Study on the effect of hydrogel and chitosan on the growth and productivity of wheat under drought condition

Wheat is the most important stable diet for more than one third of the world population and contributes more calories and protein to the world diet than any other cereal crops (Abd-El-Haleem et al ., 2009). Water is one of the most important factors which contribute significantly to the growth and productivity of a crop. Water stress causes a decline in relative water content, chlorophyll and carotenoid content, membrane stability and nitrate reductase activity and increases accumulation of abscisic acid, proline (Chandrasekar et al ., 2000), soluble sugar (Kameli and Loesel, 1993) and leaf and canopy temperature (Siddique et al ., 2000). Due to raise in world temperature soil losses it’s moisture holding capacity as a result drought effect is accelerated. For wheat cultivation, efficient irrigation is an important criterion because of its growing season (October to April) relatively dry. For high wheat yield, water requirement of this crop is 450 to 650 mm depending upon soil type, climatic conditions and length of growing period (Balasubramaniyan and Palaniappan, 2001). Wheat responses to water stress from stem elongation to booting, followed by anthesis and grain-filling stages. Hussein and Samia (2004), El-Afandy (2006) and Fang et al., (2006) found that wheat plants subjected to drought stress resulted in a significant reduction in grain yield.

Bangladesh, increasing the wheat production in per unit area is the most important national objective for minimizing the gap between the production and consumption. That could be achieved by improving agricultural practices; especially, ameliorating drought conditions in rainfed areas. The production of any crop can be improved by i) increasing area under crop, which is not expected to expand, ii) increasing the productivity through efficient input management along with varietal improvement, ii) increasing the productivity by reducing the losses caused by various pests and diseases and iv) improving water use efficiency of the crop.

The one of the most recent concept for conserving moisture in field is application of hydrogel. Hydrophilic gels or “hydrogels” which are commonly known as super absorbents may be used to improve the quantity of available moisture in the root zone, thus increasing the duration between irrigations (Junping et al. 2006).

Hydrogels are cross linked polymers that can absorb 400 to 1500 times their dry weight in water (Peterson 2002), thereby acquiring the name “super absorbents”. The use of hydrogels led to the significant decrease in the number of irrigations, especially for the soils with large-scale texture (Abedi-koupai and Sohrab, 2004). The hydrogel amendment was effective in improving soil moisture availability and thus increased plant establishment (Akhter et al., 2004). Grain yield, nutrient uptake and water-use efficiency improved in winter wheat when hydrogel was applied at the rate of 5 kg ha^-1 in a sandy loam soil (Tyagi et al., 2015), while in a clay loam soil with the same dose of hydrogel application along with recommended dose of fertilizer 8.48% increase in yield was observed (Borivoj et al., 2006).

Anti-transpirant is a chemical compound whose role is to train plants by gradually hardening them to stress and is involved in increasing drought stress resistances (Pandey et al., 2017). Bittelli et al,. (2001) reported that occasional or episodic drought events can be counteracted through the use of anti-transpirants, compounds applied to foliage to limit the water loss. Recently, chitosan has been one of the most preferred biopolymers due to its biocompatibility, antioxidant, anticancer, biodegradability, antimicrobial, and non-toxic properties as well as being an economical material and compatible with various stresses such as drought stress (Dzung et al., 2011). Beneficial roles of chitosan in enhancing tolerance of plants to biotic and abiotic stresses and its relevance to agriculture have been described (Farouk et al., 2011; Farouk and Amany, 2012). Gornik et al. (2008) reported that application of chitosan increased key enzymes (nitrate reductase, glutamine synthetase and protease) activities of nitrogen metabolism and improved the transportation of nitrogen in the functional leaves which enhanced plant growth and development. Foliar sprays of chitosan markedly increase all growth parameters and relative leaf water content and may reduce transpiration (Ahmed, 2014).

Research works on hydrogel and chitosan on improvement of drought tolerance of wheat in Bangladesh is very limited. Considering the above facts, the present research work was undertaken to study the effect of hydrogel and chitosan on improving tolerance capacity of wheat under drought condition.

