Inheritance And Effects Of Quantitative Trait Loci Controlling Scab Resistance In Wangshuibai

Wheat is one of the most important food crops in the world, and is frequently attacked by Fusarium head blight (FHB) leading to yield reduction and poor grain quality in wheat production. This disease is caused mainly by Fusarium graminearum (telemorph Gibberella zeae). The scab resistance performs quantitative characters that are controlled by polygene. Five different types of FHB resistance have been described as follows:resistance to initial penetration by the pathogen (type I), resistance to spread of FHB syptoms within an infected spike (type Ⅱ), resistance to the accumulation of toxin (type III), reducing fusarium-damaged kernal (type IV), and tolerance to disease (type V). QFhs.nau-6B has been located in Wangshuibai6BS chromosome as well as a major effect type Ⅱ resistance QTL to FHB. For further analysis and exploit this QTL, NILs of QFhs.nau-6B was developed in PH691and Yangmai12background. The results revealed that all of NILs performed much better resistance than recurrent parent, affected by background differences simultaneously. In order to determine genetic mode of QFhs.nau-6B, we analyzed a distribution of resistance and susceptible in progenies of heterozygous plant. The results manifested that the resistance segregation was1:3, so QFhs.nau-6B was a single recessive Mendelian inheritance factor. Using13recombinants in PH691background, QFhs.nau-6B was precisely mapped in the interval of Xwmc398-Xgwm644through genotyping and phenotyping.In order to further study on four major QTLs from Wangshuibai chromosome3BS,6BS,5AS, and4BL for resistance to FHB, this research using susceptible materials PH691, Mianyang2000-1, and Yangmai12as recurrent parents, Wangshuibai as donor parent, near-isogenic lines (NILs) of different genetic backgrounds and different QTL combinations had been developed, with the help of molecular markers assisted selection. Field evaluation of type I and type Ⅱ resistance were implemented in all of above NILs. The survey results showed that QFhs.nau-3B and QFhs.nau-6B had type Ⅱ resistance but no type I resistance; however, QFhi.nau-4B and QFhi.na.u-5A had type I resistance but no type II resistance. There was a certain degree additive effect between the same types of QTLs. Furthermore, field resistance could be improved after pyramiding different types of resistance QTLs.The effect of resistance to initial penetration on chromsome5AS was highly correlated with flag leaf width (FLW), so the lines with narrow leaf performed much better rsistance than recurrent parent. In order to elucidate the genetic relationship between the pair of traits, recombinants were selected from Nanda2419xWangshuibai RILs, PH691background NILs, and Mianyang99-323background NILs, and analyzed their genotypes and phenotypes. Finally, QFhi.nau-5A was located in the interval of Xgwm304-Xgwm415; meanwhile, QFlw.nau-5A was placed in the interval of Xgwm415-Xbarc752. Therefore, the two traits usually both found in the same lines because of two tightly linked loci.