Long-chain alkanes and fatty acids fromLudwigia octovalvisweed leaf surface waxes as short-range attractant and ovipositional stimulant toAltica cyanea(Weber) (Coleoptera: Chrysomelidae)

Abstract

The importance of leaf surface wax compounds from the rice-field weed Ludwigia octovalvis (Jacq.) Raven (Onagraceae) was determined in the flea beetle Altica cyanea (Weber) (Coleoptera: Chrysomelidae). Extraction, thin layer chromatography and GC-MS and GC-FID analyses of surface waxes of young, mature and senescent leaves revealed 20, 19 and 19 n-alkanes between n-C15 and n-C35, respectively; whereas 14, 14 and 12 free fatty acids between C12:0 and C22:0 fatty acids were identified in young, mature and senescent leaves, respectively. Tricosane was predominant n-alkane in young and mature leaves, whilst eicosane predominated in senescent leaves. Heneicosanoic acid, palmitic acid and docosanoic acid were the most abundant free fatty acids in young, mature and senescent leaves, respectively. A. cyanea females showed attraction to 0.25 mature leaf equivalent surface waxes compared with young or senescent leaves in a short glass Y-tube olfactometer bioassay. The insects were attracted to a synthetic blend of 0.90, 1.86, 1.83, 1.95, 0.50 and 0.18 µg ml−1 petroleum ether of hexadecane, octadecane, eicosane, tricosane, palmitic acid and alpha-linolenic acid, respectively, comparable with the proportions as present in 0.25 mature leaf equivalent surface waxes. A. cyanea also laid eggs on a filter paper moistened with 0.25 mature leaf equivalent surface waxes or a synthetic blend of 0.90, 1.86, 1.83, 1.95, 0.50 and 0.18 µg ml−1 petroleum ether of hexadecane, octadecane, eicosane, tricosane, palmitic acid and alpha-linolenic acid, respectively. This finding could provide a basis for monitoring of the potential biocontrol agent in the field.

High Concentrations of Very Long Chain Leaf Wax Alkanes of Thrips Susceptible Pepper Accessions (Capsicum spp)

“…Some insects can use the plant wax metabolites, and specifically the alkanes, as oviposition stimulants (e.g. Spencer 1996 , Müller and Hilker 2001 , Mitra et al 2017 ). The reasons why thrips or other insects prefer plants with more alkanes are thus far unknown.…”

“…For example, amyrins (triterpenoids) reduced feeding by diamandback moth larvae on cabbage (Eigenbrode and Pillai 1998 ). On the other hand, some wax metabolites can also be used for host plant recognition and as feeding stimulants by various insects such as sawflies and flea beetles (Braccini et al 2015 ; Mitra et al 2017 ; Müller and Hilker 2001 ; Udayagiri and Mason 1997 ). Relatively high amounts of leaf wax have been associated with higher susceptibility against thrips in onions and leak (Damon et al 2014 ).…”

Cuticular Waxes of Arabidopsis thaliana Shoots: Cell-Type-Specific Composition and Biosynthesis

“…The occurrence of very low amounts of compounds at the high end of the homolog distribution suggested that they are formed merely as by-products of the normal wax biosynthesis machinery rather than through dedicated processes specific to their chain lengths. Characterization of enzymes involved in wax precursor elongation in respective species may reveal whether, in these cases, single FAEs indeed form both the ubiquitous chain lengths and the C 35+ homologs [ 2 , 6 , 23 , 39 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 ].…”

Attraction of the potential biocontrol agent Altica cyanea by volatile compounds of three species of Ludwigia weeds from rice fields

“…Data were normally distributed as determined by Shapiro-Wilk tests (except those individual compounds which are not present in all treatments), and so data were analysed with one-way ANOVA followed by Tukey's test (Zar, 1999). Data on behavioural responses of A. cyanea to VOCs were analysed by v 2 test (H 0 : P = 50%) (Adhikary et al, 2015;Mitra et al, 2017b). Insects that remained in the stem of the olfactometer were excluded from the analyses.…”