Characterization of F1 hybrid tomato variety candidates using agromorphological and molecular methods

In this thesis, the characterization of F1 hybrid tomato (Lycopersicon lycopersicum) variety candidates were conducted using morphological and molecular methods. Within this scope, morphological measurements and observations were carried out on 94 variety candidates. Based on the results of these evaluations, 52 candidates were further analyzed using Simple Sequence Repeat (SSR), Sequence-Related Amplified Polymorphism (SRAP), and Insertion-Deletion (INDEL) markers. During this process, resistance levels to Meloidogyne incognita, Tomato Mosaic Virus (ToMV), Tomato Yellow Leaf Curl Virus (TYLCV), Verticillium dahliae, Fusarium oxysporum f. sp. lycopersici, and Tomato Spotted Wilt Virus (TSWV) were determined, and their genetic profiles were characterized. Morphological analyses were performed based on UPOV (International Union for the Protection of New Varieties of Plants) criteria, focusing on traits found suitable. Measurements under greenhouse conditions included growth type, leaf attitude, leaf length and width, leaf blade characteristics, number of flowers per inflorescence, flower truss position on the first node, and green shoulder formation on fruits. Post-harvest observations focused on traits such as fruit size, length/diameter ratio, longitudinal and cross-sectional shape, pericarp thickness, number of carpels, fruit firmness, dry matter content, fruit color, and pH value. Data obtained from SSR, SRAP, and INDEL markers were scored in a binary format (1/0 for presence/absence) and analyzed using the DARwin software. A Neighbor-Joining (NJ) dendrogram was constructed to illustrate the genetic relationships among F1 hybrid tomato candidates, revealing three major groups. A Mantel test confirmed a strong correlation between the distance matrix and the NJ dendrogram (r = 0.862). The resistance levels of the variety candidates were evaluated against five pathogens and one pest. A total of 20 candidates were identified as homozygous resistant (RR) to Tomato Mosaic Virus (ToMV), 17 candidates to Fusarium oxysporum f. sp., and 15 candidates to Fusarium spp. and Phytophthora spp. Nine candidates were found to be susceptible (rr) and two were heterozygous resistant (Rr) to Tomato Spotted Wilt Virus (TSWV). In addition, 17 candidates were identified as heterozygous resistant (Rr) to the pest Meloidogyne incognita (root-knot nematode). Based on the overall evaluation, five variety candidates (123x6, 103x10, 256x10, 222x10, and 105x4) were determined to carry four different resistance genes against the pathogens studied. Measurements and observations from both fall and spring seasons were analyzed using Principal Component Analysis (PCA). A single principal component axis was obtained for the fall season, explaining 69.80% of the total variation. Score plots and loading plots were generated for the first five principal components. For the spring season, six independent component axes were identified, accounting for 76.57% of the total variation.