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Assessment of genetic and nutritional diversity, and salinity tolerance of Kenyan guava (Psidium guajava L.): an underutilized naturalized fruit species

dc.contributor.advisorPawelzik, Elke Prof. Dr.
dc.contributor.authorChiveu, Chemulanga Josiah
dc.titleAssessment of genetic and nutritional diversity, and salinity tolerance of Kenyan guava (Psidium guajava L.): an underutilized naturalized fruit speciesde
dc.contributor.refereePawelzik, Elke Prof. Dr.
dc.description.abstractengCommon guava (Psidium guajava L.) fruit has a significant nutritional and medicinal potential besides its economic importance, yet is still underutilized in terms of production and consumption. The current global guava fruit production is based only on a few cultivars selected mainly based on their morphological traits, hence much of the genetic variation remains untapped. There is also limited knowledge about the impact of climatic conditions, soil properties and fruit morphological traits on the chemical and mineral composition of the guava fruit. Additionally, guava production currently faces challenges of salinity in many guava-producing countries. The objectives of this study were therefore to determine the genetic diversity, nutritional variability and salinity tolerance among accessions of guava collected from four different regions of Kenya (Coast, Eastern, Rift Valley and Western). The genetic diversity was assessed on 177 guava accessions using 13 simple sequence repeat (SSR) markers. Out of the 177 trees used for SSR analysis, a relationship between climatic factors and, chemical and mineral composition of fruits from128 trees was determined. Correlations were also performed for fruit chemical and mineral composition with their morphological traits and soil mineral contents, respectively. The effect of sodium chloride (NaCl) salinity—0 mM (control), 10/20 mM (low), 20/40 mM (medium), and 40/80 mM (high) was also investigated on ten genetically diverse accessions in a six week greenhouse experiment. Results of the genetic analysis revealed that most accessions generally clustered into multiple weakly supported groups with only 46 out of 177 accessions being supported by bootstrap values above 50%. There was a lack of clear-cut genetic groups along geographical origins and fruit flesh colour. Results of fruit chemical and mineral composition revealed a positive correlation between ascorbic acid composition and total annual precipitation while the total soluble solids (TSS) was positively linked with mean annual temperature, and was high in white-fleshed fruits. The mineral content of the fruits mainly reduced with an increase in most of the fruit weight- and size-based morphological traits and also with the total annual precipitation. Results of the salinity experiment revealed genetic differences in dry matter accumulation by some accessions. Moreover, variations were observed among the accessions with respect to accumulation of Na, and was positively correlated to dry matter (DM). Generally, guava was not so effective in excluding Na from the transpiration stream. For guava conservation, selection and improvement, we recommend sampling many individual accessions covering the geographical range of the species based on our genetic analysis results. The information on fruit chemical and mineral composition could act as a guide in the selection of specific regions for guava fruit production, selection of accessions for improvement programmes, and the design of appropriate fertilizer regimes that enhance guava fruit composition. Differences among the accessions relative to DM production and accumulation Na at varying salinities should be considered for selecting genotypes for adaptation to saline environments. The interaction between genotype, environmental conditions and fruit morphological traits should be used to select accessions with preferred traits – for instance, those with high chemical and mineral composition, high productivity and tolerance to adverse conditions such as
dc.contributor.coRefereeDippold, Michaela Prof. Dr.
dc.contributor.thirdRefereeDittert, Klaus Prof. Dr.
dc.subject.engPsidium guajavade
dc.subject.engGenetic diversityde
dc.subject.engNutritional compositionde
dc.subject.engSalinity tolerancede
dc.affiliation.instituteFakultät für Agrarwissenschaftende
dc.subject.gokfullLand- und Forstwirtschaft (PPN621302791)de

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