A spontaneous wheat-Aegilops longissima translocation carrying Pm66 confers resistance to powdery mildew
A spontaneous Robertsonian T4SlS·4BL translocation chromosome carrying Pm66 for powdery mildew resistance was discovered and confirmed by RNA-seq, molecular marker, and in situ hybridization analyses.
Powdery mildew caused by Blumeria graminis f. sp. tritici (Bgt) is a severe disease of bread wheat worldwide. Discovery and utilization of resistance genes to powdery mildew from wild relatives of wheat have played important roles in wheat improvement. Aegilops longissima, one of the S-genome diploid wild relatives of wheat, is a valuable source of disease and pest resistance for wheat. Chromosome 4Sl from Ae. longissima confers moderate resistance to powdery mildew. In this study, we conducted RNA-seq on a putative Chinese Spring (CS)-Ae. longissima 4Sl(4B) disomic substitution line (TA3465) to develop 4Sl-specific markers to assist the transfer of a Bgt resistance gene from 4Sl by induced homoeologous recombination. A pairwise comparison of genes between CS and TA3465 demonstrated that a number of genes on chromosome 4BS in CS were not expressed in TA3465. Analysis of 4B- and 4Sl-specific molecular markers showed that 4BS and 4SlL were both missing in TA3465, whereas 4BL and 4SlS were present. Further characterization by genomic and fluorescent in situ hybridization confirmed that TA3465 carried a spontaneous Robertsonian T4SlS·4BL translocation. Powdery mildew tests showed that TA3465 was resistant to 10 of 16 Bgt isolates collected from different regions of China, whereas CS was susceptible to all those Bgt isolates. The powdery mildew resistance gene(s) in TA3465 was further mapped to the short arm of 4Sl and designated as Pm66.
We thank Dr. Yuli Song from Institute of Plant Protection, Henan Academy of Agricultural Sciences, for providing Bgt isolates collected in Henan Province, Drs. Rama S. Kota and Jan Dvorak for providing seeds of TA3465, and W. John Raupp and Dr. Robert McIntosh for critical reading of the manuscript. This project was financially supported by National Natural Science Foundation of China (Grant No. 31571658), the State Key Laboratory of Crop Genetics and Germplasm Enhancement at Nanjing Agricultural University, China (ZW2011002), Henan Province Special Major Science and Technology Project (161100110400), and the State Key Laboratory of Wheat and Maize Crop Science at Henan Agricultural University, China (39990022).
Author contribution statement
This study was conceived by WL and PM; HL performed in situ hybridization. ZD and SS conducted RNA-seq data analysis and molecular marker design; CM conducted molecular marker analysis; QX and PM evaluated responses to Bgt isolates; XT prepared RNA samples; WL and HL wrote the manuscript; and D-HK and BF verified the chromosomal constitution of TA3465 maintained in KSU and amended the manuscript. All authors have read and approved the final manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflicts of interest.
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