Salinity stress is a foremost field of logical apprehension as it constraints plant as well as crop productivity. This condition has been advance damaged by social actions. Hence, there is much scientific encumber on researchers to increase crop yield under environmental stress consecutively to manage with the escalating food stress. The abiotic stress as salinity harmfully affects the survival and biomass production. Cuttings of three olive varieties namely Megaron, Chettoi and Arbequina were planted under the utilization of different levels of saline water for irrigation in tunnel to assess their survival. Olive cuttings took more time for survival than other plant cuttings. Saline water irrigation to three olive varieties cuttings showed very minute differences among treatments. Overall, saline water@4dSm^-1 showed the highest number (2) in number of cuttings survived followed by saline water@6dSm^-1. Control and other saline water application levels showed the similar number of survived olive cuttings. Among olive varieties, Chettoi variety performed better (1.40 olive cuttings) than other two varieties.

Keywords: olive varieties, saline water, callus formation, survival, salinity tolerance

In many ways the less production is caused to diverse abiotic stresses. Restricting crop reductions attributable to different environmental stresses is the foremost area of concern to deal with the mounting food necessities.¹ The most important abiotic stresses akin to elevated salinity, drought, cold, and heat harmfully affects the endurance, biomass production, and yield of staple food crops up to 70 %.^2–7 The bad effect of intemperance minerals such as Na⁺ and/or Cl⁻ on plant is known as salt stress.⁸ Soil salinity appeared long before humans and agriculture; yet, the crisis has been arisen by agricultural practices such as irrigation.⁹ The most serious limiting factor for crop growth and production is salt stress. According to an estimate of FAO, more than 6 % of the world’s land is embellished by salinity. So, salinity stress appears to be a major menace to plant and crop efficiency. Abiotic stresses for instance drought, salinity, submergence, acute temperatures, mineral toxicities, and deficiencies damage crop growth and productivity and intimidate food security of the world.^10,11 Overall temperatures are predictable to mount among 1.1°C and 6.4°C in the subsequent century (IPCC, 2007). The augmented temperatures will dislocate weather patterns, causing to expect happening of floods, drought, and salinity. Melting ice caps and glaciers are anticipated to lead an ascend in sea level,^12,13 that can dangerously influence crop yield in coastal areas due to amplified soil salinity. Global population is escalating at a shocking pace and it is estimated to produce from 6 billion to almost 8.3 billion in 2030.¹⁴ Devoid of vision in  going up arable land owing to urbanization, rapid industrialization, and water scarcity in many populous developing countries of the world,¹⁵ providing food security for the world population will require at least 57% increase in food grain production by 2050.¹⁶ Mounting salinity acceptance of the world’s major food crops is an important purpose of plant scientists as the world’s population is increasing more rapidly than the area of agricultural land to support it.¹⁷ Soils are classified as saline when the electrical conductivity (EC) is 4 dSm^-1 or more, which is the same to about 40 mM NaCl and creates approximately 0.2 MPa osmotic pressure.¹⁸

A decrease in water potential is finally quantified salinity stress. Plants defy low water potential in diverse traditions with addition of osmolytes and changing the cell walls properties during creation of protective proteins.¹⁹ Most commonly used food crops are responsive to salinity effects.²⁰ Salinity lessens the pace of leaf development, and closes stomata and thereby decreases photosynthesis, with the soil water insufficiency generated by the osmotic stress.²¹ Upon revelation to soil salinity, plants add poisonous concentrations of Na + in leaves, which enforce an supplementary restraint to growth by falling the endurance of photosynthetic tissues.²² The control of Na + transport and its valuable elimination from the mesophyll leaves cells is thus an important prerequisite for salinity tolerance. Na + segregation from leaves is linked with salt tolerance in cereal crops plus rice,^23,24 durum wheat,²⁵ bread wheat,^26,27 barley,²⁸ and its wild relatives,²⁹ tall wheatgrass.³⁰ The main gears that manage salt tolerance are abridged salt uptake or salt exclusion, enhanced K ⁺ /Na ⁺ ratio, tissue tolerance, closure of stomata, positive rule of antioxidant system for protection against reactive oxygen species (ROS), synthesis of osmolytes, water use efficiency (WUE), early flowering, and vital growth to attenuate the salt absorption in plant tissue.^31,32

