VIEW ARTICLE

Resistance

Colonization of Vascular Tissues by Clavibacter xyli subsp. xyli in Stalks of Sugarcane Cultivars Differing in Susceptibility to Ratoon Stunting Disease. N. A. Harrison, University of Florida, Institute of Food and Agricultural Sciences, Ft. Lauderdale Research and Education Center, 3205 College Avenue, Ft. Lauderdale, FL 33314; M. J. Davis, University of Florida, Institute of Food and Agricultural Sciences, Ft. Lauderdale Research and Education Center, 3205 College Avenue, Ft. Lauderdale, FL 33314. Phytopathology 78:722-727. Accepted for publication 24 November 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-722.

A novel tissue blot enzyme immunoassay was developed to identify vascular bundles colonized by Clavibacter xyli subsp. xyli in stalk internodes of sugarcane with ratoon stunting disease (RSD). Numbers of infected bundles in tissue cross sections declined progressively with increasing sampling distance of internodes from the base of stalks in cultivars CP 70-1133, CP 44-101, and CP 72-1210. CP 70-1133, the least susceptible to RSD of the three cultivars, contained significantly fewer infected bundles than did CP 72-1210 and CP 44-101. Conversely, infected bundles were most numerous in CP 72-1210, the most susceptible cultivar. Numbers of infected bundles in comparable basal internodes of 10 sugarcane cultivars were positively correlated with population densities of C. x. subsp. xyli in sap extracts from these tissues. Pathogen densities in sap from different cultivars have been shown to be correlated directly with cultivar susceptibility to RSD; results of the present study indicate that cultivar resistance to RSD also is associated with reduced pathogen colonization of vascular tissues.