Kenneth L. Deahl

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ABSTRACT Dramatic changes occurred within populations of Phytophthora infestans in the United States and Canada from 1994 through 1996. Occurrence of the US-8 genotype, detected rarely during 1992 and 1993, increased rapidly and predominated in most regions during 1994 through 1996. US-7, which infected both potato and tomato and made up almost 50% of the(More)
Pest and pathogen losses jeopardise global food security and ever since the 19(th) century Irish famine, potato late blight has exemplified this threat. The causal oomycete pathogen, Phytophthora infestans, undergoes major population shifts in agricultural systems via the successive emergence and migration of asexual lineages. The phenotypic and genotypic(More)
 Glycoalkaloids are quantitatively inherited in Solanum, and in high concentrations they can be toxic to humans. The increased use of wild potato germplasm to improve the pest resistance, yield, and quality characteristics of cultivated potato may elevate or introduce new, more toxic glycoalkaloids into the cultivated gene pool. Therefore, it is important(More)
In recent years, late blight, caused by Phytophthora infestans (Mont) De Bary, has increased in severity in many parts of the world, and this has been associated with migrations which have introduced new, arguably more aggressive, populations of the pathogen. In Taiwan, late blight has been endemic on outdoor tomato crops grown in the highlands since the(More)
Leptine I, a glycoalkaloid only known to occur in the foliage of the wild potato species Solanum chacoense (Bitt.), is a potent feeding deterrent to the economically serious insect pest, the Colorado potato beetle (Leptinotarsa decemlineata Say). In order to demonstrate, systematically, the effectiveness of leptine I, incorporation into synthetic beetle(More)
Glycoalkaloids are a class of secondary compounds (nitrogenous, steroidal glycosides), ubiquitously distributed throughout the Solanaceae. Numerous studies (in planta) have shown that certain glycoalkaloids, e.g., α-tomatine, solanocardenine, and leptine, have a negative impact on performance of the Colorado potato beetle,Leptinotarsa decemlineata (Say).(More)
Isolates of Phytophthora infestans were obtained from late blighted plants from several potato-growing regions of Uruguay in 1998 and 1999. Of these, 25 representative isolates (4 from 1998, 21 from 1999) from the main potato-growing areas of the country, were characterised in terms of mating type, metalaxyl resistance, allozyme genotype, mitochondrial(More)
Diphenyleneiodonium (DPI) has been used frequently as a specific inhibitor of NADH oxidase activity in studies of plant/pathogen interactions. The present study reports the effect of DPI on the pseudo-oxidative activity of horseradish peroxidase. DPI, like other phenolics, is able to catalytically stimulate NADH oxidation in the presence of exogenous H2O2.(More)
Twenty-one homologs of family 5 endo-(1–4)-β-glucanase genes (EGLs) were identified and characterized in the oomycete plant pathogens Phytophthora infestans, P. sojae, and P. ramorum, providing the first comprehensive analysis of this family in Phytophthora. Phylogenetic analysis revealed that these genes constitute a unique eukaryotic group, with closest(More)
A total of 18 paralogs of xyloglucan-specific endoglucanases (EGLs) from the glycosyl hydrolase family 12 were identified and characterized in Phytophthora sojae and Phytophthora ramorum. These genes encode predicted extracellular enzymes, with sizes ranging from 189 to 435 amino acid residues, that would be capable of hydrolyzing the xyloglucan component(More)