Pathogenicity test and convenient inoculation methods of Xanthomonas axonopodis pv. cyamopsidis inciting bacterial blight of Clusterbean

Abstract

Bacterial blight [X. a. pv. cyamopsidis (Patel)] is one of the major severe diseases of clusterbean [Cyamopsis tetragonloba (L.) Taub.]. The pathogen is essentially internally seed borne in nature and provides primary inoculum for secondary spread. Bacterial
blight pathogen X. axonopodis pv. cyamopsidis was isolated from diseased samples collected from different locations of major growing areas of Rajasthan. The pathogenicity test of Xanthomonas axonopodis pv. cyamopsidis was performed with following five
different inoculation methods were tried to find out most convenient and efficient method for disease production viz., (i) Spraying of bacterial suspension once, (ii) Spraying of bacterial suspension twice, (iii) Spraying of bacterial suspension thrice, (iv) Rubbing bacterial suspension with carborundum powder and (v) Spraying of bacterial suspension after multineedle pricking. The bacterium suspension (2.5x108 cfu/ml) was used as inoculum for spraying. Out of five different inoculation methods, maximum disease developed in triple sprays at 24 hrs interval followed by carborundum abrasion method spraying after multi-needle pricking, double spray and single spray in potted plants as well as in field plants. A triple spray at 24 hr. interval was found most convenient and efficient method of inoculation for producing disease on potted plants as well as in field plants.