Echinochloa colonum resistance to bispyribac-soduim in Egypt - occurrence and identification

Identification and mechanism of Echinochloa colonum (L.) resistance to bispyribac-soduim via physiological and anatomical differences between susceptible and resistant biotypes was investigated. The physiological and anatomical differences that were take into account were growth reduction, chlorophyll content reduction, protein analysis, lamina thickness and xylem vessel diameter in both susceptible and resistant biotypes of E. colonum. The results showed the growth reduction fifty (GR50) of resistant biotype was 10.2 times higher than that of the susceptible biotype E. colonum treated with bispyribac-soduim. The chlorophyll content was highly reduced in the susceptible biotype relative to the resistant one of E. colonum treated with bispyribac-soduim. An anatomical test showed significant differences in the cytology of susceptible and resistant biotypes of E. colonum treated with bispyribac-soduim with respect to lamina thickness and xylem vessel diameter. Furthermore, leaf protein analysis showed significant differences between the susceptible and resistant biotypes of E. colonum in the number and the density of protein bands. The resistance of E. colonum to bispyribac-soduim may be due to the faster metabolism of bispyribac-soduim below the physiologically active concentration or the insensitivity of its target enzyme, (acetolactate synthase). These results implied the occurrence of E. colonum resistance to bispyribac-soduim in Egypt and provide conclusive evidence that a single resistance mechanism alone cannot explain insensitivity in E. colonum to bispyribac-soduim.