Gas chromatography–mass spectrometry analyses of volatile organic compounds from potato tubers inoculated with Phytophthora infestans or Fusarium coeruleum

Abstract

Volatile organic compounds (VOCs) collected from potato tubers inoculated with Phytophthora infestans (late blight), Fusarium coeruleum (dry rot) or sterilized distilled water (as a control) were analysed using gas chromatography±mass spectrometry (GC±MS) and gas chromatography±flame ionization detection (GC±FID). A total of 52 volatiles were identified by GC±MS in the headspaces above P. infestans-and F. coeruleum-inoculated tubers after incubation for 42 days in the dark at 108C. Of these VOCs, the six most abundant were common to both pathogens. These were benzothiazole (highest abundance), 2-ethyl-1-hexanol (second highest abundance), and at approximately equal third abundance, hexanal, 2-methylpropanoic acid-2,2-dimethyl-1-(2-hydroxy-1-methylethyl)-propyl ester, 2-methylpropanoic acid-3-hydroxy-2,4,4-trimethyl-pentyl ester and phenol. In addition, styrene also occurred at approximately equal third abundance in the headspace of F. coeruleum-inoculated tubers, but at lower abundance in the headspace of P. infestans-inoculated tubers. Some VOCs were specific to each pathogen. Butanal, 3-methylbutanal, undecane and verbenone were found at low levels only in the headspace of tubers inoculated with P. infestans, while 2-pentylfuran and copaene were found only in the headspace of tubers inoculated with F. coeruleum. Additionally GC±FID analysis identified ethanol and 2-propanol in the liquid exudate from both P. infestans-and F. coeruleum-inoculated tubers after incubation for 35 days, and in the headspace after incubation for 42 days. These data provide key information for developing a sensor-based early warning system for the detection of postharvest diseases in stored potato tubers.

Airborne Induction and Priming of Plant Defenses against a Bacterial Pathogen

“…All three compounds have repeatedly been reported in the context of plant pathogenesis: nonanal and 2-ethyl hexanol were found in the headspace of potato (Solanum tuberosum) tubers infected with different fungi (de Lacy Costello et al, 2001) and of various biological control bacteria (Dilantha Fernando et al, 2005), nonanal was released from whiteflyinfected beans (Phaseolus vulgaris; Birkett et al, 2003), and both nonanal and 2-ethyl hexanol were reported to have in vitro antifungal (Dilantha Fernando et al, 2005) and bactericidal (Nakamura and Hatanaka, 2002) activities.…”

“…However, although 2-ethyl hexanol has repeatedly been reported in the context of pathogenesis (de Lacy Costello et al, 2001;Nakamura and Hatanaka, 2002;Dilantha Fernando et al, 2005), the compound is also a very common contaminant. In fact, no convincing study has ever reported a clear case of plant-derived 2-ethyl hexanol (W. Boland, personal communication).…”

Cereal crop volatile organic compound induction after mechanical injury, beetle herbivory (Oulema spp.), or fungal infection (Fusarium spp.)

“…VOC induction has also been detected in fungal inoculated potatoes (De Lacy Costello et al, 2001;Kushalappa et al, 2002), peanuts (Cardoza et al, 2002), wheat (Piesik et al, 2007), onions (Vikram et al, 2005), and higher ethylene emission from Monterey pine (Bonello et al, 2001). Plant responses to biotic and abiotic perturbation often reduce the severity of future damage through complex changes.…”

Maize Voc Induction after Infection by the Bacterial Pathogen, Pantoea ananatis, Alters Neighbouring Plant Voc Emissions

“…Thus, certain pathogens may be severe enough, or infect maize in such a manner, that VOC induction results (Piesik et al 2011, current study). Studies with other plant species have also detected VOC induction after pathogen infection (Bonello et al 2001, De Lacy Costello et al 2001, Cardoza et al 2002, Vikram et al 2005. More needs to be understood to determine whether certain mechanisms of pathogen infection result in VOC induction and other types of pathogens do not, and the extent to which this is generalizable across plants and pathogens.…”