Abstract
A population is a group of individuals sharing a unique pool of genetic variation. For Phytophthora, populations often contain a large proportion of mitotically derived isolates known as clonal lineages. The phenotypes, proteins and DNA fragments, single nucleotide variation and the whole genome, species and surveys, clonal lineages, sexual recombination, sampling, allele frequency, sex, and survival of Phytophthora populations are discussed.