Potential to use n-alkanes in plant cuticular waxes to discriminate plant parts of subterranean clovers eaten by ruminants

Abstract

Proc. Aust. Sot. Anim. Prod. 1994 Vol. 20 POTENTIAL TO USE N-ALKANES IN PLANT CUTICULAR WAXES TO DISCRIMINATE PLANT PARTS OF SUBTERRANEAN CLOVERS EATEN BY RUMINANTS S.K. BAKER ABC and L. KLEIN AB ACSIRO Division of Animal Production, Private Bag PO, Wembley, W.A. 6014 BCLIMA, The University of Western Australia, Nedlands, W.A. 6009 CFaculty of Agriculture, The University of Western Australia, Nedlands, W.A. 6009 Differences in concentrations of n-alkanes in the cuticular waxes of plants can be used to estimate the species composition of herbage mixtures when they contain plant species from different genera (Dove 1992). In this study n-alkanes from a single plant species were used to discriminate among the leaf, stem and petiole fractions of cultivars of subterranean clover. Six cultivars of subterranean clover (Trifolium subterraneum) Geraldton, Daliak, Dalkeith, Dinninup, Trikkala (ssp yanninicum) and Clare (ssp brachycalycinum) were grown in individual boxes (3 replicates per cultivar) in open-sided shade houses. They were defoliated to ca. 2 cm above the soil surface twice during their growth and were harvested when the plants were senesced and dry. Concentrations of nalkanes in the leaf, petiole and stem fractions were determined by gas chromatography (see Dove 1.992). The concentrations of the n-alkanes Cz7, Cc), C,, and C,, differed among genotypes and plant parts (P c 0.005). In general petiole contained more of each alkane, especially Cz9, than the other plant parts. The ratios of the concentrations of the alkanes one to another together with logarithmic transformations of the concentrations of the alkanes were used in canonical variate analysis. The first 3 canonical factors accounted for about 70% of the variance and the error rate in classification of cases was 3%. Discrimination among the genotypes and in most cases among their plant parts is clear from comparison OOests that selection by sheep of plant parts from of bivariate plots of the first 3 factors (Figure 1). This su,, mixed swards of cultivars of subterranean clover during summer and autumn could be determined from the faecal recovery of n-alkanes. This work is supported in part by the Wool Research and Development Corporation. Figure 1. Bivariate plots of the first 2 canonical factors in canonical variate analysis, used to discriminate leaf (L), petiole (P) and stem (S) fractions of cultivars of subterranean clover: Geraldton (open squares), Clare (closed squares), Daliak (open circles), Dalkeith (closed circles), Dinninup (open triangles) and Trikkala (closed triangles) DOVE, H. (1992). Aust. J. Agric. Res. 43: 171 l-24. 419