* goro@affrc.go.jp

For developing cereal cultivars with improved yield, quality, and other complex traits, it is essential to establish a robust technology that can accumulate many useful genes in a short period of time. Here, we accumulated three to five genes within 1 year by combining consecutive crossing, high-throughput genotyping, and a speed breeding method (accelerating generation advancement).

First, we selected one allele of each of 11 genes in wheat genetic resources as targets for accumulation. Using the spring wheat ‘Yumeshiho’ as a recurrent parent, we conducted five consecutive crosses to produce near isogenic lines (NILs) for each target gene by selecting heterozygous individuals using Kompetitive Allele Specific PCR (KASP) markers.

This step took 18 months with speed breeding. Next, to accumulate the target gene alleles, we crossed the NILs with each other and repeated crossing for three generations. During these steps, the frequency of the target alleles was gradually increased, and individuals homozygous for the target alleles in three genes were obtained within 1 year.

By three consecutive crosses, a population in which the frequency of target alleles was around 19% was developed, and individuals homozygous or heterozygous for the target allele in up to five genes were obtained. In general, a large population size is required to accumulate genes in a short period of time. Here, however, the population size per generation was kept at 384 individuals for the convenience of KASP genotyping, which was performed in 384-well PCR plates.

To investigate whether the technology can be applied to other genetic backgrounds, we examined a method called “seed-green vernalization” using cultivars with different vernalization requirements. Cultivars with winter alleles in three Vrn-1 genes usually require about two months for vernalization.

However, using this method, about 30 days of vernalization was sufficient to fully vernalized and the time from sowing to heading was 60 days. The result suggests that this technology can be applied to cultivars with different backgrounds.