Assessment of varietal susceptibility to ratoon stunting disease of sugarcane

Ratoon stunting disease (RSD), caused by the small xylem-inhabiting coryneform bacterium Clavibacter xyli subsp. xyli it present in most sugarcane growing countries (Anon., 1093). Its effect on sugarcane crops is related to the degree of stress, e.g. drought or waterlogging, to which crops are subjected during growth. Under unfavourable conditions, intolerant varieties may suffer yield losses as high as 50%. The work described in this paper was undertaken to find a method for rating varieties for RSD susceptibility. Such ratings could assist in the breeding and selection of RSD resistant varieties, and assist growers in managing varieties with varying levels of resistance.