Using the 6RL(Ku) Minichromosome of Rye (Secale cereale L.) to Create Wheat-Rye 6D/6RL(Ku) Small Segment Translocation Lines with Powdery Mildew Resistance

Long arms of rye (Secale cereale L.) chromosome 6 (6RL) carry powdery mildew resistance genes. However, these sources of resistance have not yet been successfully used in commercial wheat cultivars. The development of small segment translocation chromosomes carrying resistance may result in lines carrying the 6R chromosome becoming more commercially acceptable. However, no wheat-rye 6RL small segment translocation line with powdery mildew resistance has been reported. In this study, a wheat-rye 6RL(Ku) minichromosome addition line with powdery mildew resistance was identified, and this minichromosome was derived from the segment between L2.5 and L2.8 of the 6RL(Ku) chromosome arm. Following irradiation, the 6RL(Ku) minichromosome divided into two smaller segments, named 6RL(Kumi200) and 6RL(Kumi119), and these fragments participated in the formation of wheat-rye small segment translocation chromosomes 6DS/6RL(Kumi200) and 6DL/6RL(Kumi119), respectively. The powdery mildew resistance gene was found to be located on the 6RL(Kumi119) segment. Sixteen 6RL(Kumi119)-specific markers were developed, and their products were cloned and sequenced. Nucleotide BLAST searches indicated that 14 of the 16 sequences had 91–100% similarity with nine scaffolds derived from 6R chromosome of S. cereale L. Lo7. The small segment translocation chromosome 6DL/6RL(Kumi119) makes the practical utilization in agriculture of powdery mildew resistance gene on 6RL(Ku) more likely. The nine scaffolds are useful for further studying the structure and function of this small segment.