Identification Of Parental Dwarf Genes In Wheat And Their Effect On Heterosis

Wheat is the third largest food crops in the world.With the increase of population and the reduction of arable land,increasing the yield per unit of wheat has become an important way to increase wheat yield.The use of dwarf genes has played a great role to increase wheat yield since the 1960 s.The plant height of hybrid wheat has a general super-parent advantage,however,the too tall plant height is easy to reduce yield due to lodging.To explore the effect and application potential of different dwarf genes or dwarf gene combinations on wheat hybrid heterosis,and to provide a basis for the application of dwarf genes in hybrid wheat breeding for lodging resistance.In the field,our laboratory found a male sterile line with a height of 55～65 cm,which was significantly different from their parents.In order to determine whether the gene mutation or the combination of dwarf genes caused plant dwarf,the dwarf gene analysis of this line was carried out.After that,4 restorer lines,6 sterile lines and 22hybrid combinations were configured in the field by incomplete dialectics.Common PCR techniques and parental analysis were utilized to determine the dwarf genes in the parents and genotypes in their hybrid combination.Then their agronomic traits and yield-related traits of the hybrid combinations with different genotypes were analyzed.The potential application value of different genotypes,sterile lines and restorer lines was determined by analyzing the heterosis of each trait and combining ability of the parents.The main findings are as follows:1.The dwarf genes identification in the male sterile and restorer linesThe gibberellin susceptibility analysis and the plant height separation ratio analysis of the F₂population were carried out in the male sterile lines 17L7030,17L7106 and 17L7140,which were derived from the original dwarf sterile line found in the field dwarf.It was found that the dwarf sterile line is insensitive to gibberellin and contains more than one pair of dwarf genes.The PCR results showed that 17L7030,17L7106 and 17L7140 contained Rht1 and Rht2,suggesting that the dwarf sterile line is not a mutant,and its dwarfness is caused by the combination of two dwarf genes.The parental dwarf gene analysis showed that all sterile lines in this study contained dwarf gene Rht1.Besides,male sterile lines 19L4105,19L5018,19L5047 and19L5065 had dwarf gene Rht2,19L5006 contained dwarf gene Rht21.The restorer lines Chuanmai 93 and Chuan 14 pin 16 contained dwarf gene Rht1,while MR1101and MY3271 did not contained any of the tested dwarf genes in this study.2.Comparison of heterosis analysis between different genotypes of hybrid combinationsThe 22 hybrid combinations were divided into 6 dwarf genotypes,and the yield per plant differed significantly among some genotypes.The plant heights of different dwarf genotypes were all between the middle parent value and the restorer line,indicating that the plant height of hybrids was effectively reduced,and each dwarf genotype was beneficial their restorer lines and to enhance the lodging resistance of hybrids.The yield potential was affected by their parents,and the yield of the hybrids denpended on the the parents’yield.Genotypes Rht1′+Rht21′,Rht1′+Rht2′and Rht1′′+Rht2′had super-high parental heterosis in yield per plant,genotype Rht1′+Rht21′had higher heterosis in number of spike per plant,1000-grain weight,and biomass per plant.Genotype Rht1′+Rht2′showed super-parental heterosis in 1000-grain weight and yield per plant.Except for Rht1′and Rht1′′+Rht21′,all other genotypes had super-high parental heterosis of more than 10%yield increase per plant,which can be used for the breeding of hybrid wheat to sreeen strong heterosis combinations.The correlation analysis of genotypes Rht1′+Rht2′and Rht1′′+Rht2′showed that the same traits had different correlations among different genotypes,but there was no significant correlation between plant height and yield per plant.The yield per plant of the two genotypes was significantly correlated with the number of spike per plant and the biomass per plant.Among them,the yield per plant of genotype Rht1′+Rht2′was also significantly positively correlated with the ear length,indicating that choosing the number of spike per plant in the same genotype is beneficial to obtain a strong heterosis hybrid combination.3.Analysis and comparison of parental general combining abilityIn order to clarify the potential value of the parents used in this study,the general combining ability analysis of 10 parents was carried out.The results showed that the restorer lines Chuan 14 pin 16 and Chuanmai 93,and the sterile lines 19L4105 and19L5065 were better in the general combining ability.The hybrid combination used them as parents not only can meet the requirements of hybrids for plant height,but also has a positive effect on yield and multiple yield-related traits.More hybrid combinations can be made,and strong heterosis hybrid combinations can be selected for hybrid wheat production.In conclusion,the heterosis in plant height of wheat is widespread,and the dwarf genes identified in this study are all beneficial to reduce the plant height of hybrids and improve their lodging resistance.The four dwarf genotypes can breed hybrids with high parental heterosis,and their yield potential is affected by the yield level of both parents.The hybrid combination with genotype Rht1′+Rht21′had the largest super-parent heterosis,followed with genotype Rht1′+Rht2′.Therefore,it is easier to obtain a strong heterosis combination when these two genotypes are used in hybrid wheat breeding.