The Resistance Components In Relation To The QTL For Resistance To Rhizoctonia Cerealis In Wheat

Wheat(Triticum aestivum L.)plays a significant role in grain safety.Sharp eyespot disease,caused by Rhizoctonia cerealis,results in a devastating yield loss in wheat production every year.Growing resistant cultivars of wheat is believed as the most economic,efficient and environmentally-friendly strategy compared to applying fungicides in fields.No immune gene against sharp eyespot disease was found until now.Nonetheless,many cultivars with low to moderate and high resistance to the disease have been reported.In addition,a number of quantitative loci(QTLs)for sharp eyespot resistance have been identified in genetic linkage maps.With a cross combination of Luke x AQ,we have previously reported seven resistance QTLs to sharp eyespot disease(QSe.cau-1AS,QSe.cau-2BS,QSe.cau-3BSfQSe.cau-4AL,QSe.cau-5DL,QSe.cau-6BL,and QSe.cau-7BL).The objective of this work was to study the potential resistance mechanism of the seven QTLs,in order to figure out their relationships with plant architecture characteristics,stem lignin content and two pathogen-related genes.Therefore,the current study worked on four experimental tasks as following.First,cooperating with other people in our lab,we generated a high-density genetic map to enrich the genotype data for QTL mapping of plant morphological traits,containing 613 DNA molecular markers with 266 recombinant inbred lines(RILs).Second,we investigated 15 wheat traits of plant architectural characteristics and heading date from 5 biological replicates in two growth seasons for the 266 RIL population aiming to analyze their genetic relationships with the resistance QTLs on chromosomes.Third,we determed the lignin content of 8 RILs in fields,which individually possesses single one QTL of the seven sharp eyespot resistance and no resistance.Fourth,we inoculated the 8 RILs with sharp eyespot strain in the greenhouse and detect thetranscription level of catalase gene and pathogen-related gene 1(PR-1)with qRT-PCR.Finally,we obtained four main results as following.(1)Among the seven resistance QTLs to sharp eyespot disease,QSe.xau-1AS,QSe.cau-2BS,QSe.cau-6BL were detected to be tightly linked with plant morphological traits,including heading date and the relative distance between flag leaf and penultimate leaf.This provides more evidence to the understanding of the resistance mechanism of disease escape,which works by adjusting the microenvironmental factors to lessen disease expansion.Similarly,this will be expected to exhibit more sustainable resistance instead of race specificity of disease.(2)QSe.cau-7BL resistance was found to be related to stem lignin content,suggesting that the resistance works by modulating the accumulation level of cell wall lignin and the mechanical strength of the plant stem.Therefore,no specificity of races is indicated to be involved in the resistance of QSe.cau-7BL.(3)Close associations were observed between QSe.cau-2BS,QSe.cau-3BS,QSe.cau-4AL and gene expression of catalase and PR-1,both of which have been identified as marked metabolic mechanism of plant resistance to fungal pathogens.(4)There is no consistent correlation found between QSe.cau-5DL and the characteristics described above.More research will be required to test the actual resistance mechanism of QSe.cau-5DL.