Inhibition of susceptible water soaking and/or hypersensitive reaction in cotton by Exopolysaccharide of avirulent Xanthomonas campestris pv. malvacearum

The exopolysaccharide (EPS) of avirulent Xanthomonas campestris pv. malvacearum race-32 did not contain the watersoaking (WS) - inducing factor but contained necrotic reaction (NR)-inducing factor and induced NR on resistant cotton (cv. 101-102B) on which the viable cells of the same avirulent race-32 produced hypersensitive reaction (HR). NR and HR were differentiated on the basis of the induction period required, visible reaction on infiltrated areas, bacterial constituents or metabolite responsible, involvement of host constituent during these reactions and its chemical inhibition. Pre and/or challenge inoculation of EPS of avirulent race-32 (3 mg per infiltration or lesion) in susceptible or resistant cotton cultivars, on pre- and/or post-infiltrated (0-8 h) exponential-phase culture of virulent race-32 inhibited the WS and/or HR of the virulent race in susceptible or resistant cotton.