Effect of salt stress on the vegetative and reproductive growth of two genotypes of tomato (Solanum lycopersicum L.) plants in climatic condition of district Quetta, Balochistan

The experiment conducted to evaluate the growth of two different genotypes of tomato plants under salt stress. The effect of sodium chloride measured using four different concentrations (0.0M, 0.1M, 0.2M, and 0.3M) in a dose dependent manner. Seedling Height, Number of leave, Leave Area Index, Fresh weight, Dry weight (Biomass), Number of Flowers, Number of Fruits, Weight of Fruits and Maximum height of plant were measured in experiments. Results showed that tomato plants treated with a control group or less salt concentration presented better growth and survive for a longer period as compared to salt dominant groups. The results designates that salinity influences almost every parameter of plant growth, which concludes that salt stress has an antagonistic effect on plant growth.


Introduction
The salt level in the soil now became the world major (related to surrounding conditions or the health of the Earth) trouble in agriculture. That restricts the farmingbased yield overall the world. Different (related to the chemicals in living things) and body-structure-related responses happened in plants by salinity [1]. Salinity produces hyper-osmotic stress and ionic disturbance; which make major cellular functions disable in a plant. Water availability increased, the respiratory rate changed mineral distribution, membrane instability, failure turgor pressure maintenance is few of the condition and tension prevailed at that time. To overcome these condition plants attempt to tolerate these stresses or go to the dormant stage [2]. When plants are exposed to a salt solution of (200 mMNaCl) it makes the leaves and roots growth restricted to a certain degree [3]. When salt water is added to water, it's resulting in decline availability of nutrients that decrease the osmotic potential of root cells [4]. The high salt concentration affect key processes such as seed hampers flowering fruit set, as well as germination, seedling growth, and vigor, growth of plants. This ultimately results in a reduction of crop yield and quality [5]. It has been reported that an abundant amount of salinity is found in cultivated areas, mostly in the arid and semi-arid regions of the earth. Stunting of plants could also occur due to salinity condition [6,7]. Salinity affected every aspect of a plant life cycle, included seed germination, vegetative growth, reproduction cycle of a plant, which caused low production and loss of economic yield [8]. In previous literature it has been investigated that increasing salinity in soil resulting in increased vegetative growth of tomato plant and also its yield [9]. Salt tolerance effectors and regulatory components gain importance near this juncture to salinity are modified and produce a unique variety of tomato that show more resistance to salt stress. These crops can be cultivated in saline condition and that will have significant importance for such purpose an extensive study is being taken place to invent a new tomato variety that shows more tolerance and resistance to salinity. For such design, an expression vector-like AtNHX1 is utilized, which is a gene that regulates Na+/H+ antiport protein, an example of such process is the use of Arabidopsis thaliana to produce modified salinity tolerance plant [10]. Plants growth and development are influenced by salt stress, as it inhibits the absorption of essential nutrients and compounds, which is compulsory for plant growth, due to an accumulation of toxic ions like Na + and Cl - [11]. Different crops have been investigated to have different level of salt tolerance and if the salt level is increased in soil solution that might cause high osmotic potential and thus also increase its ion toxicity. Primitive found that both antagonistic and synergistic interaction cause nutrient absorption problems and plant growth might be decreased when it's exposed to salt containing growth media because it decreases uptake of an essential nutrient [13].

Materials and methods Plants material and methods
The experiment was conducted at the Botanical Garden University of Baluchistan. Two different genotypes (YAQUI and Prince F1) seedswere bought from the local market in Quetta. These varieties of tomato are often cultivated in Baluchistan.

Sowing of seeds
Seeds were sown in water for 24 hours before germination. 150 seeds of each genotype were implanted into the soil for germination. Seeds were irrigated every third day. Maximum of 14 and a minimum of 12 hours sunlight provided to seeds regularly. Healthy and flourishing seedling were selected for the experiment.