MATERIALS AND METHODS

The experiment was conducted at the research farm of Crop Physiology and Ecology Department, Hajee Mohammad Danesh Science and Technology U niversity, Dinajpur, Bangladesh and located at 25º39′ N latitude and 88º41′ E longitude with an elevation of 37.58 meter above the sea level. The experiment was carried out in Split Plot Design with three replications. The unit plot size was 2m×1.5m having a plot to plot and block to block distance of 0.75 and 1m, respectively. There were thirty plots. Five growing conditions were set up in the main plots and two wheat varieties were set up in the sub plots. The experiment treatments were-

• A.    Main plot treatments: Five treatments

T 1 : Well water condition (Three irrigation levels)

T 2 : Water stress condition (No irrigation after germination)

T 3 : Soil application of hydrogel (5 kg ha^-1) under water stress condion.

T 4 : Foliar application of chitosan (90 ppm) under water stress condion.

T 5 : Combined application of hydrogel (5 kg ha^-1) and chitosan (90ppm) under water stress condion.

• B.    Sub-plot treatments: Two wheat varieties: Shatabdi and BAR Gom-28

The recommended production technology of wheat developed by Bangladesh Wheat and Maize Research nstitute, Dinajpur was followed. Well-watered plots was irrigated three times (at 25, 55 and 75 days after sowing) but the remaining plots (water stressed) will not be irrigated (after germination) throughout the growing period and the crop was protected from rainfall by taking plastic covering before raining to maintain water deficit stress condition.

Application of hydrogel: The required amount of hydrogel (5 kg ha^-1) was mixed with sand and applied by hands in lines in the respective plots just before sowing.

Preparation and application of chitosan: 1 g of the chitosan was solubilized in 1% acetic acid. Then, 100 mL distilled water was added to the above solution under constant stirring until it was completely dissolved. Next, the solution was alkalized to pH 6.0 with 1 M NaOH solution. Finally, respective dose of the chitosan (90 ppm) was prepared for the application. n order to improve the spray retention, 1% Tween 20 was mixed into the spray solution. Foliar application of anti-transpirant chitosan was done at tillering, stem elongation and booting stage by a hand sprayer until all leaves was completely wetted.

Data collection: Data were recorded on different phonological traits, yield and yield attributes of wheat as follows-

Phenological stages: The following phenological stages was recorded in days when 50% plants of each plot reached a definite stage as the representative of that stage. i. Seedling emergence, ii. Tillering, iii. Booting, iv. Heading, v. Anthesis, vi. Physiological maturity and vii. Harvest maturity.

Plant height, yield and yield contributing attributes: At harvest the following attributes related to Plant height, yield and yield contributing attributes were measured from five selected plants and average values were calculated - i. Plant height (cm), ii Spike length (cm), iii. Number of spikes plant^-1, iv. Number of spikelets spike^-1, v. Number of grains spike^-1, vi. Thousand grain weight (g), vii. Biological yield (t ha^-1), viii. Grain yield (t ha^-1) and ix. Harvest ndex (%).

Statistical analysis: The collected data were analyzed by partitioning the total variance using Statistix 10.0 program and the treatment means were compared using Tukey’s test.

RESULTS AND DISCUSSION

This chapter includes the presentation and possible discussion of the results obtained from the study. The results on different growth and yield contributing traits of wheat and analysis of the variance of data obtained from the present study have been presented in several tables and appendices with adequate discussion and possible interpretations.

Phenological traits (days)

Phenology of two wheat variety at different growing conditions is shown in (Table 1.) Results reveal that the phenology was not significantly influenced by the interaction effect of varieties and growing conditions except physiological maturity. For each variety, a definite days was required to attain certain phenological stages of growth. At well water condition, Shatabdi required for seedling emergence, tillering, booting, heading, anthesis, physiological maturity and harvest maturity (5.33, 20, 54, 66, 76, 112.33 and 122.67 days, respectively), whereas BAR Gom-28 required (5.66, 19, 55, 66.33, 76.66, 114.33 and 123.33 days, respectively). At water stress condition, Shatabdi required for seedling emergence, tillering, booting, heading, anthesis, physiological maturity and harvest maturity (6, 18, 50, 65.66, 72, 108 and 120 days, respectively), whereas BAR Gom required (5.66, 18, 50, 65, 71, 109 and 118.67 days, respectively).

