In their study, researchers examined more than 2,000 barley plants — 940 wild and 1,110 domesticated varieties of Hordeum vulgare. Their focus was the genetic region surrounding the PPD-H1 gene, which influences when barley flowers. By sequencing this area, they looked for small but important genetic changes, known as single nucleotide polymorphisms (SNPs), that could explain delayed flowering.
Alongside the genetic work, the team measured flowering times—recording the number of days until heading — in field trials across multiple locations. They also conducted genome-wide association studies to identify genes linked to flowering time and tested 41 selected genotypes under both long- and short-day conditions to assess how day length affects plant development.
To trace the gene’s history, the researchers analyzed a 6,000-year-old barley sample from Yoram Cave in Israel, identifying one of the earliest forms of the PPD-H1 allele. Comparing these results with climate data from the plants’ collection sites revealed how the gene evolved and spread.
Their findings pinpointed the key change behind late flowering: a single mutation known as SNP22, according to a press release.
“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 trace back to a single ancestral lineage known as haplotype H10. This original genetic variant was identified in 16 wild barley accessions, most of them from Israel. Through natural selection, these plants multiplied and spread northward, allowing barley to adapt and thrive in regions with long summer days — such as those found across Northern Europe.
