Identification of waxy wheat by near-infrared reflectance spectroscopy

Newly developed low amylose wheats (Triticum aestivum L.) have unique processing characteristics, and thus allow millers to blend defined levels of amylose in mixes requiring low-amylose flour. The amount of amylose synthesised during grain fill is dependent on the expression of three structural genes that encode isoforms of granule-bound starch synthase (GBSS). Lines possessing null alleles at the three waxy (wx) loci produce starch that lacks amylose. While such wheats are readily identified by iodine staining, their identification in wheat marketing and production systems would be facilitated by the use of rapid, spectral methods. The present study was undertaken to determine the feasibility of using near-infrared (NIR) spectroscopy to identify waxy wheats, and differentiate them from partial waxy and wild-type phenotypes. Nearly 200 lines from each of two harvest years, with a range of zero (waxy) to three (wild-type) active genes, were ground and scanned (1100-2500 nm) in NIR reflectance. Linear or quadratic discriminant functions of the scores from principal component decomposition cross validation demonstrated that within a crop year, near-perfect separation of fully waxy (27 of 27 samples from Year 1, and 23 of 24 samples from Year 2 correctly identified) from non-waxy lines (165 of 165 samples from either Year I or Year 2 correctly identified) was achievable. Further classification among the three non-waxy classes was more difficult, with an average overall accuracy of 60%. Misclassifications were most often assignments into neighbouring gene classes (e.g. 1-gene line assigned to the 2-gene class). The method should prove useful in the identification of waxy wheats, or of blends of waxy and non-waxy cultivars. (C) 2002 Elsevier Science Ltd.