Back to Contents

FREE FULL TEXT PDF

MOVEMENT OF BEET CURLY TOP VIRUS OUT OF PHLOEM CELLS IN BEAN PLANTS CO-INFECTED WITH TOBACCO MOSAIC VIRUS

WAQAR AHMED AND PETER E. THOMAS

Abstract: Pinto bean (Phaseolus vulgaris L.), cultivar ouray, was inoculated with beet curly top virus (BCTV) at the crook neck seedling stage using beet leafhoppers (Circulifer tenellus Baker). After 7-10 days, primary leaves of each plant were rub-inoculated with one of two isolates of tobacco mosaic virus (TMV). These plants were routinely infected by both viruses. Infection with BCTV did not affect TMV movement or symptoms. TMV remained confined in the local lesions and could not be detected in systemic tissue by enzyme-linked immunosorbent assay (ELISA), tissue blotting, or by local lesion assay. In contrast, infection with TMV did affect BCTV infection. Severe BCTV symptom developed in the growing points of bean plants that were also infected with TMV while relatively mild BCTV symptoms developed on plants infected with BCTV only. Concentration of BCTV in plants infected by both viruses was 8-10 fold higher than in plants infected with BCTV only. Using tissue-blotting ELISA, it was demonstrated that BCTV escaped the phloem and invaded the parenchyma cells of both shoots and roots in plants infected by both BCTV and TMV. However, BCTV remained confined to phloem tissue in plants infected only with BCTV. No difference was observed between two TMV isolates used regarding their effectiveness in enhancing the concentration of BCTV in systemic leaf tissue and in roots of co-infected plants. When plants were first inoculated on primary leaves with TMV and later inoculated with BCTV, neither control nor test plants were systemically infected by BCTV.

Ayub Agricultural Research Institute, Jhang Road, Faisalabad, Pakistan.