Upon germination the diploid oospore undergoes meiosis, producing four haploid nuclei. This primarily occurs by the use of oospore encrusted seeds for planting. The storage material is starch, except in the oospore, where oil also occurs. In adverse environmental conditions, the pathogen exists in a structure called an oospore. After fertilization, the zygote develops into an oospore. Bracteoles (leaf-like structures) slightly longer than the oospore. The zygote produced is named an oospore. The oospore is dark brown or black. Their only diploid stage in the life cycle is the unicellular oospore. Once infection season comes to an end, sexual reproduction occurs to form an oospore. In indirect germination, the oospore produces sporangia which release zoospores. Oospore germination occurs when the oospore senses chemicals released by seeds or roots. The oospore will overwinter and germinate to produce infectious sporangia once conditions improve. The oospore germinates and produces sporangium on sporangiophores in damp late spring to autumn. The oospore is then ready to germinate and develop into an adult diploid somatic stage.