Aerial diffusion of phytopathogenic fungi

Summary Aeriobiological studies are essential for understanding the distribution, ecology and deposition patterns of both phytopathogenic and nonpathogenic fungal spores which are carried away from their source. Many spores and conidia are devitalized during aerial transportation as a consequence of being exposed to atmospheric agents. Nonetheless, a sufficient number remain viable, causing infections of various kinds, some of which extremely serious and with an epidemic trend.In order to predict the onset of fungi-induced diseases, it is necessary to be able to determine the inoculum source of the pathogenic agent. As air is the main vector transporting pathogenic fungal spores and conidia, periodical monitoring is required. Thus, having established the critical stages of plant infection, necessary precautionary measures can be undertaken in order to control diseases onset and development.It is therefore necessary to gain a through understanding of spore takeoff and dispersal mechanisms so as to determine how the spores and conidia are transported by air currents onto the plants and how they cause infective impaction. Spores and conidia suspended in the atmosphere can be collected by means of appropriate traps filtering a predetermined amount of air at predetermined time intervals in order to be able to make predictions as to the possibility of plant infection. Volumetric air sampling allows not only to determine the concentration of spores and conidia in a given period of time but also to establish the hours of the day in which they are present in highest concentrations and in which therefore they are more liable to cause infection. This information may be used in estimating the incidence of disease symptoms, the duration of infection and the seriousness of the disease.On the basis of this data, mathematical models for predicting epidemics can be worked out.     

Large-scale population analysis challenges the current criteria for the molecular diagnosis of fascioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy (FSHD) is a common hereditary myopathy causally linked to reduced numbers (≤8) of 3.3 kilobase D4Z4 tandem repeats at 4q35. However, because individuals carrying D4Z4-reduced alleles and no FSHD and patients with FSHD and no short allele have been observed, additional markers have been proposed to support an FSHD molecular diagnosis. In particular a reduction in the number of D4Z4 elements combined with the 4A(159/161/168)PAS haplotype (which provides the possibility of expressing DUX4) is currently used as the genetic signature uniquely associated with FSHD. Here, we analyzed these DNA elements in more than 800 Italian and Brazilian samples of normal individuals unrelated to any FSHD patients. We find that 3% of healthy subjects carry alleles with a reduced number (4–8) of D4Z4 repeats on chromosome 4q and that one-third of these alleles, 1.3%, occur in combination with the 4A161PAS haplotype. We also systematically characterized the 4q35 haplotype in 253 unrelated FSHD patients. We find that only 127 of them (50.1%) carry alleles with 1–8 D4Z4 repeats associated with 4A161PAS, whereas the remaining FSHD probands carry different haplotypes or alleles with a greater number of D4Z4 repeats. The present study shows that the current genetic signature of FSHD is a common polymorphism and that only half of FSHD probands carry this molecular signature. Our results suggest that the genetic basis of FSHD, which is remarkably heterogeneous, should be revisited, because this has important implications for genetic counseling and prenatal diagnosis of at-risk families.     

Effects of waterlogging on soil aeration and on root and shoot growth and yield of winter oats (Avena sativa L.)

Summary Winter oats were grown outdoors in lysimeters containing monoliths of a sandy loam soil. The soil was either freely-drained throughout the experiment or waterlogged to the soil surface from mid-January until mid-April. After the start of waterlogging the oxygen flux density decreased most rapidly nearer the soil surface and in the upper 50 cm declined to zero. At 80 cm depth the oxygen flux density at the end of the waterlogging still had not diminished to zero. While the soil was waterlogged root growth was negligible in the 20–50 cm zone of the soil profile, whereas below that depth root growth continued, reaching 95 cm by the end of the treatment. During the latter part of the waterlogging period root growth resumed in the upper 10 cm, and in the upper 2.5 cm was greater than in the freelydrained treatment.At the end of the waterlogging period, the total root length and shoot dry weights were 77 and 60% of those in the freely-drained treatment, tillering was restricted and leaf area index diminished. However, by anthesis, root length and shoot weights of the plants that had been waterlogged were only 10 and 12% less respectively than for the freely-drained plants. At harvest, total dry matter and grain yields were only 9% less, the latter largely through fewer grains per panicle.