Traditional and modern breeding strategies towards developing resilient crops: Two case studies in tomato

Abstract

Crop designing for resilience traits to produce satisfactorily under adverse conditions and scenarios is a priority for the future of global food security. In this thesis, two different approaches addressing major stress factors for tomato cropping are presented. We first aimed to domesticate tomato de novo as a high-salinity resistant crop using the wild relative, S. cheesmaniae via gene editing. We conducted single-gene and multiplex knock-out strategies using CRISPR/Cas9 genome editing to create loss-of-function alleles for the domestication-related genes BIF, CycB, J2, EJ2, MULTI, SP, SP5G, and FW11.3 in order to create a novel, halophyte tomato harboring an inherent high-salinity resistance along with desirable cultivation traits. In the second study, we employed traditional breeding strategies together with modern molecular techniques for in vitro culture and chromosomal mapping to generate introgression lines and backcrossing generation populations harboring a resistance trait against a fungal disease of tomato, Septoria leaf spot (S. lycopersici). Taken together, this research demonstrates how traditional and new breeding approaches can be integrated to boost the development of novel resources for tomato breeders and growers. Furthermore, the value of employing genomic and biotechnological resources in both traditional and modern breeding scopes towards an ideotype tomato crop is discussed and further recommendations are explored.