A Comparative Study of Pyrenophora Teres Drechs. F. Teres and Pyrenophora Teres Drechs. F. Maculata Smedeg. Cause of "Net" and "Spot" Type Net Blotch Respectively on New Zealand Barley

<p>Net blotch is caused by Pyrenophora teres Drechs. (stat. conid. Drechslera teres (Sacc.) Shoem., syn. Helminthosporium teres Sacc). P. teres produces symptoms which appear initially as small necrotic spots and streaks on the leaf. These increase to produce the characteristic net-like symptoms, which have given rise to the name net blotch. Sometimes, lesions develop from small necrotic spots, to form elliptical lesions. This is the "spot" type of P. teres and was first noticed in 1967 in isolates from North America, Mexico, Israel and Holland. It was thought that these isolates were mutants of P. teres. Since 1969 however, other workers have reported similar observations widely occurring in Norway, Denmark and Finland. Based on minor morphological differences, Ito and Kuribayashi proposed a new species, called P. japonica. Smedegård-Petersen disagreed, and showed that the spot-producing isolate represents a deviating type of P. teres, only differing from the usual "net" type in the symptoms induced on barley plants. He based his reasoning on morphological, cultural and genetical investigations. Consequently, Smedegård-Petersen described two new forms of the fungus, Pyrenophora teres Drechs. f. teres Smedeg., which produces the usual net lesions, and Pyrenophora teres Drechs. f. maculata Smedeg., which produces well defined dark brown circular or elliptical lesions without netting. The aim of the research undertaken in the present study was to conduct a comparative study on the morphology and fitness of a range of New Zealand "net" and "spot" type isolates. An attempt was also made at crossing a "net" type with a "spot" type. Although Smedegård-Petersen had stated that there was no morphological difference between the "net" and "spot" types, this project was undertaken because no research had been done on New Zealand isolates. Furthermore, different features were studied using different methods not used by other workers in studying P. teres. The only morphological difference that was distinctive was that the "spot" types of P. teres formed coremial strands, which were fan-like in morphology, which produced conidia in culture, and the "net" types did not. There was no way to tell the "net" isolates apart from the "spot" isolates, based on conidia colour, length, width, volume or the number of cells per conidium. One fact that did emerge, was that the longest conidia had the greatest number of cells per conidium and the reverse was also true. The germination of monoconidial isolates showed that there were no major differences in branching between the two types of P. teres. However, it was revealed that two germ tubes were capable of emerging from one cell in the "spot" isolates. All cells in a conidium in both the "net" and "spot" types were able to germinate, cells that germinated tended to be at opposite ends, and the first cell to germinate in a conidium was usually the cell at the hilum. Examination of the growth rates showed that there were no significant differences in the growth rates of the "net" and "spot" types when grown on MEA+B. The "spot" types were able to penetrate cellulose faster than the "net" types and hence may produce cellulose faster as well. ANT148, which had previously been an unknown type, was proved to be a "spot" type in the pathogenicity tests. It may have been the source of the New Zealand "spot" type inoculum because the seed it came from was imported into New Zealand in 1984, two years prior to the discovery of the "spot" type of P. teres in the South Island. Both forms of P. teres penetrated the leaf through the epidermal cell wall, and occasionally entered through the stomata. Even though the "spot" type may be present inside the leaf, the symptoms are not usually manifested until later, compared with the "net" type where the symptoms tend to be an indication of the amount of hyphae present in the leaf. In the screening of the progeny from the crossing, the "spot" type of P. teres had lost up to 78.9% of its resistance to triadimenol and flutriafol, when compared to the sensitivity tests carried out in 1986 and 1987. It is hypothesised that 13Y, the "net" type is dominant, and the "spot" type, KF2, recessive, as none of the progeny had any resistance to triadimenol or flutriafol, after undergoing somatic recombination. It was concluded that the "spot" and "net" types are two types of the same species, and there was not enough evidence to suggest otherwise. Further studies should be done, using more current isolates of the "net" and "spot" types of P. teres, and the old D. japonica isolates from New Zealand, to establish if the cultures identified as D. japonica, are different in any way.</p>

A Comparative Study of Pyrenophora Teres Drechs. F. Teres and Pyrenophora Teres Drechs. F. Maculata Smedeg. Cause of "Net" and "Spot" Type Net Blotch Respectively on New Zealand Barley

