Introducción. En la actualidad la mancha en red, causada por Dreschlera teres en cebada, no posee una escala visual para evaluar la severidad de la enfermedad a campo, por lo tanto, la falta de un ...método estándar de la cuantificación visual de la enfermedad puede llevar a estimaciones imprecisas que induce a conclusiones equivocadas. Objetivo. Desarrollar una escala para evaluar la severidad de la mancha en red en hojas de cebada. Materiales y métodos. Se recolectaron cien hojas de diferentes cultivares de cebada cervecera, utilizados en un ensayo en el campo experimental de la Universidad Nacional del Noroeste de la Provincia de Buenos Aires, en la localidad de Junín, Buenos Aires, Argentina, durante el año 2017, las cuales presentaron diferentes niveles de severidad. La escala se determinó con los siguientes valores de severidad: 1 %, 2,1 %, 4,5 %, 9,1 %, 17,8 %, 31,7 % y 50 %. La validación de la escala propuesta se realizó con base en cincuenta hojas de cebada con diferentes niveles de severidad de mancha en red, distribuidas a veinte evaluadores sin experiencia en la estimación de daños de esta enfermedad. Se procedió a su validación al evaluar la severidad de las hojas primero sin escala y después con la escala propuesta. Los análisis estadísticos se relizaron a través de una prueba de t y regresión lineal simple. Resultados. El uso de la escala mejoró la valoración de la severidad en hojas con mancha en red, debido a que en promedio la pendiente de la regresión de la mayoría de los evaluadores aumentó en un 15 % cuando utilizaron la escala visual para evaluar la enfermedad. Conclusión. Se logró desarrollar una escala para evaluar la severidad de la mancha en red en hojas de cebada.
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.
•Drechslera teres alters the expression of defense genes in barley leaves.•Infected barley leaves show changes in lipid and phenolic compounds.•Strain B25 mitigates the expression of defense genes in infected barley leaves.•Fewer defense compounds are produced in barley leaves bacterized with strain B25.
The relation between host reaction and yield losses due to net blotch disease was tested in six commercial barley cultivars through two seasons 2017/18 and 2018/19 under field infection compared with ...same six cultivars protected with fungicide (Montero). Net blotch incidence was also recorded as disease severity % and area under disease progress curve (AUDPC). Yield losses were parallel to net blotch severity and area under disease progress curve in both seasons. Net blotch triggered losses irrespective of the level of resistance obsessed by the cultivars. Gizal34 and 135 showed lowest levels of severity% and AUDPC followed by Giza 124 and 125 which exhibited lower levels of losses as compared to the highly susceptible cultivar Giza 2000 and 121 in which grain reduction reached 8.71% to 11.32% and 5.53% to 8.83% respectively. Contrariwise, losses in yield per plot in Gizal34 and 135 ranged from 2.80 % to 5.00% and 3.05% to 5.03% respectively, compared to Giza 2000 and 121 ranged from 26.70% to 29.11% and 19.58% to 22.89% respectively. The cultivars Giza 2000 and 121 had great values for susceptibility while, the average grain yield potential for both cultivars were less than others as Giza 134 and 135. This indicated that Giza 2000 and 121 have low tolerance level. Phonotypical scoring of disease with yield losses were resistance cultivars (Giza 134 and 135), moderately resistance (Giza 124 and 125) and Giza 2000 and 121 were also identified as susceptibility to net blotch at natural infection. This is an important study to prove that Giza 134 and Giza 135 barley cultivars are resistant under natural infection compared to treated cultivars with Monte-ro. This study is very important to the plant breeders to protect the resistant cultivars from breakdown and create new resistant cultivars, consequently decreasing the fungicides use and environmental pollution.
Net blotch foliar diseases of barley are important in Turkey, lowering grain yields and quality. There are two forms, the spot form (caused by Pyrenophora teres f. maculata (Ptm)) and the net form ...(caused by P. teres f. teres (Ptt)). To determine the pathotypes of Ptt and Ptm in Turkey, surveys were carried out during 2012, 2013 and 2015. Pyrenophora teres samples were collected from 34 provinces of Turkey. From these samples, 258 Ptm and 167 Ptt single conidium isolates were obtained. Pathotypes of 50 P. teres f. maculata and 40 P. teres f. teres isolates were assessed by inoculating onto a differential set of 25 barley genotypes. Twenty six Ptm pathotypes and 24 Ptt pathotypes were identified, and significant pathogenic variation was found among the isolates. Barley breeding programmes in Turkey should consider the pathotypes identified for incorporation of net blotch resistance. Continuous virulence monitoring for the P. teres population should be carried out to inform resistance breeding priorities.
