LAUSR

Breeding high-yielding bunt resistant wheat cultivars faces many difficulties related to: (1) The poor agronomic performance of most known sources of resistance. Our data show that, even after several cycles of crossing with high-yielding cultivars, the association of bunt resistance with some unfavourable traits remains difficult to break; (2) The incomplete expressivity of susceptibility alleles. Even under artificial inoculation, susceptible genotypes are not 100% diseased, and this creates difficulties in selection for resistance; (3) The need to pyramid genes giving complete resistance for achieving durability. Our work, aiming at the use of molecular markers for alleviating these problems, has been directed towards: (1) Use of already published marker for the gene Bt10 to understand the resistance of breeding lines obtained by crossing with PI178383 (a Bt9 + Bt10 carrier); (2) Work for identifying markers for the gene Bt8. A set of 23 randomly extracted lines from the cross F 676T2-1 (Yala 305/2*Aura//2* Rapid – Bt-8 resistant) × Delabrad was phenotyped for bunt resistance, during 2 years. Resistance and susceptible lines have been analyzed with 56 primers. Preliminary results will be presented; (3) Preliminary identification of DNA polymorphism, possibly associated with bunt resistance genes Bt11, Bt12, Bt5, based on a comparison between resistance lines selected after several cycles of crossing and the respective susceptible parents. Results obtained so far will be used for a detailed analysis in specially built genetic population.