Measuring late blight attack of potato foliage in field trials: optimal resource allocation in assessment trials

Ein empirischer Datensatz wurde analysiert, um Empfehlungen zur optimalen Faktorallokation in einem Feld­versuchssystem zur Erfassung des Krautfäulebefalls bei Kartoffel zu geben. Der Datensatz stammt von einem Experiment mit 854 Genotypen, drei Jahren, zwei Wiederholungen pro Jahr und 16 bis 18 Boniturterminen pro Jahr. AUDPC (area under disease progress curve) Werte wurden auf der Basis von Prozent Krautbefall berechnet. Zur Etablierung der Krautfäule im Bestand wurde künstliche Inokulation verwendet. Drei Prüfjahre, zwei Wiederholungen pro Jahr, und drei Boniturtermine werden als ausreichend empfohlen. Diese Ergebnisse gehen von der Voraussetzung aus, dass die Qualität der Daten unabhängig ist von der Häufigkeit der Datenerhebung. Diese Voraussetzung wird kritisch diskutiert.An empirical data set was analysed in order to give recommendations on the optimal resource allocation in a field testing system to measure late blight attack in potato. The data set was derived from an experiment comprising 854 genotypes, three years, two replicates per year, and 16 to 18 scoring dates per year. AUDPC (area under disease progress curve) values were calcu­lated based on percentage of attacked haulm. Artificial inoculation was used to establish late blight in the testing field. Three testing years, two replicates per year, and three scoring dates per year are recommended to be sufficient. The results are based on the assumption, that the quality of data is independent of the frequency of data collection. This assumption is critically discussed

Empirical comparison of different methods for correcting late blight (Phytophthora infestans (Mont.) de Bary) data for maturity in selection experiments of potato (Solanum tuberosum subsp. tuberosum)

Ein Vergleich verschiedener Maßzahlen zur Ermittlung der Resistenz gegenüber Krautfäule bei Kartoffel wurde mit Hilfe des multivariaten Verfahrens der Clusteranalyse durchgeführt. Bei der Darstellung einer Gruppe von Maßzahlen kam das BLUP-Verfahren (Best Linear Un­biased Prediction) zur Anwendung. Die Maßzahl rAUDPC_3, die vom Abreifeverhalten des jeweiligen Genotyps abhängt, wird zur Erfassung der reifekorrigierten Resistenz favorisiert, da sie bei ansonsten ähnlichem Verhalten mit den wenigsten theoretischen Annahmen im Vergleich zu den anderen Maßzahlen auskommt.A comparison of different measures to calculate resistance against late blight in potato was accomplished by means of the multivariate statistical tool of cluster analysis. One group of measures was based on the BLUP technique (Best Linear Unbiased Prediction). The measure rAUDPC_3, which takes into consideration the maturity group of the respective genotype, is recommended to capture maturity-corrected resistance, because of less theoretical assumptions with otherwise similar behaviour as compared to the rest of the measures

Phenotypic plasticity in the response of aphids to host plant quality

The objective of this study was first to determine whether the chemical defence of lupin is more effective against the generalist aphids that occur on lupins than the host specific, M. albifrons. Secondly, to determine whether the host specific aphid shows an increase in performance over time if it is reared on sweet lupin and whether the process is reversed when transferred back to a bitter variety of lupin. Of the lupin cultivars tested only those with strongly reduced alkaloid contents were acceptable as host plants by the generalist species of aphid tested, and only M. albifrons reproduced on the “bitter” cultivars. In order to define the performance of M. albifrons, developmental time, mean relative growth rate and number of embryos were recorded for two strains reared for several generations on a bitter cv. of lupin and then transferred for several generations to sweet lupin and then reared again on a bitter cv. of lupin. The performance of M. albifrons was not better on lupins rich in alkaloids. However, the results also indicate that this aphid can adapt and thrive on a previously resistant cultivar within five generations even when reproducing parthenogenetically and that this change is reversible