Characteristics of in vitro- and ex vitro-propagated blueberry plants at morphological, chemical and molecular levels

Goyali, Juran Chandra (2018) Characteristics of in vitro- and ex vitro-propagated blueberry plants at morphological, chemical and molecular levels. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The lowbush blueberry (Vaccinium angustifolium Ait.), a commercially important fruit crop in Canada and USA, is one of the richest sources of antioxidant metabolites which have highly potential to reduce the incidence of several degenerative diseases. The aim of this study is to investigate the effect of propagation on the morphological, chemical and molecular characteristics of blueberries. The study evaluated the genetic and epigenetic variation in micropropagated plants. A lowbush wild clone ‘QB9C’ and the cultivar ‘Fundy’ were studied after being propagated by conventional softwood cutting (SC), and by tissue culture (TC) using nodal explants. The antioxidant metabolites in leaves and fruits of both genotypes were investigated in different maturity stages. The TC-regenerated plants were grown more vigorously and produced higher number of stems, branches, and larger leaves compared to SC plants. However, TC plants of both genotypes produced less flowers and fruits compared with SC counterparts. Micropropagation influenced the synthesis of phenolic and flavonoid compounds, and their antioxidant activities in blueberry which were genotype specific. ‘QB9C’ plants were highly influenced by micropropagation for their phytochemical content and antioxidant capacity. Leaves contained substantially higher levels of polyphenolics, flavonoids and proanthocyanidins than berries. The total soluble phenolic and flavonoid content and reducing power of ferric ion were boosted in fruits of the micropropagated plants, whereas the levels of these metabolites and total antioxidant activity were decreased in the leaves of TC plants. Red leaves had higher phenolic and flavonoid content and antioxidant potential than the green leaves, and green fruits had higher levels of bioactive phytochemicals than semi-ripe and full ripe berries. In contrary, anthocyanin content increased with the advancement of fruit maturity. Molecular marker analysis with expressed sequence tag (EST)-simple sequence repeat (SSR) and EST-polymerase chain reaction (PCR) makers detected the identical monomorphic amplification profiles within the TC plants of each genotypes which confirmed their genetic integrity. Methylation sensitivity amplification polymorphism (MSAP) analysis demonstrated that TC plants of both genotypes had higher DNA methylation compared to SC plants. Discrete methylation polymorphism was observed among the tissue culture regenerated plants. These results indicate that although in vitro derived plants maintained trueness-to-type genetic makeup, tissue culture induces DNA methylation alterations and the possibility of involvement of these DNA fragments in the dynamic processes regulating plant growth and development under prevailing growth conditions.

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