Key physiological traits for drought tolerance identified through phenotyping a large set of slicing cucumber (Cucumis sativus L.) genotypes under field and water-stress conditions

Cucumber is one of the important salad vegetables cultivated worldwide and is highly sensitive to water stress. However, till date, no drought-tolerant cucumber genotypes have been identified using a large set of diverse germplasms via high-throughput phenotyping methods. This study involved screening of a large set of Indian-origin cucumber germplasms for drought stress response using water-deficit and polyethylene glycol (PEG)-induced stress conditions in hydroponic solutions. Water-deficit and PEG-induced methods were optimized before screening of an entire set of germplasm for key physiological traits. Pearson's correlation revealed non-significant difference between these two methods. Hierarchical cluster analysis and drought tolerance matrix score (DTMS) were calculated based on key physiological traits for ranking of the genotypes. Furthermore, the entire set of genotypes was exposed to water stress (< 8% soil moisture) for 15 d under field conditions to record yield-related traits for validation of the hydroponic-based ranking. Finally, eight tolerant genotypes were identified with high seedling survivability percentage, minimum reduction in root-shoot dry weight, fresh weight and water content percentage, highest DTMS and minimum yield reduction under field stress conditions compared with seven identified sensitive genotypes. The optimized rapid phenotyping method and identified drought-tolerant lines will be instrumental in understanding the physiological and molecular basis of drought tolerance and in facilitating the development of climate-resilient improved cucumber genotypes in the future.

Automated summary

By screening and evaluating a large set of Indian-origin cucumber germplasms, eight drought-tolerant genotypes were identified, showing higher drought tolerance and yield stability under field conditions. These research findings provide important references for further studying the drought tolerance mechanisms of cucumber and developing drought-resistant varieties.