Pyrenophora Avenae Research Articles

Impact of foliar diseases and its interaction with nitrogen fertilization and fungicides mixtures on green leaf area dynamics and yield in oat genotypes with different resistance

Crown rust (Puccinia coronata f. sp. avenae P. Syd & Syd) and leaf spot [Pyrenophora avenae Ito and Kurib, anamorph Drechslera avenae (Eidam) Sharif] are considered the most important oat fungal diseases in the world, causing high yield and grain quality losses. A major aspect for the management of foliar diseases (mainly crown rust) is the use of host resistant; however most of the oat cultivars available behave as moderately resistant to susceptible. Considering this, fungicides application is a common method of control of fungal diseases in order to reduce yield losses. The objective of this work was to evaluate the effect of foliar diseases and the interaction between N fertilization and fungicides on green leaf area (GLAI), healthy area duration (HAD), grain yield and its components in three oat genotypes; two of them were genotypes obtained by the Breeding Program of the Facultad de Ciencias Agrarias y Forestales (FCAyF), Universidad Nacional de La Plata (UNLP) and a commercial cultivar (Bonaerense INTA Calén). The trials were carried out during two years using a split-split-plot design with three replications. Main plots were two environments: 2011–2014, the sub-plots were the fungicide treatments: with and without fungicide, the sub-sub plots were the fertilization treatments with 0 and 60 kg N.ha−1 and the sub-sub-sub plots were the oat genotypes. Fungicide application decreased the severity percentages at the three growth stages (GS) evaluated during 2014, whereas N fertilization caused increases in the severity of rust, which may be associated with the biotrophic habit of this causal pathogen. However, in the year with high levels of crown rust, N application did not cause effects in GLAI and HAD, due to the effect of N application in increasing the severity of the disease. Fungicide application increased GLAI, HAD and grain yield (GY) with higher responses in the most susceptible genotype (Calén). Results of this study suggest that relating HAD to Grain Yield could be an effective tool in order to improve the quantification and modelling of yield losses under foliar diseases infections. Moreover, the lines belonging to the breeding program of the FCAyF-UNLP showed values of resistance and grain yield superior to the commercial variety evaluated.

Study Toward the Total Synthesis of Pyrenophorin

Macrodiolides are macrocyclic compounds containing two ester groups in a cyclic chain. Of this class of compounds, Pyrenophorin ( 1 ) shows antifungal activity, and is produced from the pathogenic fungus Pyrenophora avenae. As this substance, derived from nature, is isolated in small quantities, an asymmetric synthesis using a simple and efficient methodology would be of great interest. The proposed synthetic route starts with the protection of propargyl alcohol 3 using DHP and feldspar as catalyst. Compound 5 obtained in this reaction was then subjected to acid-base reaction between the acetylenic proton and 1 eq. n-BuLi, leading to formation of the acetylide 5A . The 1,2- addition reaction between 5A and g -valerolactone ( 6 ) leads to the formation of alkinone 7 in 67% yield. Subsequently, compound 7 was subjected to a ketalization reaction using the same feldspar catalyst. Ketal 8 was formed under concomitant removal of the THP group. The product of this reaction ( 8 ) was then submitted to a reduction reaction of the triple bond to form olefin 9 with E configuration. Currently, the conditions for obtaining 10 by oxidation using Jones reagent, are being optimized. Compound 10 , obtained as described, is being subjected to a macrolactonization reaction. Various conditions including the use of enzymes are being studied. In addition, a study involving the enantioselective synthesis of (R,R)-(-)-pyrenophorin, using enzymatic kinetic resolution of the racemic mixture of compound 8 , is in progress in the group

