Abstract
Salt stress reduces the yield and quality of rice. It is of great significance to screen out salt-tolerant varieties for the development and utilization of saline land. The study was carried out on 114 rice varieties; first, seven varieties were selected and treated with different salt concentrations (0, 50, 85, 120, 155, 190, 225 mM), and seven traits, including germination energy, germination capacity, shoot length, root length, root number, plant fresh weight, and seedling vigor index, were measured. The salt concentration at which the sodium chloride injury index was 50% of the control was considered the optimal salt concentration. Second, 114 rice germplasms were carried out under an optimal salt concentration (120 mM). Then, principal component analysis, fuzzy function analysis, stepwise regression analysis, correlation analysis, and systematic cluster analysis were carried out on each parameter. There was a significant correlation between each parameter and the D-value, and the correlation coefficient between the seedling vigor index and D-value was the highest. D-value = − 0.272 + 1.335 × STI − SVI + 0.549 × STI − RN − 0.617 × STI-RL + 0.073 × STI − GE, R2 = 0.986. Using this equation, the sodium chloride tolerance of rice in the germination experiment could be quickly identified. This study showed that the seedling vigor index was a reliable parameter to identify the salinity tolerance of rice varieties. Five groups were obtained by classification at a Euclidean distance of 5. There were 8 highly salt-tolerant cultivars, 23 salt-tolerant cultivars, 42 cultivars with moderate salt tolerance, 33 salt-sensitive cultivars, and 8 highly salt-sensitive cultivars. In this study, we found that Riguang was the most salt-tolerant rice variety, and Xiangxuejing15 was the most salt-sensitive variety.
Highlights
Coastal mudflat improvement and utilization have a long history, and coastal mudflats are a vital reserve resource for crop cultivation [1], but soil salinity in coastal regions is a major impediment to soil [2]
Rice seedlings were stunted in shoot length, root length, root number, fresh plant weight, and seedling vigor index [33]. This present study shows that the sodium chloride injury index (SII)-SL, SII-RL, SII-RN, and SII-SVI were 1.0 at 225 mM salt, which is in agreement with Wu et al.; their results showed that when the salt concentration was 250 mM, the SII-SFW, SII-RFW, SII-SL, SII-RL, SII-TFW, and the average SIIs were 1.0 [15]
The vigor index, root number, root length, and germination energy of seedlings were determined by the mathematical model equation D-value = − 0.272 + 1.335 × salt tolerance index (STI) − SVI + 0.549 × STI − RN − 0.617 × STI − RL + 0.073 × STI − GE, which can quickly judge the salinity tolerance of rice at the germination stage
Summary
Coastal mudflat improvement and utilization have a long history, and coastal mudflats are a vital reserve resource for crop cultivation [1], but soil salinity in coastal regions is a major impediment to soil [2]. Plants under saline stress are more vulnerable to disease attacks [5]. Rice is grown under waterlogged conditions [6], and rice is the earliest crop for utilizing coastal saline lands after salt leaching and improved measures of tidal flat soil [7]. Developed and screening salt-tolerant rice cultivars moderate the impacts of salinity on rice production and contribute to progress towards food security at a worldwide scale
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