Genetic Analysis And Gene Mapping Of Thermo-inducible Chlorophyll-Deficient Mutant In Barley

Photosynthesis is the basis for the survival of the entire biological world and is an important medium for the carbon-oxygen cycle on the earth.Chlorophyll is the vital photosynthetic pigment in plant photosynthesis,whose main function is absorbing and transferring electrons.Mutants in leaf color are important bridge to cloning genes involving chlorophyll synthesis,and perfect materials for research in photosynthetic pigments' biosynthesis network,development,structure and function of chloroplast and establishment of light morphogenesis.In this study,a thermo-inducible chlorophyll deficient mutant,named V-V-Y,was identified from a gamma-radiated population of the barley variety Vlamingh.The leaves of V-V-Y turned yellowish but took longer to senesce under heat stress in the field experiment.The leaves of the mutant were green under normal growing temperature but turned yellowish under high temperature in the glasshouse experiment.The ratio of chlorophyll a and chlorophyll b in the mutant declined much faster in the first 7–9 days under heat treatment.Genetic analysis indicated that a single nuclear gene controlled the mutant trait.The V-V-Y × Buloke DH population was used for mapping the mutant gene(vvy).The vvy was mapped to the long arm of chromosome 4H between SNP markers 1-0269 and 1-1531 with a genetic distance of 2.2 cM and a physical interval of 9.85 Mb.Fine mapping,based on the barley reference genome sequence,further narrowed the vvy gene to a physical interval of 0.428 Mb with 11 annotated genes.Analysis on the candidate gens indicated that the vvy gene may be a new gene that involving synthesis of chlorophyll.Filed yield analysis in the V-V-Y × Buloke DH population under Mediterranean climate showed that the yield of the DH lines varied from 470 to 4953 kg/ha,the average yield in the mutant V-V-Y and Vlamingh was 3755 ± 246.7 and 4194 ± 249.6 kg/ha.The average yield of Buloke was 4340 ± 254 kg/ha.A QTL was mapped on chromosome 4HL linked with marker WR33 explained 10.4% of the yield variation with a LOD = 4.This QTL is coincident with the vvy gene interval that is responsible for the thermo-inducible chlorophyll-deficient trait.This is the first report of fine mapping a thermo-inducible chlorophyll-deficient gene in barley,which lay a foundation for the cloning and gene function studies.