CHROMOSOME LOCATION OF MYCORRHIZAL RESPONSIVE GENES IN WHEAT

Symbiotic relationships between wheat plants and mycorrhizal fungi may play an important role in the growth and productivity of wheat as a c rop. Wheat cultivars differ in their ability to form such relationship s, but little is known concerning the genetic basis of such difference s. A set of intervarietal substitution lines having individual chromos omes from 'Cheyenne' (nonresponsive to mycorrhizae) substituted into ' Chinese Spring' (nonresponsive to mycorrhizae) were tested for mycorrh izal response in greenhouse experiments. Chromosomes 1A, 5B, 6B, 7B, 5 D, and 7D of 'Cheyenne' had positive effects on the trait, with homolo gous groups 5 and 7 in the B and D genomes having the largest effects. Chromosome 5B of 'Hope', a nonresponsive cultivar, also had a positiv e effect in a 'Chinese Spring' background. In addition, the mycorrhiza l responsiveness of a range of other cultivars and ancestors was teste d to expand information on the trait in wheat and its relatives. Data on chromosome location of mycorrhizal-response genes and genotypic res ponsiveness will permit more effective genetic manipulation of this tr ait.