HorTILLUS-A Rich and Renewable Source of Induced Mutations for Forward/Reverse Genetics and Pre-breeding Programs in Barley (Hordeum vulgare L.)

TILLING (Targeting Induced Local Lesions IN Genomes) is a strategy used for functional analysis of genes that combines the classical mutagenesis and a rapid, high-throughput identification of mutations within a gene of interest. TILLING has been initially developed as a discovery platform for functional genomics, but soon it has become a valuable tool in development of desired alleles for crop breeding, alternative to transgenic approach. Here we present the HorTILLUS (Hordeum-TILLING-University of Silesia) population created for spring barley cultivar Sebastian after double-treatment of seeds with two chemical mutagens: sodium azide (NaN3) and N-methyl-N-nitrosourea (MNU). The population comprises more than 9,600 M-2 plants from which DNA was isolated, seeds harvested, vacuum-packed, and deposited in seed bank. M progeny of 3,481 M-2 individuals was grown in the field and phenotyped. The screening for mutations was performed for 32 genes related to different aspects of plant growth and development. For each gene fragment, 3,072-6,912 M-2 plants were used for mutation identification using LI-COR sequencer. In total, 382 mutations were found in 182.2Mb screened. The average mutation density in the HorTILLUS, estimated as 1 mutation per 477 kb, is among the highest mutation densities reported for barley. The majority of mutations were G/C to A/T transitions, however about 8% transversions were also detected. Sixty-one percent of mutations found in coding regions were missense, 37.5% silent and 1.1% nonsense. In each gene, the missense mutations with a potential effect on protein function were identified. The HorTILLUS platformis the largest of the TILLING populations reported for barley and best characterized. The population proved to be a useful tool,