Development of smart fruit crops by genome editing

Plant genome editing tools as Zinc-Finger Nucleases (ZFNs), Trans Activator-Like Effector Nucleases (TALENs), and Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) associated with Cas proteins are offering new possibilities for crop improvement and new insights for functional genomics. In this review, we discuss (i) the new findings in gene editing technologies, (ii) a comparison between them, and (iii) their applications for genetic analysis and manipulation of fruit crops. Different editing technologies, especially the CRISPR/Cas9 system, were successfully used in fruit crops such as apple, banana, cacao, citrus, grape, kiwifruit, and pear. Experimental designs used to analyze the efficiency of the CRISPR/Cas9 genome editor are presented, including manipulating key genes associated with carotenoid biosynthesis that could allow the development of complete albino and variegated phenotypes in some cultivars. The most recent outcomes of the application of genome-editing tools to improve the quality and yields of fruit crops, such as manipulation of juvenile phase and flowering period, gibberellin biosynthesis and generation of dwarf cultivars, ethylene biosynthesis, fruit ripening and parthenocarpy, development of resistant/tolerant cultivars to numerous pests and diseases are also summarized.