Occurrence and levels of the phytoalexin phaseollin in relation to delimitation at sites of infection ofPhaseolus vulgarisbyColletotrichum lindemuthianum

摘要

Sequential quantitative analyses of phaseollin associated with individual sites of infection byColletotrichum lindemuthianumon etiolated hypocotyls ofPhaseolus vulgarisprovide further insight concerning the possible function of phaseollin in compatible and incompatible host response. When detected, phaseollin was localized in and (or) around individual infection sites; it was not detected in adjacent healthy tissue. Its occurrence was correlated with the time of appearance of visible, necrotic flecks at sites of incompatible response. It was not detected at visibly necrotic sites of compatible response until these became delimited in appearance, after which it occurred in large amounts. Delimitation at these sites occurred well after visible necrosis was first apparent. At high levels of infection, individual sites of compatible infection coalesced before delimitation, and in such instances phaseollin was virtually absent for the duration of the experiments. The levels of phaseollin occurring at individual infection sites indicate that it does not function as the primary determinant of interaction type, but is associated with delimitation at sites of both compatible and incompatible interaction. With respect to phaseollin production, the difference between these interactions was clearly one of time of occurrence, rather than amount produced.