Molecular Mapping of Adult Plant Resistance Gene to Powdery Mildew in Tetraploid Wheat
Tetraploid wheat is the ancestor specie of common wheat and an important food crop.Aiming to pro-vide new resistance sources for wheat variety breeding,the resistance tetraploid wheat germplasm was explored and their resistance genes were identified.TDI-1 is a cultivated emmer wheat that has been immune to powdery mildew in the field for many years.To determine the resistance genes carried by TDI-1,and provide a theoretical basis for genetic improvement of wheat resistance,a durum wheat TDU-1 that was susceptible to powdery mildew was used to hybridize with TDI-1,and their F1 plants,F2 population,and F2∶3 lines were obtained.Genetic analysis of resistance was conducted on parents TDI-1,TDU-1,and their hybrid offspring that were inoculated with powdery mildew isolate E09.Then,bulked segregant analysis method combined with molecular markers was used to map the resistance gene.The results showed that TDI-1 was susceptible to E09 during the seedling stage but immune during the adult stage.F,plants derived from the cross of TDI-1 and TDU-1 were immune to E09 during the adult stage.The resist-ance of adult F2individuals was separated,and the ratio of resistant and susceptible plants was 3∶1(x23∶1=0.11,P=0.74);the ratio of the number of homozygous resistant,separated resistant,and homozygous susceptible F2∶3 lines was 1∶2∶1(x21:2∶1=0.47,P=0.79),indicating that the resistance to powdery mildew in the adult stage of TDI-1 was controlled by one dominant gene,temporarily named PmTDI-1.Subsequently,a set of molecular markers was used to amplify the parents and their F2 population,and then four markers on chromosome 2A,including Xwmc407,NRM-2AS29,NRM-2AS45 and NRM-2AS84,confirmed to be linked to PmTDI-1.PmTDI-1 was between the flanking markers NRM-2AS45 and NRM-2AS84,with genetics distances of 1.8 cM and 4.6 cM,respectively.Therefore,the adult stage powdery mildew resistance gene PmTDI-1 was preliminarily localized on chromosome 2A.This study identified a novel dominant adult-plant-resistance powdery mildew gene PmTDI-1 from tetraploid wheat TDI-1.
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