Mapping QTLs associated with Fusarium-damaged kernels in the Nanda 2419 × Wangshuibai population

Fusarium head blight (FHB), or scab, is a devastating wheat disease worldwide, reducing both grain yield and quality. The percentage of Fusarium-damaged kernels (FDK) directly reflects the damage level caused by scab on wheat grains and its variation represents the so-called type IV scab resistance in germplasm. To identify genes governing type IV resistance and investigate its relationship with other scab resistance types, we mapped QTLs associated with percent FDK using data from three different field evaluations of the recombination inbred line (RIL) population derived from the susceptible cultivar Nanda 2419 × the scab-resistant cultivar Wangshuibai. Five QTLs related to percent FDK were identified in at least two different trials, for which Wangshuibai contributed four of the resistance alleles. Most of the FDK-related QTLs, including the three with larger effects, QFdk.nau-2B, QFdk.nau-3B and QFdk.nau-4B , mapped to intervals associated with either type IV resistance or type II resistance. Moreover, most of the major type I and type II resistance QTLs detected previously were associated with type IV resistance, suggesting that resistance to initial infection and disease spread play major roles in conditioning less FDK. Therefore, breeders have options to choose inoculation methods based on their expertise and resources without risking significant loss of information when using percent FDK as the disease index. The most useful scab resistance QTLs for breeding would be those with stable influences on FDK and/or deoxynivalenol (DON) accumulation besides the initial infection and disease spread.