Agro-morphological And Molecular Genetic Diversity And Cytogenetic Analysis Of Ethiopian Potato Plectranthus Edulis (vatke) Agnew From Ethiopia

Agro-morphological and Molecular Genetic Diversity, and Cytogenetic Analysis of EthiopianrnPotato [Plectranthus edulis (Vatke) Agnew] from EthiopiarnFekadu GadissarnAddis Ababa University, 2018rnEthiopian potato syno. Ethiopian dinich [Plectranthus edulis (Vatke) Agnew] (Lamiaceae) is one of thernancient annual edible tuber crops, originating in Ethiopia. The crop is commonly cultivated byrnsmallholder farmers around homesteads in the highland and semi-highland areas, usually for householdrnconsumption and rarely for marketing. In spite of its’ wide economic importances, the crop is neglectedrnby research and development community and currently it is at risk of total extinction.rnHence, this study was conducted with the main aims of assessing agro-morphological and molecularrn(EST-SSRs) markers-based extents of genetic diversity analysis as well as chromosome number andrnploidy level determination using 174 accessions from diverse agro-ecologies in Ethiopia.rnFor agro-morphological diversity analysis, the experimental samples were tested at Ambo and Holetarnagricultural research centres, using an alpha lattice design at the locations and three blocks/replicationrnfollowed by appropriate management practices. Agronomic and morphological traits-based data wererncollected on twenty-eight (12 qualitative and 16 quantitative) traits at the right growth stage andrnanalysed using SAS v9.0, MINITAB® v14.13 and FigTree v1.4.3. Cytogenetic characterization wasrnalso carried out using very young root tips generated from soil covered stem rings, followed byrnappropriate pre-treatment, fixation and maceration. For molecular genetic diversity analysis, genomicrnDNA was extracted form silcagel dried young leaves collected from 287 plants (1-3 plants perrnaccessions) following CTAB protocol. EST-SSRs marker were designed from Plectranthus barbatusrncDNA sequences deposited in the GenBank, followed by PCR amplification, capillary electrophoresis,rnpeak identification, and scoring. The scored allele size data were analysed for polymorphism, diversityrnindices and genetic relationship and structure using windows compatible applications.rnThe agro-morphological traits considered showed varied morphotypes in all of the leaf (four in leafrncolor, three in leaf arrangement, three in leaf shape), stem (three in stem color, two in each of stem spotrnand stem spot colors) and tuber (four in tuber skin color, three in each of tuber texture, tuber shape andrntuber hair) characterstics. Similarly, the traits revealed a wide range of variability in mean performancern(minimum range of 1.39 – 2.13 cm observed in tuber diameter and maximum range of 112.90 – 165.10rnxviirndays observed in days to 50% flower initiation) and variance components among and within thernaccessions. Similarly, the mean square of all the traits showed a highly significant (P< 0.001) variationrnamong the tested accessions. Such wide variation suggests the presence of variability which can bernexploited through selection. Several of the traits showed a slightly greater or nearly equal phenotypicrncoefficient of variation (PCV) to that of genotypic coefficients of variation (GCV), suggesting largerrncontribution of the genotypic effect for phenotypic expression of such characters and hence, phenotypicrnvalues-based selection for the traits may be effective. High estimates of GCV (>23%) coupled with highrnestimate of heritability (Hb%) (>94%) and high genetic advance as a percent of mean (GAM) (>46)rnwere revealed in tuber weight per hill, number of primary branches per plant, number of tubers per hill,rnand number of plants per hill indicating the importance of such traits for selection in Ethiopian potatornimprovement programs. The significantly positive phenotypic, and genotypic correlation in tuberrnweight per hill and number of tubers per hill with each other and several other traits as well as theirrnnegative phenotypic correlation with some other traits indicates the direction of selection. Moreover,rnthe significantly higher absolute magnitudes in genotypic correlation compared to their correspondingrnphenotypic correlation suggest the genetic base of those traits.rnCytogenetic characterization revealed a very smaller sized metaphase chromosome with a count of 2nrn= c.56 and hepta- or octa-ploidy was speculated on the bases of basic chromosome number reports (x =rn8 or 7) for the species of genus Plectranthus and other members of the Lamiaceae family. Suchrnchromosome count and ploidy level report could serve as a baseline information in selection and crosshybridizationrnof Ethiopian potato with other closely related species.rnIn total, twenty new polymorphic expressed sequence tag based simple sequence repeat (EST-SSRs)rnmarkers have successfully been developed and used in genetic diversity analyses. The marker detectedrna total of 128 alleles (6.4 alleles per locus) over the entire loci and populations with effective numberrnof alleles ranging from 1.06 - 3.17 (an average of 1.67). The marker showed an overall highest (94.17%)rnpercent polymorphism, and extents of PIC in the range of slightly informative to highly informativernsuggesting the potential of those developed markers as a valuable genetic tool and resource to evaluaternthe extent of genetic diversity and population structure of not only Ethiopian potato but also variousrnother species within the Lamiaceae family.rnThe ranges and levels of mean observed heterozygosity (0.33 – 0.429), Shanon’s information indexrn(0.523 – 0.663), and Nei’s gene diversity (0.307 – 0.384) across loci showed a medium degree ofrnvariation among the populations which is a direct reflection of sharing of most of the alleles among thernpopulations that partly resulted from high overall gene flow (Nm=18.29). Comparatively, Wenberarn(Wen), Wolaita Sodo (WSo), Hadiya and Kambata-Tembaro (HKT) and Southwest Shewa (SwSh)rnpopulations could be considered as Ethiopian potato diversification and in-situ conservation sites.rnxviiirnHierarchical analysis of molecular variance (AMOVA) showed significant but low populationrndifferentiation with at most 3% of the total variation in each of the groupings, such as among thernpopulations, among geographic regions, and among regions of accessions. Likewise, cluster analysis inrnall the cases and STRUCTURE analyses did not group the populations into sharply distinct clusters,rnwhich could be attributed to historical and contemporary gene flow and/or the reproductive biology ofrnthe crop.rnIn conclusion, this study has wider implications in bringing such a ‘super-neglected’ crop to thernscientific agenda and thus, opens up the door to its improvement and conservation. However, it isrnimportant to exhaust all areas and regions in the country and more number of SSRs or other up-to-daternmolecular marker systems to come up with more accurate level of genetic diversity estimates.

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