XVI International Botanical Congess

To define the genetics of symbiotic lifestyles,176 non-pathogenic gene-disruption mutants were isolated by REMI transformation (Tx) from the cucurbit pathogen Colletotrichum magna. The mutants retained the ability to colonize plants and expressed three symbiotic lifestyles based on protecting plants against virulent fungi: A mutualistic (80-100% protection), B undefined, (20-65% protection), and C commensalistic, (0% protection). Genetic analysis indicated that the mutants resulted from single locus disruptions. The Tx vector and flanking DNA from REMI A and C mutants were recovered and designated pFSLm and pFSLc, respectively. pFSLm and pFSLc were used to disrupt homologous sequences in pathogenic wild types and generated the same phenotypes. Ecological and evolutionary aspects of these studies will be discussed.