<p>Net blotch is caused by Pyrenophora teres Drechs. (stat. conid. Drechslera teres (Sacc.) Shoem., syn. Helminthosporium teres Sacc). P. teres produces symptoms which appear initially as small necrotic spots and streaks on the leaf. These increase to produce the characteristic net-like symptoms, which have given rise to the name net blotch. Sometimes, lesions develop from small necrotic spots, to form elliptical lesions. This is the "spot" type of P. teres and was first noticed in 1967 in isolates from North America, Mexico, Israel and Holland. It was thought that these isolates were mutants of P. teres. Since 1969 however, other workers have reported similar observations widely occurring in Norway, Denmark and Finland. Based on minor morphological differences, Ito and Kuribayashi proposed a new species, called P. japonica. Smedegård-Petersen disagreed, and showed that the spot-producing isolate represents a deviating type of P. teres, only differing from the usual "net" type in the symptoms induced on barley plants. He based his reasoning on morphological, cultural and genetical investigations. Consequently, Smedegård-Petersen described two new forms of the fungus, Pyrenophora teres Drechs. f. teres Smedeg., which produces the usual net lesions, and Pyrenophora teres Drechs. f. maculata Smedeg., which produces well defined dark brown circular or elliptical lesions without netting. The aim of the research undertaken in the present study was to conduct a comparative study on the morphology and fitness of a range of New Zealand "net" and "spot" type isolates. An attempt was also made at crossing a "net" type with a "spot" type. Although Smedegård-Petersen had stated that there was no morphological difference between the "net" and "spot" types, this project was undertaken because no research had been done on New Zealand isolates. Furthermore, different features were studied using different methods not used by other workers in studying P. teres. The only morphological difference that was distinctive was that the "spot" types of P. teres formed coremial strands, which were fan-like in morphology, which produced conidia in culture, and the "net" types did not. There was no way to tell the "net" isolates apart from the "spot" isolates, based on conidia colour, length, width, volume or the number of cells per conidium. One fact that did emerge, was that the longest conidia had the greatest number of cells per conidium and the reverse was also true. The germination of monoconidial isolates showed that there were no major differences in branching between the two types of P. teres. However, it was revealed that two germ tubes were capable of emerging from one cell in the "spot" isolates. All cells in a conidium in both the "net" and "spot" types were able to germinate, cells that germinated tended to be at opposite ends, and the first cell to germinate in a conidium was usually the cell at the hilum. Examination of the growth rates showed that there were no significant differences in the growth rates of the "net" and "spot" types when grown on MEA+B. The "spot" types were able to penetrate cellulose faster than the "net" types and hence may produce cellulose faster as well. ANT148, which had previously been an unknown type, was proved to be a "spot" type in the pathogenicity tests. It may have been the source of the New Zealand "spot" type inoculum because the seed it came from was imported into New Zealand in 1984, two years prior to the discovery of the "spot" type of P. teres in the South Island. Both forms of P. teres penetrated the leaf through the epidermal cell wall, and occasionally entered through the stomata. Even though the "spot" type may be present inside the leaf, the symptoms are not usually manifested until later, compared with the "net" type where the symptoms tend to be an indication of the amount of hyphae present in the leaf. In the screening of the progeny from the crossing, the "spot" type of P. teres had lost up to 78.9% of its resistance to triadimenol and flutriafol, when compared to the sensitivity tests carried out in 1986 and 1987. It is hypothesised that 13Y, the "net" type is dominant, and the "spot" type, KF2, recessive, as none of the progeny had any resistance to triadimenol or flutriafol, after undergoing somatic recombination. It was concluded that the "spot" and "net" types are two types of the same species, and there was not enough evidence to suggest otherwise. Further studies should be done, using more current isolates of the "net" and "spot" types of P. teres, and the old D. japonica isolates from New Zealand, to establish if the cultures identified as D. japonica, are different in any way.</p>

A biological agent modulates the physiology of barley infected with Drechslera teres

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 Fv/Fm 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.

Expression Analysis of Cell Wall-Related Genes in the Plant Pathogenic Fungus Drechslera teres

Drechslera teres (D. teres) is an ascomycete, responsible for net blotch, the most serious barley disease causing an important economic impact. The cell wall is a crucial structure for the growth and development of fungi. Thus, understanding cell wall structure, composition and biosynthesis can help in designing new strategies for pest management. Despite the severity and economic impact of net blotch, this is the first study analyzing the cell wall-related genes in D. teres. We have identified key genes involved in the synthesis/remodeling of cell wall polysaccharides, namely chitin, β-(1,3)-glucan and mixed-linkage glucan synthases, as well as endo/exoglucanases and a mitogen-activated protein kinase. We have also analyzed the differential expression of these genes in D. teres spores and in the mycelium after cultivation on different media, as well as in the presence of Paraburkholderia phytofirmans strain PsJN, a plant growth-promoting bacterium (PGPB). The targeted gene expression analysis shows higher gene expression in the spores and in the mycelium with the application of PGPB. Besides analyzing key cell-wall-related genes, this study also identifies the most suitable reference genes to normalize qPCR results in D. teres, thus serving as a basis for future molecular studies on this ascomycete.

