Uniconazole application strategies to improve lignin biosynthesis, lodging resistance and production of maize in semiarid regions

Lodging stress significantly reduces the grain yield and quality. Uniconazole is a plant growth regulator and it can potentially reduce lodging stress by enhancing lignin metabolism and lodging resistance. We conducted a field study in the semiarid regions of China to determine suitable uniconazole application strategies based on the culm morphological characteristics, rind penetration strength, lignin metabolism, lodging stress, and grain yield from summer maize during 2015 and 2016. Seeds were soaked in uniconazole at concentrations of 0 (SCK0), 25 (SU25), 50 (SU50) and 75 (SU75) mg kg(-1). In another experiment, uniconazole was applied to the foliage at concentrations of 0 (FCK0), 25 (FU25), 50 (FU50) and 75 (FU75) mg L-1 at the eight-leaf stage. Our results suggested that uniconazole significantly alleviated lodging stress by enhancing lignin metabolism and optimizing the culm morphological characteristics. Uniconazole significantly increased the lignin content and activities of lignin-related enzymes such as phenylalanine ammonia-lyase, cinnamyl alcohol dehydrogenase, tyrosine ammonia-lyase, and peroxidase, where their maximum values were obtained with SU25 and FU25 treatments. The grain yield and ear characteristics increased but then decreased as the uniconazole concentration increased, where treatments SU25 and FU25 obtained the highest grain yield and ear characteristics. Seed soaking significantly enhanced lignin accumulation and alleviated lodging stress compared with foliar application. Our results suggest that the lignin content is closely related to lodging resistance in maize and higher lignin accumulation in the third basal internode can improve lodging resistance. Uniconazole application significantly reduced the risk of lodging stress and improved the grain yield of maize, where the most effective treatments were soaking seeds at 25 mg kg(-1) and foliar application of 25 mg L-1 at the eight-leaf stage.