Browsing by Author "Belay Getachew (PhD)"

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    Phenotypic and Isozyme Diversity in Tetraploid Wheats (Triticum Turgidum L.) From Bale and Wello Regions of Ethiopia
    (Addis Ababa University, 2001-06) Eticha Firdissa; Bekele Endashaw (PhD); Belay Getachew (PhD)
    Phenotypic and isozyme diversity of 32 landrace populations of tetraploid wheats originating from two regions (Bale and Wello) of Ethiopia was analysed in this study. A total of 2559 individual plants (45-110 plants pel' population) representing each landrace were considered for the phenotypic diversity investigation. Investigations were also made on the species richness (biological diversity) of the popUlations whereby individuals in each landrace were classified into their own taxonomic classes and analysis of the species diversity was made for each population, altitudinal class and region of collection. Seven heritable qualitative traits (seed colDl; glume color, awn color, glume hairiness, beak awn, spike density, and awn length) were studied. The frequencies of each phenotypic class were used to compute the ShannoncWeaver index (H') to estimate and analyse the diversity at different levels. For isozyme analysis, three enzyme systems, Esterase (EST), Aspartate amino trans ph erase (AAT), alld Leucine amino peptidase (LAP) were used to study the genetic variatioll in 14 - . landrace populations selected based on the clustering of the populations from the phenotypic frequencies. Each population was represented by twenty individuals. The analysis of species diversity indicated that seven species of wheats from two ploidy levels, tetraploid and hexaploicl, are planted in mixtures at vG/ying proportions, Triticum turgidum ssp. durum was the most dominant species accountillg for about 67.32 % of the total population. A maximum of four species was recorded per each population. Analysis of phenotypic frequencies and diversity indices were done for tetraploids lumped together and for durum alolle. Considering tetraploid species, seed color alld beak awn contributed the highest diversity index (H' = 0.92 for both). Awn color contributed the lowest diversity index (H' = 0.59). When durum treated alone, glume color followed by beak awn and seed color contributed the highest diversity index (H' = 0.90, 0.84, alld 0.84, respectively), whereas glume hairiness had the 10IVest diversity index (H' = 0.48). Traits sllch as awn color, awn length, glume color and seed color showed statistically significant differences (p < 0.05) between regions while significant differences (p < 0.05) were observed for awn length, beak awn, glume hairiness and seed color across gradients of altitudillal classes in tetraploid wheats. Sigllificallt differences were also observed betweell altitudes and regions for traits in dU1'II1ll treated alone. Variations were, however, largely due to the differences in the level of the different characters within populations. On regional basis, higher lIIean diversity index was observed for Wello than Bale. Awn color was monolllOlphic and jixed for color types in collections originating fi'om Bale whereas a variety of fi'equencies were observed in Wello. Considering tetraploids, the overall diversity index was cOlllputed to be H' = 0.81 ± 0.08. The overall region value of H' for durum wheat is 0.63 ± 0.08 indicating a decline in the alllount of diversity in durulII wheat as compared with the index for tetraploid wheats. The isozyme assay resulted into a total of 5 isozyme loci; 2 of the distinct polymO/phic regions of enzyme activity (banding paUe/'ll) detected for EST, 2 for AAT, and one fO/; LAP. The isozyme data also indicated presence of allelic polymO/p/zism was detected at all loci. The mean number of alleles per locus ranged fi'om 1.4 to 2.2. Considerillg the genetic variability at the 5 loci, the percentage polymO/phic loci varied fi'om 40% to 80%. A pairwise comparisoll of populations over jive isozyme loci indicates that the ullbiased genetic identity rangedfi'om 0.904 to 1.00. Whereas the gelletic distallce rallgedfi'om 0.00 to 0.053, indicatillg that there is small amount of variatioll amollg populatiOlls. Populations were grouped/clustered illto six clusters. The landraces ji'om Bale and Wello grouped differently similar to that of clustering that was based on phenotypic frequencies.
