Content area
Full text
Breeding oat cultivars high in (1[arrow right]3)(1[arrow right]4)β-D-glucans (referred to as β-glucans here) is becoming increasingly important because of their proven ability to lower serum cholesterol (Braaten et al 1994; Kalra and Jood 2000). In spite of the importance of this trait, its inheritance is poorly understood (Buckeridge et al 2004) and cannot be predicted using molecular markers. Furthermore, most Avena sativa breeding germplasm has a narrow range of β-glucan-typically between 4.5 and 7.0% (w/w, dry), although a larger range of values is found in wild relatives such as A. atlantica (11.3%, w/w); A. longiglumis (2.3%, w/w) (Welch et al 2000). The environment also influences the final β-glucan levels in oat (Givens et al 2000; Cervantes-Marlines et al 2002). This leaves breeders with the difficult task of breeding for a poorly understood trait lacking variation in elite germplasm, and with an important environmental component (Petersen et al 1995). Despite this, breeding for elevated β-glucan is an important priority and requires a high-throughput assay for rapid and economical measurement.
Traditionally breeders select for agronomic suitability early on, waiting several generations before making quality-based selections, even when quality is a major objective. This reduces the number of lines in advanced generations and ensures a reasonably large seed sample for quality testing but it means that poor-quality lines are advanced unnecessarily. It would be preferable to assay quality characteristics earlier to improve overall efficiency. The intermediate heritability of β-glucan in oats and the predominantly additive inheritance (Holthaus et al 1996; Kibite and Edney 1998) suggest the possibility of substantial improvement through early generation selections (Cervantes-Martines et al 2001).
The currently recommended Approved Method 32-23 (AACC International 2000) for testing β-glucans in flour employs the enzymatic degradation of β-glucans, followed by the spectrophotometric measurement of liberated glucose, and subtraction of non-β-glucan-derived glucose with a mathematical formula. Although accurate and quantitative, this test is expensive and relatively slow and is thus unsuited for early generation screening for thousands of plants with low quantities of seed available. Other assays include viscosity measurement, near-infra red spectroscopy and calcofluor white fluorescence (Wood and Weisz 1984; Lim et al 1992; Doehlert et al 1997), each with their own advantages and disadvantages. With an enzyme-linked immunosorbent assay (ELISA), monoclonal antibodies are used to detect...