Clusterbean seed health testing is warranted since the pathogen (Xanthomonas campestris pv. cyamopsidis (Xccy)) is seed-borne and seed-transmitted. A polyclonal antibody was developed in rabbit via subcutaneous and intramuscular injections and characterized for sensitivity, specificity and its applicability to ELISA which: (i) was sensitive in detecting as few as 10 2 cells ml −1 at a titre of 1: 4000; (ii) was specific, since it reacted only with Xccy and not with other xanthomonads; (iii) reacted both with Xccy cells and culture filtrate, indicating that the antigenic determinant is a secretory component; (iv) was applicable and reliable in seed health testing since it reacted only with infected seeds and plant materials and not with healthy seeds and (v) a purified fraction of antibody was virulent-specific since heat-denatured and avirulent isolates were not detected. The ELISA thus developed is highly reproducible and therefore suitable for the evaluation of the potential disease status of seeds and plant health, which is appropriate for routine seed health testing.