An Efficient Approach to Identify Salt Tolerance of Upland Cotton at Seedling Stage

Abstract

Three-leaf cotton seedlings of two salt-tolerant varieties and two salt-sensitive varieties were treated by water and 4%(40 g L–1) NaCl solution, respectively. A total of 13 parameters related to salt tolerance including salt injury index(SII), shoot fresh weight(SRW), root fresh weight(RFW), leaf relative water content(RWC), chlorophyll fluorescence parameters(Fo, Fm, Fv/Fm), relative conductivity(RC), manlondialdehyde(MDA) content and the activity of antioxidant enzymes were monitored after 72 h of treatment. Comprehensive assessment of salinity tolerance based on grey relation clustering method, principal component analysis and stepwise regression analysis indicated that the maximum quantum yield of PSII was the most significant correlated indices with salt tolerance in upland cotton, which could be used as a single parameter to assess salt tolerance based on the equation: y = 1.943x – 0.882(where y is the salt tolerance index, x is the related value of maximum efficiency of photosystem II). The other two salt-tolerant varieties and two salt-sensitive varieties were used to rate the classification of salt tolerance. Salt tolerance index(y) of 23 varieties with known salt tolerance were calculated to validate the accuracy of the equation, the result was consistent with field investigation. In this study, the maximum efficiency of photosystem II was used as the main index to validate the salt tolerance in cotton, together with the construction of salt tolerance index equation and salt tolerance rating, which could greatly improve the efficiency of salinity tolerance evaluation for massive germplasm in future.