Evaluation of Field Experiments by Direct Allozyme Analysis of Late Blight Lesions Caused by Phytophthora infestans

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.Abstract: The glucose-6-phosphate isomerase genotype of Phytophthora infestans was determined directly from individual foliar lesions or portions of lesions collected into microcentrifuge tubes in the field. Fresh or frozen samples were processed and subjected to standard starch gel electrophoresis. This method was used to determine the frequencies of two isolates of known but different glucose-6-phosphate isomerase genotype in a competitive aggressiveness experiment and to quantify the effect of contamination between field experiments. The direct analysis confirmed a large difference in tomato aggressiveness between the two isolates, but also suggested a difference in aggressiveness on potato between the two isolates. The direct assay enabled a single person to determine the allozyme genotype of the isolate causing each of 1,404 lesions during the 29 d of the field experiment.

Host adaptation to potato and tomato within the US−1 clonal lineage of Phytophthora infestans in Uganda and Kenya

“…Field experiments should be done to test competitive fitness on potato and tomato, since additional factors in the field could be very important. Legard & Fry (1996) and Lebreton et al . (1999) performed field experiments to compare isolates from potato and tomato that could be differentiated by allozyme analysis.…”

“…Tomato‐adapted isolates (US−1) in Ecuador ( Oyarzun et al ., 1998 ) were less aggressive on potato than were potato‐adapted isolates (EC−1). Differential adaptation was demonstrated in a field experiment in the USA ( Legard & Fry, 1996) and in Europe ( Lebreton et al ., 1999 ). These data are also consistent with the hypothesis that adaptation to tomato is associated with a loss of pathogenic fitness on potato.…”

“…Adaptation of P. infestans to potato and tomato has been detected in other locations ( Brommonschenkel, 1988; Fry et al ., 1991 ; Goodwin et al ., 1992b ; Koh et al ., 1994 ; Legard & Fry, 1996; Oyarzun et al ., 1998 ; Fraser et al ., 1999 ; Lebreton et al ., 1999 ). In those cases, the two populations generally belonged to different clonal lineages, or were different genotypes from areas where sexual recombination occurs, but there were exceptions.…”

The Genetics and Biology ofPhytophthora infestans:Modern Approaches to a Historical Challenge

“…Variation between isolates in their aggressiveness on different potato cultivars, their ability to grow on tuber versus foliage tissue, and their relative abilities to colonize potato versus tomato have been described (Legard et al, 1995;Legard and Fry, 1996;Marshall and Stevenson, 1996;Mills, 1940). Further study may lead to an understanding of the factors involved in pathogenesis and how P. infestans evades different plant defenses.…”