struduraI Resistance of Cashew (Anacardium ocCidentaie) against Powdery Mildew (Oidium WUlCardU)

Tanzania Journal of Agricultural Sciences 1999, Vol.2(1) : 115-125Studies were conducted in the laboratory at RYe College, University of London, to investigate some aspects of pre-infection structurai resistance on cashew leaf and flower sUlfaces. Using the Scanning, Transmission Electron Microscppes and the light microscope, cashew leaf suTjaces were found to be covered by a layer ofepicuticular wax, whichappeared to develop with age. Flower suTjaces werefound to be covered by hairs of varying shape and length which appeared to help trap tiny mildew spores. Ihis appears to explain why flower organs are extremely susceptible to mildew infection. Using artificial inoculation, mildew in:ie"ction was possible on young leaves, but infection did not occur on older leaves. Epicuticular waX layer observed on. cashew leaf suTjace, as a pre-infection resistance factor, appeared to be responsible for inhibition of germination and development of O. anacardii on older leaves