Shifting of seedling to pots
After 45 days of seeds germination the seedlings were shifted to pots. Size of a pot in diameter ranged from 12cm to 16cm in height. At that stage, the height of the seedling were measured using scale. The data collected from the seedling height shown no significant difference among groups. Four groups of each genotype were arranged in the experiment and each group treated with different levels of salt concentration (T0=0.0M, T2=0.1M, T3=0.2, T4=0.3M) respectively. Three replicates of each treatment were used in the experiment. The pots were irrigated every day. Plants were exposed to natural light in between 12 to 14 hours each day. Parameters examine in the experiment Parameters of plant growth were measured at continuous and various stages of the experiment. As mention earlier that seedling height was measured at the time of transformation to pots and the fresh weight of plants was calculated just after harvesting. The parameters measured were as under:

Statistical analysis
For statistical interpretation, SPSS software was utilized. Two Way Analysis implemented to check variation within treatments and between varieties of tomato plant. The value of significance was considered as α<0.05. or p<0.05.Completely Randomized Design (CRD) was performed, with 3 replicationsand each pot contain one tomato seedling and one plant per replicate in group.

Seedling height
Data analysis has shown that there is no significant difference (p > 0.05) in the seedling height of the plants. Both independent variable salt stress and genotypes (YAQUI, Prince F1) possess almost the same height when exposed to an identical environment. Table 1 displays the evidence that the p-value of salt stress among the treatments is 0.995 which is higher than 0.05, thus it confirms there is no significant difference in seedling height among the treatments in both varieties. And if we concentrate on the column "Varieties salt stress" we find the same result no significant variation. The estimated significant value displayed in table 1 is (0.995 and 0.937) for genotypes or within varieties respectively, which is greater than (p >0.05) evidence that there is no significant variation in the seedling height of the tomato plant at that degree. Table 2 refines two different outcomes of two different independent variables (salt treatments and genotypes).

Salt stress
In table 2 significant value of salt stress is 0.000 which is less than 0.05, which suggests that treatment among the groups show significant variation. Different level of salt treatments is adversely affecting the number of flowers. It has been reported that salinity affect flowering more than any other parameter of plant growth [14].
As we move from the control group (To) towards higher levels of salt concentration, we found that salt stress is decreasing the number of plants per plant that ultimately reducing the average of the flowers in each group. If we review in table 2, we find a significant difference among the growth rate of tomato flowers, that result confers that salinity greatly reduces the flowering rate of the tomato plant. So we can presume that the salinity reduces the flower growth in the tomato plant.

Number of flowers of tomato plants
There is no sign of variation among the salt genotypes or varieties, which determines both of the varieties affected equally from salt stress in a completely randomized design (CRD) experiment (Table 2).

Leaf area index
Tomato plant leaf area index is greatly influenced by salt stress.

Biomass
Just after harvesting plants were reserved in bags to ensure no loss of data. Later biomass of each plant of both varieties (YAQUI and Prince F1) was collected. To obtain biomass plants were incubated in the oven at 65 centigrade for 15 minutes to remove the water content from plants. Later every plant weight was calculated with an electrical balance in gram (g). Demonstrated data shown in table.8 strongly suggest that there is a significant difference within the groups, the outcome of data analyzed display a result of 0.03 which indicates the chance of similarity among the treatments in each variety is only 3%. If we examine the result in Table 3, we can see the reduction of biomass when the salt treatments are increased. Confirms that salinity adversely affects the dry weight of the tomato plant. Previous study also found that salinity reduce biomass of tomato plant. Plant like L. peruvianum and L. pennellii when exposed to a different level of salt stress produce a decrease in root biomass [25]. Table 8 also elaborate that there is no significant variation in the second independent variable of the experiment, which is in between genotypes of tomato, Table.8 shows a value of 0,469 greater than 0.05. Verifying that salt stress affects the biomass of both varieties uniformly. Based on our experimental data we can estimate there is a reduction in tomato biomass with an increase in salt levels both in YAQUI and Prince F1 varieties. But there is no significant difference between the genotypes which justified that the salt treatments influence both varieties (YAQUI and Prince F1) correspondingly.

Discussion
The effect of salt stress on the growth parameters of tomato was investigated. Salinity not only influenced the fruits yield of tomato plants but all other parameters. It is noticed in (Table 1)