Evaluation and prediction of salinity tolerance behavior of citrus rootstocks

The information on relative salt tolerance of citrus rootstocks is lacking for semi-arid conditions of Punjab (India). Therefore, the response of Carrizo, Cleopatra, Volkamer lemon, Rangpur lime, Rough lemon, Sour orange and Macrophylla was evaluated considering membership function value (MFV) approach during 2018 and 2019. In a pot culture experiment, about one and half year old rootstock seedlings were subjected to salt stress for 60 days at Regional Research Station Abohar of Punjab Agricultural University, Ludhiana, India. The mean MFV for different rootstocks ranged between 0.263-0.591, with an average of 0.469 +/- 0.087 and from 0.288-0.639, average being 0.460 +/- 0.085 during 2018 and 2019, respectively. Accordingly, Carrizo was rated salt sensitive, Cleopatra, Volkamer lemon, Rough Lemon, Rangpur Lime and Macmphylla were grouped under moderately salt tolerant and Sour orange was found as most salt tolerant citrus rootstock. Further, of all the parameters tested, relative growth rate, photosynthesis rate, stomatal conductance, water use efficiency and peroxidase activity showed highest correlation with the salt tolerance levels in terms of MFV. These parameters were used as predictors and a mathematical model was established. The model precisely and accurately predicted the salt tolerance behavior of tested citrus rootstocks.