QTL Analysis Of Phenotypic Plasticity Of Maize Husk

Global climate and disaster weather exhibited a drastic change in recent years.The plasticity of plants in variable environments is increasingly important.Phenotypic plasticity is a phenomenon that same genotype in different environments exhibit different phenotype.It is ubiquitous in plants and controlled by genetic regulation at the molecular level.Maize husk is an abnormal leaf sheath tissue attached to ear stalk and plays an irreplaceable role in the growth and development of maize ears.Husk defends the ear from the deleterious environment factors and contributes to organic matter transportation and photosynthetic nutrition.It is particularly important that the morphological structure of husk significantly affects the dehydration efficiency of maize kernel at harvest time.Therefore,the morphological structure of husk is closely related to the growth and development of ear and the mechanically harvested kernel.However,remarkable changes of husk traits in different environments have been observed.The appearance of plasticity of husk hinders the breeding in different places and the mechanically harvested kernel.Till now,the genetic mechanism of husk related phenotypic plasticity has not been reported.Thus,in this study,four recombinant inbred lines were used as experimental materials and planted in three environments,respectively.At maturity,the husk traits(length,width,layer number)were measured at the same time.The coefficient of variation(CV)of husk traits in different environments was calculated,which was taken as the representative value of phenotypic plasticity of husk traits.The genetic basis of the phenotypic plasticity of husk length(PHL),the phenotypic plasticity of husk width(PHW)and the phenotypic plasticity of husk layer number(PHN)were analyzed by QTL mapping in each linkage population,providing theoretical basis for maize breeding in different locations and mechanical harvesting.The main results were as follows:1.There were significant differences in the phenotypic plasticity of husk among different linkage populations.Except BYK,the transgressive inheritance was observed in the other three RILs.All of the three husk phenotypic plasticity in four RILs exhibited normal distribution,which could be suitable for genetic analysis.Significant correlation between PHL and PHW among the four populations were detected,indicating a common regulation pathway may exist.Across the populations,PHL and PHW showed small differences.While,PHN showed significant difference.The PHN of MX and CIK was the lowest and highest.The former was suitable and the later should be used with caution for the breeding in differentlocations.2.Through the construction of the recombinant map,it was found that the parental markers of the four populations were widely distributed and the heterozygosity rate was low,which was conducive to QTL mapping analysis.QTL mapping analysis of the phenotypic plasticity of husk traits in four linkage populations,thirteen QTL intervals were detected.Two Major QTL associated with PHW were observed.In addition,apart from the overlapping sites across the centromere,two overlapping QTL intervals were found on chromosomes 2 and 8.Comparing with the previous publication QTL associated with husk,the QTL related to PHW,PHN and husk length overlapped,indicating similar regulatory system among these traits.3.Base on bin map to narrow the QTL interval,a total of 109 protein coding genes were found in all mapped QTL interval.For two large-effect QTL,two candidate genes,GRMZM2G302233 and GRMZM2G412503,were identified as GTP family protein and histone family protein involving in signal transduction and epigenetic pathway.4.In V3-V6 stage of husk primordium formation and R1 stage of husk elongation,significant changes were observed in relative humidity and mean rainfall.Therefore,these two meteorological factors may play important roles affecting the phenotypic plasticity of husk.Above all,husk traits showed significant performance in various environments.The phenotypic plasticity of husk was controlled by large and small effect QTL.PHW may be mainly controlled by signal transduction and epigenetic pathway.The relative humidity and mean rainfall may play important roles affecting the phenotypic plasticity of husk.