Abstract
Cucumber (Cucumis sativus L.) is one of the most important vegetable crops cultivated worldwide. The fruits of the cucumber are highly perishable and become unfit for consumption within 2–3 days of harvesting when stored under ambient conditions. Understanding the physio-chemical basis of extended shelf-life and associated molecular mechanisms was the main objective of the present study. Seven diverse genotypes for shelf-life-related traits were investigated for important physio-chemical characteristics and expression of the essential genes at different developmental stages. Photosynthetic activities, physiological loss in weight (PLW), fruit firmness, change in pH of the fruits and chlorophyll content in the leaves and fruits were estimated. Expression analysis of selected genes associated with cell wall modification, ethylene and cytokine biosynthesis were also investigated at 5 different developmental stages of the fruits. Photosynthetic rates were higher in the genotype with extended shelf-life, indicating its role in maintaining the cell wall integrity. However, the retention of the green colour of the fruits was not associated with the photosynthetic rate. Lower PLW, greater fruit firmness and minor changes in pH of the fruits were recorded in fruits with higher shelf-life. Significantly higher expression of the cell wall degradation genes except for Xyloglucan endonuclease with the development of the fruits was recorded in the genotypes with poor shelf-life. More robust expression of the cytokinin biosynthesis genes like IPT, cytokinin oxidase 1 and cytokinin dehydrogenase in the genotype with poor shelf-life indicated the absence of correlation of this unique trait with the functional stay-green trait. Higher expression of the ethylene biosynthesis genes was recorded in the genotypes with poorer shelf-life. The nature of the photosynthesis rate, chlorophyll content and expression of the cytokine pathway genes indicated the cosmetic nature of the novel type of stay-green trait of the fruits after harvest. Differential expression of cell wall modification genes in combination with the lower chlorophyll catalytic activities were the principal factors associated with extended shelf-life in cucumbers. This study provides a solid foundation for understanding the role of physio-chemical traits and critical genes related to extended shelf-life in cucumbers.