Genotype analysis of the wheat semidwarf Rht-B1b and Rht-D1b ancestral lineage

In wheat, semidwarfism resulting from reduced height (Rht)-B1b and Rht-D1b was integral to the green revolution'. The principal donors of these alleles are Norin 10', Seu Seun 27' and Suwon 92' that, according to historical records, inherited semidwarfism from the Japanese landrace Daruma'. The objective of this study was to examine the origins of Rht-B1b and Rht-D1b by growing multiple seed bank sources of cultivars comprising the historical pedigrees of the principal donor lines and scoring Rht-1 genotype and plant height. This revealed that Norin 10' and Suwon 92' sources contained Rht-B1b and Rht-D1b, but the Seu Seun 27' source did not contain a semidwarf allele. Neither Rht-B1b nor Rht-D1b could be definitively traced back to Daruma', and both Daruma' sources contained only Rht-B1b. However, Daruma' remains the most likely donor of Rht-B1b and Rht-D1b. We suggest that the disparity between historical pedigrees and Rht-1 genotypes occurs because the genetic make-up of seed bank sources differs from that of the cultivars actually used in the pedigrees. Some evidence also suggests that an alternative Rht-D1b donor may exist.