Browsing by Author "Admas, Sintayehu"

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    Characterization of Ethiopian Chickpea (Cicer Arietinum L) Genotypic Diversity Population Structure Cold Tolerance and Assessment of Change of Variability Over time
    (Addis Ababa University, 2021-12-29) Admas, Sintayehu; Shiferaw, Eleni (PhD); Tesfaye, Kassahun (Professor); Hailesilassie, Teklehaimanot (Professor)
    Plant genetic resources are valuable source of desirable agronomic traits that can be used in crop improvement. These resources are constantly threatened by both natural and human-caused risks. Chickpea (Cicer arietinum L.) germplasm is one of the crops affected by these factors. Regular chickpea diversity monitoring in farmers' fields, as well as characterization and evaluation of Ethiopian chickpea germplasm in ex-situ, are essential in order to build viable conservation strategies and undertake breeding initiatives. However, in Ethiopia chickpea, the abovementioned information is limited. As a result, this research began with the general objective of determining the diversity of Ethiopian chickpea germplasm and its potential for frost resistance, as well as determining the degree to which chickpea on-farm diversity has changed over time. In the study, molecular analysis was conducted to determine the genetic diversity, population structure, and relationships of 152 chickpea genotypes using simple sequence repeats (SSR) markers. There were 133 alleles observed using 23 polymorphic SSR markers, with a mean of 5.8 alleles per locus. Pairwise population Nei's genetic distance, heterozygosity (0.4), Shannon's information index (1.2), Gene Diversity (0.67), polymorphic information content (0.63), and percent polymorphism (99.5%) were among the genetic-based statistics used in the study. These studies demonstrated that there was high genetic variation within and among chickpea genotypes. The 152 genotypes were divided into two groups on UPGMA tree developed based on Nei's genetic distances. The exotic genotypes were all grouped together in one cluster, showing that they are distinct from Ethiopian genotypes. However, seed exchange caused inconsistencies in the patterns of grouping Ethiopian chickpea genotypes by geographic location. Two separate populations were discovered using model-based population structure clustering. These findings can be used to create efficient conservation approaches and breeding initiatives to enhance the genetic diversity of chickpeas. To assess the potential of Ethiopian chickpea for frost resistance, a frost screening study was carried out in a natural field and in controlled conditions. Six hundred seventy-three genotypes were characterized for two years (2018/2019 to 2019/2020) using an augmented design at Bakelo, Debre Birhan, Ethiopia, a place as national frost screening site. A significant (p<0.01) variability amongst genotypes was recorded for all agronomic traits considered. In terms of agronomic performance, 94 (12.6%) of the genotypes examined outperformed the frost susceptible genotypes. Stem/leaf pigmented genotypes had a better response to frost stress than non-pigmented genotypes. The majority of black seeded chickpeas were adapted well to frost stress, when compared to brown and white seeded genotypes. According to the freezing tolerance rate (FTR) and plant survival rate (SR), 83 (12.3%) and 85 (12.6%) genotypes were identified as frost tolerant. Grain yield had a significant (p<0.01) correlation with FTR, SR, seed shriveling score, stem/leaf pigmentation, and seed color. Based on the field experiment genotypes performances, 72 genotypes were selected and evaluated further for cold tolerance variability at seedling stage under controlled environment using a complete randomized design with two replications. The analysis of variance revealed a significant (P<0.01) difference among genotypes for plant height, number of foliage, number of primary branches and fresh weight. Cold tolerant genotypes had a higher growth rate than susceptible genotypes, which had a slower growth rate or completely failed. According to SR, 31 (43.1%) genotypes scored above 0.8 values. Based on FTR, 37 (51.4%) and 31 (43.1%) genotypes were rated at a score of 1 to 3 in freezing test 1 (T1) and freezing test 2 (T2), respectively indicating better frost tolerance than others. Fresh biomass yields had a high negative correlation (p<0.01) with SR, but a substantial positive correlation (p<0.01) with FTR value. At seedling stage, based on the combined results of FTR and SR scores, 26 genotypes were shown to be cold tolerant genotypes at temperatures as low as -5oC. Therefore, the field and controlled environment experiments results revealed that Ethiopian chickpea landraces have a good genetic potential for cold tolerance traits for use in breeding programs. In addition, a diversity