Translocation and metabolism of14C-2,4-D [(2,4-dichlorophenoxy)acetic acid] and effects of 2,4-D on protein synthesis were compared in ‘T–68’ (2,4-D tolerant) and ‘Viking’ (susceptible) birdsfoot trefoil (Lotus corniculatusL.) in an attempt to elucidate some tolerance mechanisms. After14C-2,4-D was applied to upper trifoliate leaves, significantly less 2,4-D was found in stems, in leaves below the treated leaves, and in roots of T–68 compared to Viking. More 2,4-D was bound to alcohol-insoluble cellular constituents of T–68 leaves, stems, and roots. When alcohol-soluble components were fractionated, slightly more14C water-soluble compounds were found in T–68, indicating further inactivation by glycosylation. No amino acid-2,4-D conjugates were found. The rate of14CO2evolution from14C-2,4-D treated seedlings in T–68 was five times that in Viking. Protein synthesis appeared to be more rapid in T–68 but the relationship to 2,4-D was not clear. In part, 2,4-D resistance in T–68 may result from its ability to inactivate 2,4-D by differential binding and conjugation and by side chain breakdown as indicated by14CO2release.

Xylella fastidiosa has been associated with citrus variegated chlorosis (CVC) by electron microscopy and serology using antisera to isolates of X. fastidiosa other than citrus. Antiserum has now been developed against X. fastidiosa isolated from CVC-affected citrus. This antiserum has been used to develop a sensitive, reliable serological assay based on a modification of dot immunobinding assays previously reported, coupled with western blotting, to detect X. fastidiosa in CVC affected trees. The procedure detects X. fastidiosa even in CVC-inoculated trees even before they develop symptoms, in some non-symptomatic trees in groves affected by CVC, and in healthy appearing sectors of trees which are showing CVC symptoms in other sectors. Bacteria were not detected in many healthy appearing trees from groves in non-CVC affected areas or in healthy greenhouse plants. This sensitive serological assay was developed to better enable screening of symptomless CVC-affected nursery plants and budwood source trees to reduce the possible spread of CVC via infected nursery materials.Index words. Xylem-limited bacteria, dot immunobinding assay, western blotting assay.