Genetic Variability of Citrus Rootstock Cultivars under Saline Regime

Using sand culture technique, an experiment was conducted to study the genetic variability of citrus rootstock varieties to salt tolerance. Ten different varieties of citrus rootstock (Rough Lemon, Bitter Sweet Orange, Carrizo Citrange, Yuma Citrange, Gada Dahi, Sanchton Citrumillo, Citrumillo-1452, Citrus Obvidea, Rangpur Lime, and Rubidux) acquired from different fruit research stations were grown in plastic pots having four salt treatments ie control (no salt application), 30 mM, 60 mM, and 90 mM of NaCl with five replications. After germination, the six-month old seedlings were transferred to 9-L plastic pots. The plants were allowed to grow with 0.5% Hoagland solution as a growth medium for 90 days. The salinity treatments were applied along with the Hoagland solution. Ten days after the salinity application, plants were harvested for the estimation of growth, physiological, and biochemical parameters. The fresh and dry weight per plant, number of leaves per plant, shoot and root length, chlorophyll content, photosynthesis rate, transpiration rate, stomatal conductance, total nitrogen (N), potassium (K), and phosphorus (P), contents decreased while sodium (Na) and chloride (Cl) ions increased with increase in salinity in all rootstocks studied. 'Rubidux' showed the maximum values for plant height, shoot fresh weight, tap root fresh weight, fibrous root fresh weight, shoot dry weight, tap root dry weight, fibrous root dry weight, photosynthesis rate, stomatal conductance, WUE, Cholophyll a, chlorophyll b, and chlorophyll ab, N, K,  and phosphorus as compared to the rest of the rootstocks. All the varieties gave variations in their morpho-physiological attributes under saline conditions but 'Rubidux' and 'Rangpur Lime' attained the top position by giving the excellent performance at all salinity treatments especially the 90 mM. 'Carrizo Citrange' and 'Sanchton Citrumillo' are categorized as salt sensitive varieties because they failed to gave satisifacory performance under salt stressed conditions. Therefore it is clear that 'Rubidux' and 'Rangpur Lime' are salt tolerant, 'Gada Dehi' and 'Rough Lemon' moderately tolerant, while 'Carrizo Citrange' along with 'Sanchton Citrumillo' are salt sensitive.