Genetic, biochemical and molecular characterization of exotic tomato lines for key economic traits

Abstract

This study aimed to characterize 60 newly acquired exotic genotypes to identify superior lines for use as parental material in breeding programs. The genotypes were evaluated under field conditions during 2023-25 for yield components, processing traits, and resistance to tomato leaf curl disease (ToLCD). Gene-specific DNA markers were employed to detect ToLCD resistance genes Ty-2 and Ty-3. Substantial genetic variation was observed among the genotypes for the traits assessed. The genotypic coefficient of variation (GCV) ranged from 5.41 to 94.82%, which was lower than the phenotypic coefficient of variation (PCV), which ranged from 5.70 to 97.11%. High heritability values (> 60%) combined with high genetic advance as a percentage of the mean (> 20%) suggest that additive gene action is responsible, supporting the effectiveness of selection. Hierarchical clustering using the unweighted pair group method with arithmetic mean (UPGMA) classified the genotypes into four clusters (I-IV), revealing distinct variation among genotypes from the United States and Taiwan. Principal component analysis (PCA) explained a total of 76.56% of the variation, with the first and second principal components accounting for 49.16 and 27.40%, respectively. Field assays for ToLCD resistance identified 11 genotypes as highly resistant (HR), 4 as resistant (R), 5 as moderately resistant (MR), and the remaining 40 genotypes as moderately susceptible to highly susceptible. Genotypes AVTO1174, AVTO1219, AVTO1424, AVTO1707, and AVTO2151 possessed both Ty-2 and Ty-3 genes in homozygous form and exhibited field resistance to ToLCD. The following genotypes, AVTO1174, AVTO1219, AVTO1424, AVTO2101, AVTO1906, AVTO1907, AVTO2149, AVTO2151, AVTO1909, and AVTO1915, are recommended as parental lines for advanced breeding programs.