Diagnostic application of fatty acid methyl ester (FAME) analysis for the identification of Meloidogyne species

Previous studies have indicated that fatty acid methyl ester (FAME) analysis has the potential to be used as a diagnostic tool for diagnostic nematode identification. Four experiments were carried out from May 2010 to April 2012 to evaluate field-based applications, environmental influence, extraction and analysis methods, and detection limits on FAME analysis of Meloidogyne species. Utilizing Solanum lycopersicum root tissue samples infected with M. arenaria, M. hapla, M. incognita, or M. javanica, FAME analysis was able to separate the four nematode-infected tissues from each other and uninoculated tissue (D2 > 14.08, P ≤ 0.0205). To assess the effect of varying temperatures on nematode FAME profiles, populations of M. incognita and M. javanica were maintained on S. lycopersicum in three diurnal environments and two fixed-temperature environments. Temperature did not have a significant impact on FAME profiles of M. incognita-infected tissue (D 2 ≤ 5.69, P ≥ 0.3192) or uninoculated S. lycopersicum tissue (D2 ≤ 3.13, P ≥ 0.1006) sustained in three diurnal environments, but did influence M. javanica-infected tissue (D2 ≥ 27.64, P < 0.0001). FAME profiles of M. incognita- and M. javanica-infected tissues maintained at 20°C and 26°C became more distinct over 135 days (D2 ≥ 91.83, P ≤ 0.0151), but these infected tissues could not be differentiated at 20°C (D2 = 43.27, P = 0.2221). A comparison of FAME extraction and analysis methods determined Instant FAME extraction and Rapid analysis methods produced more robust and reliable FAME profiles (D2 ≥ 25.08, P < 0.0001) than standard methods (D2 = 2.95, P = 0.9999) and reduced the sample size and time required for analysis. By assessing FAME analysis of M. graminis females at densities of 1, 2, and 5 individuals, single males, and single juveniles, it was possible to calculate the predicted response of a single nematode and establish a preliminary regression ( Response = 13,019*(Number) - 10,827; R 2 = 0.5928, P < 0.0001) that could potentially be used to quantify nematodes in a sample. These experiments indicate that further development of FAME analysis for diagnostic identification of Meloidogyne species should be considered as an alternative to morphological or molecular methods.