A five-minute field test for on-farm detection of pre-harvest sprouting in wheat

Field trials have shown that the extent of preharvest sprouting after rainfall can vary markedly between and within fields. Testing of grain from different fields or parts of fields before harvest would permit separate harvesting and binning of damaged grain from sound grain, and financial losses resulting from downgrading of the crop could be reduced. An immunochromatography method, based on detection of alpha-amylase isozymes, using specific antibodies was developed for field-level detection of preharvest sprouting in wheat (Triticum aestivum L.). In the test, alpha-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 less than 5 min. If the grain is sprouted, amylases in the samples become 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 (negative) correlations between test color and Falling Number in large sets of samples comprising many cultivars. Precision is as good as or better than the Falling Number test. Methods for obtaining representative samples from a standing wheat crop were developed, and an extensive trial of the new method with farmers and elevator company staff was conducted in late 1998. Six wheat samples varying in Falling Number were tested blindly by a group of 75 farmers and grain handling company staff, with the vast majority obtaining correct results for each sample. The method should be suited for rapid screening on-farm prior to harvest, use at elevators, or as a rapid laboratory test.