Growing severity of ratoon stunting disease of sugarcane in India

Abstract

Ratoon stunting disease (RSD) caused byLeifsonia xyli sub sp.xyli has been considered as a minor sugarcane disease in tropical India. However, recently severe incidence of RSD was noticed in varieties such as Co 419, CoVC 89249, CoSi 95071 and CoSi 96071 in Mandya region of Karnataka. In addition to characteristic RSD symptoms viz., dots, commas and streaks at nodal region, pinkish red discolouration of entire nodal tissues was noticed in severely affected canes. Affected canes also showed severe stunting, reduced cane thickness, shrinking of internodes toward acropetal end and external rind discolouration around the nodal region. Indirect ELISA studies revealed that all the cane varieties with the suspected RSD symptoms were positive to the bacterial pathogen. The varieties with severe RSD symptoms recorded ELISA values from 0.904 (KHS 3296) to 1.742 (CoVc 93136) and the varieties with mild symptoms recorded absorbance values from 0.178 (Co 8371) to 0.836 (Co 86032). Observations on the effect of RSD pathogen on bane thickness in sugarcane varieties Co 419, Co 6511, Co 7514, Co 8336, Co 86032, CoA 8201, CoS 687, CoS 770, CoS 767 and CoVc 9319 showed that infection by the bacterium causes significant reduction in cane thickness. The growing severity of RSD warrants careful seed selection and proper monitoring of the disease in the field in addition to the suggested management practices such as steam therapy and meristem culture.