Evaluation of collection spring barley varieties for valuable economic features for breeding in the central forest-steppe of Ukraine

Aim. To conduct immunological monitoring of collection spring barley varieties against pathogens of the most common diseases. To select starting material with a set of valuable features for in breeding for pathogen resistance and productivity in the central forest-steppe of Ukraine. Results and Discussion. The Erysiphe graminis f. sp. hordei, Bipolaris sorokiniana and Drechslera teres populations were found to be the most widespread in the Central Forest-Steppe of Ukraine. Drechslera graminea, Pyrenophora tritici-repentis Drechsler and Puccinia hordei were not common, and in only waterlogged years their damage intensity amounted to 10-15%. Complex resistance (damage 10.0 %) to three diseases – E. graminis f. sp. hordei, B. sorokiniana and D. teres was identified in the following varieties: Dokaz, Aspekt, Kuburas, Hanka, and STN 115. The recessive genes mlo were shown to be extensively and highly effective against E. graminis f. sp. hordei. Varieties Adonis, Bojos, Aspen, Barke, Class, Eunova, Josefin, Danuta, Breemar, and Madeira were resistant to these genes. Structural analysis performed with varieties of spring barley, which were resistant to disease. The following varieties were superior to the check variety in terms of length, grain number and weight from the main ear: Kuburas, Troychan, Sanktrum, and Yevroprestyzh. Conclusions. We selected sources of complex resistance to diseases (damage  10.0%): Aspekt, Dokaz, Hanka, Kuburas, and STN 115. The donors of resistance to E. graminis f. sp. hordei (damage  3.5%) are Adonis, Barke, Bojos, Aspen, Сlass, Danuta, Eunova, Josefin, Breemar, and Madeira. The sources of valuable economic features are: by the ear length (9.7-10.2 cm) - varieties Kuburas, Vivaldi, Troychan, Sanktrum, Yevroprestyzh; by the grain number from the main ear (25.5-27.8) - varieties Kuburas, Troychan, Sanktrum, Koloryt, Yevroprestyzh, Danuta, and Eunova; by grain weight from the main ear (1.5-2.0 g) - varieties Kuburas, Vivaldi, Troychan, Sanktrum, Hanka, Koloryt, Yevroprestyzh, Barke, Danuta, Pivdennyi,and Eunova.

Viability of seed-borne fungi Alternaria alternata, Bipolaris sorokiniana and Drechslera teres in barley seeds in the south of Brazil

ABSTRACT Some seed-borne fungi can survive in barley seeds; nevertheless, their survival period is unknown in barley seeds under storage conditions in Brazil. The aim of this study was to quantify the viability of the fungi Alternaria alternata, Bipolaris sorokiniana and Drechslera teres in barley seeds stored for 315 days during the off-season in the south region of Brazil. Each cultivar had 400 seeds disinfested and subjected to seed health testing in potato-dextrose-agar (PDA) from December 2011 to September 2012 at 35-day intervals. Data on fungal incidence and viability as a function of the storage time underwent regression analysis. All three fungi were detected in the five cultivars in all evaluated periods, and their incidence and viability significantly reduced with increasing storage periods. Monthly average reduction in the viability of A. alternata was 8%, while that of B. sorokiniana and D. teres was 10%. At the end of the off-season, viability of A. alternata, B. sorokiniana and D. teres, considering the average of cultivars, remained 49.8, 29.6 and 31.0%, respectively.

