Ib 371 General Mycology Laboratory

IB 371 _ GENERAL MYCOLOGY LABORATORY OOMYCOTA – PERONOSPORACEAE, ALBUGINACEAE Thursday, October 16, 2003

I. Peronosporaceae. All members of this family are obligate parasites of plants and some cause destructive diseases of economic plants. The diseases are generally described as “downy mildews”. We have prepared slides of two species in this family: Plasmopara viticola and Bremia lactuca. Examine slides of the colonized host material and locate the sporangia and sporangiophores. Where are they located on the host material? Contrast the morphology of the sporangiophore of Plasmopara to that of Peronospora. One is monopodial and the other is sympodial. Locate the hyphae in the host tissue. Find a haustorium and describe how it relates to the host cell. Look for sexual stages and describe their morphology. With the help of material available in lab, outline the life cycle of P. viticola. II. Albuginaceae. This family contains one genus and ~ 44 species. The species are all obligate parasites on flowering plants and the diseases they produce are generally called “white rusts”. You will examine prepared slides of Albugo blitii and Albugo candida. Look for the sporangia, which are produced in chains. Look for the hyphae in the plant tissue. How did the disease get the name of “white rust”? Using materials available in lab, construct a life cycle diagram for one species of Albugo. Indicate which stages are important in (1) dissemination, (2) increasing infection, and (3) surviving unfavorable conditions.