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RESULTS

Total proteins
The data pertaining to changes in protein concentration recorded at periodical interval of 24 hrs till a week in response to selected best doses of JA, SA and BTH i.e, at 500 µM and BABA at 50 mM, revealed statistically significant difference amongst the various elicitors applied on three different varieties of potato namely; Kufri Badshah, Kufri Jyoti, Kufri Pukhraj (Table 1). Mean maximum protein induction was observed at 500 μM of SA in Kufri Jyoti i.e. 7.3 mg/gFW followed by 6.8 mg/gFW in Kufri Badshah and 6.4 mg/gFW in Kufri Pukhraj. JA at 500 μM  proved to be second best treatment with mean maximum protein induction observed in Kufri Jyoti i.e. 7.0 mg/gFW followed by 6.4 mg/gFW in Kufri Badshah and by 6.0 mg/gFW in Kufri Pukhraj. BTH at 500 μM gave mean maximum protein induction of 5.2 mg/gFW in both Kufri Badshah, and Kufri Jyoti, whereas 4.6 mg/gFW in Kufri Pukhraj. BABA gave mean maximum protein induction of 6.0 mg/gFW at 50mM of concentration in Kufri Jyoti and 5.8 and 4.9 mg/gFW in Kufri Badshah, Kufri Pukhraj respectively. Statistically significant difference for all four elicitors w.r.t. time interval was observed. SA was found to induce mean maximum protein 8.1mg/gFW at 3rd day interval respectively followed by JA showing maximum protein 7.7 mg/gFW at 3rd day interval. BABA and BTH showed maximum protein 6.7 and 5.9 mg/gFW at 3rd day interval in Kufri Jyoti. Whereas minimum protein varied from 3.2 to 4.2 mg/gFW for control treatment between all the respective time intervals with mean value of 3.7 mg/gFW. Similar pattern was also observed  in other two varieties.

Table 1. Effect of different doses of JA, SA, BABA and BTH on leaf protein concentration (mg/gFW) potato leaves after 21 days of sowing

Total  protein content (mg /g FW)
Variety	Treatment	Days after spray							Mean
		1	2	3	4	5	6	7
Kufri Badshah	Control	2.8	3.2	3.5	3.7	3.9	3.9	3.7	3.5
	SA (500µM)	6.3	6.6	7.4	7.2	6.9	6.7	6.4	6.8
	JA(500 µM)	6.3	6.4	6.8	6.7	6.4	6.2	5.8	6.4
	BABA(50mM)	5.6	5.8	6.5	6.3	5.7	5.4	5.2	5.8
	BTH (500µM)	4.6	5.0	5.8	5.7	5.4	5.1	5.0	5.2
Kufri Jyoti	Control	3.2	3.3	3.6	3.7	4.0	4.2	4.2	3.7
	SA (500µM)	7.3	7.4	8.1	7.8	7.2	6.9	6.5	7.3
	JA(500 µM)	6.6	7.0	7.7	7.7	7.1	6.7	6.4	7.0
	BABA(50mM)	6.1	6.3	6.7	6.5	5.9	5.6	5.2	6.0
	BTH (500µM)	5.0	5.4	5.9	5.5	5.1	4.9	4.6	5.2
Kufri Pukhraj	Control	2.7	3.1	3.4	3.5	3.8	3.8	3.6	3.4
	SA (500µM)	5.6	6.1	7.2	6.9	6.4	6.2	6.0	6.4
	JA(500 µM)	6.0	6.1	6.5	6.3	5.8	5.6	5.4	6.0
	BABA(50mM)	4.5	4.8	5.5	5.2	4.9	4.7	4.6	4.9
	BTH (500µM)	4.5	4.6	5.1	4.9	4.5	4.4	4.3	4.6
CD (5%)	Variety (A)-0.028;  Elicitor (B)- 0.037; Time interval (C)-0.043 ; AB- 0.064;AC-0.075; BC-0.097; ABC- 0.16

b-1, 3 glucanase
Amongst the different elicitors treatment in Kufri Badshah;   SA caused 50 % increase in β-1, 3-glucanase activity  in leaves, whereas JA resulted in 34%, BABA gave 37% and BTH gave 43% increase in β-1, 3-glucanase activity concentration w.r.t control. Similarly, in Kufri Jyoti SA caused 57 % increase in β-1, 3 glucanase activity  in leaves, whereas JA resulted in 34%, BABA gave 26% and BTH gave 20% increase in β-1, 3 glucanase activity w.r.t control. In Kufri Pukhraj SA caused 57%  increase in β-1, 3 glucanase activity  in leaves, whereas JA resulted in 47%,  BABA gave 43% and BTH gave 47% increase in β-1, 3 glucanase activity w.r.t  control indicating that SA is better inducer of β-1, 3 glucanase activity  among all the four elicitors with maximum β-1, 3 glucanase activity in Kufri Jyoti (Fig1).
            The total β-1, 3 glucanase activity increased upto 3rd day in all three elicitors except JA were peak value observed on second day of spray and thereafter registered decline irrespective of variety and elicitor treatment.