Synthesis of (-)-Pyrenophorol

Macrodiolide antibiotics, which possess interesting structural and biological properties are found in fungi and marine sponges. These macrodiolides are classified into two groups; one includes homodimers that consist of two identical units, and the other includes heterodimers that consist of two different units. Macrodiolides such as pyrenophorol (1), pyrenophorin (2), and vermiculine (3), which have 16membered rings are homodimeric macrodiolides, and macrocylic dilactones such as colletallol (4) and grahamimycin A1, which have 14-membered rings, are heterodimeric macrolides (Fig. 1). Analogs with various degrees of unsaturation such as tetrahydropyrenophorol (5) and dihydropyrenophorin (6), have also been reported. These naturally occurring macrodiolides show antifungal and anthelmintic activities. Pyrenophorol (1) is isolated from the fungi Byssochlamys nivea and Stemphylium radicinum. Pyrenophorin (2), an analog of pyrenophorol (1), is originated from the fungi Pyrenophora avenae and Stemphylium radicinum. These macrodiolides have attracted significant attention of synthetic chemists because of their interesting biological properties and structural features. Kibayashi, Zwanenburg, and, recently, Yadav have reported the synthesis of (–)pyrenophorol. For the preparation of the key intermediate, chiral 4-hydroxy-2-alkenoate, Zwanenburg group exploited the photo-induced rearrangement of the corresponding expoxy diazomethyl ketone. On the other hand, Kibayashi group, synthesized (−)-pyrenophorol using C2 symmetric (R,R)-diepoxide as a chiral building block. Recently, Yadav group synthesized (–)-pyrenophorol employing the hydrolytic kinetic resolution developed by Jacobson and the McMillan α-hydroxylation. In connection with our interests in the synthesis of natural products, we, herein, report the total synthesis of (–)pyenophorol (1). Our synthetic approach is based on the utilization of a chiral building block 8, which was used in our previous synthesis of ophiocerins (Scheme 1). The chiral building block 8, prepared from D-glucose, has the potential to be used as a versatile chiral synthon. As summarized in Scheme 2, the key starting chiral building block 8 was prepared from methyl α-D-glucopyranoside (9), which was prepared from α-D-glucose, in four steps. Regioselective reductive opening of the epoxide ring in 8 was the key step to establish the required stereocenter.

QTLs for important breeding characteristics in the doubled haploid oat progeny

A homozygous mapping population, consisting of doubled haploid (DH) oat (Avena sativa L.) plants generated through anther culture of F1 plants from the cross between the Finnish cultivar 'Aslak' and the Swedish cultivar 'Matilda', was used to construct an oat linkage map. Ten agronomic and quality traits were analyzed in the DH plants from field trials in 2005 and 2006. Leaf blotch (caused by Pyrenophora avenae) resistance was also evaluated in a greenhouse test with 2 different isolates. One to 8 quantitative trait loci (QTLs) were found to be associated with each trait studied. Some chromosomal regions affected more than 1 trait; for example, 4 regions affected both protein and oil content. This study gives valuable information to oat breeders concerning the inheritance of important traits, and it provides potential tools to assist breeding.

Fungal populations in subcrown internodes and crowns of oat crops in Saskatchewan

Discoloration of subcrown internodes (SIs) and crowns/lower culms (CLCs) of 87 oat crops across Saskatchewan in 1998-1999 and of SIs in 31 oat crops in eastern Saskatchewan (Black Soil Zone) in 2000-2001 was evaluated. Fungi in discolored tissue were isolated, identified and quantified, and the percentage of fields from which each fungus was isolated at least once (occurrence) and their relative percentage isolation levels were determined. In the 1998-1999 survey, discoloration severity varied more between years than among soil zones. Fusarium was the most common genus present, and F. culmorum the most common species. This was followed by F. equiseti, Microdochium bolleyi, Cochliobolus sativus, and F. avenaceum. Levels of C. sativus were lower in oat than those reported for wheat and barley in parallel province-wide surveys. Percentage isolation of F. culmorum was higher in the Brown than in the Black/Dark Gray Soil Zone, whereas the percentage occurrence of F. avenaceum was highest in the Black/Dark Gray Soil Zone. In 2000-2001, in eastern Saskatchewan, M. bolleyi, F. avenaceum, C. sativus, F. equiseti, Alternaria spp., and Pyrenophora avenae were the most common fungi isolated from discolored oat SIs. Similar to reports from wheat and barley, F. graminearum was isolated from SIs in eastern Saskatchewan at low levels. For the most part, neither previous crop nor tillage system affected fungal levels in SIs. P. avenae levels increased when the previous crop was another oat rather than wheat or barley. We conclude that oat could maintain or increase inoculum levels of Fusarium pathogens that cause damage to cereal crops in Saskatchewan. This is supported by results from a crop residue study in eastern Saskatchewan that showed that F. avenaceum, F. culmorum and F. graminearum occurred at similar or higher levels in oat fields than in fields of wheat or barley. Key words: Oat, root rot, crown rot, crop rotation, tillage system, Fusarium head blight, Fusarium spp., Fusarium avenaceum, Fusarium culmorum, Fusarium graminearum, Cochliobolus sativus, Pyrenophora avenae