monitoring research was conducted to look into the differences in phenotypic diversity between the present (2017) and prior chickpea collections (1979-1983). The experiment was conducted using simple lattice design with two replications at Debre Zeit Agricultural Research Center for two consecutive years (2018/2019 to 2019/2020). The result showed that chickpea has been under genetic erosion ranging from 30.4% to 100% during the last 35 years. During this time, estimations of Shannon-Weaver diversity index for black seeded and ivory white seeded chickpea kinds have declined from 1.99 to 0.69 and 1.33 to 0.0, respectively. In previous collections, 25.8% of black coated genotypes and 6.5% of white coated genotypes were found, but these chickpea varieties are now rare (black 6.5%) or unobtainable (white 0.0%). Cluster analysis revealed that genotypes clustered according to the time of collections regardless of their geographic origins. The genotypes of chickpeas in the current and prior collections were different. Landraces of black and white seeded chickpeas were vulnerable to genetic erosion and chickpea genotypes at farmer’s field are found to be losing their variability. Black and white seeded chickpea are missing at farmers’ fields and are under greater threat of extinction. So, implementation of immediate restoration of chickpea landraces is required to recover and maintain the lost chickpea landraces in the studied region and we strongly recommended revision of the current conservation strategies.
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    Study on Variation in Recombinant Inbred Lines of Eragrostis tef x E. pilosa for Drought-Resistance Related Traits and Meiotic Behavior in their F1-Hybrid
    (Addis Ababa University, 2008-06) Admas, Sintayehu; Dagne, Kifle (PhD); Eshete, Million (PhD)
    Tef (Eragrostis tef (Zucc.) Trotter) is major cereal crop cultivated in Ethiopia. It occupies two million hectares of land each year. However, its productivity is constrained by drought. To curb the situation, assessment of drought-resistance related traits variability among recombinant inbred lines (RILs) is essential. Morpho-physiological drought related (pot) and meiotic behavior (laboratory) studies were conducted at Debre Zeit and Addis Ababa in 2007/08. For pot experiment, twenty-five RILs of a cross between Eragrostis tef and E. pilosa, their parental lines and standard check cultivar were laid dawn in RCB design with three replications under moisture stressed and non-stressed conditions to examine differences in some drought related traits. There was significant (p<0.05%) difference among lines for all characters considered except thousand seed weight and peduncle length under non-stressed and panicle seed weight under stressed conditions. Under non-stressed condition, GCV and PCV ranged from 1.4% to 58.96% and 1.8% to 52.6%, respectively while GCV range of 3.5% to 71.9% and PCV range of 3.8% to 72.3% was observed under stressed condition. More than 45% heritability was observed for all traits except number of tillers (21.8%) at stressed condition. Generally considerably high genetic advance as % of mean was obtained for most of the traits considered in the study except for days to maturity. Under non-stressed condition, strong positive correlation was revealed for grain yield with number of tillers, excised leaf water loss and water use efficiency, and strong negative correlation with total root length, root biomass and relative growth rate. Under stressed conditions, total root length, root biomass, water use efficiency and relative growth rate were positively correlated with grain yield, while drought susceptible index and excised leaf water loss showed strong negative correlation. Moisture stress prolonged the time to anthesis in few RILs and Key Murri, but accelerated for most other RILs, E. pilosa and standard check cultivar. Drought hastened root growth in most RILs, E. pilosa and the check but not for Key Murri and some RILs. RILs with lowest drought susceptibility index showed better yield under stress except RIL-183. Seventeen RILs were identified to be resistant and eight were drought susceptible. The laboratory study was conducted to examine meiotic behavior of F1-hybrid (E. tef x E. pilosa) and pollen fertility of the F1-hybrid, parental lines and RILs. The F1-hybrid showed regular meiotic cell division and high level of pollen fertility (94.3%). Pollen fertility test of the parental lines and selected RILs was also high (90 to 95%). The result demonstrated the presence of wide variability among RILs for drought related trait and the potential of E. pilosa to diversify tef germplasm for drought related traits. Therefore, drought resistant RILs were identified which can serve as breeding materials for further research work. Key wards: Drought resistance, meiotic behavior, RILs