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

Field trials have shown that the extent of preharvest sprouting after rainf all can vary markedly between and within fields. Testing of grain from diff erent fields or parts of fields before harvest would permit separate harves ting and binning of damaged grain from sound grain, and financial losses re sulting from downgrading of the crop could be reduced. An immunochromatogra phy method, based on detection of alpha-amylase isozymes, using specific an tibodies 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 w indow. 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 tha n the Falling Number test. Methods for obtaining representative samples fro m a standing wheat crop were developed, and an extensive trial of the new m ethod with farmers and elevator company staff was conducted in late 1998. S ix wheat samples varying in Falling Number were tested blindly by a group o f 75 farmers and grain handling company staff, with the vast majority obtai ning 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 labora tory test.