Aggressiveness of Phytophthora infestans on detached potato leaflets in four Nordic countries

Abstract

Potato fields in Denmark, Finland, Norway and Sweden were sampled for single-lesion isolates of Phytophthora infestans . The aggressiveness of the isolates was determined on detached leaflets of potato cvs Bintje (susceptible) and Matilda (moderately resistant). The aggressiveness tests were carried out in the respective home countries of the isolates, with the exception of the Danish isolates. Fifteen Danish isolates were studied in each of the other three countries, including five isolates tested in all three laboratories. Results obtained from the Danish isolates revealed substantial differences between the test laboratories for infection efficiency, lesion growth rate and sporulation capacity on detached leaflets. When the laboratory effect was taken into account, the differences in aggressiveness between the countries were generally small or inconsistent between the test cultivars and epidemiologically insignificant. By contrast, variation among isolates within countries was substantial. The magnitude of the variation depended on country and cultivar. Maximal variation for the means of the isolates was between 89 and 185 h for latent period, between 100 and 1297 sporangia mm − 2 for sporulation capacity and between nearly zero and 6 mm day − 1 for lesion growth rate. Typically less than 1% of sporangia were able to cause infections, except in Norway. These extraordinarily low values may be an artefact of the testing method. High variation in results between the test laboratories emphasizes the need for caution when comparing results obtained by different research groups.

Epidemiology and Integrated Control of Potato Late Blight in Europe

“…This study also disclosed differences between isolates in other aggressiveness parameters, e.g., sporulation capacity and lesion growth. Complementary experiments showed a good correlation between the aggressiveness indices obtained in the laboratory and results from inoculated field trials (Lehtinen et al 2009). However, we have no earlier experimental data from this region to compare these data to in order to show if changes in epidemiological parameters have occurred.…”

Plant-mediated gene silencing restricts growth of the potato late blight pathogen Phytophthora infestans

“…The effect of PiGPB1 silencing on spore formation was assayed by analysing the shape and number of sporangia using an epifluorescence microscope (Leica DMI 4000). Sporangia were collected at 24, 48, 72, and 96 hpi from detached leaves and counted 1h after leaf detachment as described by Lehtinen et al (2009) .…”

Quantitative proteomics and transcriptomics of potato in response to Phytophthora infestans in compatible and incompatible interactions

“…Five-week-old plants were transferred to an infection chamber with 100% humidity and 10:14 light:dark cycle. After 6 hours, plants were sprayed with an encysted zoospore suspension from P. infestans isolate SE-03058 [ 46 ] until the leaf surfaces were fully saturated with the zoospore suspension (15000 sporangia/ml). Relative humidity was maintained at 100% for 2 days after inoculation and then adjusted to 90% for the rest of the experiment.…”