Abstract:
Domesticated plants have shaped the current human society as crops have been selectively bred over generations to meet human needs. However, this process has led to an inevitable narrowing of the cultivated plant’s germplasm, resulting in the domesticated species only possessing a subset of the genetic diversity of its progenitor species. The vulnerability of the plant that results from the decrease in genetic diversity has been a topic of concern over the last two centuries and wild germplasm has emerged as a reservoir of alleles that may improve the agricultural traits of a plant in productivity, quality and resistance to disease and pest. The domesticated apple, Malus x domestica, is one of the most important fruits in the temperate region and are widely consumed around the world because of their high nutrition and year-round availability. However, domestication and vegetative propagation of the domesticated apple has also resulted in a decrease in genetic diversity due to only a small number of elite cultivars being used for breeding purposes. Various studies have suggested Malus sieversii, the wild apple species found in Central Asia to be the progenitor species of the domesticated apple. Investigating this wild germplasm has already identified many important traits such as resistance to diseases, pests as well as biotic and abiotic stress. With the recent developments in molecular genetic techniques such as RNA-sequencing and the completed genome sequencing of the domesticated apple cultivar, ‘Golden Delicious’, a detailed study comparing the genetic diversity between wild and domesticated apple seemed necessary. A comparative transcriptomic and non-targeted metabolomic study was undertaken on M. domestica, M. sieversii and M. sylvestris, the European wild crabapple. The metabolomic profiles of these three species showed how each species are characterized by a different group of metabolites. Also, ascorbyl glucoside, a stable form of vitamin C, was isolated for the first time in apple to the best of my knowledge and was found to be present in high concentrations in two M. sylvestris genotypes. Various possibilities of ascorbyl glucoside synthesis in apple are explored.