Variation Among Isolates ofSphaeropsis sapineain the North Central United States

Palmer, M. A., Stewart. E. L., and !d, M. J. 1987. Variation among isolates of SjJhaeropsis sapinea in the north central United States. Phytopathology 77:944-948. Isolates of Sphaeropsis . ( = ()iplodia pinea) from naturally infected Pinus spp. in the north central United States differed in cultural characteristics and virulence. Isolates designated as type A produced fluffy white to gray~green mycelia on a variety of media. Conidia of these isolates produced in culture ere 34.3-39.4 X 12.6-12.8 pm. Isolates designated as type B produced whitc to black mycelia closely appressed to the agar surface with conidia 33.5--34.3 x 11.6-12.1 pm. Type H isolates produced conidia on sterile pine needles incubated in the dark at 25 C. whereas type A isolates sporulated only in light. Type B isolates also produced spermatia~ like spores in dark and light. Type B isolates generally grew more slo\\','!} Addiliollal key 1I'0rd: isozyme analysis. than type A isolates at 20 and 25 C, although optimum growth for most type A and B isolates occurred at 25 C. Type A and B isolates had identical iso/yme banding patterns for four of six enzymes. Greenhouse inoculations demonstrated that a representative type H isolate required wounds to infect young shoots. whereas the type A isolate did not. Once wounded, hosl tissue showed no difference in the extent of discoloration belween isolales. as demonstraled by field inoculations. In the north central United Slates. type B isolates are apparently opportunistic and colonize wounded or declining host tissues.