Recognized as the causal agent of net blotch, Drechslera teres is responsible for major losses of barley crop yield. The consequences of this leaf disease are due to the impact of the infection on ...the photosynthetic performance of barley leaves. To limit the symptoms of this ascomycete, the use of beneficial bacteria known as "Plant Growth Promoting Rhizobacteria" constitutes an innovative and environmentally friendly strategy. A bacterium named as strain B25 belonging to the genus Burkholderia showed a strong antifungal activity against D. teres. The bacterium was able to limit the development of the fungus by 95% in detached leaves of bacterized plants compared to the non-bacterized control. In this study, in-depth analyses of the photosynthetic performance of young barley leaves infected with D. teres and/or in the presence of the strain B25 were carried out both in and close to the necrotic area. In addition, gas exchange measurements were performed only near the necrotic area. Our results showed that the presence of the beneficial bacterium reduced the negative impact of the fungus on the photosynthetic performance and modified only the net carbon assimilation rate close to the necrotic area. Indeed, the presence of the strain B25 decreased the quantum yield of regulated non-photochemical energy loss in PSII noted as Y(NPQ) and allowed to maintain the values stable of maximum quantum yield of PSII photochemistry known as F
/F
and close to those of the control in the presence of D. teres. To the best of our knowledge, these data constitute the first study focusing on the impact of net blotch fungus and a beneficial bacterium on photosynthesis and respiratory parameters in barley leaves.
The barley net blotch agent Pyrenophora teres (Died) Drechs. is one of the dominant fungal pathogens in agricultural crops worldwide. Here we aim to study the aggressiveness and virulence of P. teres ...populations collected at different ontogenesis stages (BBCH 30 and BBCH 47) from winter barley cultivars of various resistance types: moderately resistant, moderately susceptible and highly susceptible. We observed a direct proportional relationship between cultivar resistance and the aggressiveness of P. teres populations collected in both growth phases of the host plant. The isolates collected at an early stage of host plant development have a large difference in aggressiveness criteria: colony growth rate, sporulation intensity, latency period, plant damage degree, and the number of identified races. At the BBCH 30 growth stage, the growth rate of fungus colonies selected from a resistant cultivar is 1.2 times higher than that of a susceptible cultivar. The growth rate of colonies selected from resistant and susceptible cultivars in the earlier BBCH 30 stage is 1.04 times higher than the growth rate of colonies selected from the later phase. The sporulation intensity of fungal populations selected from a resistant cultivar is higher than that of populations selected from a susceptible cultivar (for BBCH 30–5.4 times, for BBCH 47–4.0 times); and it is 1.3 times higher in an earlier phase of plant development. Correlation between colony growth rate and spore formation rate in the BBCH 30 is r = 0.4. A high correlation level (r = 0.9) and notable difference between the variants were revealed when studying the duration of the latent period. The average value of plant damage by the P. teres from resistant cultivar is 4 times higher than from the susceptible cultivar in the BBCH 30 stage; and 12 times – in the BBCH 47 stage. There is a moderate negative correlation between the plant damage degree and the number of races identified from the fungal population, r = −0.59 for the BBCH 30, r = −0.8 for the BBCH 47. The number of races identified from P. teres populations collected in the late phase of plant growth was one third less. Our study helped to acquire new knowledge about intrapopulation processes under the influence of various factors – plant growth stage and cultivar genotype. The results obtained are the basis for the development of adaptive-integrated techniques for managing populations of the hemibiotrophic pathogen, barley net blotch.
