IMPORTANCE AND QUANTIFICATION OF PLANT TOLERANCE IN CROP PEST-MANAGEMENT PROGRAMS FOR APHIDS - GREENBUG RESISTANCE IN SORGHUM

Selected papers dealing with the tolerance mechanism of host plant res istance to aphid species in crop plants have been critically reviewed herein. Some of the researchers employed techniques that were incorrec tly assumed to be measuring tolerance. In other research, no attempt w as made to separate tolerance and antibiosis components, while in othe r research the effect of variation in plant biomass on tolerance expre ssed among cultivars was not considered. After testing a series of ana lysis of covariance models, as well as several other techniques, a new model for assessing tolerance to the greenbug, Schizaphis graminum (R ondani), in sorghum was developed. This new model is independent of an tibiosis effects and is a combination of three different techniques, w ith the greatest importance placed on the slope described by the relat ionship between infested and control seedling weights at the end of th e experiment.