Volatile Compounds in Endophyte Infected Festuca arundinacea: Impact on Heteronychus Arator Host Selection

Abstract

Abstract Mediterranean (M) and Continental (C) Festuca arundinacea cultivars in Australia are either endophyte–free (E–) or uniquely infected with the fungal endophyte Neotyphodium coenophialum strain AR542 (EAR542). The impact of volatile oils produced by Mediterranean and Continental cultivars in response to EAR542 on enhancing the grass’s resistance to insects is still largely unknown. In this study, we determined the volatile-oil profiles produced by ME–, CE–, MEAR542 and CEAR542 cultivars and their impacts on the host-selection behavior of H. arator adults. A total of 22 volatile compounds were detected in all F. arundinacea samples tested irrespective of being from Mediterranean or Continental cultivars and with or without endophyte. Octanal, 2-ethylhexanol, dodecane, (Z)-2-hexen1-1-ol, butyl hexanoate, (Z)-3-hexen-1-ol, 1-octen-3-ol, and butylated hydroxytoluene were the major compounds identified and variably influenced by the germplasm and endophyte infection status. Quantitatively, ME– expressed lesser quantities of 1,6-octandien-1-ol, hexanal, hexanol, 1-octen-3-ol and ethyl-3-hydroxypentanoate compared with CE– but greater quantities of butylated hydroxytoluene and hexylhexanoate. Compared with ME–, the quantities of octanal, 2-ethylhexanol, pentanal, hexanal, undecanal, 1-octen-3-ol, (Z)-2-octen-1-ol and clovene were greater in MEAR542. However, compared with CE–, hexanal, undecanal, undecane, i-octen-3-ol, (Z)-2-octen-1-ol, cloven and butylated hydroxytoluene were greater in CEAR542. In four-choice assay, the percentage of the numbers of H arator adult males choosing one of the choices ME–, MEAR542, CE– or CEAR542 was not significantly different compared to females choosing any of the respective choices. The impact of the germplasm on the host selection of H. arator adults was determined using two-choice assay olfactometer. The H. arator adults significantly (χ2 = 10 d.f. = 1, P < 0.002) preferred ME– compared with CE–. In contrast, the CEAR542 was significantly (χ2 = 26.67, d.f. = 1, P < 0.05) preferred host by same beetles compared with MEAR542. Mediterranean germplasm is different to the Continental germplasm in relation to the quantities of volatile compounds produced and these quantities in Mediterranean and Continental cultivars variably influenced by EAR542 infection. Whether changes in quantities of the volatile compounds in EAR542–infected grasses impose any agricultural or ecological impact require further investigation.