Sources of valuable crop features of spring barley varieties for breeding in the central forest-steppe of Ukraine

The population of Erysiphe graminis f. sp. hordei Em. Marchal, Bipolaris sorokiniana Shoem. and Drechslera teres Ito. was found to be the most widespread in the central forest-steppe of Ukraine. Drechslera graminea Ito and Puccinia hordei Otth. were not common. For an average of 7 years of research, the sources of the disease complex have been identified on a provocative background. Resistance (lesions up to 10.0 %) to two diseases – Erysiphe graminis and Drechslera teres were characterized by the following varieties: Etyket, Obolon, Parnas, Khadar, Edem, Pivdennyi, Koloryt (Ukraine), Josefin (France), Ebson, Malz, Aspen (Czech Republic), Barke, Bojos, Breemar, Brenda, Landora, Madeira, Danuta, Adonis, Сlass (Germany), Vivaldi, Eunova, Secuva (Austria). Complex resistance (lesions up to 10.0 %) to three diseases – Erysiphe graminis, Bipolaris sorokiniana and Drechslera teres were characterized by the following varieties: Aspekt, Dokaz (Ukraine), Hanka, Kuburas (Germany), STN 115 (Poland). The recessive genes mlo: mlo9, mlo11 and the combination of genes: mlo + Mla13 + Ml (La), mlo + Mla1 and mlo + Mla12 have been shown to be highly effective for Erysiphe graminis for a long time. High resistance and resistance were characterized by varieties protected by these resistance genes: Adonis, Barke, Bojos, Aspen, Сlass, Danuta, Eunova, Josefin, Breemar і Madeira. In spring barley varieties that showed disease resistance, structural analysis was performed by plant height, number of stems, spike length, number of grains, and weight of spikelets. In terms of length, number of grains and weight of grain of the main ear, the following varieties were better than the standard: Kuburas, Koloryt, Troichan, Barke, Danuta, Hanka, Ievroprestyzh, Sanktrum and others. Dedicated sources and donors of resistant varieties of spring barley to common pathogens can be used for immunity selection. Selected varieties by yield are the material for the selection of spring barley as a source of valuable features. These varieties are involved in hybridization. Key words: varieties, immunological monitoring, resistance, Erysiphe graminis, Bipolaris sorokiniana і Drechslera teres, valuable crop features, sources, donors.

Management of barley net blotch using Trichoderma asperellum (T34), eugenol, non-traditional compounds and fungicides

Barley plants (cv. Giza 2000) are infected by Drechslera teres which causes net blotch disease symptoms and yield losses. Plants were treated with commercial molecular products such as Trichoderma asperilium (T34), eugenol compared to non-traditional compounds (potassium silicate, nano-selenium) and fungicides (Maven, Montoro, and Decent) which selected from 12 treatments according to their important effects on infected barley plants. Bio-arc, Tilt, Rush up, Curve, and Amisto treatments were left out because of their lower efficiency of some treatments and similarity of the active ingredients of some other of them.Disease severity (%) was significantlty decreased as a result of the selected treatments, except eugenol which showed less reduction than the control. Disease symptoms were suppressed and electrolyte leakage % was reduced significantly due to all treatments than the control treatment. As a consequence of treatments, endogenous reactive oxygen species (ROS) such as superoxide (O2−) was significantly elevated early after the inoculation, consequently, later on catalase (CAT), peroxidase (POX), and polyphenol oxidase (PPO) activities were increased significantly than the control. Elevated levels of O2− early after inoculation could play essential role in killing or suppressing the fungus and inhibiting disease symptoms as well as stimulated enzyme activities. Interestingly, the treatments were effective so that the yield characters (1000 K.W. and grain yield/plo) were increased significantly than the control treatment. These results indicated that the biological commercial product of Trichoderma asperilium 34 and non-traditional biological compounds in this research study are so effective and could be used as an alternative to fungicides.

Antagonism and modes of action of Chaetomium globosum species group, potential biocontrol agent of barley foliar diseases.

“Net blotch” (Drechslera teres) and “Bipolaris spot blotch” (Bipolaris sorokiniana) are foliar diseases of barley. Biological control is currently considered as an efficient alternative to chemical management of these plant diseases. The aim of the present study was to identify 2 isolates of Chaetomium (C2 and C5), endophytics on barley seedlings and to study the in vitro interactions with D. teres and B. sorokiniana, isolated from seeds of the same host. Cultural and morphologicalcharacterization of all microorganisms was done. In addition, molecular characterization of Chaetomiumspp. was conducted and dual culture tests were carried out to find, by microscopic observations, the effects of the antagonist on the morphology of the pathogens. The results confirm the identity of the pathogens and the isolates of Chaetomium spp. as Chaetomium globosum species group. Inhibition of B. sorokiniana and D. teres by C2 and C5 accounted for 30% and 31.2 %, and 40% and 36% respectively, compared with the control. The mechanisms of action against B. sorokiniana and D. teres were antibiosis and competition and mycoparasitism, respectively. Microscopic observation revealed deformed conidia in B. sorokiniana and plasmolisis, coiling and orange pigmentation in D. teres.