Wakeyo, Gemechu Keneni (2012) Genetic Potential and Limitations of Ethiopian Chickpea (Cicer arietinum L.) Germplasm for Improving Attributes of Symbiotic Nitrogen Fixation, Phosphorus Uptake and Use Efficiency, and Adzuki Bean Beetle (Callosobruchus chinensis L.) Resistance. PhD thesis, Addis Ababa University.
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Abstract
Chickpea (Cicer arietinum L.) is one of the most important food legumes grown all over the world. In Ethiopia, chickpea is among the most important food legumes both in terms of area coverage and volume of production. The production of chickpea is important not only in terms of human and animal nutrition but also in terms of ecological sustainability through symbiotic nitrogen fixation. Despite the importance, productivity of chickpea is constrained at least in part by production problems related to the inherent low-yielding potential of the local cultivars, production without application of adequate inputs including fertilizers and post-harvest insect pest damage particularly adzuki bean beetle (Callosobruchus chinensis L.). Ethiopia is known as one of the centers of secondary diversity for chickpea. Genetic resources with proven performance for better symbiotic nitrogen fixation, phosphorus uptake and use efficiency and adzuki bean beetle resistance are limited for focused utilization in chickpea breeding programs. Characterization and evaluation of genetic make-up of the Ethiopian chickpea germplasm accessions is, therefore, essential to designing effective breeding programs. Genetic diversity and population structure of 155 chickpea genotypes were studied using 33 microsatellite (SSR) markers. A series of field and laboratory experiments were also undertaken in 2009-2010 in Ethiopia to characterize and evaluate Ethiopian chickpea germplasm for attributes of symbiotic nitrogen fixation, phosphorus use efficiency and adzuki bean beetle resistance. The field studies for symbiotic nitrogen fixation and phosphorus use efficiency were undertaken at Ambo and Ginchi while the adzuki bean beetle resistance study was conducted in entomology laboratories at Debre Zeit, Holetta and Ambo in Ethiopia. The tests for symbiotic nitrogen fixation and phosphorus uptake and use efficiency were conducted with 155 genotypes and 130 genotypes were tested for adzuki bean beetles resistance. Randomized complete block designs with 4 replications for symbiotic nitrogen fixation, 2 for phosphorus uptake and use efficiency and 3 for resistance to adzuki bean beetle were used. The difference technique, with a non-nodulating reference genotype was employed to estimate nitrogen fixation and the balance method was used to estimate phosphorus uptake and use efficiency. Molecular analysis of variance showed variation of 73% within and 27% between populations. Introduced genotypes had higher polymorphism (70.27%) than the local accessions (36-57%). Collections from Shewa, Harargie, W. Gojam and S. Gonder regions showed the second higher polymorphism (50-57%) than the rest of the local accessions (36-45%). Accessions from adjoining eco-geographical origins mostly showed tendencies for more genetic similarity than those from far isolated origins. Cluster analyses at the molecular level grouped the genotypes into five clusters. The first cluster (C1) constituted accessions from Arsi, the second (C2) from Gojam and Gonder, the third (C3) from Harargie and E. and N. Shewa, the fourth (C4) from W. Shewa, Tigray and Wello regions and the fifth (C5) all improved genotypes. Improved Kabuli and Desi types fell into a distinct cluster (C5) regardless of the difference in seed types. Analysis of variance of symbio-agronomic characters, phosphorus uptake and use efficiency and adzuki bean beetle resistance showed significant differences among the genotypes, locations and genotype by location interaction effects for a number of traits. Genotype by phosphorus level interaction effects were non-significant except in a few cases. A number of landraces superior to introduced genotypes were identified for attributes of symbio-agronomic characters except for seed size where the best genotypes were all from exotic sources. The amount of fixed nitrogen ranged from 13-49% in foliage, 30-44% in grain and 28-40% in total above ground biomass. Grain yield performance varied from 31-70 g 5 plants-1 and seed size from 82-288 g/1000 seeds. The top 5% best accessions for total (shoot + grain) nitrogen fixation include Acc. Nos. 41222, 41029, 41021, 41074, 41075, 41129, 41320 and 41026. There were also some other genotypes which had better fixations either in their shoots (e.g. 41103) or grains (e.g. 207734). Two introductions from ICRISAT, namely ICC 5003 and ICC 4973, were also among the top 5% best fixers of nitrogen in their shoot. The best assimilators of fixed nitrogen were Acc. Nos. 41115, 207659, 219799, 207150, 41277, 41113 and 207894. The application of phosphorus fertilizer increased a number of characters including symbiotic nitrogen fixation. Yield increments of 15% at Ambo and 17% at Ginchi were recorded due to application of phosphorus. The top 5% best efficient, responder genotypes for grain yield include Acc. No. 41274, 41111, 207742, 207563, 207763, 231328, ICC 19180 