Identification of Waxy Wheat by Near-infrared Reflectance Spectroscopy

Nrwly tlrvrloprti low amylosr lvhrats (fiitzrum ciu.rtii.um L.) liavr u~i iqur procrssirlg c.harac.trristic.s, 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 grlirs that rrlcotir isofi~rms of'gi-anulr-l-)ourid starch synthasr (GBSS). L i ~ i r s posaraairig null allrlrs at tllr tllrrr wax?(zx) 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 1)y tllr usr of' rapid. sprc.ti-a1 mrthotis. Tlir prrsrrit stutiy lvas uridrrtakr~i to tlrtrrmirir tlir f"aail)ility ofuai~ig ~irar-irlfi-ai-rti (SIR) sprctroacopy to itlr~itify waxy ujllrats, arltl tliffrrrritiatr tlirm fi-om partial xvaxy arltl wilti-t)pr phrnotyprs. Nrarly 200 lirirs fi-om rach of two liarvrat yrars, wit11 a raligr of zero (I\-axy) to three (wild-type) active genes; were ground and scanned (1 100-2500 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 1 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. l-gene line assigned to the 2-gene class). The method should prove useful in the identification of \vaxy wheats, or of blends of waxy and non-tvaxy cultivars. O 2002 6lscvic1S c i c ~ ~ c c I.td Kfyreords: wheat, starch, amylose, waxy, classification, near-infrared.