The leaf spot form of the barley disease net blotch, caused by the fungus Pyrenophora teres f. maculata (PTM), is an increasingly important foliar disease of barley. Studies of population genetic ...structure and reproductive mode are necessary to make predictions of the evolutionary potential of the pathogen. Sources of resistance to PTM have been found in Iranian landraces, which may have the potential to improve plant breeding efforts. However, little is known about the population genetic structure of this fungus in Iran. In this study, we analysed the frequency of the mating type genes to assess the potential for sexual mating of PTM collected from four provinces—Khuzestan, Hamadan, Golestan, and East Azerbaijan—and we investigated the population genetic structure using seven simple sequence repeat markers. High genotype diversity, linkage equilibrium, and equal ratios of mating types frequencies in the PTM populations at Khuzestan and Hamadan support the occurrence of sexual reproduction in these populations, while in Golestan and East Azerbaijan populations, significant gametic disequilibrium and relatively low genotype diversity suggest a higher incidence of clonality or different demographic histories. Unequal mating type frequencies in Golestan confirm a predominance of asexual reproduction. Finally, we found significant evidence for strong population structure with most of the genetic variation represented within regional populations (89%). Overall, our study provides evidence for high genetic variation in Iranian PTM populations, which may be the basis for rapid adaptive evolution in this pathosystem. This highlights the need for integrated efforts to control the disease.
Genetic structure of four populations of Pyrenophora teres f. maculata causing spot form net blotch of barley in Iran, representing the four genetic clusters.
Introduction. At present, the net blotch caused by Dreschlera teres in barley, does not have a visual scale to assess the severity of the disease in the field, therefore, the lack of a standard ...method for visual quantification of the disease can lead to imprecise estimates that induce to wrong conclusions. Objective. To develop a scale to assess the severity of net blotch in barley leaves. Materials and methods. One hundred leaves of different malting barley cultivars used in a trial at the experimental field of the Universidad Nacional del Noroeste de la Provincia de Buenos Aires, in the locality of Junin, Buenos Aires, Argentina, were collected in 2017, which presented different severity levels. The scale was determined with the following severity values: 1 %, 2.1 %, 4.5 %, 9.1 %, 17.8 %, 31.7 %, and 50 %. The validation of the proposed scale was carried out based on fifty barley leaves with different levels of net blotch severity, distributed to twenty evaluators without experience in estimating the damage from this disease. Validation was carried out by evaluating the severity of the leaves first without scale and then with the proposed scale. Statistical analyzes were performed using a t-test and simple linear regression. Results. The use of the scale improved the assessment of the severity in leaves with net blotch, because on average the slope of the regression of most of the evaluators increased by 15 % when they used the visual scale to evaluate the disease. Conclusion. The development of a scale to assess the severity of the net blotch in barley leaves was achieved.
Introducción. En la actualidad la mancha en red, causada por Dreschlera teres en cebada, no posee una escala visual para evaluar la severidad de la enfermedad a campo, por lo tanto, la falta de un método estándar de la cuantificación visual de la enfermedad puede llevar a estimaciones imprecisas que induce a conclusiones equivocadas. Objetivo. Desarrollar una escala para evaluar la severidad de la mancha en red en hojas de cebada. Materiales y métodos. Se recolectaron cien hojas de diferentes cultivares de cebada cervecera, utilizados en un ensayo en el campo experimental de la Universidad Nacional del Noroeste de la Provincia de Buenos Aires, en la localidad de Junín, Buenos Aires, Argentina, durante el año 2017, las cuales presentaron diferentes niveles de severidad. La escala se determinó con los siguientes valores de severidad: 1 %, 2,1 %, 4,5 %, 9,1 %, 17,8 %, 31,7 % y 50 %. La validación de la escala propuesta se realizó con base en cincuenta hojas de cebada con diferentes niveles de severidad de mancha en red, distribuidas a veinte evaluadores sin experiencia en la estimación de daños de esta enfermedad. Se procedió a su validación al evaluar la severidad de las hojas primero sin escala y después con la escala propuesta. Los análisis estadísticos se relizaron a través de una prueba de t y regresión lineal simple. Resultados. El uso de la escala mejoró la valoración de la severidad en hojas con mancha en red, debido a que en promedio la pendiente de la regresión de la mayoría de los evaluadores aumentó en un 15 % cuando utilizaron la escala visual para evaluar la enfermedad. Conclusión. Se logró desarrollar una escala para evaluar la severidad de la mancha en red en hojas de cebada.
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