Effects Of Hormone Priming On Salt Tolerance, Yield, And Fiber Quality Of The Hybrid Cotton

Due to the characteristics of economy, convenience and high-efficiency, seed priming techniques has been widely studied. However, there were only a few reports on the researches about the effects of seed priming with hormones on cotton growth, especially on salt tolerance, yield, fiber quality in hybrid cotton. Two transgenic insect resistant hybrid cotton cultivars. ZD13-1 and ZD13-2, were used to investigate the effects of seed priming with water,20 mg/L of auxin (IAA),20 mg/L of kinetin (KT), 50 mg/L of gibberellins (GA),0.5 mg/L of brassonolide (BR) on salt resistence, yield, and fiber quality in present work. In order to explore the mechanism of the effects of hormone priming on improving salinity tolerance in hybrid cotton, the dynamic changes of the superoxide dismutase (SOD) and peroxidase (POD) activity, malondialdehyde (MDA), and chlorophyll contents, and photosynthetic rate were also studied. The main results were as follows:1. The germination rate of ZD13-1 and ZD13-2 without priming treatment was 88.33% and 54.33%, respectively, and the germination rate of ZD13-1 was significantly higher than that of ZD13-2. There were no significantly different between the treatment with 0.5% NaCl and control in the germination rate of two cultivars, which indicated that 0.5% NaCl treatment was not sufficient to produce abiotic stress to the two varieties. However, the germination rate and seedling growth of the two cultivars were significantly affected under the treatment of 1.0% NaCl, and the salt tolerance of ZD13-1 was better than ZD13-2.2. The results showed that the germination rate of ZD 13-1 and ZD13-2 after treatment of seed priming with IAA were increased by 5.34% and 15.67% respectively, however, under 1.0% NaCl stress, that of two cultivars were increased by 11.34% and 14.67%, respectively. The treatment of seed priming with IAA could significantly improve the germination ability and salt resistance. While, other hormone has no effects or even negative influence on the promotion of germination and salt tolerance for two hybrid cotton cultivars.3. The results of analysis for SOD, POD, and MDA for two hybrid cultivars showed that seed priming with IAA could increase the contents of MDA and the activities of SOD and POD, significantly, while other hormones priming treatments have no effects on improving antioxidant enzyme activity which suggested that IAA priming could significantly enhance the oxidation resistance of hybrid cotton.4. Under NaCl stress, the activities of SOD, chlorophyll contents, and the photosynthetis rate of the two hybrid cotton cultivars decreased, significantly, and their activities of POD and MDA contents increased, greatly. IAA priming could enhance the salt tolerance of hybrid cotton due to increasing the antioxidant enzyme activity, chlorophyll contents, and the photosynthetis rate, but reducing the MDA accumulation in cotton leaves of two cotton cultivars, significantly. In addition, IAA priming had the capability to inhibit the rapid decrease of chlorophyll contents and a sharp change of antioxidant enzyme activity in the later season under NaCl stress. It was indicated that IAA priming might help to improve the salt tolerance capability for two hybrid cotton cultivars.5. There were no significant effects of hormone priming on the seed cotton yield and lint yield of two hybrid cotton cultivars. However, the percentage of immature cotton bolls for ZD13-1 and ZD13-2 with the treatment of IAA priming were 4.30% and 3.82%, respectively, significantly higher than control, which indicated that IAA priming could prevent from premature senescence in late season of two hybrid cotton cultivars. The boll rot rate of ZD13-1 was increased significantly after priming with hormone, especially for GA priming, which was 18.59% significant higher than that of control (7.35%). The boll rot rate of ZD13-1 and ZD13-2 were 10.31% and 4.95% for the IAA priming treatments, respectively, which was insignificant higher than their non priming control for ZD13-1 and significant lower for ZD13-2. Determination of fiber quality showed that priming with IAA and BR could increase the fiber length, micronaire value, and fibre strength of ZD13-2, but the differences were not significant.