QTL Mapping For Leaf Size In Barley

Leaf is the main photosynthetic organ of plant.Barley yield is closely related to the morphological trait of flag and top second leaf.Understanding the genetic variation and related genes of flag and top second leaf can provide basic information for barley molecular breeding.Cell is the basic unit of forming organ.Epidermal cell is the most easily observed cell in the leaf,and its shape is very stable.Therefore,clarifying the relationship between epidermal cell width and leaf width will help understand the physiological and molecular basis of leaf phenotypic variation.In this study,two barley varieties were identified with significant difference of leaf width,Zangqing 320 and Haruna Nijo.F₂ separation population were constructed.A large number of SNPs obtained by whole genome resequencing were used to develop KASP molecular markers,and QTLs related to flag and top second leaf size of barley were determined.The results are as follows:?1?Epidermal cell width at different sampling points of same leaf were measured in Zangqing 320 and Haruna Nijo,it showed that epidermal cell width at different sample points was significantly different in the same leaf,and the epidermal cell width was wider as it was closer to the leaf vein.The epidermal cell width of Zangqing 320 was significantly larger than that of Haruna Nijo at the same sampling point,for example,at sampling point 4 near the leaf vein in the middle of the leaf,the epidermal cell width of Zangqing 320 was 24.75?m,significantly larger than that of Haruna Nijo's 20.76?m.Besides,epidermal cell width of flag and top second leaf in different tillers were measured in parent plants and F₂ population.It was found that there was no significant difference in epidermal cell width of flag and top second leaf between main stem and different tillers;The epidermal cell width of top second leaf was significantly larger than that of flag leaf.Finally,correlation analysis between the epidermal cell width and leaf width of flag and top second leaves showed that there was significant positive correlation between the epidermal cell width and leaf width in the F₂population.It provides important information for the genes cloning for leaf width in barley.?2?By comparing and screening the whole genome resequencing data of Haruna Nijo with the reference genome of Zangqing 320,a total of 129,100 effective SNP sites were obtained which could be used for molecular marker development of KASP.According to its physical position of barley,112 SNP sites were selected for KASP-SNP molecular marker transformation.KASP-SNP molecular markers were verified by genotyping in F₂ population,and 64 pairs of KASP-SNP molecular markers were obtained,with a conversion success rate of 57.1%.The genetic map for QTL mapping was constructed initially,which laid a foundation for the mapping and cloning of genes related barley leaf width in this study.?3?Leaf length,width and area of flag and top second leaf of 1152 individual in F₂population were analyzed.It was found that the coefficient of variation ranged from 0.11 to0.38,and they were all normally distributed,which could be used for QTL analysis.Then,The leaf width,leaf length,leaf area and leaf epidermal cell width of flag and top second leaf were analyzed by using 64 pairs of KASP-SNP molecular markers.A QTL associated with flag leaf and top second leaf width was identified near chromosome 6H 236Mb and named qLW-6-1,which was linked to the molecular marker ZQHN-265,and the physical distance between the interval of qLW-6-1 is 10.4mb.qLW-6-1 can explain 5.7%flag leaf width variation and 9.6%top second leaf width variation.The results showed that the molecular marker ZQHN-265 has potential value in the identification of barley leaf width phenotype,which can provide an important basis for the subsequent identification of barley leaf morphology genotype.