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An international research team led by the Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) has discovered a gene mutation (PPD-H1) that causes barley to flower later in regions with long spring days. This ultimately enables higher yields.

The scientists analyzed extensive collections of wild and domesticated barley for their study and were also able to show that the mutation only emerged in domesticated barley after it was first cultivated in the southern Levant. This refutes earlier assumptions about its place of origin. The results have been in the journal Theoretical and Applied Genetics.

For their study, the research team examined a collection of more than 2,000 barley plants, comprising 940 wild varieties and 1,110 domesticated varieties of Hordeum vulgare. The scientists focused their genetic analysis on the area around the PPD-H1 gene. They sequenced this region because they suspected the presence of small but significant changes to the plant's genetic material, known as single nucleotide polymorphisms (SNPs), responsible for delayed flowering.

At the same time, they measured the flowering times of these plants (i.e. the number of days until heading) in field trials at various locations, while conducting genome-wide association studies to identify the genes that influence flowering time.

Additionally, the research team conducted an in-depth survey of 41 selected genotypes under long-day and short-day conditions in a controlled environment. This allowed them to determine the phenotypic response to day length. They also examined a 6,000-year-old barley sample from Yoram Cave in Israel to identify the earliest forms of the PPD-H1 allele. By comparing all the data with the climatic characteristics of the collection sites, they could trace the origin and spread of the gene.

The genetic change that enables late flowering is the SNP22 mutation. "Our data clearly show that this small but crucial genetic change in the PPD-H1 gene triggers delayed flowering under long-day conditions. Earlier studies led to different assumptions, but we have now been able to correct them," explains Dr. Rajiv Sharma, the study's first author.

The PPD-H1 allele, responsible for late flowering, originated in wild barley that grew, and still grows, in the desert regions of the southern Levant—specifically, along the eastern coast of the Mediterranean Sea and the surrounding area.

"This important trait only emerged after the initial domestication of barley, which is surprising," says Dr. Kerstin Neumann, head of the Automated Plant Phenotyping research group at the IPK. "It was not a characteristic cultivated barley had from the beginning, but rather a later adaptation that enabled it to spread to Europe."

All modern late-flowering barley varieties can be traced back to a common ancestor: haplotype H10. This original haplotype was found in 16 wild barley varieties, primarily in Israel. Under pressure from selection, these varieties multiplied and spread rapidly as they moved toward Northern Europe. This enabled barley to grow well even in more northerly regions with long summer days.