Draft genome sequence of Pseudomonas fuscovaginae, a broad-host-range pathogen of plants.

addresses: International Centre for Genetic Engineering & Biotechnology, Trieste, Italy.notes: PMCID: PMC3347198types: Journal Article; Research Support, Non-U.S. Gov'tFreely available on Open AccessPseudomonas fuscovaginae was first reported as a pathogen of rice causing sheath rot in plants grown at high altitudes. P. fuscovaginae is now considered a broad-host-range plant pathogen causing disease in several economically important plants. We report what is, to our knowledge, the first draft genome sequence of a P. fuscovaginae strain

Assessing the Interplay between Weather and Septoria Leaf Blotch Severity on Lower Leaves on the Disease Risk on Upper Leaves in Winter Wheat

peer reviewedSeptoria leaf blotch (SLB) is among the most damaging foliar diseases of wheat worldwide. In this study, data for seven cropping seasons (2003–2009) at four representative wheat-growing sites in the Grand-Duchy of Luxembourg (GDL) were used to assess SLB risk on the three upper leaves (L3 to L1, L1 being the flag leaf) based on the combination of conducive weather conditions, simulated potential daily infection events by Zymoseptoria tritici, and SLB severity on lower leaves between stem elongation and mid-flowering. Results indicated that the variability in SLB severity on L3 to L1 at soft dough was significantly (p < 0.05) influenced by the disease severity on the lower leaf L5 at L3 emergence and the sum of daily mean air temperature between stem elongation and mid-flowering. Moreover, analyzing the predictive power of these variables through multiple linear regression indicated that the disease severity on L5 at L3 emergence and mild weather conditions between stem elongation and mid-flowering critically influenced the progress of SLB later in the season. Such results can help fine tune weather-based SLB risk models to guide optimal timing of fungicide application in winter wheat fields and ensure economic and ecological benefits

Effect of Temperature and Air Humidity On Multiplication of Xanthomonas-campestris Pv. Undulosa and Symptom Expression in Susceptible and Field-tolerant Wheat Genotypes

Multiplication of Xanthomonas campestris pv. undulosa in the leaf tis sues of susceptible and field-tolerant wheat genotypes was determined at the seedling stage, under different incubation conditions of temperature and air humidity. Dry air conditions did not hamper the multiplication of the bacteria in the leaf tissues, and temperature had a direct effect on the population trend. Symptoms were not observed at 15 degrees C. The occurrence of lesions coincided with populations of bacteria that had reached an estimated threshold of 10(8) colony forming units/ leaf. Differences in populations between genotypes Alondra and Pavon were only noticeable at 25 degrees C and dry air conditions, without correlation to differences in symptom expression. Considering these two genotypes, resistance to bacterial leaf streak did not seem to operate at the seedling stage when plants were inoculated by infiltration. In both genotypes, lesions did not extend significantly. An active mechanism stopping bacterial growth which is apparently temperature-dependent or a saturation of the target sites was possibly involved, as shown in the different experiments by the fit-curves calculated for Alondra and Pavon. This study provided information on the role of climatic factors in relation to epidemics. Temperature appeared to have a major effect on the disease and results confirmed that the risk of bacterial leaf streak prevails in warmer non-traditional wheal growing areas. Several types of resistance are likely to exist in the X. c. pv. undulosa/wheat system

Evidence for a heterothallic mating system in Tapesia acuformis using benomyl sensitivity and esterase isoenzyme profiles

Ascospore progenies from eight apothecia of Tapesia sp., collected from wheat stubble in Belgium and Germany, yielded strains characteristic of T. acuformis and strains characteristic of T. yallundae. The colony and conidium morphology, esterase isoenzyme profiles and sensitivity to benomyl, diethofencarb and triadimenol of these and of isolates from eyespot lesions were compared. Differences were detected amongst the ascospore offspring from single apothecia using these markers, but all strains from a single apothecium were always of a single species of Tapesia. Single-ascospore strains from a single ascus could always be grouped into four pairs using a combination of markers. In vitro pairwise crossings between four representative single-ascospore strains of T. acuformis yielded some mature and fertile apothecia on moist wheat straw inoculated with mycelium and incubated in test tubes under a mixture of nuv light and daylight at 8-12 degrees C for at least 6 months. Recombination was observed between the parental esterase zymograms and sensitivities to benomyl, leading to new phenotypes in the progeny. The results of pairing reference single-ascospore strains of both T. acuformis and T. yallundae with 115 isolates from eyespot lesions strengthened the contention that T. acuformis exhibits a two-allele heterothallism and that T. acuformis and T. yallundae are sexually incompatible species

Study On Yield Loss Due To Xanthomonas-campestris Pv Undulosa in Wheat Under High Rainfall Temperate Conditions

Yield losses due to bacterial leaf streak caused by Xanthomonas campestris pv. undulosa in wheat were evaluated using a method based on assessing infection in single tillers in a high rainfall temperature environment in Mexico. Trials conducted over 3 years showed that yield was significantly reduced in relation to the percentage area of flag leaf damaged at early milk-dough stage. The 1000-grain-weight was affected every year. The number of kernels per spike was affected during 2 years. Data over 3 years showed that, on average, losses below 5% can be expected when the percent flag leaf area diseased is below 10%. However, up to 20% yield reduction can be anticipated, on average, if 50% of the flag leaf is diseased. Yield loss is a linear function of the percent flag leaf area diseased and a small leaf area damaged has already an effect on yield. A formula is proposed to calculate at Zadoks' growth stage 73-83 the expected yield losses based on disease severity and on field incidence. The aim is to provide a tool for better quantification of yield losses, particularly, in high rainfall temperature locations where the disease is sporadic and yield losses difficult to appraise. The study showed that significant losses due to X. c. pv. undulosa can be expected in wheat