and 41114. Three of these accessions, namely 41274, 207563 and 41111, also repeated best performances as efficient, responder genotypes for biomass weight. Other efficient, responder genotypes for biomass weight include: Acc. Nos. 207743, 41015, 41066, 41185 and Ejere. Complete resistance to adzuki bean beetle was not observed among the genotypes but Acc. Nos. 41320, 41289, 41291, 41134, 41315, 207658, 41103, 41168, 41142, 41174, 41029, 41207, 209087, 231327, 41161 and 41008 showed partial resistance. Significant progresses were achieved in grain yield and seed size from past breeding efforts but the same efforts had inadvertently increased seed susceptibility to adzuki bean beetle. Cluster analysis grouped the genotypes into six cluster for symbioagronomic characters, five clusters in the absence and six clusters in the presence of phosphorus, respectively, for attributes of phosphorus uptake and use efficiency and three clusters for attributes of adzuki bean beetle resistance. The higher number of clusters when the crop was grown with phosphorus may be a manifestation of more genetic diversity due to the application of phosphorus. The limited genetic diversity for response characters to infestation by adzuki bean beetle may imply the need for characterization of additional landraces and exotic genotypes. The Mahalanobis’s D2 statistics mostly showed significant genetic distances between clusters constituted local landraces on the one hand and introduced genotypes on the other. This indicated that there were distinct multivariate differences between landraces and introduced genotypes. No clear interrelationship was observed between the origins of the landraces within Ethiopia and the pattern of genetic diversity. Different characters had different contribution to the total differentiation of the populations in all the cases. The study on symbio-agronomic traits showed significant positive correlations between a number of characters. Grain yield was positively associated with fixed nitrogen assimilation efficiency, shoot, grain, and above ground biomass nitrogen yields and nitrogen harvest index. Agronomic characters like grain filling period, pod and seed numbers, shoot, and total above ground biomass accumulation, harvest index, grain production efficiency and biomass production and economic growth rates also positively correlated with grain yield. Increased nitrogen yield, nitrogen harvest index, fixed nitrogen assimilation efficiency and above ground biomass may be more important than the per se concentration of nitrogen in plant tissue. Characters like shoot, grain and total biomass nitrogen contents and fixation, fixed nitrogen assimilation efficiency, seed size, grain filling period showed higher genetic variation, broad-sense heritability and expected genetic gains from selection. The study on phosphorus uptake and use efficiency revealed significant positive correlations within plant tissue (shoot, seed and biomass) phosphorus contents (r = 0.22-0.85), between plant tissue phosphorus contents and phosphorus yields (r = 0.22-0.99), within plant tissue phosphorus yields (r = 0.23-0.89) and within parameters of phosphorus uptake and use efficiency in a number cases. Grain yield and economic growth and biomass production rates, grain production efficiency, and shoot and biomass dry weight showed significant positive correlations (r = 0.70-0.99) with phosphorus yield efficiency. Broad sense heritability values ranged from 60-93% and genetic advance values ranged from 4-62% in the absence of phosphorus. The corresponding broad sense heritability and genetic advance values in the presence of phosphorus ranged from 59-93% and 4-79% in that order. In the study of bruchid resistance seed-related traits (seed size, percent seed coat weight and seed weight loss) exhibited larger heritable variation than insect-related traits (number of eggs and adults, days to adult emergence, number of uninfected seed and adult recovery). Broad-sense heritability for seed and insect-related traits varied from 43-76% and 0.20- 11%, respectively. The corresponding expected genetic gains from selection as percent of mean ranged from 28-42% and 0.01-6% in the same order. Significant positive correlations were found among seed weight loss and three component characters, i.e. number of eggs and adults emerged and seed size. The results from these series of studies suggests possibilities for identification of chickpea genotypes superior for symbio-agronomic characters, phosphorus uptake and use efficiency and adzuki bean beetle resistance to the varieties released so far, indicating the need for the initiation of a planned breeding program. Further implications of the findings as regard germplasm collection, conservation and eco-geographical pattern evolution are also discussed.
| Item Type: | Thesis (PhD) |
|---|---|
| Subjects: | Q Science > QH Natural history > QH301 Biology Q Science > QH Natural history > QH426 Genetics Q Science > QK Botany Q Science > QL Zoology |
| Divisions: | Africana |
| Depositing User: | Selom Ghislain |
| Date Deposited: | 12 Jul 2018 11:11 |
| Last Modified: | 12 Jul 2018 11:11 |
| URI: | http://thesisbank.jhia.ac.ke/id/eprint/7411 |
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