An anatomical basis for resistance of sugar cane to ratoon stunting disease

When water was sucked through healthy, single-node cuttings of a number of sugar-cane clones, a slow flow rate generally indicated resistance to ratoon stunting disease (RSD) while a fast flow rate indicated susceptibility. The differences in flow rate between clones were maximized by sucking air for a few seconds before testing, presumably because resistant clones formed more air-locks in the nodes than susceptible clones. Microscopic studies showed that resistant clones with slow flow rates had more profuse branching of the large metaxylem vessels in the nodes than susceptible clones. Cuttings affected by ratoon stunting disease of red-rot disease, or taken from very thin stalks, had much reduced flow rates and should be avoided in flow-rate tests