No abstract

Barley yellow dwarf virus (BYDV) is a phloem-limited virus that is persistently transmitted by aphids and causes significant yield losses in wheat (Triticum aestivum L.). The present study was conducted to investigate the effects of BYDV in wheat on physiological and morphological traits, yield attributes and pasting properties of flour, and to determine any differences for these traits between susceptible and resistant genotypes under BYDV infection. Significant impact on physiological and morphological traits and yield was observed in plants inoculated at the 2-leaf stage (Zadoks scale, Z12), with a greater impact in the three susceptible genotypes than in the resistant genotype. Yield reduction with inoculation at Z12 was 18–49%, and yield reduction with inoculation mid tillering (Z25) was 6–31%. There was a significant reduction in effective tiller number with both inoculation times, but 1000-kernel weight was affected only with early inoculation. Pasting properties were little affected by BYDV infection, with genotype having a larger effect than infection. Grain yield showed negative correlation with tissue-blot immunoassay and visual symptom score, and positive correlation with all gas-exchange parameters, chlorophyll fluorescence, leaf area and biomass weight. The results suggest that stomatal conductance, transpiration rate and chlorophyll fluorescence measurements are suitable for assessment of BYDV infection and for screening BYDV of susceptible and resistant wheat genotypes.

BackgroundBarley yellow dwarf (BYD) is an important virus disease that causes significant reductions in wheat yield. For effective control of Barley yellow dwarf virus through breeding, the identification of genetic sources of resistance is key to success. In this study, 335 geographically diverse wheat accessions genotyped using an Illumina iSelect 90 K single nucleotide polymorphisms (SNPs) bead chip array were used to identify new sources of resistance to BYD in different environments.ResultsA genome-wide association study (GWAS) performed using all the generalised and mixed linkage models (GLM and MLM, respectively) identified a total of 36 significant marker-trait associations, four of which were consistently detected in the K model. These four novel quantitative trait loci (QTL) were identified on chromosomes 2A, 2B, 6A and 7A and associated with markers IWA3520, IWB24938, WB69770 and IWB57703, respectively. These four QTL showed an additive effect with the average visual symptom score of the lines containing resistance alleles of all four QTL being much lower than those with less favorable alleles. Several Chinese landraces, such as H-205 (Baimazha) and H-014 (Dahongmai) which have all four favorable alleles, showed consistently higher resistance in different field trials. None of them contained the previously described Bdv2, Bdv3 or Bdv4 genes for BYD resistance.ConclusionsThis study identified multiple novel QTL for BYD resistance and some resistant wheat genotypes. These will be useful for breeders to generate combinations with and/or without Bdv2 to achieve higher levels and more stable BYD resistance.