The exchanges among root-zone conditions and whole-plant effects to better potential gradi­ents and specific ion concentrations, uptake, and toxic­ity are mostly convoluted and exceedingly intricate to compute.^33,34 The capability of some plant species, including olives, to eliminate or sort out specific ions³⁵ complicates the relationships between ion toxicity, ion concentration in the external solution, and ion concentration in the plant tissue. Saturated-paste EC (ECe) values databases are used for reporting plant tolerance and responses to salinity.³⁶ It has been recommended that normal whole-plant response functions to salinity may be better presented in terms of the π of the solution in the growing media than in terms of ion concentration or EC.³⁴ Root zone salinity even at relatively low exposure levels reduces water potential and relative leaf water content.³⁷ Cell and tissue culture systems have been considered relevant for selection of plant species tolerant to salinity, drought, and other stresses.^38,39 Such systems offer greater control than in vivo growth conditions.^40–43 In vitro culture systems allow a precise measurement of growth and response to the imposed treatment.^42–46 The exact tolerance of cells to salinity stress is not understood although,^47,48 growth parameters in vitro could reflect the exact tissue response.^40–49 It has been suggested that whole plant response to salinity is associated with a cellular response,^48–50 and the response of cultures to in vitro induced stress mimics the in vivo plant exposed to similar stress.^42–49 There is still a controversial question in the essence of plant cell, callus, or whole plant response to salinity in either way.^49,50 Osmotic has been modified as a technology to tolerate or adapt to ambient conditions in many plants.^51,53  This methodology facilitates in the endurance and adaptation processes of stressed plant or tissue cultures.^49,51Reduction level indicated, but, significant variation according to the cultivar type and the duration of salt exposure.^41–54 Secondary salinization causes when soils that once had a low concentration of salt indicating saltier because of irrigation and poor drainage.⁵⁵ Salinity may besides consequence in the decline of soil structure and reduce water holding capacity or aerate. Preferably, farmers must irrigate fields with fresh water in dry regions, other than since the stipulate for fresh water in many other sectors, growers use water with a higher salt content such as ground water, drainage water, or treated waste water. Na⁺, Ca²⁺, Mg²⁺, Cl^-, SO₄^2- and HCO₃^- are cations and anions that caused salinity.⁵⁶

The experiment was planned at Land Resources Research Institute, NARC Islamabad during January ---- April, 2018 for investigation the impact of salinity on growth of three months sprouted olive cuttings of 3 olive varieties i.e. Megaron, Chettoi and Arbequina under different levels of saline water in tunnel. Seven levels of saline water artificially developed (ECw= 0, 4,6,8,10,12 and 14dSm^-1). Saline water was applied after alternate days. Completely randomized design was applied.

Cuttings of three olive varieties namely Megaron, Chettoi and Arbequina were planted under the utilization of different levels of saline water for irrigation in tunnel to assess their survival. Olive cuttings took more time for survival than other plant cuttings. Data presented in Table 1 indicated different parameters of olive cuttings survival. Saline water irrigation to three olive varieties cuttings showed very minute differences among treatments. Overall, saline water@4dSm^-1 showed the highest number (2) in number of cuttings survived followed by saline water@6dSm^-1. Salinity is damaging worldwide more farm lands owing to brackish irrigation water, poor drainage, brackish water flooding of coastal land, and salt addition in arid lands. Escalating salinity decreased leaf and shoots growth parameters and augmented the quantity of leaf proline, and leaf and root Na⁺ and Cl^-. Gibberellins minimized sodium and chloride concentrations in plants and increased the quantities of potassium and chlorophyll contents.⁵⁷ Gibberellin increased the synthesis and accumulation of proline in two cultivars under different sodium chloride levels, however, this increase was more pronounced in “shiraz”. “Shiraz” showed more vegetative growth than “zard and rate of Na⁺ accumulation in leaves and roots was lower in “shiraz” than in “zard”. Control and other saline water application levels showed the similar number of survived olive cuttings. Among olive varieties, Chettoi variety performed better (1.40 olive cuttings) than other two varieties.⁵⁸

Number of survived cuttings with callus is also an important parameter to assess the survival of cuttings. Saline water@4dSm^-1 and  6dSm^-1 got similar and better performance than other saline water applications. Megaron and Chettoi olive varieties attained the similar and more number of survived in olive cutting than other variety. The use of cell and callus culture helps to focus on the physiological and biochemical mechanism, which help plant tolerance to stress. In the first spring experiment cutting forming callus percentage was generally elevated. High proportion i.e. 81% average was developed callus among three groups of cuttings (with leaves and buds, with leaves and without leaves and buds) but the group without leaves but 62% of cuttings with callus reached only with buds.⁵⁹ Number of survived cuttings without callus showed the highest and similar number by Saline water@8dSm^-1 and 14dSm^-1. Megaron olive cuttings survived better than other two olive varieties in number of survived cuttings without callus. However, number of cuttings survived with roots under saline water irrigation is the most important character to screen the olive cultivars at certain level of saline water. Saline water@4dSm^-1 showed the highest number of olive cutting survival (1.33) among other saline water levels. Chettoi olive cultivar produced more olive cuttings than other two cultivars. Soil physicochemical parameters are highly sensitive to roots.⁵⁹ ROS such as singlet oxygen, superoxide, hydrogen peroxide, and hydroxyl radicals under abiotic stress can generate.^60,61 The removing capacity of the antioxidant system cause important oxidative damage to proteins, lipids, and photosynthetic pigments as well as inactivation of photosynthetic enzymes when exceeds accumulation of ROS.⁶²

This work is supported financially by the University Ibn Zohr. We are grateful to DPA (Zagoura) and farmers in Rasmouka for their substantial help in collecting the watermelon landraces.

The author declares there is no conflicts of interest.

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