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 wheat landraces of Ethiopian origin. The study consisted of two trials which were planted separately at two locations representing different environmental conditions for two consecutive seasons. The design employed was the randomized complete block with three replications. Two polymorphic loci, glume pubescence and awn condition were utilized as markers. The rate of outcrossing was based on the number of hybrids found in the recessive class of each marker. The overall level of outcrossing was higher in the pure stand trial than in the mixed stand trial. A higher rate of outcrossing occurred in the higher altitude 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 loci was also different, with the long awn displaying more outbreeding tendency. Both locational and seasonal differences in the amount of outcrossing 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 landrace populations. The level of outcrossing detected in this study could have a bearing on the maintenance of the genetic purity of diverse breeding lines being handled together in a breeding nursery and varietal purity in seed multiplication.