Screening and Identification of Saline-Tolerant Germplasm in Melon

Melon ( Cucumis melo L.) holds significant importance as a horticultural crop, but it faces several yield-limiting factors, including salinity stress. While salinity traditionally hampers the vegetative growth of melon and detrimentally impacts fruit development and quality, certain melon cultivars exhibit the ability to flourish in conditions of relatively high soil salinity. However, truly salt-tolerant melon varieties are quite rare. In this article, we conducted seedling indoor tests, assessed morphological, physiological and biochemical indices, and explored different salt tolerance types among five melon varieties. As a result, we identified three salt-tolerant varieties, with ‘kuizilike’ (KLK) demonstrating the most impressive performance under salt stress. ‘KLK’ exhibited minimal growth and development constraints during salt stress, with the lowest Na + content, the highest K + content, and the highest K + /Na + ratio. Moreover, it displayed the lowest content of malondialdehyde, the highest concentrations of osmoregulation substances, and the highest activity of antioxidant enzymes. Real-time fluorescence quantitation PCR results revealed significantly elevated gene expression levels of TPK , NHX2 , LTP , POD , SuSy , HK , PRP and P5CR in ‘KLK’ compared to other varieties. These newly identified salt-tolerant melon germplasms will serve as valuable genetic resources for future studies on the mechanisms underlying melon salt tolerance, and provide insights into melon improvement and molecular breeding.