ESTIMATION OF OUTCROSSING RATE IN LANDRACES OF TETRAPLOID WHEAT (TRITICUM-TURGIDUM L)

A study was undertaken to assess the amount of natural outbreeding in tetraploid wheal landraces of Ethiopian origin. The study consisted of two trials which were planted separately at two locations representin g different environmental conditions for two consecutive seasons. The design employed was the randomized complete block with three replicati ons. Two polymorphic loci, glume pubescence and awn condition were uti lized as markers. The rate of outcrossing was based on the number of h ybrids found in the recessive class of each marker. The overall level of outcrossing was higher in the pure stand trial than in the mixed st and trial. A higher rate of outcrossing occurred in the higher altitud e area in the pure stand trial while the opposite was the case in the mixed stand trial. The average rate of outcrossing due to the marker l oci was also different, with the long awn displaying more outbreeding tendency. Both locational and seasonal differences in the amount of ou tcrossing were observed. Generally, the study has revealed that there is a considerable amount of outbreeding in the landraces and that this genetic factor could play a role in preserving Variation in the landr ace populations. The level of outcrossing detected in this study could have a bearing on the maintenance of the genetic purity of diverse br eeding lines being handled together in a breeding nursery and varietal purity in seed multiplication.