Genetic diversity and structure of tetraploid wheat landraces of the central highlands of Ethiopia

Genetic diversity in crop species is essential for tackling vulnerability to pests and abiotic stresses. It is also of paramount importance in breeding populations to maintain continued genetic improvement. Landraces are important sources of genes for desirable traits in plant breeding and their conservation and utilisation has attracted attention. The conservation and effective utilisation of plant genetic resources requires an understanding of their genetic variation and structure. This study was initiated to obtain a quantitative assessment of the amount and nature of diversity and rate of natural outcrossing in tetraploid wheat landraces collected from the central hihglands of Ethiopia. The landraces had a considerable amount of diversity and were found to consist of different genotypes. They also displayed variable levels of diversity. The within population component of variation was much higher than the between one. Their distinctness with respect to seed colour did not coincide with genetic distances between the seed colour groups. Linkage which is an indicator of the presence of coadapted associations of loci was detected. There was also evidence for selection of alleles and genotypes. The relationships among the landraces did not appear to reflect a geographic pattern. Besides, there was no correspondence between isozyme diversity and variation for agronomic traits suggesting the poor predictability of variation of one based on the other. An appreciable rate of outcrossing was detected suggesting that it is a factor playing an important role in the evolution of these landraces and maintaining diversity in them. Outcrossing was also influenced by environmental and genetic factors. The consideration of certain localities or populations with higher diversity for in situ conservation has been suggested. Moreover, on account of the higher within population diversity sampling more within a population or locality covering as diverse populations or localities as possible has been forwarded as a better approach for ex situ conservation.