Disease Cycle
Pythium aphanidermatum survives in the soil as oospores, hyphae and/or sporangia. Oospores can produce a germ tube and infect the plant directly, or, if the environment is favorable (that is an adequate amount of water is present), the oospore may produce sporangia, which in turn produce motile, biflagallete zoospores that swim to the host plant, encyst, and germinate. This infection can occur on seeds, which can rot, or produce a weak seedling. If it infects the roots of a seedling, the mycelium will grow throughout the plant tissue, releasing digestive enzymes which break down plant cell walls allowing the pathogen to absorb the nutrients, effectively killing the plant overtime. P. aphanidermatum is a polycyclic disease A polycyclic plant pathogen has several life cycles during a season, meaning it can reinfect the host plant, or travel to another plant. After infection, several things can happen that progress the infection: 1)More asexual structures form, including sporangiophores and sporangia, which release more zoospores which can reinfect the host plant, or move to other plants. 2)There can also be sexual reproduction when two different mating hyphal types meet, creating an oogonium (female structure), and an antheridium (male structure). This results in genetic recombination and exists as an oospore-the original overwintering stage of the pathogen.
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