Phenotypic diversity of tetraploid wheat landraces from northern and north-central regions of Ethiopia

Twenty–seven tetraploid (2n = 4x = 28) wheat (Triticum turgidum L.) landrace populations consisting of 2876 entries collected from the north and north-central administrative regions of Ethiopia were studied for variation of eleven phenotypic characters that have two or more classes. Using the frequencies of each phenotypic class within a character, the Shannon-Weaver index (H') was employed to estimate and analyse the diversity on the basis of four regions and five altitudinal gradients. Most traits were polymorphic. However, monomorphism was common in many of the populations for dense spike, long beak, and glabrous glume. On character basis, seed colour, seed shape, and glume pubescence contributed the highest mean diversity indices (H' = 0.99, 0.96, and 0.88, respectively). Spike density contributed the lowest index (H' =0.24). However, it was the only trait that displayed significant differences (p < 0.01) among regions, lax-spike types being frequent only in Gojam region. Significant differences (p <0.05) among altitude groups were detected only for glume colour and beak length. Much of the variance was among populations within region and within altitude group. For the overall characters, significant differences (p<0.01) were revealed only among populations within region and altitude group, but not among regions or altitude groups. However, the highest mean diversity indices were obtained in Tigray region (H' = 0.70). and in the altitude range between 2401 and 2600 m.a.s.1. (H' = 0.68). No clear association was detected between overall phenotypic diversity and altitude. The overall index (H' = 0.70) for the north and north-central regions of this country is of the same magnitude as that of previously reported regions. Therefore, before any collection mission is undertaken, we suggest further studies to gain information on the interrelationships among morphological diversity, variation for biochemical markers, and ecogeographical variables.