Effect Of Seed Priming With Melatonin On Salt Tolerance And Agronomic Characters Of Upland Cotton (Gossypium Hirsutum L.)

Cotton is a salt-tolerant crop.However,its salt tolerance has a certain threshold.Melatonin which promotes plant tolerance to stress and regulates the growth,development and biological rhythm of plant.In this study,upland cotton（Gossypium hirsutum L.）Coker 312（C312）and Coker 312 glandless（C312W）were used as materials,and melatonin solution was used for seed priming.To explore the effect of melatonin priming on seed germination,the salt tolerance of seeding,field production and fiber quality of a pair of glanded cotton and glandless cotton near-isogenic lines（NILs）.The main findings are as follows:1.Effect of melatonin priming on seed germination（1）The germination and radicle length induced by melatonin were significantly better than those induced by water or non-priming.（2）The germination of both strains were significantly inhibited by 0.5%NaCl,which could be alleviated by seed priming.What’s more,25μmol/L melatonin priming showed the best result.（3）The radicle length of C312W was significantly longer C312.2.Effect of melatonin priming on cotton growth（1）In the absence of salt stress,seed priming significantly increased leaf area,leaf thickness and root length,increased the relative chlorophyll content and the photosynthesis,improved the autioxidant enzyme activities,and decreased the content of MDA and gossypol in the two cotton varieties.（2）Melatonin priming significantly alleviated the inhibition of phenotypic traits and the increase of gossypol content and MDA content in the two tested strains with salt stress.（3）The chlorophyll content of C312 was significantly lower than C312W,but the net photosynthetic rate and intercellular CO₂ concentration were significantly higher than C312W.3.Effect of melatonin priming on the yield of cotton（1）Melatonin priming significantly decreased plant height and fruit branches,and improve the fiber quality of C312 with a certain extent;melatonin priming significantly increased fruit branches and decreased immature bolls of C312W.（2）Between the two near-isogenic lines,the cotton yield and fiber quality of C312 were significantly higher than C312W.In conclusion,melatonin priming can significantly improve seed salt tolerance and promote seed germination under salt stress,increasing photosynthetic activity and antioxidant enzyme activity,and reducing MDA and gossypol content;The yield of upland cotton fiber was increased by improving its agronomic characters,but there was no significant effect on cotton yield and fiber quality.