Neil Havis

Scotland's Rural College | SRUC · Crop Protection Team

Ramularia collo-cygni (Rcc) is a major barley pathogen that causes yield and grain quality losses worldwide. The main sources of Rcc inoculum are the seed and asexual airborne spores. In Argentina, Rcc is considered to be an emerging threat to barley crops, especially as most varieties are susceptible to Rcc and have a European genetic background....

Barley crops are at risk of being attacked by several leaf diseases. Net blotch, brown rust, Rhynchosporium and Ramularia leaf spot are among the most widespread and can cause severe attack and yield losses. Two trial protocols targeting Ramularia and net blotch, respectively, have been tested in several countries in 2021 and 2022. Ramularia trials...

Ramularia leaf spot is a major economic disease of barley caused by the dothidiomycete fungus Ramularia collo-cygni. The fungus has a complex life cycle which includes extensive late season spore release events and a seed-borne phase. Predicting disease epidemics during the growing season remains a difficult challenge. To better understand the inte...

Ramularia leaf spot is a major economic disease of barley caused by the dothidiomycete fungus Ramulariacollo-cygni. The fungus has a complex life cycle which includes extensive late season spore release events and a seed-borne phase. Predicting disease epidemics during the growing season remains a difficult challenge. To better understand the inter...

Plants have evolved a highly sophisticated immune system to resist pathogen attack comprising both preformed and inducible mechanisms. Over the last 50 years, various biological and chemical inducers have been used to artificially trigger the defense response in plants, thereby promoting an ‘induced resistance’ (IR) to subsequent pathogen attack. I...

Ramularia leaf spot (RLS) caused by the fungus Ramularia collo-cygni (Rcc) has become a threat to barley production in Argentina. All barley varieties are susceptible to RLS; thus, disease management relies on fungicides like quinone-outside inhibitors (QoIs), demethylation inhibitors (DMIs) and succinate dehydrogenase inhibitors (SDHIs). Europe re...

Ramularia leaf spot is an emerging pathogen across barley growing regions of the world. It's rise from minor to major disease has been rapid over the last twenty years. The causal pathogen, Ramularia collo-cygni is poorly understood but it has been shown to have a complex life cycle and the ability to exist on many hosts in an endophytic state. The...

Ramularia collo-cygni is the causal agent of Ramularia leaf spot disease (RLS) on barley and became, during the recent decades, an increasing threat for farmers across the world. Here, we analyze morphological, transcriptional, and metabolic responses of two barley cultivars having contrasting tolerance to RLS, when infected by an aggressive or mil...

Septoria tritici blotch (STB; Zymoseptoria tritici) is the most important leaf disease of wheat in Northern and Western Europe. The problem of fungicide resistance in Z. tritici populations is challenging future control options. In order to investigate differences in azole performances against STB, 55 field trials were carried out during four seaso...

Septoria tritici blotch - STB (Zymoseptoria tritici) is the most serious leaf disease of wheat in Northem Europe. Problems with fungicide resistance in the populations of Z. tritici have caused concems for future control options. During two seasons (2017 and 2018), a common protocol was applied fortesting the field performance of six azoles across...

Ramularia collo‐cygni , the agent responsible for Ramularia leaf spot disease of barley, possesses many mechanisms for avoiding detection by the host, which enables it to survive as an endophyte for much of the plant's life cycle before eventually turning pathogenic. The fungus has also eluded farmers and scientists for decades as it is a late seas...

Integrated Disease Management of barley.

Ramularia leaf spot (RLS) is a newly-important disease of barley which is caused when the fungus Ramularia collo-cygni enters necrotrophic development during colonisation of the host. Mutant alleles at the barley MILDEW LOCUS O, mlo, locus confer broad spectrum durable resistance against the powdery mildew fungus, Blumeria graminis f. sp. hordei, b...

Microdochium nivale and Microdochium majus cause brown foot rot and snow mould in cereals. The aim of the present study was to evaluate the population genetic structure of Microdochium spp. associated with foot rot of wheat in the Czech Republic and the reaction of that population to the succinate dehydrogenase inhibitor (SDHI) fungicide penthiopyr...

