Morphological and Molecular Genetic Diversity and Cytogenetics of Cultivated Anchote (Coccinia abyssinica (Lam.) Cogn) from Ethiopia

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Addis Ababa Universty


Anchote (Coccinia abyssinica), is a perennial climbing, monoecious root crop, endemic and indigenous to Ethiopia. It is distributed over a wide range of agro-ecologies adapted to various altitudinal ranges. The root of anchote stays for several years in the soil without being damaged and its shoot sprouts during rainy season and gives fruit, then die out as the rain season ends. The root accumulates more food nutrients every growing season, and enters into dormancy until the next rainy season resumes. C. abyssinica is not only a valuable tuber food crop but also used as folklore medicines. Despite these importances, there are very limited works available in literature regarding its genetics, agronomy, phylogeography, and evolutionary studies. In this study, agro-morphological and molecular marker based genetic diversity and cytogenetic characterization of anchote has been done. Data on 28 agro-morphological traits were collected under five different experimental conditions, for a total of 182 accessions collected from southwestern part of Ethiopia. The results showed variations among and within accessions. On the basis of some traits, the plants were grouped into few to several phenotypic classes. Deep green (Stcdg) and purple (Stcp) stem colors are observed as rare traits. In molecular diversity study, a total of 47 EST-SSR markers were designed on watermelon’s [Citrullus lanatus (Thunb.)] DNA sequences and only 13 of them amplified the target regions of which eight were polymorphic and the latter were used for diversity and population structuring analyses. Twenty four alleles were observed across eight loci, where the number of alleles per locus ranged from 2 to 6, with an average of 3. Effective number of alleles ranged from 1.06 to 4.8 with an average of 1.93. Overall allelic frequency per locus (0.007-0.967) revealed larger variations. Polymorphic information contents extracted per locus were as low as 0.0619 and the largest was 0.76. Larger Shannon indices (average = 0.633) observed were the indication of better genetic diversity existing among anchote accessions. The top allelic rich populations (Arjo-Leka Dulecha, Gimbi-Nejo, Abay Chomen-Bako Tibe and Dale Sadi-Dale wobera) are leading accessions in genetic diversity parameter (He), but it is only Arjo-Leka Dulecha population that possesses 100% polymorphic loci. Although, no linkage disequilibrium was evident in this study, three loci (WM-24, WM-34 and WM-29) showed significant deviation from Hardy-Weinberg equilibrium. The genetic diversity (He = 0.35, 0.06-0.79) estimated shows that there is a possibility of improving anchote germplasm, especially by focusing on some accessions collected from Abay Chomen-Bako Tibe, Dale Sadi-Dale Wobera, and Gimbi-Nejo, where both allelic richness and observed genetic diversity were high. Anchote crop may be considered as panmictic population in which higher gene flow is common as it is observed in this study. Analysis of molecular variance (AMOVA) revealed the highest proportion of genetic diversity within individuals (83.75%) and the least (7.87) among populations indicating high gene flows among populations. Wider overall loci differentiation (FST = 0.01 to 0.3, with an average of 0.11) was observed. A range of 0.01-0.127 pair wise population differentiation was observed indicating that some populations are very closely related, while others are somehow distant in kinship. Cluster analyses based on EST-SSR data of different levels of anchote groups, i.e., populations, accessions and individual samples did not show clear geographical patterns of origin, except for very few. In general, however, three apparent clusters were obtained. From neighbor joining tree (phylogram) Dale Wobera, Gimbi, Metu, Yayo, Sayo, Gechi, Dhidhesa, and Shebe Sombo represent the older lineages (groups), while Abay Chomen and Leka Dulecha look recent population. Although, population structuring analysis of anchote accessions gave about maximum of seven sub-groups (K = 7), there is no clear variation among the groups based on the allelic proportions of the sub-groups. Some populations were found to have experienced bottleneck. These include Sibu Sire-Wayu Tuka, Guto Gida-Diga, Gera-Shebe Sombo, and Gumay-Goma. In cytogenetic investigation, 2n = 20 chromosomes have been evidenced. All the chromosomes are metacentric in shape. No anchote cytotypes were recognized in this study. The result of this study has many implications for breeding and conservation strategies, specially the results from cytogenetic characterization and EST-SSR based analyses. The morphological descriptors we used may also contribute for further anchote description, variety development and improvement. Key Word: Anchote accession, Coccinia abyssinica, morphological trait, cytogenetics, EST-SSR, genetic diversity, population structure



Anchote accession, Coccinia abyssinica, Morphological trait, Cytogenetics, EST-SSR, Genetic diversity, Population structure