Spectrophotometer-aided evaluation of cyanogenic potential in white clover(Trifolium repens L.)

In comparison with ordinary methods of colorimetric evaluation of cyanogeni c potential based on visual evaluation of the alkaline picrate reaction, a spectrophotometer-aided method could be more accurate (since it determines the exact amount of hydrogen cyanide released by the plant material), and l ess time-consuming as it can be performed on bulk material rather than on a number of individual plants. Ten white clover populations were evaluated b y a spectrophotometer-aided method and by two visual evaluation criteria. A ll methods indicated the presence of large variation between populations. V isual methods gave almost identical results and allowed only for the distin ction between cyanogenic and substantially acyanogenic populations. The res ults were only moderately consistent with those obtained by the spectrophot ometer-aided method, which could detect the presence of variation also betw een cyanogenic populations. The effects of various incubation times (from 4 to 48 h) and of the addition of beta-glucosidase on hydrogen cyanide relea se were also investigated. Comparable results for ranking of populations co uld be obtained over a range of incubation times, but at least 24 h were ne eded for a reliable estimation of the hydrogen cyanide produced by plants. The addition of enzyme did not increase the released cyanide. The effect of season and/or conditions of evaluation was marked on mean cyanogenic poten tial but limited on ranking of populations, Copyright (C) 2000 John Wiley & Sons, Ltd.