GENETIC-CONTROL AND CHROMOSOMAL LOCATION OF TRITICUM TIMOPHEEVII-DERIVED RESISTANCE TO SEPTORIA-NODORUM BLOTCH IN DURUM-WHEAT

The genetic control of resistance, expressed as restricted lesion deve lopment in seedling plants, to septoria nodorum blotch of wheat was st udied under controlled environmental conditions, using the parental, F -1, F-2, F-3, BC1F2, and BC1F2 generations of crosses of Triticum timo pheevii-derived resistant durum lines S3-6, S9-10, and S12-1 with the susceptible durum cv. Sceptre. The seedling resistance of these three resistant sources, derived from T. timopheevii (PI 290518), was monoge nically controlled. The chromosomal location of the resistance gene id entified was determined by crossing the complete set of 'Langdon' - 'C hinese Spring' D-genome disomic substitution lines with S12-1. Tests o f the F-1 and F-2 generations of each cross indicated that only chromo some 3A was associated with resistance. Therefore, the resistance gene is considered to be located on chromosome 3A and has been designated temporarily as SnbTM.