Phenotypic variation in the phenology of ascospore production between European populations of oak powdery mildew

? Oak powdery mildew severity (Erysiphe alphitoides) is usually mild in Europe because epidemics start late in spring, at the end of the first oak growth unit maturation. However, the disease can occasionally be very severe when strong infection occurs early during the development of the first growth unit, suggesting that host-pathogen synchrony in spring could be a critical factor in disease severity.

? We studied the timing of ascospore production in a given environment for four E. alphitoides populations sampled from SW France to the Czech Republic to determine whether this trait shows variation within Europe.

? Timing of ascospore production was clearly influenced by environmental factors as chasmothecia from a single origin showed very different dates of optimal ascospore production when transferred for overwintering in locations with different climate. In common garden experiments, no differences were observed between populations for the date of optimal ascospore production.

? Results suggest little genetic differentiation for timing of ascospore production for E. alphitoides populations across Europe and therefore a lack of local adaptation to their host phenology. Availability in ascospore inoculum is limited during host budburst, explaining the low infection usually observed on the first oak growth unit.

     

Incidence and economics of clinical mastitis in five Holstein herds in the Czech Republic

Data on clinical mastitis (CM) collected between 1996 and 2003 on five Holstein dairy farms in the Czech Republic were analyzed. Lactational incidences of CM, averaged across farms and calculated only from cows with complete lactations, were 0.35, 0.45 and 0.57 for the first, second and third plus subsequent lactations, respectively. The mean numbers of CM cases per cow and lactation were 0.63, 0.94 and 1.22, and the incidence of CM cases per cow-year at risk were 0.68, 1.00 and 1.27 for the first, second and third plus subsequent lactations, respectively. Longitudinal analysis of CM prevalence based on daily records showed the highest proportion of infected cows in the first 10 days of lactation. The within-farm incidence of CM cases per cow per year, averaged over lactations, ranged from 0.53 to 1.56 with a mean value of 0.94 in the whole data set. Direct financial losses from CM per cow per year within farm ranged from 43.63 to 84.84 euros. They included losses from discarded milk, cost for drugs, veterinary service, herdsman's time, cost for an extra milking machine and cost for antibiotic drying of cows. The economic value of CM incidence (change in direct losses per cow per year when increasing CM incidence by one case above the average value) ranged from 58.3 to 80.1 euros per CM case per cow per year with the mean value of 62.6 euros per CM case per cow per year in the total data set. Daily prevalence rate of CM was shown to be the best among various indicators of CM susceptibility, because it accounted for the censored character of the data and for repeated cases of CM within lactations. In order to reduce the incidence of clinical mastitis for dairy cattle in the Czech Republic, we recommend that it should be included as a goal in the breeding program.