Allelic variation at the dwarfing gene Rht8 locus and its significance in international breeding programmes

A microsatellite marker WMS261 developed at I.P.K., Gatersleben, Germany, co-segregates with the semi-dwarfing gene Rht8. Screens of over 800 wheat varieties from 20 countries show 90% carry WMS-261 alleles with 165, 174 or 192 base pairs (bp). The 192bp allele diagnostic of Rht8 occurs in most screened Southern European varieties. An allele with 165 bp occurs in the majority of CIMMYT Mexican varieties and in most varieties bred in countries that utilize CIMMYT germplasm. Agronomic studies of single chromosome recombinant line mapping populations segregating for WMS 261 alleles with 165, 174 or 192 bp, show compared to the 174bp allele the 192bp allele reduces height by around 8 cm and the 165 bp allele increases height by around 3cm. The results indicate the importance and widespread utilization of Rht8 as a dwarfing gene in southern Europe and suggest an adaptative significance to the height promoting 165 bp allele in CIMMYT material.