A programme of field trials for the study of the winter barley – Rhynchosporium commune pathosystem is reported. The associated seed‐borne disease Rhynchosporium leaf scald is regarded as having an important impact on barley yields. The analysis reported here relates to the impact of the seed source (commercial or farm‐saved seed) on disease incide...

Ramularia leaf spot disease (RLS), caused by the ascomycete fungus Ramularia collo-cygni, has emerged as a major economic disease of barley. No substantial resistance has been identified, so far, among barley genotypes and, based on the epidemiology of the disease, a quantitative genetic determinacy of RLS has been suggested. The relative contribut...

With the threat of certain plant protection products becoming ineffective due to reduced pathogen sensitivity to fungicides or through the removal of products due to changes in legislation, alternative compounds are sought for use in disease management programmes. The effects of an arabinoxylan film-forming polymer derived from maize cell walls to...

Leaf diseases cause major yield losses in winter wheat every year across Europe. Septoria leaf blotch – STB (Zymoseptoria tritici) is the most serious leaf disease in Northern Europe, but also yellow rust (Puccinia striiformis) and brown rust (Puccinia triticina) are known to cause major problems in some regions and seasons. Problems with fungicide...

Ramularia leaf spot (RLS) has emerged as a serious threat to barley production across temperate regions of Europe, South America and New Zealand. The disease, typified by characteristic reddish brown, rectangular lesions visible on both sides of the leaf and often ringed by a chlorotic halo is caused by the dothideomycete fungus Ramularia collo-cyg...

Ramularia leaf spot (RLS) caused by Ramularia collo-cygni (Rcc), has become one of the main constraints to barley production in Argentina and Uruguay. Grain yield losses as high as 70% have been reported in susceptible cultivars. The emergence of RLS as a major disease in the last six years has redirected coordinated research efforts to advance on...

Plant defence elicitors are compounds that can induce host defence responses against plant pathogens and offer a novel strategy for disease management. Disease control by elicitors can be inconsistent and is often dependent on the crop, the variety and the environment. The use of foliar application of defence elicitors to control light leaf spot (L...

Background Ramularia collo-cygni is a newly important, foliar fungal pathogen of barley that causes the disease Ramularia leaf spot. The fungus exhibits a prolonged endophytic growth stage before switching life habit to become an aggressive, necrotrophic pathogen that causes significant losses to green leaf area and hence grain yield and quality. R...

Ramularia leaf spot (RLS) is a newly important disease of barley across temperate regions worldwide. Despite this recent change in importance, the infection biology of the causal agent Ramularia collo-cygni (Rcc) remains poorly understood. Confocal microscopy of the infection process of two transgenic Rcc isolates, expressing either GFP or DsRed re...

Ramularia leaf spot and Rhynchosporium leaf scald are two of the major diseases of barley crops in cooler temperate countries. The methods below are aimed at the identification and quantification of fungal DNA in leaf samples but can also be used for pathogen detection from seed or DNA extracted from environmental samplers. The methods describe in...

Ramularia collo-cygni (Rcc) is the biotic factor responsible for the disease Ramularia leaf spot (RLS) of barley (Hordeum vulgare). Despite having been described over one hundred years ago and being considered a minor disease in some countries, the fungus is attracting interest in the scientific community as a result of the increasing number of rec...

The ability of the resistance elicitors acibenzolar-S-methyl (ASM), β-aminobutyric acid (BABA), cis-jasmone (CJ), and a combination of the three products, to control infection of spring barley by Rhynchosporium commune was examined under glasshouse conditions. Significant control of R. commune was provided by ASM and CJ, but the largest reduction i...

The fungus Ramularia collo-cygni B. Sutton & J. M. Waller (Rcc) was identified as the causal agent of this emerging disease on barley (Hordeum vulgare L.) based on symptoms and signs on leaves and attributes of the fungus. The common name given to the disease was "necrotic sprinkling." This disease was found for the first time on barley in fields o...

Ramularia collo-cygni (Rcc) is becoming an increasing problem for barley growers across Europe. However, the life cycle of the pathogen is only slowly being elucidated. In this study, Rcc DNA was detected in a number of harvested seed samples from 1999 to 2010, with mean levels peaking in winter barley samples in 2009. A number of experiments were...

