Genetic diversity in tef (Eragrostis tef (Zucc) Trotter) for osmotic adjustment, root traits, and amplified fragment length polymorphism
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Tef is one of the most important cereal crops in Ethiopia. However, it suffers from several production constraints. Drought is one of the major problems in tef cultivation. Yield loss due to drought in tef may reach 40%. Physiological and morphological screening criteria coupled with recombinant DNA technology (e.g., DNA marker-assisted selection) would improve the efficiency of tef breeding for drought resistance. This greenhouse and laboratory study was, therefore, conducted (1) to screen tef germplasm materials for key drought resistance traits (osmotic adjustment and root depth) with an objective of identifying contrasting lines for these characters, (2) to assess the impact of osmotic adjustment and root depth on productivity of tef using contrasting lines that were obtained in the context of the first objective and (3) to assess the diversity of germplasm lines in tef and its wild relatives using amplified fragment length polymorphism marker. Prior to screening genotypes for osmotic adjustment (OA), six methods of measuring OA were compared using six cultivars of tef in two experiments. In the first method (method 1), OA was derived from a linear regression of leaf relative water content (RWC) on leaf osmotic potential (OP), both of which were collected during the stress period. In the second method (method 2), OA was calculated as the difference in OP at full turgor of stress and unstressed control plants. Osmotic potential at full turgor was calculated from a point measurement of OP and relative water content at a given level of plant water deficit, with or without correction for tissue apoplastic water. The third method estimated OA as a difference in OP value between stressed plants rehydrated to full turgor and unstressed control plants. In the fourth method (method 4), estimates of OP at a given RWC using a simple linear regression line developed in method 1 was taken as an indicator of OA. Estimates of RWC at a given OP using the regression line was the fifth method (method 5) of OA measurement. In the six method (method 6), the slope of the regression line was a measure of OA. Method 2 and 3 were found to be easier and faster, and hence more suitable for a large-scale genotype screening experiment. We used method 3 in our subsequent genotype screening experiment for OA. Screening of genotypes of Because of such G X E interaction, it was not possible to get sufficient number of contrasting genotypes with stable performance for evaluation of the impact of root depth and OA on productivity. The association among OA, root depth and altitude was also investigated and discussed.