The identification and quantification of the plant allelochemicals, microbial transformation products and microbial transformants would provide critical data on the weed suppression observed from early vigour wheat lines in the field and over the course of the growing season. Such data as will be gained from this investment will provide the missing link towards understanding the variation observed among wheat genotypes in weed competitiveness or interference. This and related information will allow a quantification of the economic value of weed suppressive early vigour genotypes to Australian producers in contrast to commercial cultivars currently under production. This information would allow determination of additional efforts to commercialise early vigour traits can be justified based on suppression of weeds alone.