The ascomycete pathogen Ramularia collo-cygni causes Ramularia leaf spot (RLS) on barley. Although R. collo-cygni is considerd an emerging disease of barley, little is known about genetic diver-sity or population genetic structure of this pathogen. We applied a set of polymorphic AFLP (Amplified Fragment Length Polymorphism) markers to investi-gate...

Disease risk curves are simple graphical relationships between the probability of need for treatment and evidence related to risk factors. In the context of the present article, our focus is on factors related to the occurrence of disease in crops. Risk is the probability of adverse consequences; specifically in the present context it denotes the c...

A number of different types of induced resistance have been defined based on differences in signalling pathways and spectra of effectiveness, including systemic acquired resistance and induced systemic resistance. Such resistance can be induced in plants by application of a variety of biotic and abiotic agents. The resulting resistance tends to be...

Barley is one of the world’s most important crops providing food and related products for millions of people. Diseases continue to pose a serious threat to barley production, despite the use of fungicides and resistant varieties, highlighting the impact of fungicide resistance and the breakdown of host plant resistance on the efficacy of control me...

The influence of host genotype on the expression of induced resistance was examined in several cultivars of spring barley (Hordeum vulgare). Induced resistance was activated using a combination of elicitors (acibenzolar-S-methyl, beta-aminobutyric acid, and cis-jasmone) shown in previous work to induce resistance effectively in barley. The barley c...

A combination of three resistance elicitors, acibenzolar-S-methyl (ASM), beta-aminobutyric acid (BABA) and cis-jasmone (CJ) was shown to control powdery mildew (Blumeria graminis f. sp. hordei) and leaf scald (caused by Rhynchosporium secalis) in two spring barley varieties under field conditions. However, over the two consecutive years of field ex...

Ramularia collo-cygni, the causal agent of ramularia leaf spot disease in barley was transformed to express the green fluorescent protein and DsRed fluorescent protein using a combined protoplast and Agrobacterium tumefaciens-mediated transformation technique. Regenerated protoplasts from mycelial fragments were transformed with A. tumefaciens stra...

A combination of three resistance elicitors, acibenzolar-S-methyl (ASM), β-aminobutyric acid (BABA) and cis-jasmone (CJ) was shown to control powdery mildew (Blumeria graminis f.sp. hordei) and leaf scald (caused by Rhynchosporium secalis) in two spring barley varieties under field conditions. However, over the two consecutive years of field experi...

The aim of this study was to develop a real-time quantitative PCR test to recognize and quantify the DNA levels of the increasingly important barley pathogen Ramularia collo-cygni. The method described uses specifically designed primers and a molecular beacon probe based on an internal transcribed spacer (ITS) sequence. Pathogen extracted from barl...

When plants resist pathogen attack, resources must be diverted from growth and reproduction towards defense. Induced resistance in plants provides protection against a broad spectrum of pathogens, and defenses can be activated directly, or following pathogen attack, a phenomenon known as priming. Direct induction of resistance incurs costs in Arabi...

The effects of α-difluoromethylornithine (DFMO) on in vitro ornithine decarboxylase (ODC) activities from three plant pathogenic fungi, Pyrenophora avenae, Pyricularia oryzae and Uromyces viciae-fabae, were studied. DFMO concentrations from 0·01 to 1·0 mmol/l produced no significant effects on ODC activities from the three fungi. However, increasin...

A method of inoculating seedlings with the fungus Ramularia collo-cygni, the causal agent of ramularia leaf spot (RLS), an increasingly important problem in barley in Europe and elsewhere, is described. Symptoms of RLS similar to those found in the field were reproduced on seedlings and the fungus was re-isolated from them, fulfilling the third and...

Ramularia collo-cygni is now recognized as an important pathogen of barley in Northern Europe and New Zealand. It induces necrotic spotting and premature leaf senescence, leading to loss of green leaf area in crops, and can result in substantial yield losses. The fungus produces a number of anthraquinone toxins called rubellins, which act as host n...