n water stress condition, Shatabdi and BAR Gom-28 attained tillering, booting, heading, anthesis, physiological maturity and harvest maturity earlier than well water condition. n the treatment of soil application of hydrogel, Shatabdi required for seedling emergence, tillering, booting, heading, anthesis, physiological maturity and harvest maturity (5.66, 20, 52, 64, 74.33, 112 and 122 days, respectively), whereas BAR Gom-28 required (5.66, 21, 51.66, 64.66, 74, 110 and 119.67 days, respectively). n the treatment of soil application of hydrogel required more days for tillering, booting, heading, anthesis, physiological maturity and harvest maturity in Shatabdi and BAR Gom-28 from water stress condition.

n the treatment of foliar application of chitosan, Shatabdi required for seedling emergence, tillering, booting, heading, anthesis, physiological maturity and harvest maturity (5.33, 20.66, 52, 64, 72.33, 110 and 121.67 days, respectively), whereas BAR Gom-28 required (5.66, 19.33, 50, 64.66, 72, 109 and 119.33 days, respectively). n the treatment of combined application of hydrogel and chitosan, Shatabdi required for seedling emergence, tillering, booting, heading, anthesis, physiological maturity and harvest maturity (5.33, 20.66, 52, 64, 76, 113 and 122.33 days, respectively), whereas BAR Gom-28 (6, 20, 52.66, 65.66, 76, 113 and 120.33 days, respectively). n this treatment, Shatabdi and BAR Gom required more days for tillering, booting, heading, anthesis, physiological maturity and harvest maturity from water stress but less days from well water condition. n principle, the length of growing period and phenological development of crops can affect the yield either by consuming more resources or by decreasing the environmental tensions or by reducing the length of the periods (Attarbashi et al., 2002). The plants strive to complete their life cycle as early as possible to cope with drought stress conditions. Therefore, days required to initiate heading or flowering in wheat are generally decreased due to early start of reproductive stage (Riaz, 2003).

Plant height, yield and yield contributing attributes

Plant height (cm): Plant height of wheat at harvest was significantly (P<0.05) influenced by the interaction effect of varieties and growing conditions (Table 2). The maximum plant height (97.82 cm) was obtained in BAR Gom-28 under well water condition, whereas the minimum plant height (94.16 cm) was observed in Shatabdi under non-irrigated water stress condition. Non-irrigated water stress reduced the plant height by 3.58% in Shatabdi and 3.23% in BAR Gom-28. Under non-irrigated water stress condition foliar application of chitosan and soil application of hydrogel improved the plant height of wheat. Soil application of hydrogel improved the plant height of wheat by 1.28% in Shatabdi and 1.03 % in BAR Gom-28. Foliar application of chitosan improved the plant height of wheat by 0.75% in Shatabdi and 0.64% in BAR Gom-28. Combined application of hydrogel and chitosan improved the plant height of wheat by 3.07% in Shatabdi and 2.24% in BAR Gom-28. Plant height was decreased under water deficit condition and it might be due to dehydration of protoplasm, decrease in relative turgidity associated with turgor loss and decreased cell expansion and cell division. Drought is the most devastating abiotic stress factor, affecting growth and yield of various crops. Among the other environmental stresses, it is by far adversely reducing the crop productivity (Pennisi, 2008; Farooq et al., 2008). Pusa hydrogel have been reported to increase the activity of cell division, cell expansion and cell elongation, ultimately leading to an increased plant height (Singh, 2015). Similar results have been reported by Kumaran et al. (2001) in tomato.

Number of spikes plant-1: The interaction effect of varieties and growing conditions was not significant on number of spikes plant-1 of wheat (Table 2). The maximum number of spikes plant-1 (6.21) was found in BAR Gom-28 under well water condition, whereas the minimum number of spikes plant-1 of wheat (3.44) was found in Shatabdi under non-irrigated water stress condition. Non-irrigated water stress reduced the spikes number plant-1 of wheat in two wheat varieties at different magnitude (40.38% in Shatabdi and 39.30% in BAR Gom-28). Under nonirrigated water stress condition foliar application of chitosan and soil application of hydrogel improved the number of spikes plant-1 of wheat. Soil application of hydrogel improved the number of spikes plant-1 of wheat by 29.06% in Shatabdi and 20.68% in BAR Gom-28. Foliar application of chitosan improved the number of spikes plant-1 of wheat by 37.20% in Shatabdi and 15.11% in BAR Gom-28. Combined application of hydrogel and chitosan improved the number of spikes per plant of wheat by 56.97% in Shatabdi and 44.82% in BAR Gom-28. Baque et al., (2006) have reported that water stress at tillering or at booting significantly affected the formation of tillers in wheat.

