Xenoparasite-Nonhost Reactions inPuccinia-Gramineae Pathosystems

Luke, H. H., Barnett, R. D., and Pfahler, P. L. 1987. Xenoparasite-nonhost reactions in Puccinia-Gramineae pathosystems. Phytopathology 77:1488-1491. Histological studies of six species of Gramineae inoculated with five leaf of a nonhost plant inoculated with a pure race of a xenoparasite. species of Puccinia were conducted to determine the kinds of defense Nonhost reaction types were clear cut, independent, and easily systems involved in xenoparasite-nonhost interactions. Although all distinguished one from the other. The nonhost had specific and nonspecific nonhost types had active (physiological) defense mechanisms, two resistance to most of the xenoparasites, indicating that these two types of exhibited quasi exclusion, but the few xenoparasites that penetrated resistance had a common origin. Another histological response was stimulated a physiological response similar to specific resistance. characterized by fluorescent-collapsed cells that did not retard radial Histological responses associated with cessation of fungal growth included growth of the hyphae. This reaction reduced haustorial mother cell fluorescent-collapsed mesophyll cells (specific resistance), fluorescent- formation and inhibited development of macroscopic symptoms in the noncollapsed (nonspecific resistance), and a nonfluorescent-noncollapsed nonhost. The nonhosts used in our study had five defense mechanisms, four type (unknown). These three defense mechanisms were observed in a single physiological and one quasi exclusion type.