The hypothesis that the increased use of the powdery mildew-resistance gene mlo has caused the increase in spotting diseases of barley over the past 20 years was tested in field trials. Near-isogenic lines with alleles of the Mlo gene for susceptibility or resistance to mildew in two parental backgrounds were trialled at four sites in Scotland and...

Mycelial growth, polyamine concentrations and the activities of enzymes of polyamine biosynthesis and catabolism were examined in Phytophthora infestans and Pythium ultimum grown in the presence of difluoromethylornithine (DFMO), an inhibitor of omithine decarboxylase (ODC), and difluoro‐methylarginine (DFMA), an inhibitor of arginine decarboxylase...

Ramularia collo-cygni is a barley pathogen of increasing importance in Northern and Central Europe, New Zealand and South America. Accurate visual and microscopic identification of the pathogen from diseased tissue is difficult. A nested PCR-based diagnostic test has been developed as part of an initiative to map the distribution of the pathogen in...

Mycelial growth, polyamine concentrations and the activities of enzymes of polyamine biosynthesis and catabolism were examined in the late blight fungus Phytophthora infestans, grown in the presence of the putrescine analogue (E)-(N,N,N′,N′-tetraethyl)-1,4-diaminobut-2-ene (E-TED). Growth of P. infestans was significantly reduced by 5 mmol l−1 E-TE...

A function was derived to predict fungicide efficacy when more than one application of a single active ingredient is made to a crop, given parameters describing the dose–response curves of the component single-spray applications. In the function, a second application is considered to act on that proportion of the total pathogen population which was...

More efficient use of reduced dose fungicide applications could be achieved by monitoring fungicide residue in crops and tailoring the dose accordingly in later applications. In an HGCA funded project, a specific antibody was produced to the triazole fungicide, tebuconazole, and a test system developed to use it to determine tebuconazole residues i...

More efficient use of reduced dose fungicide applications could be achieved by monitoring fungicide residue in crops and tailoring the dose accordingly in later applications. In an HGCA funded project, a specific antibody was produced to the triazole fungicide, tebuconazole, and a test system developed to use it to determine tebuconazole residues i...

A number of novel, cyclic diamines were synthesized and examined for fungicidal activity as part of a continuing program of work on polyamine analogues. The novel synthetic cyclic diamines trans-1,2-bis(diethylaminomethyl)cyclopentane (compound 1) and trans-5,6-bis(aminomethyl)bicyclo[2.2.1]hept-2-ene (compound 2) and the synthetic cyclic diamine 1...

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 p...

Mycelial growth, polyamine concentrations and the activities of enzymes of polyamine biosynthesis and catabolism were examined in the late blight fungus Phytophthora infestans, grown in the presence of the putrescine analogue (E)-(N,N,N',N'-tetraethyl)-1,4-diaminobut-2-ene (E-TED). Growth of P. infestans was significantly reduced by 5 mmol 1-1 E-TE...

As part of an ongoing program of work on polyamine analogues, a number of alicyclic diamines were synthesized and examined for fungicidal activity. The alicyclic diamine 1,2-bis(aminomethyl)-4,5-dimethylcyclohexa-1,4-diene (BAD), synthesized as the dihydrochloride salt, controlled the important crop pathogen Erysiphe graminis f.sp hordei. Greatest...

The putrescine analogue. (E)-1,4-diaminobut-2-ene (E-BED), synthesized as the dihydrochloride salt, controlled five economically important crop pathogens, Erysiphe qraminis DC f.sp. hordei Marchal. Uromyces viciae-fabae (Pers.) Schroet, Botrytis fabae Sardina, Podosphaera leucotricha (Ell. & Ev.) Salm. and Phytophthora infestans (Mont) De Bary. The...

The synthetic putrescine analogues (E)-N,N,N′,N′-tetraethyl-l,4-diaminobut-2-ene(E-TED), the (Z)-isomer (Z-TED) and (E)-N,N-dimethyl-1,4-diaminobut-2-ene(E-DMD) were prepared as their salts, and controlled five important crop pathogens (Erysiphe graminis DC f.sp. hordei Marchal, Uromyces viciae-fabae (Pers.) Schroet, Botrytis fabae Sardina, Podosph...