Fig. 7.

Hypothetical mechanism for host-induced phenotypic diversification and associated chromosomal alterations in P. ramorum. The K-means Cluster 1 (Fig. 2) is comprised of individuals that are aggressive on host foliage, showing wt colony type, and carrying euploid genomes (including sCNV euploid). When individuals in Cluster 1 undergo stress such as during colonizing a sub-optimal host plant, epigenetic changes occur which will cause reduction in aggressiveness. Epigenetic changes may also result in increased rate of genome aberration while growth rate and colony morphology are unaffected (Cluster 2). The transition of membership between Cluster 1 and 2 is possibly reversible. Accumulation of aberrated nuclei in the multinucleated cells will result in the manifestation of nwt colony type and detection of chromosomal aberrations (Cluster 3). Transition from Cluster 2 to 3 is likely irreversible