Pratylenchus penetrans populations, root rot and net blotch severity on barley

Population levels of the root lesion nematode, Pratylenchus penetrans, which produces necrotic lesions in the root cortex, were recorded in barley (Hordeum vulgare) in experimental plots during 1988, 1989, and 1990. Root lesion nematodes were the onlyendoparasitic nematodes recovered from barley roots and were the dominant nematode group found in the soil. Based on 3-yr averages, root rot ratings, caused primarily by Cochliobolussativusand Fusarium spp., increased from 27% at Zadoks Growth Stage (ZGS) 30-32 in July to 73 % at ZGS 70-72 in late August and early September. Net blotch (incited by Pyrenophora teres) was suppressed by a fungicide treatment consisting of a seed application of carbathiin and thiram, and a foliar application of propiconazole. Aldicarb suppressed the populations of root lesion nematodes in the soil, in the total root System, and in crown and seminal roots of barley. Yields were increased by ca 30% where aldicarb and fungicides were applied as a combined treatment. Population densities of root lesion nematodes were much greater in seminal roots than in crown roots at ZGS 30-32 and 55-60. Correlation coefficients between nematodes and yield data were often negative and significant (P≤0.05). There were no consistent trends in the numerical relationships between numbers of root lesion nematodes in roots or soil, and incidences of net blotch or root rot of barley.

Impact of seedbed utilization and fungicide application on severity of net blotch [Pyrenophora teres] and production of barley

Limited information is available regarding the impact of seed placement and row spacing, and their interaction with fungicides, on leaf diseases and agronomic performance of barley. A direct-seeding field experiment was conducted at three locations in Canada (Lacombe and Beaverlodge (Alberta) and Melfort (Saskatchewan)), in 1999–2000, to evaluate the effect of three seedbed utilization treatments and six foliar fungicide timing and rate treatments on disease severity and production characteristics of barley. Seedbed treatments included row spacing at 23 or 30 cm with a knife opener, or spread bands with a 28-cm sweep and a 23-cm row spacing. Fungicide treatments included full and split applications of propiconazole at Zadoks growth stages (GS) 12, 37, and 58 with an untreated control. Severity of net blotch [Pyrenophora teres] was higher for the 23- and 30-cm distinct row spacings compared with the spread-band placement using sweeps. The interaction between seed placement and fungicide application was not significant for net-blotch severity, indicating that disease response to fungicide did not vary with seed-placement configuration. Overall, grain yield was affected by seed placement, with the spread band having slightly higher yield, especially when compared with the 30-cm distinct row spacing, but the response to seed placement did vary over year × location combinations, and with fungicide treatment. Kernel weight, plumpness, and test weight were greatest for the spread-band placement, although this response varied among year × location combinations. Fungicide applications at late growth stages (GS 37 and GS 58) reduced net-blotch severity and increased grain yield and kernel quality, whereas applications at GS 12 generally had a limited impact. Planting in distinct rows may have resulted in higher disease severity and lower kernel weight, plumpness, and test weight by facilitating spore dispersal and subsequent net-blotch development compared with the spread-band placement.

Sensitivity of Resistance to Net Blotch in Barley

The aim of this study was to demonstrate various methods of analysing terminal net blotch, Pyrenophora teres Drechs. f. teres Smedeg., severity data from 15 spring barleys, Hordeum vulgare L., grown in Finnish official variety trials in five environments. The analyses have been developed and used principally by plant breeders for assessing crop yield, but lend themselves to use by plant pathologists. Pyrenophora teres is the major barley phytopathogen in Finland and improved resistance to it is sought. Joint regression analysis (JRA) and an additive main effects and multiplicative interaction (AMMI) model were used to investigate the data. Statistically significant genotype by environment (GE) interaction for resistance was indicated, and this included qualitative (crossover) interactions among genotypes over environments. A stable, non‐sensitive, response to net blotch over environments, combined with a low mean score for terminal severity of the disease characterized the six‐row barley ‘Thule’ which showed statistically significant crossover interaction only with ‘Tyra’. ‘Kustaa’ exhibited the lowest mean terminal net blotch severity, but was relatively sensitive to net blotch. ‘Arve’ exhibited severe terminal net blotch in all environments, was relatively sensitive to environment and exhibited no crossover interaction with other genotypes. AMMI analysis appeared to represent a useful method for analysing these disease severity data, facilitating the selection of useful sources of resistance. Plots of AMMI‐adjusted mean net blotch severities against first principal component axis (PCA) scores were informative for differentiating genotype response over environments, and are therefore potentially useful to plant pathologists and barley breeders seeking to gauge and subsequently improve the resistance status of barley to net blotch.