Synthesis and antifungal activity of two novel spermidine analogues

Two spermidine analogues were synthesised and examined for antifungal activity. Both compounds used as 1 mM post-inoculation sprays reduced infection of barley seedlings by the powdery mildew fungus, Erysiphe graminis f.sp. hordei, infection of broad bean seedlings by the rust fungus, Uromyces viciae-fabae, and infection of apple seedlings by the powdery mildew fungus, Podosphaera leucotricha. Since these fungal pathogens cannot be cultured axenically, the effects of the two spermidine analogues on mycelial growth in vitro, as well as preliminary investigations on polyamine biosynthesis, were undertaken using the oat stripe pathogen, Pyrenophora avenae. Although neither compound affected radial growth of the fungus on plates, both analogues reduced fungal biomass in liquid culture substantially. The two spermidine analogues, used at a concentration of 1 mM, had no significant effect on the conversion of labelled ornithine into polyamines in P. avenae.

The putrescine analogue (E)-1,4-diaminobut-2-ene reduces DNA methylation in the plant pathogenic fungus Pyrenophora avenae

The synthetic putrescine analogue (E)-1,4-diaminobut-2-ene is known to possess antifungal and fungicidal properties. Although it perturbs fungal polyamine metabolism, this is not thought to be its primary mode of action. This paper reports that (E)-1,4-diaminobut-2-ene reduces DNA methylation in the plant pathogenic fungus Pyrenophora avenae. These reductions in DNA methylation were accompanied by greatly reduced methionine uptake by the fungus, although it is not known whether this was responsible for the altered DNA methylation. Reduced DNA methylation may result in the expression of specific genes, although which genes are affected and whether such changes are linked to reduced fungal growth awaits further investigation.

Synthesis and antifungal activity of six benzylic diamines

Six benzylic diamines were synthesised and examined for antifungal activity. Four of the compounds, KB 2, KB 4, KB 5 and KB 6, reduced radial growth of the oat leaf stripe pathogen Pyrenophora avenae, the largest reduction obtained with 25 μM KB 4, which reduced radial growth by 47%. Surprisingly, these four amines had no effect against infection of barley seedlings with the powdery mildew fungus Erysiphe graminis f.sp. hordei. Instead, two different amines, KB 1 and KB 3, reduced powdery mildew infection on barley. The greatest reduction was obtained with 25 μM KB 3, which reduced mildew infection by 69%. All of the amines which exhibited antifungal or fungicidal properties perturbed polyamine formation as measured by the incorporation of labelled ornithine into polyamines.

Detection and transmission of Drechslera avenae from oat seed

Detection, symptoms and symptomless transmission of Drechslera avenae (teleomorph Pyrenophora avenae) from seed were investigated. The present study reported that the D. avenae is frequently found in oat (Avena sativa) seed in Argentina. The prevalence of the seed lot infected was 54%. The incidence of seeds infected by D. avenae in the various seed lots from different regions ranged from 0 to 52% (overall mean of 7%). Besides conidia on conidiophore and immature pseudothecia, D. avenae produced small, spherical to pear-shape picnidia containing tiny conidia, on the seed surface. The pathogen was efficiently transmitted at a rate of 55% from seed to coleoptile tips in symptomless seedlings and at 12.5% to plumules. The importance of the infected seed and its epidemiological role are discussed.

