Use of chlorophyll a fluorescence in screening for herbicide susceptibility in several Nicotiana tabacum L. cultivars and breeding lines

Abstract

Possible differential sensitivity of newly released tobacco cultivars to different herbicides must be determined, as possible unfavourable combinations could exist which may have large financial implications in terms of cultivars bred, herbicide and tobacco line combinations used, and concentrations in which the herbicide should be applied if the former combination is compatable. The use of chlorophyll fluorescence measurements, as possible screening parameters to indicate herbicide-induced pertubations, was evaluated in five newly released tobacco cultivars and five breeding lines in combination with six herbicides at two different localities. Statistically, highly significant (p < 0.01) positive correlations were found to exist between the herbicide used, the tobacco cultivar and/or the breeding line to which it was applied, the change in the F_o and F_V/F_M fluorescence parameters, and yield. A change in the F_o fluorescence level seemed to indicate that a statistically significant deviation in yield might be expected with the specific herbicide tobacco cultivar and/or breeding line combination in which it occurred, the nature of which was determined by the direction the F_V/F_Mratio deviated from the control. If the F_V/F_M ratio remained the same or increased, a normal or higher yield was obtained. However, if the F_V/F_M ratio decreased, so did the yield. This would seem to hold true irrespective of the primary site of action of the herbicide used, or the nature of the herbicide-induced pertubation caused in the tobacco cultivar and/or breeding line used.