Phenylalanine ammonia lyase (PAL)
Amongst the different elicitors treatment in Kufri Badshah;   SA caused 128 % increase in PAL activity  in leaves, whereas JA resulted in 100%, BABA gave 92% and BTH gave 72% increase in PAL activity  w.r.t  control. Similarly, in Kufri Jyoti SA caused 122% increase PAL activity in leaves, whereas JA resulted in 87%, BABA gave 86% and BTH gave 70% increase PAL activity w.r.t control. In Kufri Pukhraj SA caused 138% increase in PAL activity in leaves, whereas JA resulted in 105%, BABA gave 89% and BTH gave 76% increase in PAL activity w.r.t  control indicating that SA is better inducer of PAL activity  among all the four elicitors with maximum PAL activity in Kufri Jyoti. Statistically significant difference for all four elicitors w.r.t. time interval was observed. SA was found to induce mean maximum PAL activity 6.23 μg t-cinnamic acid/min/g FW at 4th day interval respectively followed by JA showing maximum PAL activity 5.23 μg t-cinnamic acid/min/g FW at 4th day interval (Fig 2). Peroxidase (POD)
Mean maximum peroxidase   activity was observed at 500 μM of SA in Kufri Jyoti i.e. 41.96 ΔA /min/g FW followed by 37.06 ΔA /min/g FW in Kufri Badshah and 36.16 ΔA /min/g FW in Kufri Pukhraj. JA at 500 μM  proved to be second best treatment with mean maximum peroxidase   activity observed in Kufri Jyoti i.e.36.26 ΔA /min/g FW, and 34.46 and 33.96 ΔA /min/g FW in Kufri Badshah and Kufri Pukhraj. BTH at 500 μM gave mean maximum peroxidase  activity of 31.65 and 32.10 ΔA /min/g FW in Kufri Badshah, and Kufri Jyoti, whereas 30.5 ΔA /min/g FW in Kufri Pukhraj. BABA gave mean maximum peroxidase   activity of 33.26 and 32.16 ΔA /min/g FW at 50mM of concentration in Kufri Jyoti and Kufri Badshah and 32.06 ΔA /min/g FW in, Kufri Pukhraj respectively (Fig 3). The total peroxidase activity increased upto 3rd day in all four elicitors and thereafter registered decline irrespective of variety and elicitor treatment. In general, 500 µM SA resulted in higher mean peroxidase   activity followed by JA followed by BABA and then BTH. Tolerant variety, Kufri Jyoti showed better peroxidase activity followed by Kufri Badshah and Kufri Pukhraj. BABA and BTH treatments were at par w.r.t. peroxidase  activity in all the three varieties.

Polyphenol oxidase (PPO)
Statistically significant difference for all four elicitors w.r.t. time interval was observed. JA was found to induce mean maximum PPO   activity 0.55 ΔA /min/g FW at 4TH day interval respectively followed by SA showing maximum PPO  activity 0.54 ΔA /min/g FW at 4TH day interval. BABA and BTH showed maximum PPO   activity 0.51 and 0.50 ΔA /min/g FW at 4TH day interval in Kufri Jyoti. Whereas minimum PPO activity  varied from 0.22 to 0.27 ΔA /min/g FW for control treatment between all the respective time intervals with mean value of 0.25 ΔA /min/g FW. Similar pattern were also observed in other two varieties. The total PPO activity increased upto 4TH day in all four elicitors and thereafter registered decline irrespective of variety and elicitor treatment. In general, 500 µM JA resulted in higher mean PPO   activity followed by SA followed by BABA and then BTH. Kufri Jyoti showed better PPO activity followed by Kufri Badshah and Kufri Pukhraj (Fig 4).
Spike in protein content in control samples was also observed because proteins (enzymes, Pr proteins etc) increase in plants on basis of age upto 30-60 days depending upon crop and variety. This daily change especially on micro molar level (biochemically) is also controlled by environmental conditions but control plants do not show peaks as in case of primed (elicitor treated) plants.