Antifungal activities of four fatty acids against plant pathogenic fungi.

The effect of the fatty acids linolenic acid, linoleic acid, erucic acid and oleic acid on the growth of the plant pathogenic fungi Rhizoctonia solani, Pythium ultimum, Pyrenophora avenae and Crinipellis perniciosa were examined in in vitro studies. Linolenic and linoleic acids exhibited activity against all of the fungi. However, whereas linolenic acid reduced mycelial growth of R. solani and C. perniciosa at 100 microM, the concentration had to be increased to 1000 microM before any effect on mycelial growth of P. ultimum and P. avenae was observed. Linoleic acid only reduced mycelial growth of R. solani, P. ultimum and P. avenae at 1000 microM, but led to a significant reduction in growth of C. perniciosa at 100 microM. In contrast, oleic acid had no significant effect on growth of R. solani or P. avenae, but gave significant reductions in mycelial growth of P. ultimum at 100 microM and reduced growth of C. perniciosa significantly at 1000 microM. All of the fatty acids reduced biomass production by all of the fungi significantly in liquid culture when added to the media at 100 microM. Erucic acid had no effect on fungal growth at any concentration examined. The antifungal activities exhibited by linolenic, linoleic and oleic acids may be useful in the search for alternative approaches to controlling important plant pathogens, such as those examined in this study.

In Vitro Effects of Film‐Forming Polymers on the Growth and Morphology of Pyrenophora Avenae and Pyricularia Oryzae

Ethokem (Midkem Agrochemicals, Northampton, UK) and Bond (Newman Agrochemicals, Cambridge, UK) completely inhibited linear growth of Pyricularia oryzae at 1 and 2% concentrations of the compounds and strongly inhibited growth of Pyrenophora avenae in vitro. Vapor Gard (Miller Chemical & Fertilizer Corporation, Hannover, PA, USA) was less effective with relatively little inhibition of P. oryzae, but was a more effective inhibitor of P. avenae. All three compounds decreased cell lengths of both pathogens and increased cell diameters of P. avenae. Vapor Gard and Ethokem did not significantly alter cell diameters of P. oryzae, but a highly significant increase was observed with Bond. Gross changes in hyphal morphology were observed including swollen shortened cells, granulation of the cytoplasm, increased branching and collapsed empty cells. Ethokem and Bond decreased growth rate and inhibited biomass production of P. avenae.

Synthesis of six novel N, N-dialkyl derivatives of spermidine and effects on growth of the fungal plant pathogen Pyrenophora avenae

Six novel N, N-dialkyl derivatives of spermidine were synthesised and examined for activity against the oat stripe pathogen Pyrenophora avenae. Two of these spermidine analogues, N, N-dimethyl- N 1-(3-aminopropyl)-1,3-diaminopropane trihydrochloride ( 27) and N, N-dimethyl- N 1-(3-aminopropyl)-1,4-diaminobutane trihydrochloride ( 28), reduced radial extension of P. avenae on plates when used at 2 mM, and caused more substantial reductions in fungal growth in liquid culture when used at 1 mM. Preliminary data suggest that neither compound affected polyamine biosynthesis, determined by following the incorporation of label from ornithine into polyamines and examining intracellular polyamine concentrations in fungal tissue.

Synthesis of six novel N,N-dialkyl derivatives of spermidine and effects on growth of the fungal plant pathogen Pyrenophora avenae.

Six novel N,N-dialkyl derivatives of spermidine were synthesised and examined for activity against the oat stripe pathogen Pyrenophora avenae. Two of these spermidine analogues, N,N-dimethyl-N1-(3-aminopropyl)-1,3-diaminopropane trihydrochloride (27) and N,N-dimethyl-N1-(3-aminopropyl)-1,4-diaminobutane trihydrochloride (28), reduced radial extension of P. avenae on plates when used at 2 mM, and caused more substantial reductions in fungal growth in liquid culture when used at 1 mM. Preliminary data suggest that neither compound affected polyamine biosynthesis, determined by following the incorporation of label from ornithine into polyamines and examining intracellular polyamine concentrations in fungal tissue.

