Analysis of Basic Helix-Loop-Helix Gene Related to Virus Resistance in Squash

Viral diseases in squash are damaging during the early stages of development and cause loss of crop yield and economic value. To reduce the damage caused by viral diseases, resistant cultivars should be bred. The objective of this study was to determine whether there was a relationship between virus resistance and a basic helix-loop-helix (bHLH) gene in squash (Cucurbita pepo L.). To do this, the bHLH transcription factor, known to be related to virus resistance, was isolated and analyzed using C. pepo individuals that were resistant or susceptible to zucchini yellow mosaic virus (ZYMV) and watermelon mosaic virus (WMV). The results showed that a three bp (GAC) deletion in the nucleotide sequences were found in the regulatory region of the CpbHLH gene in susceptible lines. It was confirmed that the deletion region was located near the binding site of the MYB transcription factor associated with the bHLH gene. It could be hypothesized that the susceptibility of susceptible lines may have been due to the lack of important sequences near the transcription factor binding region due to the deletion in the regulatory region, thus suppressing the expression of the gene. Quantitative real-time PCR (qRT-PCR) revealed that the expression level of the bHLH gene in resistant lines was 2.17 times higher than in susceptible lines.