Spike length (cm): Spike length of wheat was significantly (P<0.01) influenced by the combined effect of varieties and growing conditions (Table 2). The longest spike of wheat (10.67cm) was observed Shatabdi, whereas the minimum spike length (8.5cm) was observed in BAR Gom-28 under non-irrigated water stress condition. Non-irrigated water stress reduced the spike length of wheat in two wheat varieties at different magnitude (11.62% in Shatabdi and 14.82% in BAR Gom-28). Under non-irrigated water stress condition soil application of hydrogel and foliar application of chitosan improved the spike length of wheat. Soil application of hydrogel improved the spike length of wheat by 4.34% in Shatabdi and 12.23% in BAR Gom-28. Foliar application of chitosan improved the spike length of wheat by 3.49% in Shatabdi and 11.41% in BAR Gom-28. Combined application of hydrogel and chitosan improved the spike length of wheat by 11.55% in Shatabdi and 14.94% in BAR Gom-28. Water deficit stress negatively affected both vegetative and reproductive growth of wheat plant. Reduction in vegetative growth results in reduced ear length which ultimately reduced grain yield. The decrease in stem height and ear length due to water stress has been reported earlier in wheat ( qbal et al., 1999). Water stress during vegetative and reproductive development had an equal suppressive effect on number of spikelet per spike in wheat varieties (Qadir et al., 1999).

Number of spikelets spike-1: Number of spikelets spike-1 of wheat significantly varied (P<0.05) of varieties and growing conditions (Table 3). The maximum number of spikelets spike-1 of wheat (21.21) was observed in Shatabdi under well water condition, whereas the minimum number of spikelets spike-1 (17.88) was observed in BAR Gom-28 under non-irrigated water stress condition. Non-irrigated water stress reduced the number of spikelets spike-1 of wheat in two wheat varieties at different magnitude (14.09% in Shatabdi and 10.51% in BAR Gom-28. Under non-irrigated water stress condition soil application of hydrogel and foliar application of chitosan improved the number of spikelets spike-1of wheat. Soil application of hydrogel improved the number of spikelets spike-1 of wheat by 6.53% in Shatabdi and 3.74% in BAR Gom-28. Foliar application of chitosan improved the number of spikelets per spike of wheat by 2.62% in shatabdi and 2.52% in BAR Gom-28. Combined application of hydrogel and chitosan improved the number of spikelets spike-1 of wheat by 14.6% in Shatabdi and 8.73% in BAR Gom-28. Water deficit stress significantly reduced spike length results in less number of spikelets spike-1.

Number of grains spike-1: Number of grains spike-1 of wheat significantly varied (P<0.05) of varieties and growing conditions (Table 3). The maximum number of grains spike-1 (47.77) was observed in BAR Gom-28 under well water condition, whereas the minimum number of grains spike-1 (40.33) was observed in Shatabdi under non-irrigated water stress condition. Non-irrigated water stress reduced the number of grains spike-1in two wheat varieties at different magnitude (8.77% in Shatabdi and 4.87% in BAR Gom-28). Soil application of hydrogel and foliar application of chitosan improved the number of grains spike-1 under non-irrigated water stress condition. Soil application of hydrogel improved the number of grains spike-1 by 5.50% in Shatabdi and 1.93% in BAR Gom-28. Foliar application of chitosan improved the number of grains spike-1 of wheat by 3.30% in Shatabdi and 1.18% in BAR Gom-28. Combined application of hydrogel and chitosan improved the number of grains spike-1 by 6.86% in Shatabdi and 3.90% in BAR Gom-28. Drought stress at flowering or grain filling stage adversely affected the plant production by causing drastic decrease in number of grains per spike. The decrease in number of grains per spike under water stress condition might be due to reduced root growth about the time of spike formation that resulted in reduced nutrient uptake. Richards et al. (2001) also reported that the numbers of grains per spike were decreased adversely under water stress in wheat that supporting the present investigation. Water stress limits seed numbers by either influencing the amount of dry matter produced by the time of flowering or by directly influencing pollen or ovule function, which leads to decreased seed set (Prasad et al., 2008).

