The Phytotoxin Coronatine Can Improve Cotton Defoliation and Boll Opening As a Defoliant

Defoliants can increase machine harvest efficiency of cotton, prevent lodging and reduce the time from defoliation to harvest. Coronatine (COR) is a chlorosis-inducing non-host-specific phytotoxin produced by several members of the Pseudomonas syringae group of pathovars. This phytotoxin was tested whether it could be a potential cotton abscission chemical in the present study. The field experiment was conducted in 2010 and 2011, on the Guoxin Research Farm at Hejian county, Hebei province of China. The sprayed COR at high concentration of 300 mg/L significantly accelerated abscission compared with control. Twenty-one days after treatment, the defoliation percentage of COR reached 79%, whereas only 54% for control. Furthermore, we observed decreased break strength of petiole abscission zone by COR application. COR also significantly enhanced boll opening without affecting boll weight, lint percentage, seed quality and fiber qualities. Therefore, COR may be a potential cotton defoliant with different mechanism from current thidiazuron (TDZ) etc.