Spot Form of Net Blotch Resistance in a Diverse Set of Barley Lines in Australia and Canada.

The responses of 95 barley lines and cultivars to spot form of net blotch (SFNB) caused by Pyrenophora teres f. maculata were analyzed as seedlings and adults in Australia and Canada. Cluster analyses revealed complex reaction responses. Only 2 lines (Esperance Orge 289 and TR3189) were resistant to all isolates at the seedling stage, whereas 15 lines and cultivars (81-82/033, Arimont, BYDV-018, CBSS97M00855T-B2-M1-Y1-M2-Y-1M-0Y, C19776, Keel, Sloop, Torrens, TR326, VB0111, Yarra, VB0229, WI-2477, WI2553, and Wisconsin Pedigree) were resistant toward the two Canadian isolates and mixture of Australian isolates at the adult stages. In Australian field experiments, the effectiveness of SFNB resistance in three barley cultivars (Barque. Cowabbie, and Schooner) and one breeding line (VB9104) with a different source of resistance was tested. Barque, which possessed a resistance gene that provided complete resistance to SFNB, was the most effective and showed no effect on grain yield or quality in the presence of inoculum. Generally, cultivars with seedling or adult resistance had less disease and better grain quality than the susceptible control. Dash, but they were not as effective as Barque. A preliminary differential set of 19 barley lines and cultivars for P teres I. maculata is proposed

The epipolythiodioxopiperazine (ETP) class of fungal toxins: Distribution, mode of action, functions and biosynthesis

Epipolythiodioxopiperazines (ETPs) are toxic secondary metabolites made only by fungi. The best-known ETP is gliotoxin, which appears to be a virulence factor associated with invasive aspergillosis of immunocompromised patients. The toxicity of ETPs is due to the presence of a disulphide bridge, which can inactivate proteins via reaction with thiol groups, and to the generation of reactive oxygen species by redox cycling. With the availability of complete fungal genome sequences and efficient gene-disruption techniques for fungi, approaches are now feasible to delineate biosynthetic pathways for ETPs and to gain insights into the evolution of such gene clusters

Interaction of cowpea with Phytophthora vignae: inheritance of resistance and production of phenylalanine ammonia-lyase as a resistance response

The interactions between Phytophthora vignae and two cowpea cultivars are described. The cultivars are near-isogenic but differ in their resistance to P. vignae race 2. Cultivar Caloona is resistant, cv. Poona is susceptible. Resistance of cv. Caloona to race 2 is controlled by a single dominant gene and is expressed throughout the life of the plant in all tissues at temperatures up to 35°C. Inoculation of cut cowpea epicotyls with a plug of agar containing race 2 hyphae provides a reliable method of obtaining host tissue which responds in a predictable way to the pathogen. Phenylalanine ammonia-lyase (PAL) activity increases rapidly in invaded epicotyl tissue of cv. Caloona in response to inoculation with race 2. Increased PAL activity in advance of the hyphae is not detected. Low levels of PAL are produced by cv. Poona and cv. Caloona in response to inoculation with a race virulent on both cultivars (race 3). Application of l-2-aminooxy-3-phenylpropionic acid (1 mm) or aminooxy acetic acid (10 mm) through the cut bases of hypocotyls of cv. Caloona seedlings results in this cultivar, normally resistant to P. vignae race 2, becoming susceptible

Comparative efficiency of domestic hot water systems

2. ed.; Reports supersede nos 57800/1 and 57800/2, pub. Aug 1989; Work carried out for Waterheater Manufacturers AssociationSIGLEAvailable from British Library Document Supply Centre- DSC:7389.20(BSRIA--57800/1-2) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Deletions, repeat-induced point mutations and amino acid substitutions drive evolution of linked effectors in a fungal plant pathogen