Grain yield, net blotch and scald of barley in Finnish official variety trials

Data on grain yield, and terminal severity of net blotch (Pyrenophora teres f. teres) and scald (Rhynchosporium secalis) from Finnish official barley (Hordeum vulgare) variety trials were analysed to indicate the pattern of disease incidence over six years and five sites for nineteen barley genotypes, and the effect of the diseases on yield and the genotype by environment interaction for yield. The effect of climatic factors on net blotch severity were also investigated. The genotype by site interaction for net blotch severity was not statistically significant, but that for yield was. Net blotch severity differed between years, but was similar across sites and there were statistically significant first order interactions between year, site and genotype. ‘Saana’ and ‘Thule’ had relatively low mean terminal net blotch scores and their reaction to the disease was less sensitive to the environment than was that of ‘Tyra’ for example. Analysis of yield data adjusted for net blotch severity indicated that the magnitude of the genotype by environment interaction terms were not accounted for to any significant degree by differences in relative net blotch resistances among the barley genotypes. Overall, mean scores for scald severity were lower than those for net blotch. Terminal net blotch severity was correlated with May rainfall and growing degree days.

Assessment of Western Canadian Barleys of Historical Interest: I. Yield and Agronomic Traits

Changes in yield components and agronomic traits may contribute to historical yield advances. The purpose of this study was to determine the yield advances that have been made in spring barley (Hordeum vulgare L.) cultivars released in western Canada from 1910 to 1987 and to evaluate the contribution of yield components and agronomic traits to yield advancement. An important goal was to determine the value of individual traits to an ideotype of barley for the western Canadian prairies. Twenty cultivars of both six‐ and two‐rowed types were tested at Botha, Lacombe and Olds, Alberta, Canada, in 1989 and 1990. Grain yields increased by 12.7 to 41.4 kg ha−1 yr−1 with the greater responses being in the more favourable environments. This increase in grain yield was associated with increased harvest indices of 0.08 to 0.17% per year. Lodging decreased by 0.01 to 0.05 points per year (0–10 scale). Seed protein content decreased by 0.01 to 0.02 g kg−1 yr−1. Test weights responded positively to year of release in the 1990 tests at Botha and Olds. Spike number per square meter and net blotch severity were associated with year of release in some location‐years but response was limited. Vegetative biomass, plant stand establishment, kernel weight, kernels per spike, and response to scald had not changed over years. Increases in grain yield associated with increased harvest indices and reduced lodging have been made in western Canadian barley cultivars. Further efforts to increase vegetative yield, kernel weight and kernel number per spike, while maintaining harvest indices and lodging resistance would appear warranted.

EFFECT OF LATE-SEASON FUNGICIDE APPLICATION ON GRAIN YIELD AND SEED SIZE DISTRIBUTION IN WHEAT AND BARLEY

Field trials were conducted to determine the effect of foliar fungicides on grain yield, kernel size and seed size distribution in wheat and barley. Tilt (propiconazole) was applied at 125 g a.i. ha−1 between Zadoks growth stages 49 and 59. Following harvest, seed samples from treated and untreated plots were stratified into different size classes. In barley trials, net blotch was the most prevalent leaf disease while in wheat trials, tan spot, leaf rust and Septoria leaf spot were most prevalent. Under high levels of disease, Tilt reduced the level of disease and significantly increased grain yield and the amount of large kernels in both wheat and barley. Under low levels of disease, Tilt rarely increased grain yield, but frequently increased the amount of large kernels. In barley, the increase in amount of seed in the larger size classes across all sites was correlated (P &lt; 0.05) with reduction in net blotch severity. No significant effect of Tilt on germination at 5 °C was observed for any of the wheat cultivars considered in this study. Increases in the yield of large kernels indicate that late season applications of fungicide may be useful in pedigreed seed production, where large kernels are desired.Key words: Seed crops, kernel weight, seed vigor, tan spot, Septoria, net blotch

Abstracts of papers presented at the annual meeting of the Canadian Phytopathological Society University of Saskatchewan, Saskatoon 27-30 July 1986

Abstracts of papers presented at the annual meeting of the Canadian Phytopathological Society University of Saskatchewan, Saskatoon 27-30 July 1986

Disease progression and yield loss in barley associated with net blotch, as influenced by fungicide seed treatment

Fungicide seed treatment significantly reduced the severity of net blotch of barley induced by Pyrenophora teres. Triadimenol and maneb treatments were more effective than etaconazole, Vitaflo 280 (carbathiin plus thiram), or Vitaflo 250 (carbathiin). Disease severity at growth stage 73 (Zadoks) was reduced on the penultimate leaf from maneb and triadimenol seed treatments. Apparent infection rate (r) did not effectively identify relative treatment efficacy or potential. Estimated time to 50% disease severity on the second to fourth leaf from the head, based on logit disease transformation, was delayed by 2.5 to 9.2 days with triadimenol treatment. Triadimenol and maneb treatments provided a 12.6% and 12.4% yield increase, respectively, which was in part directly related to control of net blotch. Significant correlations of yield and thousand kernel weight to percent net blotch on the penultimate, third, and fourth leaves were obtained. It was estimated that net blotch on Volla barley was responsible for a 15.2% yield loss and 6.7% reduction in thousand kernel weight. Estimations of relative treatment efficacy and of yield loss were more reliable when based on disease assessments of the fourth leaf from the head than from higher leaf positions.