Borlaug, Strampelli and the Worldwide Distribution of RHT8

Abstract

The height-reducing gene Rht8 was introduced by breeder Nazareno Strampelli from the Japanese landrace ‘Akakomugi’ and has been widely used in wheats adapted to southern and eastern Europe ∈dent Definitive identification of Rht8 is difficult because it does not make seedlings insensitive to gibberellin application and its height effect may be confounded with other genes affecting plant height or flowering time. Following identification of a close linkage between microsatellite WMS261 and Rht8, the marker has been used extensively to screen large numbers of diverse international germplasm. A 192bp allele at the WMS261 locus was assumed to be ‘diagnostic’ for Rht8 and its international distribution was inferred from the marker data ∈dent We report several instances of cultivars and mapping populations which vary for the presence of the Xgwm261-192bp allele, but with no associated reduction in height, suggesting a lack of linkage with Rht8 ∈dent Our studies have identified that Norin10, used by Norman Borlaug to introduce Rht-B1b and Rht-D1b into Mexican wheats, also carries WMS261-192bp, and this allele was retained in some of his varieties. The widespread use of Norin10-derived germplasm during and after the green revolution represents a second source of WMS261-192bp microsatellite allele in international germplasm, with no linkage to Rht8. Therefore, the presence of this allele can only be indicative of Rht8 in wheat varieties with a clear pedigree relationship to Akakomugi or Strampelli