Antifungal activity of three spermidine conjugates

Three tri-substituted spermidines, di- p-coumaroyl-caffeoylspermidine, tri-caffeoylspermidine and tri- p-coumaroylspermidine, isolated from pollen of Quercus alba, were examined for antifungal activity. Both di- p-coumaroyl-caffeoylspermidine and tri- p-coumaroylspermidine reduced mycelial growth of the oat leaf stripe pathogen, Pyrenophora avenae and reduced powdery mildew ( Blumeria graminis f. sp. hordei) infection of barley seedlings when applied as a post-inoculation treatment. When used as a pre-inoculation treatment, only di- p-coumaroyl-caffeoylspermidine reduced powdery mildew infection significantly. Growth of P. avenae in the presence of 100 μM di- p-coumaroyl-caffeoylspermidine reduced activity of S-adenosylmethionine decarboxylase (AdoMetDC), and led to a reduction in the incorporation of labelled ornithine into spermidine. The other two spermidine conjugates increased AdoMetDC activity and the flux label from ornithine into spermine in P. avenae significantly.

Antifungal activity of three spermidine conjugates.

Three tri-substituted spermidines, di-p-coumaroyl-caffeoylspermidine, tri-caffeoylspermidine and tri-p-coumaroylspermidine, isolated from pollen of Quercus alba, were examined for antifungal activity. Both di-p-coumaroyl-caffeoylspermidine and tri-p-coumaroylspermidine reduced mycelial growth of the oat leaf stripe pathogen, Pyrenophora avenae and reduced powdery mildew (Blumeria graminis f. sp. hordei) infection of barley seedlings when applied as a post-inoculation treatment. When used as a pre-inoculation treatment, only di-p-coumaroyl-caffeoylspermidine reduced powdery mildew infection significantly. Growth of P. avenae in the presence of 100 microM di-p-coumaroyl-caffeoylspermidine reduced activity of S-adenosylmethionine decarboxylase (AdoMetDC), and led to a reduction in the incorporation of labelled ornithine into spermidine. The other two spermidine conjugates increased AdoMetDC activity and the flux label from ornithine into spermine in P. avenae significantly.

Especificidade de Pyrenophora avenae aos tecidos da semente de Avena sativa e sua atividade enzimática

Manchas nos grãos de aveia (Avena sativa) é limitante à sua comercialização por tornar o produto escuro e não permitir seu uso pela indústria alimentícia. A localização do micélio de Pyrenophora avenae nos grãos de aveia e sua atividade enzimática podem esclarecer a causa das manchas. O objetivo deste trabalho foi determinar a localização de P. avenae, na cariopse de aveia, avaliar a sua atividade enzimática e seu efeito sobre proteínas e lipídios dos grãos de aveia. A localização do micélio nos tecidos da cariopse foi determinada após hidratação e cortes da mesma, seguido da análise dos tecidos sob lupa e microscópio. Para avaliação da atividade enzimática foram utilizados 18 isolados de P. avenae obtidos das principais regiões produtoras de aveia do Brasil, avaliando-os quanto às suas atividades amilolítica, proteolítica e lipolítica, sendo realizada por plaqueamento das estruturas vegetativas em meio sólido específico para as enzimas testadas. As determinações do percentual de proteínas e lipídios foram obtidas pelos métodos de Kjeldahl e Bligh & Dyer, respectivamente. O micélio de P. avenae é a principal causa da mancha nos grãos de aveia, localizando-se nos três tecidos do pericarpo. O fitopatógeno apresenta boa atividade enzimática para lipase e protease porém insignificante para a amilase. Os grãos de aveia manchados e sadios não diferiram nos teores de proteínas e de lipídios. Esses teores foram mais elevados nos tecidos superficiais do pericarpo e aleurona independente da presença ou não de manchas, justificando o crescimento superficial de P. avenae sobre os grãos de aveia.

