Patterns of morphological diversity in tetraploid wheat (Triticum turgidum L) landraces from Ethiopia

Thirty-four tetraploid (2n = 4x = 28) wheat (Triticum turgidum L.) landrace populations collected from four regions in Ethiopia, and consisting of 4099 entries were characterized for glume colour, glume pubescence, beak awn, seed colour and spike density. The main objective was to analyse the diversity and distribution of these traits on the basis of administrative regions and altitudinal gradients. The Shannon-Weaver Diversity Index (H') was used to estimate the magnitude of diversity. With the exception of spike density, all characters were polymorphic in all regions and most altitude groups. However, clinal patterns were observed in only a few cases. At the population level, the mean H' varied from completely monomorphic (H' = 0.00) to highly polymorphic (H' = 0.80 +/- 0.07). The highest diversity was found in regions with relatively better climatic conditions and in optimal altitude ranges. On country basis, seed colour (H' = 0.98) and spike density (H' = 0.43) displayed the highest and the lowest diversity indices, respectively. Spike density was the only character that exhibited significant differences (P < 0.01) both "between regions" and "between altitude groups". Across characters, most of the variance was due to the lowest hierarchy, the "within-population'' component. The "between region" and "between altitude group" variances were significant, but spike density alone was responsible for the differences. The overall mean H' for Ethiopia was 0.77 +/- 0.09 and did not seem to have reduced appreciably within the past 25 years or so, when compared to previous estimates.