QTL Analysis Of Stem Solidness And Stem Strength In Bread Wheat

Wheat is one of the most important crops in our country.Lodging,the permanent displacement of stems from an upright position due to internal and external factors,is an important constraint limiting wheat yields and quality in both developed and developing countries.Wheat breeding increased lodging resistance through the introgression of dwarfing genes during the second half of the 20th century.However,the yield is reduced when plants are shortened too much with dwarfing genes.Improving the physical strength of the basal part of the culm internode is the major target for improving the lodging resistance.Solid stem traits,including thickness-diameter ratio of culm,stem diameter,culm wall thickness and pith diameter,are the main targets for improvement of stem strength in wheat.In the present study,a F2 population and F2:3 families derived from the cross N18 × WYSG was used to study the influence of stem solidness on stem strength and to identify QTLs for the related traits.A set of F2population,RIL groups,BC groups and natural groups are derived from the cross N18×WYSG.The results are as following:Solid stemmed WYSG showedthe greatest amount of pith material for the first and second internodes,whereas N18 had hollow stems.Significantdifferences were also detected in the anatomical characteristicsof the three genotypes,especially the transverse sections of solidstemmed wheat WYSG,which had more mechanical andparenchyma tissues than N18;F1plants were almost intermediatebetween their parents in the corresponding values;It was found that stem strength,thickness-diameter ratio and culm wall thickness in the solid stemmed and F1plantswere significantly larger than that of N18 for both first and second internode.In contrast,therewere only minor differences in stem diameter for the first internode;The result showed that thickness-diameter ratio of culm,stem diameter,culm wall thickness and pith diameter were significantly correlated with stem strength;By using composite interval mapping(CIM),a total of 23 QTLs on chromosomes 1B,3B,4A,4B and 5A were identified to be significant for the five traits.Phenotypic variations explained by individual QTLs ranged from 3.48%to 44.0%.Pleiotropic QTLs were found onchromosomes 3B(gwm547-gwm247),4A(wmc718-wmc468)mind 5A(gwm156-gwm443),all contributing very high phenotypic variations;Thereliability of the marker gwm247 was confirmed using 24 F7lines derived from the N13(hollow stem)× WYSG(solid stem)cross.The markers linked to major QTLs could be valuable in wheat breeding for lodging resistance with marker assisted selection technology.