Thousand grain weight (g): Thousand grain weight of wheat was not significantly influenced by the combined effect of varieties and growing conditions (Table 3). The maximum thousand grain weight of wheat (47.06 g) was observed in BAR Gom-28 under well water condition, whereas the minimum thousand grain weight of wheat (40.30 g) was found in Shatabdi under non-irrigated water stress condition. Non-irrigated water stress reduced the thousand grain weight of wheat in two wheat varieties at different magnitude (13.14% in Shatabdi and 10.32% in BAR Gom-28). Soil application of hydrogel and foliar application improved the thousand grain weight of wheat under non-irrigated water stress condition. Soil application of hydrogel improved the thousand grain weight of wheat by 7.20% in Shatabdi and 6.87% in BAR Gom-28. Foliar application of chitosan improved the thousand grain weight of wheat by 4.46% in Shatabdi and 4.73% in BAR Gom-28.

Combined application of hydrogel and chitosan improved in thousand grain weight of wheat by 9.68% in Shatabdi and 9.47% in BAR Gom-28. Decreased thousand grain weight under drought was due to less efficient and disturbed nutrient uptake and limited photosynthetic translation within the plant which hastened maturity and producing shriveled kernels. Due to water stress at heading reduced weight of thousand grains was reported by Royo et al. (2000). Khan et al. (2005) and Qadir et al. (1999) who observed that 1000-grain weight of wheat was reduced mainly due to increasing water stress.

Biological yield (t ha-1): Biological yield of wheat was significantly (P <0.05) influenced by the interaction effect of varieties and growing conditions (Table 4). The maximum biological yield of wheat (11.45 t ha-1) was recorded for Shatabdi under well water condition, whereas the minimum biological yield (9.26 t ha-1) was recorded both in Shatabdi and BAR Gom-28 under non-irrigated water stress condition. Non-irrigated water stress reduced the biological yield of wheat in two wheat varieties by 19.12% in Shatabdi and 12.31% in BAR Gom-28. Soil application of hydrogel and foliar application of chitosan improved the biological yield under non-irrigated water stress condition. Soil application of hydrogel improved the biological yield of wheat by 4.31% in Shatabdi and 1.72% in BAR Gom-28 under non-irrigated water stress condition. Foliar application of chitosan improved the biological yield of wheat by 3.68% in Shatabdi and 2.60% in BAR Gom-28. Combined application of hydrogel and chitosan improved the biological yield of wheat by 10.58% in Shatabdi and 6.47% in BAR Gom-28. Due to water shortage, the ability of absorbing nutrients, composing and transferring assimilate is decreased that leads to a reduction in biological yield. The results of many researches show that drought stress at different stages of the growth of wheat lead to a reduction in the yield of biomass, grain yield, harvest index and grain yield components of wheat (Gooding et al., 2003), (Garcia et al., 2003), and (Zaharieva et al., 2001).

Grain yield (t ha^-1): nteraction effect of varieties and growing conditions significantly interacted (P<0.01) grain yield of wheat (Table 4). BAR Gom-28 produced the maximum grain yield (5.23 t ha^-1) under well water condition and the minimum grain yield (2.42 t ha^-1) was observed in Shatabdi under non-irrigated water stress condition. Non-irrigated water stress reduced the grain yield of wheat in two wheat varieties at different magnitude (47.95% in Shatabdi and 46.08% in BAR Gom-28).

Under non-irrigated water stress condition soil application of hydrogel and foliar application of chitosan improved the grain yield of wheat. Combined application of hydrogel and chitosan improved the grain yield of wheat by 81.81% in Shatabdi and 75.88% in BAR Gom-28. Soil application of hydrogel improved the grain yield of wheat by 48.76% in Shatabdi and 38.29% in BAR Gom-28. Foliar application of chitosan improved the grain yield of wheat by 27.68% in Shatabdi and 32.62% in BAR Gom-28.

Droughts stress either at vegetative or flowering stage considerably decreased grain yield and yield components in wheat (Anjum et al. 2011). This decrease was due to reduced production of photosynthates under water deficit conditions (Anjum et al. 2003, Wahid and Rasul 2005). Soil addition of hydrogel to Valencia orange trees increased total yield and implement fruit characters, also, mixing soil with hydrogel loaded fertilizers improving the growth of Zea mays plant (Elbarbary and Ghobashy, 2017).

