Fig. 1

Design of Sw-5b specific molecular markers. a Nucleotide sequence alignment between the resistance allele Sw-5b^R and the susceptibility allele Sw-5b^S. The alignment was used to generate a heatmap using the ggplot2, R package, with black marks indicating positions diverging from the reference Sw-5b^R sequence. Different colors distinguish the SD, CC, NB-ARC, and LRR regions of Sw-5b^R and Sw-5b^S. b Nucleotide sequence alignment between the LRR regions of Sw-5b^R and Sw-5b^S, highlighting the location of the Sw-5b-specific primers Sw-5b-F1, F2, and R1. c Positions of the Sw-5b-specific primer pairs, Sw-5b-F1/R1 and Sw-5b-F2/R1, within the Sw-5b gene. The expected PCR products sizes are indicated. Sw-5b-F1/R1 was designed to amplify Sw-5b^R exclusively, producing a 660-bp fragment, and Sw-5b-F2/R1 to amplify Sw-5b^S exclusively, resulting in a 459-bp fragment. d Validation of the specificity of the Sw-5b-specific molecular markers. Genomic DNA extracted from the tomato cultivar G17-60, IVF3545, and Heinz1706, representing the Sw-5b^R homozygote, Sw-5b^R/S heterozygote, and Sw-5b^S homozygote, respectively, was used as template for PCR amplification. Genomic DNA from Nicotiana benthamiana was used as the negative control