Pathogen effectors, molecules that include small secreted proteins such as avirulence proteins, facilitate infection or induce defence responses by plants. We report the first large scale study of evolutionary processes affecting linked effector-like genes in a fungal plant pathogen. Mutations affecting seven genes and four single copy non-coding regions located in a 520 kb repetitive element-rich region of Leptosphaeria maculans, a pathogen of Brassica napus (canola) are described. Two genes are avirulence genes, AvrLm1 and AvrLm6, which are complementary to B. napus resistance genes, Rlm1 and Rlm6. Analyses of 295 Australian isolates showed that deletions, Repeat-Induced Point (RIP) mutations and/or non-RIP derived amino acid substitutions account for rapid evolution of four small secreted proteins. RIP was confined to three genes and two other single copy regions and appeared to have ‘leaked’ from flanking repetitive sequences. The RIP alleles were monophyletic and present only in isolates collected after 2004, the year when canola cultivars with resistance conferred by Rlm1 suffered severe yield losses. This co-incided with a large increase in the frequency of isolates with virulence alleles of AvrLm1 and AvrLm6, even though the canola cultivars lacked Rlm6. Evolution of these two effectors thus appears to be influenced both by the genomic environment (flanking repetitive elements) and by selection pressure from extensive sowing of crop varieties with resistance genes complementary to the avirulence effector gene

Comparative efficiency of domestic hot water systems

2. ed.; Reports supersede nos 57800/1 and 57800/2, pub. Aug 1989; Work carried out for Waterheater Manufacturers AssociationSIGLEAvailable from British Library Document Supply Centre- DSC:7389.20(BSRIA--57800/1-2) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

AT-rich isochores as ecological niches for effectors in the genome of Leptosphaeria maculans

International audienceAT-rich isochores as ecological niches for effectors in the genome of Leptosphaeria maculans The genome of the ascomycete Leptosphaeria maculans shows the unusual characteristics to be organized in isochores. GC-equilibrated isochores (average 52% GC) are gene-rich whereas AT-rich isochores (40–43% GC) are mostly devoid of active sequences and are made up of mosaics of intermingled and degenerated repeated elements. The three avirulence (AvrLm) genes identified so far in this species are isolated in the middle of large AT-rich isochores. Our postulate thus was that AT-rich isochores were specific “ecological niches” for avirulence genes and effectors in L. maculans. This was firstly validated by analysis of three genes lying in the same genome environment (LmCys genes) and showing the same characteristics as AvrLm genes (low GC content, strong overexpression at the onset of plant infection, encoding for small secreted proteins -SSP- often rich in cysteines). Of these, one, LmCys2, was shown to act as an effector, probably contributing to suppression of plant defense. A systematic search for SPP as effector candidates was performed using bioinformatics. 455 AT-rich isochores were extracted from the genome data and their repeat content masked using the L. maculans repeat database. Non-repeated regions were then investigated with a pipe-line dedicated to the identification of SSP. This provided us with three datasets: 529 SSP-encoding genes in GC-equilibrated isochores, 498 non- SSP- and 122 SSP-encoding genes in AT-rich isochores. Part of this latter set of genes was analyzed for their occurrence in natural populations and expression data in culture and in planta. Finally, the 122 AT-SSP putative proteins showed structural features reminiscent of the AvrLm and LmCys genes. Possible diversification mechanisms as a function of genome location will be discussed

Brassica napus plants infected by Leptosphaeria maculans after the third to fifth leaf growth stage in south-eastern Australia do not develop blackleg stem canker

The original publication can be found at www.springerlink.comBlackleg (Phoma stem canker) caused by Leptosphaeria maculans is the most damaging disease of Brassica napus (canola, rapeseed, colza) worldwide and is controlled by sowing blackleg resistant cultivars and crop management strategies that reduce exposure to inoculum and fungicide application. In experiments in south-eastern Australia, canola cultivars inoculated after the three to five leaf growth stage did not develop stem canker. Although mature canola plants are known to be less susceptible to blackleg than seedlings, this highlights for the first time the specific importance of protecting seedlings up to the three to five leaf growth stage in Australia. This would typically correspond to a period of four to six weeks after emergence. Canola plants are likely to be significantly less vulnerable to infection after this growth stage. However, this timing may vary due to the influence of environmental conditions.S.J. Marcroft, M.R. Sosnowski, E.S. Scott, M.D. Ramsey, P.A. Salisbury, B.J. Howlet