Regulation Mechanism Of Novel Plant Growth Regulators On Growth And Lodging Of Maize In The North China Plain

Adopting spring maize to replace part of winter-wheat summer-maize rotation system can resolve agricultural water scarcity issue in the North China Plain(NCP).However,the main hindrance to increasing spring maize production is caused by high-temperature stress(HTS)at grain filling stage,simultaneously,the complex weather changes in this area increase the risk of maize lodging.Application of plant growth regulators is an effective strategy to improve crop resistance and control lodging.The first part of our research was conducted in 2015-2016 to study the effects of a new plant growth regulator 1-(2,4-dichloromyl cyclopropylic acid)that named B2 for short on alleviating HTS during grain filling stage of spring maize in field condition.The second part of our research was conducted in 2016-2017 to study the effects of COR on lodging resistance and the sensitivity of different maize genotypes to COR in the field,and evaluate the regulation mechanism of COR on maize intemode growth-related genes under the greenhouse condition.Our results were in order to provide a theoretical basis for high yield,high efficiency,lodging-resistance and calamity-diminished sustainable cultivation technology system.Main results are as follows:1.The mechanism of B2 relieving HTS during filling stage.B2 significantly increased grain yield by 8.5%by increasing thousand-kernel weight(TKW)and decreasing the bare tip length compared to control.Additionally,B2 significantly increased the SPAD value and ABA content of the ear leaf,positively enhancing net photosynthesis rate and heat resistance.B2 also improved grain filling rate,grain volume,and grain dry weight,which contributed to the higher grain yield.Moreover,B2 decreased plant height and ear height,neither of which were affected by ABA.These results indicated that B2,with the similar biological activity of ABA,could help maintain relatively higher photosynthetic capacity,heat resistance,and grain filling rate during the grain filling stage under HTS,resulting in a stable method to increase grain yield.2.The mechanism of Caronatine(COR)lodging resistance.COR remarkably decreased the plant height,ear height,leaves area per plant,the length of basal internodes,and dry weight of basal internode,significantly increased internode diameter,dry weight per unit intemode length,breaking resistance,structure material content.The effects became more significant with the increasing concentration of COR.COR promoted the growth of maize roots and significantly improved root traits with the increasing concentration of COR.The optimal COR concentration of Xianyu335 for lodging resistance was 10 ?mol L-1 and Zhengdan958 was 1?mol L-1,indicating that different maize varieties have different sensitivity level to COR.Overall,the optimal concentration range of COR should be 1-10 ?mol L-1,which could not only delay intemode elongation,enhance internode performance,and improve plant lodging resistance,but also increase grain yield.3.Differences in sensitivity level of maize genotypes to COR and RNA-Seq analysis.The COR-sensitive inbred lines were selected as follows:Mo17,B73,87-1,and PH6WC.The optimal concentration of COR for studying the mechanism of COR on internode elongation was 10 ?mol L-1.RNA-Seq was used to obtain a map of COR-regulated differentially expressed genes in maize internodes and found that COR-induced differentially expressed genes at different time points and at different sites were involved in the growth and development process,providing the basis for future work.