Breeding approaches for improvement of temperate fruit crops and nuts - a review

Abstract

Fruit breeding is an ancient technology with dynamic current technology and an exciting future (Janick and Moore, 1975, 1996). In its broadest sense, fruit breeding refers to the purposeful genetic improvement of fruit crops through various techniques including selection, hybridization, mutation induction, and molecular techniques. Its origins trace to the domestication process in prehistory and antiquity, where useful species were chosen and cultivated, and improved by continuous selection (Janick, 2005, 2011). Much of the world fruit industry is still based on grower selection from chance seedlings as well as mutations (sports) and as a result many fruit species are characterized by a narrow germplasm base. Spontaneous hybridization between wild plants and cultivated clones was critical to the early domestication of fruits. The lengthy juvenile period and the large field space required to grow temperate fruits have imposed major limitations on conventional breeding and various molecular biological techniques have been employed to make fruit breeding easier. (Igarashi et al.2016). Marker-assisted selection (MAS) uses DNA markers to provide an early DNA-based evaluation of genetic performance potential of seedlings, with the aim of improving cost and/or genetic efficiency of seedling selection (Ru, et al., 2015). Transgenic technology has facilitated the development of fruit trees with resistance to fungal or bacterial diseases, improved fruit quality, or root stocks with better rooting or dwarfing ability. In recent years, new technologies for genetic improvement, such as transgrafting, and genome-editing, have emerged. (Mudge, et al. 2009; Jia and Wang 2014). Using these techniques, no foreign genes are present in the final product, and some of them show considerable promise for application to apple breeding. Furthermore, genome editing, by which only the target gene can be accurately modified, is emerging as a novel breeding technology. These new technologies will undoubtedly facilitate fruit breeding, and yield novel and attractive fruit cultivars.