Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 21, 2003
Publication Date: October 1, 2003
Citation: Larkin, R.P., Groves, C.L. 2003. Identification and characterization of isolates of phytophthora infestans using fatty acid methyl ester (fame) profiles. Plant Disease. 87: 1233-1243 Interpretive Summary: Late blight disease, caused by Phytophthora infestans, can cause devastating losses on potato, and is one of the most important diseases in the world. Subgroups within this species have different characteristics that determine how aggressive or damaging the pathogen will be. Thus, the ability to characterize and differentiate different subgroups within P. infestans is very important for determining the impact and potential control measures for this pathogen. Currently available methods can characterize many genetic characteristics, but additional techniques for further characterization would be very useful. In this study, it was determined that analysis of cellular fatty acid composition of isolates of P.infestans can provide additional information on P. infestans subgroups and characteristics, and has potential for further differentiating subgroups of this pathogen. Fatty acid profiles corresponded with known genetic characteristics, and provided information on more isolate-specific characteristics. Individual isolates could be uniquely identified using this approach. When environmental conditions were kept constant, fatty acid profiles were distinct, consistent, and reproducible, and may provide greater differentiation of traits than is currently available. This information can be used by scientists studying late blight to provide a better understanding and better means of characterizing the populations of this pathogen, and ultimately lead toward development of improved control strategies.
Technical Abstract: The utility of fatty acid profiles for characterization and differentiation of isolates of P. infestans was investigated. Two libraries of fatty acid methyl ester (FAME) profiles (one representing average genotype characteristics and one representing individual isolate characteristics) were established from at least 8 replicate sample runs of each of 25 different isolates of P. infestans, including representative isolates of US-1, US-6, US-7, US-8, US-11, US-14, and US-17 genotypes. These libraries were then used to identify and characterize additional unknown isolates. FAME profiles from P. infestans were consistent over multiple extraction runs and distinctly different from profiles of other Phytophthora species, such as P. capsici and P. erythroseptica, as well as Pythium spp. and all fungal groups tested. Profiles from different isolates of the same genotype tended to group together, although there was overlap among some genotypes. Incubation temperature, growth medium, and prolonged storage as plate cultures all significantly affected FAME profiles, but when these conditions were kept constant, profiles were distinct, consistent, and reproducible over time. Isolate profiles were sufficiently specific that individual isolates could be identified by their FAME profiles. In general, individual isolate characteristics were more determinant than genotype group characteristics, although genotype could be determined for most isolates tested. Results indicated that FAME profiles can be an additional tool useful for characterizing isolates and populations of P. infestans.