Muhammad Fasih Khalid^1,2, Sajjad Hussain^1,a, Muhammad Akbar Anjum¹, Muhammad Arif Ali³, Shakeel Ahmad⁴, Shaghef Ejaz¹, Sajid Ali¹, Muhammad Usman⁵, Ehsan Ul Haque⁶ and R. Morillon^7
1 Department of Horticulture, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan, Pakistan
² Citrus Research and Education Centre, University of Florida, 33850 Lake Alfred, FL, United States
³ Department of Soil Science, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan, Pakistan
⁴ Department of Agronomy, Faculty of Agricultural Sciences and Technology, Bahauddin Zakariya University, Multan, Pakistan
⁵ Institute of Horticultural Sciences, University of Agriculture, Faisalabad, Pakistan
⁶ Citrus Research Institute, Sargodha, Pakistan
⁷ Equpie “Structure Evolutive des Agrumes, Polyploidie et Amelioration Genetique”, SEAPAG – CIRAD, UMR AGAP, F-97170 Petit-Bourg, Guadeloupe, France – AGAP, Université Montpellier, CIRAD, INRAE, Institut Agro, Montpellier, France

SUMMARY Introduction – Salt stress affects the growth and development of many crops. Citrus is a major global fruit crop and its production is strictly affected by salinity. The use of polyploid citrus rootstocks has been proposed as a strategy to improve salt tolerance. Although tetraploid rootstocks have been found to be more salt tolerant under low and moderate salinity. But, the mechanisms of these dynamics are unknown, including how they compartmentalize the toxic ions under moderate and high saline soils. Materials and methods – Exploring the differences in salt tolerance mechanism between tetraploid and diploid volkamer lemon rootstock, the plants were exposed to moderate (75 mM) and high (150 mM) salinity for 80 days. Various growth parameters (plant height and diameter, leaves number, dry biomass) and various minerals nutrients (N, P, K, Ca, Na and Cl) in leaves and roots of diploid and tetraploid rootstock were studied to understand tolerance mechanism. Results – The results exhibited that tetraploid rootstock behaved differently to cope with the salinity as compared to diploid. In both diploid and tetraploid rootstocks various growth traits were decreased under moderate and high salinity compared to the control. However the decrement was less in tetraploid as compared to diploid rootstocks in moderate and interestingly in high salinity. Conclusion – Tetraploid and diploid rootstocks compartmentalize the toxic ions differentially and/or different parts against moderate and high salt stress. These results suggest that the use of tetraploid citrus rootstocks will be useful and more beneficial for citrus cultivation in moderate and more importantly high saline soils. Keywords citrus rootstock, nutrients, polyploidy, salinity, toxicity

Significance of this study What is already known on this subject? Salinity is one of the major causes of yield decrease of many fruit crops including citrus. Citrus is the major fruit crop of the world but its production is decreasing by different factors, i.e., salinity. Chloride is toxic for citrus. Tetraploids are more tolerant than diploids under moderate salt stress, however, under high salt level, diploids are more tolerant than tetraploids. What are the new findings? Volkamer lemon tetraploids are more tolerant than diploids under moderate and specifically high salinity. The compartmentalization of toxic ions occur particularly in leaves under moderate salinity and in roots under high salt stress. What is the expected impact on horticulture? The use of tetraploid rootstocks under moderate and high salt affected soils is a good strategy for better citrus production.

E-mail: sajjad.hussain@bzu.edu.pk  

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Received: 10 March 2020 | Accepted: 27 June 2020 | Published: 24 September 2020 | Available online: 24 September 2020