Root Traits Diversity In Maize And Their Responses To Drought Stress

The growth and production of maize(Zea mays L.)is restricted by various abiotic stresses,in particular drought stress.Genotypes with suitable root system adapt better to water stress environment.Using an established semi-hydroponic phenotyping technique and root image analysis technology,the root trait variability across 174 maize genotypes,including 113 cultivars and 11 breeding lines from northern China,and 50 Serbian hybrids were systemataiclly assessed.Eighteen selected genotypes with contrasting root systems were further examined for their responses to drought stress uner PEG-6000.The aims were to strengthen the understanding of the genetic variation in maize roots and their responses to drought stress.The main results were as follows:1.Genetic diversity in maize seedling root traits: there were large variations in root traits at seedling stage among the tested maize genotypes.Sixteen traits showed high coefficients of variation(CVs ? 0.25).Genetic variation in root traits among diverse maize lines can be used for selecting genotypes with higher adaptation to drought and other abiotic stresses.Some typical traits,such as total root length,root length at various depths,nodal root angle,can potentially serve as parameters for future breeding programs,and 18 genotypes with contrasting root architecture traits were selected out from 174 maize genotypes.2.Adaptation of root traits to drought stress: under drought stress,maizes reduced the root numbers,paritioned more resourse for improving shoot growth and efficient water acquisition,and reduced root diameter with more fine roots.3.Adaptation of root physiological traits and shoot traits to drought stress: in this study,soluble sugar had high contribution to the drought-resistant ability of maize genotypes.The breeding lines showed greater adaptation to drought than other genotypes.Under drought stress,maize plants reduced plant height and leaf number to a certain extent,and increased root to shoot ratio,thus maintained the growth of root and shoot.In this process,the drought tolerant genotypes distributed more resourse to the shoot as much as possible.4.Potential parameters for identify maize genotypes for drought tolerance: this study suggests that some global root traits(e.g.specific root length,root density,root number,root width and root-mass ratio),local root traits(e.g.root diameter in various depth,length of thin root,topsoil root dry mass),root physiological traits(e.g.soluble sugar)and shoot traits(e.g.shoot height,leaf number)can be selected to identify drought tolerance of maize genotypes.In summary,large variation in root architecture traits among the tested genotypes were identified.Some root morphological traits,root physiological traits,and shoot traits can be used for identifying drought tolerance genotypes in maize.Optimal root traits are a promising aspect for breeding high abiotic stress adaptation genotypes.It's necessary to improve root traits for target environment,and should be the focus for future research.