The influence of different concentrations of toxin fungus Verticillium on relative growth rate of callus in cotton cultivars

Verticillium disease is one of the most important cotton diseases which led to limitations in cultivation and yeild reduction. The study was used fungal toxin Verticillium as selection agent of cotton callus cells resistant. The explants were prepared from sterilized 7-days old cotton seedling and were cultured on MS medium with 2 mg/l of each growth regulators NAA and BAP in order to produce callus. Following the initial weighing , the resulting callus were transferred to the new media mid 0.5 mg/l of NAA and BAP concentrations with zero (control ), 5, 10, 20, and 30 percent pathogen toxins, and after 3 weeks their relative growth was calculated. The highest relative callus growth was in non-toxin medium and the lowest one was in pathogen toxin concentrations of 20 and 30 percent. Golestan made more relative callus growth rate in non-toxin medium and the 5 percent toxin concentration, respectively, with 115.2, and 100 percent. Toxin concentrations of 20 and 30 percent showed the lowest relative growth rate of callus with 24.5 and 8 percent, respectively in Sahel cultivar. Golestan, Coker-100 wilt and Sahel calli that were green-white colored, didn’t change in 5 and 10 percent of toxin concentrations but discolored to brown with concentration increasing. Callus of Hashemabad Native cultivar that was cream, discolored to brown in the range of toxins from 5 to 30 percent. In general, this color change indicates the effect of the toxin on the quality of calli. So this method can be accelerate the screening of tolerance plant with selection of suitable calli.