Genotypic variation of plant species to the allelopathic effects of vulpia residues

The germination and seedling growth of 12 plant species and 12 cultivars from 2 plant species were tested in the presence of aqueous extracts of vulpia dry matter residues. Concepts of whole-range assessment and inhibition index were developed, and used, with principal component analysis, for assessing results. Species were grouped according to the inhibition index. Average threshold concentration, average I-50 (the extract concentration required to cause 50% inhibition in plant response) and average root and coleoptile lengths were used as auxiliary indices for each group. Marked differences in tolerance toward the phytotoxicity of vulpia residue extracts were observed among species and cultivars. Such differences were widespread among plant species, with generally cocksfoot, Vulpia spp., subterranean clover (cv. Trikkala), phalaris, canola, medics, and oats being relatively tolerant, while lupins, barley, and wheat (cvv. Janz, Vulcan) were the most susceptible, and subterranean clover (cvv. Seaton Park, Karridale, Glare, Woogenellup, Junee), field peas, and wheat (cvv. Ford, Darter, Dollarbird, Rosella) were relatively susceptible. The findings of this study suggest that choice of species and cultivar may be a valuable management option for minimising the negative effects of vulpia residues. The whole-range assessment developed in this study proved to be a statistically efficient summary of the plant response profiles. Together with the bioassay techniques adopted, it provides a simple and rapid screening methodology for assessing the relative tolerance of plant species to the allelopathic effects of weed residues.