Abstract:

Wheat yellow dwarf virus caused by barley yellow dwarf virus (BYDV) is one of the most serious diseases in wheat, and no resistant resource has been found in all wheat germplasms tested so far. According to our previous study, Wheat-Thinopyrum intermedium amphiploid Zhong 5 and its three derivatives, disomic addition lines Z1, Z2 and Z6, as well as three ditelosomic lines N523, N530 and N545 derived from Z6 showed high level resistance to BYDV and the resistance is associated with the alien chromosome of 2Ai-2. The objectives of this study were: i) to analyze the genetic composition of the telosome; ii) to screen and/or develop molecular markers co-segregated with the telosome; and therefore, iii) to determine the arm to which the telosome genetically belongs and consequently the location on which the BYDV resistance gene(s) and located. By using Pseudoroegneria.strigosa (St) genomic DNA as probe and Triticum astivum (ABD) genomic DNA as blocker, the results of GISH showed that two telosomes in line N530 were similar to the short arm but quite different from the long arm of 2Ai-2 chromosomes in Z6. Based on DNA sequences of five RFLP probes of chromosome homoeologous group2, six PCR primers were designed and used to develop molecular markers. One of the primers, STS₁₂₆, which was based on the sequence of psr126 from the short arm, showed that an about 730bp fragment was amplified specifically in BYDV resistant addition lines, substitution lines and ditelosomic lines but didn’t in wheat parents. It accordingly supported the GISH result that the telosome was the short arm of 2Ai-2 chromosome. In addition, the primer amplified three fragments in wheat parent which were determined by chromosome 2AS, 2BS and 2DS, respectively, according to the PCR patterns of different substitutions. The result of the tolesome being the short arm of 2Ai-2 chromosome was further confirmed by evidences from other two primers of STS₁₃₁ and STS₁₁₂. Primer STS₁₃₁ from short arm of group 2 amplified an alien chromosome-specific fragment which present in all alien addition lines and substitution lines including disomic and ditelosomic lines, while primer STS₁₁₂ from long arm of group 2 amplified an alien chromosome-specific fragment only in alien disomic addition and substitution lines, but neither in alien ditelosomic lines nor in wheat parents. This study not only localized the resistant gene on the short arm of 2Ai-2 chromosomes, but also successfully converted three RFLP probes into STS markers, named as STS₁₂₆, STS₁₃₁ and STS₁₁₂. They could be used to track the different arms of 2Ai-2 chromosome and would facilitate the screening for the translocation lines with BYDV resistance effectively.

Key words: Telosomic lines, Genomic in situ hybridization (GISH), Sequence tagged site (STS), Wheat yellow dwarf virus (BYDV), Thinopyrum intermedium