THE EFFICACY OF MIXTURES OF SUSCEPTIBLE AND RESISTANT HOSTS TO 2 WHEAT RUSTS OF DIFFERENT LESION SIZE - CONTROLLED CONDITION EXPERIMENTS AND COMPUTERIZED SIMULATIONS

Controlled-environment experiments and computerized simulations on whe at yellow rust and wheat brown rust epidemics indicated that mixtures of resistant and susceptible hosts controlled parasites with small les ions more effectively than parasites with large lesions. Experiments w ere conducted on seedlings, during two parasitic cycles. Yellow rust l esions were about 200 times larger than those of brown rust. The measu red efficacy of seedling mixtures in reducing disease spread was 22 % for yellow rust and 46 % for brown rust. Computerized simulations sugg ested that, for a given quantity of inoculum, mixture efficacy was lim ited for a large-lesion parasite because of fast host-plant saturation .