Field grown transgenic Pm3e wheat lines show powdery mildew resistance and no fitness costs associated with high transgene expression
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Pm3 from wheat encodes a nucleotide-binding leucine-rich repeat type of receptor and confers resistance to powdery mildew caused by the fungal pathogen Blumeria graminis f.sp. tritici (Bgt). Each of the 17 functional Pm3 alleles identified so far confers resistance to a distinct spectrum of Bgt isolates. Variant Pm3e has been found in wheat donor line W150 and differs only by two amino acids from the non-functional variant Pm3CS. In order to evaluate the capability of Pm3e to provide powdery mildew field resistance, we generated transgenic Pm3e lines by biolistic transformation of the powdery mildew susceptible spring wheat cultivar Bobwhite. Field trials conducted during four field seasons in Switzerland showed significant and strong powdery mildew resistance of the Pm3e transgenic lines, whereas the corresponding biological sister lines, not containing the transgene, were severely powdery mildew infected. Thus Pm3e alone is responsible for the strong resistance phenotype. The field grown transgenic lines showed high transgene expression and Pm3e protein accumulation with no fitness costs on plant development and yield associated with Pm3e abundance. Line E#1 as well as sister line E#1 showed delayed flowering due to somaclonal variation. The study shows the capability of Pm3e in providing strong powdery mildew field resistance, making its use in wheat breeding programs very promising.
KeywordsWheat Powdery mildew Genetic engineering (GE) Field trial Disease resistance
We would like to thank the staff from Agroscope in Zurich-Reckenholz and Helen Zbinden, Esther Jung and Linda Lüthi from UZH for help with the field trial and Dr. Simone Oberhänsli for helpful advice on statistical analyses. Funding was provided by a grant from the Swiss National Science Foundation 310030_163260 and by Forschungskredit Grant No. FK-15-098 from the University of Zurich to TK.
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