Harvest Index (%): Harvest index of wheat significantly varied (P<0.05) due to interaction effect of varieties and growing conditions (Table 4). The maximum harvest index of wheat (48.80%) was recorded from BAR Gom-28 under well water condition, whereas the lowest harvest index (25.47%) was recorded in Shatabdi under non-irrigated water stress condition. Non-irrigated water stress reduced the harvest index in two wheat varieties by 34.70% in Shatabdi and 37.37% in BAR Gom-28. Soil application of hydrogel and foliar application of chitosan improved the harvest index under non-irrigated water stress condition. Soil application of hydrogel improved the harvest index of wheat by 38.62% in Shatabdi and 32.13% in BAR Gom-28 under non-irrigated water stress condition. Foliar application of chitosan improved the biological yield of wheat by 23.28% in Shatabdi and 35.27% in BAR Gom-28. Combined application of hydrogel and chitosan improved the harvest index of wheat by 48.60% in Shatabdi and 53.37% in BAR Gom-28. Harvest index will decrease in the treatments under drought stress due to the effect of drought stress on grain yield (Gebeyehu, 2006).

Due to water shortage, the ability of absorbing nutrients, composing and transferring assimilate is decreased that leads to a reduction in biological yield (Kisman, 2003). The results of many researches show that drought stress at different stages of the growth of wheat lead to a reduction in the yield of biomass, grain yield, harvest index and grain yield components of wheat (Gooding et al ., 2003), (Garcia et al ., 2003) and (Zaharieva et al ., 2001).

Table 1. nteraction effect of varieties and growing conditions on phenological stages

Variety	Growing condition	Seedling emergence	Tillering	Booting	Heading	Anthesis	Physiological maturity	Harvest maturity
Shatabdi	Well water	5.33	20	54	66	76	112.33ab	122.67
	Water stress	6	18	50	65.66	72	108d	120
	Soil application of hydrogel	5.66	20	52	64	74.33	112abc	122
	Foliar application of chitosan	5.33	20.66	52	64	72.33	110bcd	121.67
	Combind application of hydrogel +chitosan	5.33	20.66	52	64	76	113ab	122.33
BAR Gom-28	Well water	5.66	19	55	66.33	76.66	114.33a	123.33
	Water stress	5.66	18	50	65	71	109cd	118.67
	Soil application of hydrogel	5.66	21	51.66	64.66	74	110bcd	119.67
	Foliar application of chitosan	5.66	19.33	50	64.66	72	109cd	119.33
	Combind application of hydrogel +chitosan	6	20	52.66	65.66	76	113ab	120.33
Level of Significance		NS	NS	NS	NS	NS	*	NS
CV (%)		14.13	5.0	1.79	1.35	1.21	0.85	1.02

Values followed by same letter(s) did not differ significantly at 5% level of probability NS Not significant. *Significant at 5% level of probability.

Table 2. nteraction effect of varieties and growing conditions on plant height, Number of spikes plant-1 and Spike length of wheat at harvest

Wheat varieties	Growing conditions	Plant height (cm)	Number of spikes plant-1	Spike length (cm)
Shatabdi	Well water (WW)	97.66a	5.77	10.67a
	Water stress (WS) (Change over WW (%)	94.16b (-3.58)	3.44 (-40.38)	9.43ab (-11.62)
	Soil application of hydrogel (Change over WS (%)	95.36ab (1.28)	4.44 (29.06)	9.84a (4.34)
	Foliar application of chitosan (Change over WS (%)	94.83ab (0.75)	4.27 (37.20)	9.76ab (3.49)
	Combined application of hydrogel + chitosan (Change over WS (%)	96.06ab	5.4 (56.97)	10.52a (11.55)
BAR Gom-28	Well water	97.82a	6.21	9.98a
	Water stress (Change over WW (%)	94.66b (-3.23)	3.77 (-39.30)	8.5b (-14.82)
	Soil application of hydrogel (Change over WS (%)	95.63ab (1.03)	4.55 (20.68)	9.54ab (12.23)
	Foliar application of chitosan (Change over WS (%)	95.26ab (0.64)	4.34 (15.11)	9.47ab (11.41)
	Combined application of hydrogel + chitosan (Change over WS (%)	96.96ab (2.24)	5.43 (44.82)	9.77a (14.94)
Level of significance		*	NS	**
Coefficient of variation (%)		2.85	4.41	5.71

