Effect And Mechanism Of Interaction Of Plant Growth Regulations And Fungicides On Cotton Seedling Diseases

Cotton seedling diseases always remain a serious problem in cotton production. Chemical controls,seed or soil treatment with single fungicide or mixed fungicide,are the most important methods in the controlling of cotton seedling diseases.Cotton seedling diseases offen happen with low temperature or dampness stess,so improving the quanlity of cotton seedling will inhance the resistance ability to adversity.The toxicity of several fungicides to three fungi (Rhizoctonia solani,Fusarium spp,Colletotrichum gossypii) were conducted in vitro.The results showed that propiconazol was more toxic to the three fungi; Each of the EC50 was 0.38,0.32,0.42mg.kg-1;tolcolfos-methyl is most toxic to Rhizoctonia solani, EC50 is 0.32 mg.kg-1; diniconazole is more toxic on Fusarium spp and Colletotrichum gossypii,EC50 were 2.60 and 0.64 mg.kg-1 respectively.Thiram and carbendazim were less toxic to the three fungi.In the greenhouse experiments, cotton seed coated with BR, PAA, SA, PP333, DPC, NAA and CC increased the quality of cotton seedling. Seed germination growth and developing of seedling were promoted. 100mg.kg-1 SA, 100 mg.kg-1 PAA, 10 mg.kg -1'NAA, 20 mg.kg -1 PP333, 100 mg.kg -1DPC, 50 mg.kg -1CC, 0.5 mg.kg-1 BR were the proper concentration to cotton. In these concentration, emergence exponent of cotton seed, fresh weight of cotton seedling or cotton root, the length of root and sprout were all promoted at the maximum in all treatments.DPC (1,1-dimethypiperidiniumchloride) +triadimefon, DPC+propiconazol, BR (Brassinolide) +triadimefon, BR+propiconazol, PP333 (paclobutrazol) +tolclofos-methyl, PP333+thiram, CC (cholinechloride) +propiconazol, CC+diniconazole,PAA+carbendazim, PAA+propiconazol, NAA (a -naphthaleneacetic acie ) +diniconazole, NAA+triadimefon, SA (saicylic acid) +tolclofos-methyl, SA+triadimefon, BR+carbendazim, PAA+diniconazole, CC+propiconazol, CC+thiram, DPC+carbendazim, DPC+thiram showed synergistic activities to the three diseases; on the contrary, SA+thiram, NAA+tolclofos-methyl, PP333+triadimefon, PAA+triadimefon showed antagonist effect. Futher study proved the synergistic activities are related to the increase of the activities of cotton root cell protecting enzyme system including SOD, POD, CAT.