Evaluation of inoculation techniques for screening sorghum genotypes against stalk rot caused by Erwinia chrysanthemi.

摘要

Results are presented of greenhouse experiments conducted to evaluate various inoculation techniques (stem injection, midrib injection, cotton wool, toothpick, leaf whorl, and root tip cut and dip) for screening sorghum ( Sorghum bicolor) genotypes against stalk rot, caused by E. chrysanthemi [ Dickeya chrysanthemi]. All the methods produced stalk rot symptoms with variable and non-uniform pattern, except for the root tip cut and dip method, in which all inoculated plants showed the most typical, reliable and uniform disease development. The disease mainly affected sorghum stem showing water-soaked symptoms that later turned reddish dark brown colour. Lower leaf and typical stalk rot type of symptoms were first observed in the root tip cut and dip method; water-soaked lesions appeared at the crown or soil line of the stalk on the 3rd day of inoculation although the upper portion remained asymptomatic. As the disease advanced, all the plants collapsed on the 4th day of inoculation. However, symptoms started appearing at 4 days after inoculation in other methods. The highest stalk rot incidence (92.40%) with typical rotting, wilting and uniform type disease development was found with the root tip cut and dip method, followed by the stem injection (85.96%), leaf whorl (80.60%) and tootpick (74.76%) methods. Partial rotting was encounted with midrib injection (29.22%) and cotton wool (22.57%) methods over the control.