Incidence of Pyrenophora avenae Ito et Kurib. in Europe between 1994-1998, and the varietal reaction of oats to it

In Europe in the period 1994–1998, Helminthosporium leaf blotch disease was recorded in Austria, Belarus, Bulgaria, the Czech Republic, Estonia, Finland, Hungary, Italy, Norway, Poland, Russia and Yugoslavia. There was large variation in the quantitative reaction of oat (Avena sativa L.) genotypes to this disease, ranging from a disease resistance index (DRI) of 71 with cv. Kasadra to 16 with cv. Pan. Oat genotypes such as Kasadra, Pc 60, Pc 61, IL 86-6404, IL 86-1158, Rodney M, Pg 15, Cc 4761, Vermiou, Roxton, IL 85-6467, IL 85-2069, Pc 54-2, Orlando, OM 1387, Pc 59, KR 3813/73, IL 86-4189, Pc 68, Melys, OA 503-1, KR 288/73L/569, POB 1429/93, Pg l6, Pc 55 and Pc 56 had a consistently high disease resistance index. On the other hand, some had a low index which confirms the existence of pathogenic specialization of the causal fungus Pyrenophora avenae Ito et Kurib. Despite the absence of detailed analyses of the reaction of oats to the pathogen, it seems feasible to breed for resistance to the disease.

Ornithine Decarboxylase of Stagonospora (Septoria) nodorum Is Required for Virulence toward Wheat

A knockout strain of Stagonospora (Septoria) nodorum lacking the single ornithine decarboxylase (ODC) allele has been created by targeted gene replacement. A central region of the S. nodorum ODC gene was isolated by polymerase chain reaction using degenerate oligonucleotides and used to probe a lambda genomic library. The gene was sequenced and the encoded ODC protein sequence was shown to be similar to those from other fungi. The functionality of the S. nodorum ODC was confirmed by complementation of an Aspergillus nidulans mutant (puA) strain devoid of ODC activity, restoring growth in the absence of exogenous polyamines. Sporulation of the transformants was reduced suggesting abberant regulation of the S. nodorum gene in A. nidulans. Transformation-mediated gene replacement was used to create strains which were auxotrophic for putrescine and lack ODC coding sequences. Pathogenicity studies on these mutants showed that they are greatly reduced in virulence compared with non-disrupted transformants. This confirms that the strains carrying an ODC disruption cannot obtain sufficient polyamines from the host plant for normal growth and, thus, that fungal ODC may be a suitable target for chemical intervention.

(1408‐1411) Proposals to conserve the names of four species of Fungi (Phomabetae, Helminthosporium avenae, Pyrenophora avenae, and Pleospora triticirepentis) against competing earlier synonyms

(1408‐1411) Proposals to conserve the names of four species of Fungi <i>(Phomabetae, Helminthosporium avenae, Pyrenophora avenae,</i> and <i>Pleospora triticirepentis)</i> against competing earlier synonyms

Ethanol perturbs polyamine metabolism in the phytopathogenic fungusPyrenophora avenae

Biomass production by the plant pathogenic fungus Pyrenophora avenae was reduced following growth in 1, 3 and 6% ethanol. Although cadaverine concentration was not affected by growth in ethanol, putrescine and spermine concentrations were increased following growth in 3% ethanol and concentrations of spermidine and spermine were substantially increased following exposure to 6% ethanol. These changes were accompanied by significant increases in the activities of the polyamine biosynthetic enzymes ornithine decarboxylase and S-adenosylmethionine decarboxylase and in the flux of label from ornithine into the polyamines. Formation of the cadaverine derivatives aminopropylcadaverine and N,N-bis(3-aminopropyl)cadaverine was greatly increased in P. avenae exposed to 6% ethanol, probably via the action of lysine decarboxylase, S-adenosylmethionine decarboxylase and the aminopropyltransferases. There was also a doubling of polyamine oxidase activity following fungal growth in 6% ethanol.