Genotypic And Environmental Variation Of Grain Quality And Their Relative Mechanism In Barley

Barley is mainly used as the materials for beer and feed production,and its quality is of important for the commercial values of the final product,thus the improvement of barley quality has been placed into a major objective of barley breeding and agronomy studies.The traits of barley quality belong to the quantitative characters, indicating that they are not only controlled by complex genetic factors,but also greatly affected by environmental factors.In the current study,the genotypic and environmental variation ofβ-amylase and limit dextrinase activities,β-glucan and protein fraction contents in barley grains and the influence of timing of nitrogen application on these malt quality characters were investigated;In addition,the possible mechanisms of P-amylase activity regulation was illustrated by using a barley mutant TL43 and its wild parent Triumph as experimental materials,and QTL analysis of these quality traits was conducted by using a double haploid population.The main results were as follows:1.The variation ofβ-amylase activity and protein fractions in barley grains as affected by genotypes and post-anthesis temperaturesThe variation ofβ-amylase activity and protein fractions in barley grains was evaluated among 148 barley genotypes grown in the same field condition and using in vitro culture of two barley cultivars under different temperatures during grain development.The results showed that there were considerable genotypic variations inβ-amylase activity and protein fractions.Correlation analysis indicated thatβ-amylase activity was positively correlated with total protein and all protein fraction contents, with the highest correlation coefficient for hordeins.Furthermore,higher post-anthesis temperature(32/26℃,day/night) significantly enhancedβ-amylase activity and protein fractions,with albumins and glutelins being least and most affected respectively,in comparison with the plants under lower temperature(22/16℃).The high temperature also altered the morphology of A granules and number of B granules, suggesting starch structure change may also be a reason for deteriorated malting quality under high temperature.2.Genotypic and environmental variation ofβ-amylase,limit dextrinase activity,β-glucan and protein fraction contents in Tibetan wild barleyThe effects of genotypes and environments(locations and years) onβ-amylase,limit dextrinase activity,β-glucan and protein fraction contents in Tibetan wild barley grown in Hangzhou for two years and Wuhan for one year were investigated in this study.Significant genotypic differences and great variations were detected in grainβ-amylase,limit dextrinase activity,β-glucan and protein fraction contents.The largest variation and highest average value ofβ-amylase activity were found in Hangzhou 06-07,while the trend of coefficient of variation was opposite to the mean content ofβ-glucan over different environments.Hordein content had the highest correlation coefficient withβ-amylase activity among four protein fractions.The great variation of these traits in Tibetan wild barley will be helpful for improving modern malting barley or utilization of barley as health food in breeding.3.Effects of the timing of nitrogen application on grain weight,protein fraction content andβ-amylase activity in barleyThe effects of four timing treatments of nitrogen fertilizer application with the same total nitrogen rate on grain weight,protein fraction contents andβ-amylase activity in barley cultivar Hua-30 were investigated.The results showed that there was no significant difference in grain weight among the four treatments.However the increasing proportion of nitrogen application at later growth stage caused the dramatic increase of hordein and glutelin contents andβ-amylase activity,while did not alter the albumin and globulin contents.It may be suggested that the influence of increased nitrogen application at later growth stage on malt barley quality is dual,i.e.improving quality through enhancingβ-amylase activity and deteriorating quality through increasing protein content.4.The influence of nitrogen application at booting stage on protein fraction and hormonal changes during grain fillingThe influence of nitrogen application at booting stage on protein fraction and hormone content change during grain filling was investigated using a European barley cultivar Triumph and its ABA mutant TL43 as the experimental materials.The results showed that TL43 had lower grain weight and higher protein content in comparison with Triumph in all nitrogen application treatments.The higher rate of nitrogen application at booting stage resulted in significant increase of protein content in grains. However the influence of the nitrogen application treatment on protein fraction contents varied with genotype,all four fraction contents being significantly increased for TL43,and only glutelin content being significantly affected for Triumph.There was little difference in GA3 content between the genotypes and among the nitrogen treatments.However significant difference was detected in ABA and ZA contents between the two genotypes.Nitrogen application at booting stage caused a marked reduction of ABA content at later grain filling stage.5.The interaction between H₂O₂ and ABA onβ-amylase accumulation under osmotic stress during seed development in barleyThe effects of exogenous ABA and PEG treatments on grain H₂O₂,ABA andβ-amylase accumulation were studied during seed development in Triumph/TL43 using a spike cultural experiment.Triumph and TL43 showed the similar pattern of ABA changes,but different patterns of H₂O₂ andβamylase accumulation during grain filling.Theβamylase accumulation was positively correlated with H₂O₂, negatively correlated with ABA,and mainly determined by the time of high ABA: H₂O₂ stage.The PEG treatment enhancedβamylase synthesis,which was associated with H₂O₂ but not closely related to ABA.Exogenous application of H₂O₂ and AsA enhanced theβamylase activity in Triumph,but reduced that in TL43.However,the endogenous H₂O₂ content in grains was consistent withβamylase accumulation.A novel model may be speculated according to the results that H₂O₂ and ABA are participated in the synthesis ofβ-amylase when barley plants are exposed to temperature stress.6.Genetic Mapping of Quantitative Trait Loci Associated withβ-amylase,limit dextrinase activities,β-glucan and protein fraction contents in BarleyInterval mapping was utilized to detect quantitative trait loci(QTLs) controlling some malt quality traits using a doubled-haploid population developed from a cross of a six-rowed(cv CM 72) and two-rowed(cv Gairdner) cultivars.A total of nine QTLs for eight traits were mapped to chromosomes 3H,4H,5H and 7H,respectively,with five QTLs on chromosome 3H,indicating an important role of 3H on malt quality. The phenotypic variation accounted by individual QTL ranged from 8.08%to 30.25%. The loci of QTLs forβ-glucan and limit dextrinase were identified on chromosome 4H and 5H,respectively.QTL for hordeins was coincident with the region of silica eluate(SE) protein on 3HS.One locus on 3H was found to be related toβ-amylase and two loci on 5H and 7H were found to be associated with glutelins.