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    Rapd Analysis for Genetic Diversity and Relationships in Tetraploid Wheats (Aabb Genome) of Ethiopia
    (Addis Ababa University, 2005-02) Yaekob Ameha; Bekele Endashaw (Professor); Belay Getachew (PhD)
    Twenty-five tetraploid wheat landraces and 15 improved durum cultivars were used to study the diversity and relationships within and among tetraploid species and regions of origin, and improved cultivars. Thirty-one polymorphic bands produced by two RAPD marker primers were used for the analysis. The mean Shannon diversity index (H) for landrace collections and improved cultivars were 0.34 and 0.23, respectively. Among the four species studied, T. durum was with the highest (0.32) diversity value whereas T. polonicum with the lowest (0.26). Similarly, Wello region collections revealed highest (0.27) tetraploid wheat diversity while Shewa collections, the lowest (0.22). The within species and regions variations were 81.4% and 72.2%, respectively. It suggests the need to collect more wheat germplasm samples within regions. Cluster analysis for all genotypes grouped mainly into landrace collections and improved cultivars. Clustering of landrace genotypes resulted in four groups mainly according to their regions of origin. However, it failed to group on the basis of their species. It suggests the presence of more genetic differentiation among regions than species. The lowest (0.00) and highest (0.73) genetic distances were observed between Wet1224 and Wet1570, and Wet1650 and Bae1117, respectively. The between species genetic distance was lowest (0.016) between T. polonicum and T. turgidum, but highest (0.051) between T. aethiopicum and T. durum. Clustering of improved durum cultivars formed four groups at 80% similarity coefficient. The lowest genetic distance (0.032) was observed between cultivars Ld357 and Boohai, Foka and Kilinto, and Tob66 and DZ 1640. The highest distance (0.34) was between Asassa and Bichena, Asassa and Boohai, and Bichena and Ude cultivars. The average distance within improved durum cultivars was 0.157. It indicates that all the 15 improved cultivars are relatively similar. Little correlation was observed between groups formed by cultivars and common parentage. positive for M. bovis. The results indicated that M. tuberculosis is the causative species for tuberculous lymphadenitis in Dera.
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    Variability and Trait Association in Recombinant Inbred Lines of Eragrostis tef x E. pilosa
    (Addis Ababa University, 2008-06) Mewa Demeke; Belay Getachew (PhD); Bekele Endashaw (Professor)
    A study was conducted to assess variability and trait association in recombinant inbred lines (RILs) of Eragrostis tef x E. pilosa crosses. A total of 81 lines were planted using RCB design with three replications at Debre Zeit and Akaki in 2007 main rainy season. The result indicated that there exists difference among the lines for most of the traits included in this study. High difference was also obtained for almost all the traits between the two environments such that more attention was given to single site analysis. Grain yield showed the maximum PCV (> 40%) and GCV (> 30%) followed by spikelet per panicle (PCV > 25%, GCV > 20%). High PCV (> 20%) and moderate GCV (> 15%) was recorded for lodging index. Moderate GCV (> 10%) was also recorded for plant height, panicle length, culm diameter and strength, and shoot biomass, but GCV was low for shoot biomass and 100-seed weight at Akaki. Most of the traits showed high heritability (not < 40%) except first culm strength and tiller. Genetic advance as % of mean was maximum for grain yield (> 50%) followed by spikelet per panicle (> 30%). For this parameter, panicle length, lodging index and plant height also revealed high values (> 20%), but large difference was recorded between the sites for shoot biomass and 100-seed weight; > 25% at Debre Zeit but < 10% at Akaki. Moderate genetic gain (> 10%) was recorded for length of growing period and culm characters. Genetic variability and potential of genetic gain for number of tillers was consistently very low. Most of the traits were found associated. Correlation study showed strong positive association of lodging index with most other traits except with culm diameter and spikelet per panicle at Debre Zeit. However, path analysis revealed that effect of some of the traits on lodging was weak mainly at Akaki and only culm strength at the second internode showed consistently strong positive effect. Plant height, days to maturity and spikelet per panicle showed strong negative effect and panicle length strong positive at Debre Zeit. Effect of most traits on grain yield was high-positive; only days to maturity showed consistently low effect. Principal component analysis showed that about 45% of the gross variance among lines laid in PC1 and explained largely by traits like plant height, panicle length, days to maturity and days to heading. Generally, the study indicated that there exists considerably high genotypic variability, up to transgression beyond the better parent, for economically valuable traits including lodging index, which verified the importance of E. pilosa in diversifying the tef germplasm base. The complex associations implied the need to consider many traits in improving those traits as grain yield and its limiting factor, lodging. The high variability between the sites indicated the need to work with much more environments to represent most tef growing conditions. Key Phrases: RIL, Variability, Association, E. tef, E. pilosa