372 WheatRite™: An immunochromatography field test for preharvest sprouting.

J. H. SKERRITT (1), R. Heywood (1), A. Ellis (2), and W. Rathmell (2). Quality Wheat CRC Ltd and CSIRO Plant Industry, (1) Canberra, ACT 2601, and (2) North Ryde, NSW 1670, Australia.

An immunochromatography method, based on detection of high-pI alpha-amylases was developed for detection of preharvest sprouting in wheat and barley. Amylase from ground grain is extracted with a salt solution and two drops of the extract is added to a zone on a disposable card. The result appears in 3–5 minutes. If the grain is sprouted, amylase becomes sandwiched between gold-labeled and immobilized antibodies, and a maroon band appears in the test window. Color intensity depends on the extent of weather damage, with good (inverse) correlations between test color and Falling Number in large sets of samples comprising many varieties. Precision is as good as or better than the Falling Number test. Field trials have shown that the extent of preharvest sprouting after rainfall can vary markedly between and within fields. If growers had tested grain from different fields or areas before harvest, it would be possible to harvest and bin the damaged grain separately from sound grain and avoid financial losses resulting from downgrading of the whole crop. An extensive trial of the new method was conducted in late 1998. Six wheat samples varying in Falling Number were tested “blindly” by over 100 farmers, and virtually all obtained correct results for each sample. The method should be suited for either rapid screening on-farm prior to harvest, use at elevators or as a rapid laboratory test.