Values followed by same letter(s) did not differ significantly at 5% level of probability. *Significant at 5% level of probability. Values in parenthesis indicate % improvement from water stress in respective variety

Table 3. nteraction effect of varieties and growing conditions on number of spikelets spike- 1, number of grains spike-1 and 1000- grain weight of wheat

Wheat varieties	Growing conditions	Number of spikelets spike-1	Number of grains spike-1	1000- grain weight (g)
Shatabdi	Well water (WW)	21.21a	44.21de	46.40
	Water stress (WS) (Change over WW (%)	18.22e (-14.09)	40.33g (-8.77)	40.30 (-13.14)
	Soil application of hydrogel (Change over WS (%)	19.44cd (6.53)	42.55f (5.50)	43.20 (7.2)
	Foliar application of chitosan (Change over WS (%)	18.88c (3.62)	41.66fg (3.30)	42.10 (4.46)
	Combined application of hydrogel + chitosan (Change over WS (%)	20.88ab (14.6)	43.10ef (6.86)	44.20 (9.68)
BAR Gom-28	Well water (WW)	19.98bc	47.77a	47.06
	Water stress (WS) (Change over WW (%)	17.88e (-10.51)	45.44cd (-4.87)	42.20 (-10.32)
	Soil application of hydrogel (Change over WS (%)	18.55de (3.74)	46.32abc (1.93)	45.10 (6.87)
	Foliar application of chitosan (Change over WS (%)	18.33e (2.52)	45.98bc (1.18)	44.20 (4.73)
	Combined application of hydrogel + chitosan (Change over WS (%)	19.44cd 8.73)	47.21ab (3.90)	46.20 (9.47)
Level of significance		*	*	NS
Coefficient of variation (%)		1.67	1.78	3.56

Values followed by same letter(s) did not differ significantly at 5% level of probability. *Significant at 5% level of probability. Values in parenthesis indicate % improvement from water stress in respective variety

Table 4. nteraction effect of varieties and growing conditions on biological yield of wheat

Wheat varieties	Growing conditions	Biological yield (t ha-1)	Grain yield (t ha-1)	Harvest index (%)
Shatabdi	Well water (WW)	11.45a	4.65bc	39.01cd
	Water stress (WS) (Change over WW (%)	9.26b (-19.12)	2.42f (-47.95)	25.47g (-34.70)
	Soil application of hydrogel (Change over WS (%)	9.66b (4.31)	3.61d (48.76)	32.76def (38.62)
	Foliar application of chitosan (Change over WS (%)	9.6b (3.68)	3.09e (27.68)	31.40efg (23.28)
	Combined application of hydrogel + chitosan (Change over WS (%)	10.24ab (10.58)	4.40c (81.81)	37.85cde (48.60)
BAR Gom-28	Well water (WW)	10.56ab	5.23a	48.80a
	Water stress (WS) (Change over WW (%)	9.26b (-12.31)	2.82ef (-46.08)	30.56fg (-37.37)
	Soil application of hydrogel (Change over WS (%)	9.42b (1.72)	3.90d (38.29)	40.38bcd (32.13)
	Foliar application of chitosan (Change over WS (%)	9.50b (2.60)	3.74d (32.62)	41.34bc (35.27)
	Combined application of hydrogel + chitosan (Change over WS (%)	9.86ab (6.47)	4.96ab (75.88)	46.87ab (53.37)
Level of significance		*	**	*
Coefficient of variation (%)		5.34	3.25	6.46

Values followed by same letter(s) did not differ significantly at 5% level of probability *Significant at 5% level of probability. Values in parenthesis indicate % improvement from water stress in respective variety

CONCLUSION

From the overall results of the present study it might be concluded that Wheat varieties (Shatabdi and BAR Gom-28) were prone to drought stress condition. Their physio-chemical, yield and yield attributes decreased from normal one (well water condition). Exogenous application of hydrogel and chitosan separately had a positive protective effect on different studied traits of wheat against drought condition. Exogenous application of both hydrogel and chitosan together showed better performance on phenological and yield parameters, result in higher grain yield (4.40 and 4.96 t ha-1 in Shatabdi and BAR Gom-28, respectively) of wheat obtained under water limiting drought environment.

CONFLICTS OF INTEREST

The authors declare that they have no potential conflicts of interest.