Rapid marker-assisted development of advanced recombinant lines from barley starch mutants

The comparative phenotypic analysis of mutants is often hampered by their diverse and poorly characterised genetic backgrounds. To overcome this problem, a suite of recombinant spring barley lines was developed for four starch biosynthesis genes in a common elite background. Rapid breeding progress was made by combining foreground and background selection with the screening of bulked families. A toolkit of perfect co-dominant PCR assays was developed for the four target genes, based on the causative single nucleotide polymorphisms underlying their starch phenotypes. These were used for foreground selection during backcrossing and selfing, and may be applied to bulks of up to ten plants. Screening bulks meant that large numbers of individuals with known family structure were rapidly assessed and that breeding effort was accurately targeted. These markers were also used for quality control during field multiplication and should be readily transferable to any crosses involving these four mutations. Background selection amongst BC1 progeny known to be heterozygous for the target starch alleles identified individuals which were relatively enriched for the recurrent parent across the rest of the genome. These were further advanced and true-breeding recombinants were selected which carry the target starch mutations in a largely recurrent parent background. The resulting set of BC2F5 pre-breeding lines should enable meaningful analysis of the starch phenotypes and facilitate their transfer into commercial breeding programmes.