PRODUCTION OF INTERVARIETAL SUBSTITUTION LINES WITH IMPROVED INTERSPECIFIC CROSSABILITY IN THE WHEAT CV COURTOT

In order to involve the semi-dwarf wheat, cultivar Courtot in the deve lopment of primary triticale, we have attempted to improve its crossab ility with rye. The Courtot chromosomes 5A, 5B, 5D were replaced by th eir counterparts from the highly crossable Japanese cultivars Norin 29 and Fukuhokomugi, using the monosomic back-crossing technique. It was confirmed that the most potent compatibility factor was on the chromo some 5B (kr1); this allele was sufficient to achieve a seed set of abo ut 50%, variable with environmental factors. Conversely, the effect of the 2 other chromosomes, whatever the donor parent, was hardly detect able: if they have the crossability alleles, these have a low level of expression, being inhibited by the Kr1 allele. Recovering the Courtot genetic background during the subsequent back-cross generations did n ot alter the degree of crossability estimated in BC1.