Total chlorophyll
Amongst the different elicitors treatment in Kufri Badshah;   SA caused 6% increase in total chlorophyll (mg/ g FW) in leaves, whereas JA resulted in 3% decrease, BABA gave 4% and BTH gave 2% increase in total chlorophyll (mg/ g FW) w.r.t control. Similarly, in Kufri Jyoti SA caused 13% increase in total chlorophyll (mg/ g FW) in leaves, whereas JA resulted in 1% decrease, BABA gave 12% and BTH gave 8% increase in total chlorophyll (mg/ g FW) w.r.t control. In Kufri Pukhraj SA caused 13% increase in total chlorophyll (mg/ g FW)  in leaves, whereas JA resulted in decrease of 1%,  BABA gave 11% and BTH gave 10% increase in total chlorophyll (mg/ g FW)  w.r.t  control indicating that  SA is better inducer of total chlorophyll among all the four elicitors with maximum content in Kufri Jyoti. It was observed that the chlorophyll content decrease on treatment with JA in foliar application, even though control values were at par with 500µM JA treated samples (Table 2).

Table 2: Effect of foliar spray with different elicitors i.e.  SA, JA, BABA and BTH on total chlorophyll (mg/gFW) in leaves of different potato varieties

Total chlorophyll (mg/gFW)
Variety	Treatment	Days After Spray							Mean
		1	2	3	4	5	6	7
Kufri Badshah	Control	1.33	1.35	1.36	1.37	1.39	1.40	1.42	1.38
	SA (500µM)	1.42	1.44	1.45	1.46	1.48	1.49	1.51	1.47
	JA(500 µM)	1.28	1.30	1.31	1.32	1.34	1.35	1.37	1.33
	BABA(50mM)	1.40	1.42	1.43	1.44	1.46	1.47	1.48	1.44
	BTH (500µM)	1.38	1.40	1.41	1.42	1.44	1.45	1.46	1.42
Kufri Jyoti	control	1.35	1.37	1.37	1.39	1.39	1.41	1.43	1.39
	SA (500µM)	1.53	1.55	1.58	1.66	1.63	1.57	1.57	1.58
	JA(500 µM)	1.31	1.33	1.39	1.41	1.41	1.40	1.39	1.38
	BABA(50mM)	1.50	1.52	1.56	1.64	1.60	1.55	1.55	1.56
	BTH (500µM)	1.46	1.48	1.51	1.59	1.56	1.50	1.50	1.51
Kufri Pukhraj	Control	1.35	1.37	1.37	1.37	1.38	1.39	1.40	1.38
	SA (500µM)	1.50	1.52	1.56	1.64	1.60	1.55	1.55	1.56
	JA(500 µM)	1.32	1.31	1.42	1.39	1.38	1.36	1.35	1.36
	BABA(50mM)	1.48	1.50	1.54	1.61	1.58	1.53	1.53	1.54
	BTH (500µM)	1.47	1.49	1.52	1.60	1.57	1.51	1.51	1.52
CD (5%)	Variety (A)-0.0021;  Elicitor (B)- 0.0028; Time interval (C)-0.0033 ; AB- 0.0049; AC-0.0058;  BC-0.0075; ABC- 0.013

Carotenoids
The data pertaining to changes in leaf carotenoids (mg/ g FW)  in response to various doses of JA, SA and BTH i.e., at 500 µM and BABA at 50 mM, revealed statistically significant difference amongst the various elicitors applied on three different varieties of potato namely; Kufri Badshah, Kufri Jyoti, Kufri Pukhraj (Fig 5).Amongst the different elicitors treatment in Kufri Badshah; SA caused 106% increase in carotenoids (mg/ g FW)  in leaves, whereas JA resulted in 131% increase, BABA gave 87% and BTH gave 100% increase in carotenoids (mg/ g FW)  w.r.t control. Similarly, in Kufri Jyoti SA treatment resulted in 131% increase in carotenoids (mg/ g FW)  in leaves, whereas JA resulted in 137%, BABA gave 112% and BTH gave 106% increase in carotenoids (mg/ g FW)  w.r.t control. In Kufri Pukhraj SA treatment resulted in 126% increase in carotenoids (mg/ g FW)  in leaves, whereas JA resulted in increase of 120%,  BABA in 113% and BTH in 100% increase in carotenoids (mg/ g FW)  w.r.t  control indicating that  JA is better inducer of carotenoids among all the four elicitors with maximum content in Kufri Jyoti followed by Kufri Badshah and Kufri Pukhraj.  It was observed that the carotenoids content showed peak on 4th day of treatment in all the tested elicitors.Electrophoretic study (SDS- PAGE)  protein extract of different potato
The potato leaf proteins extracts were subjected to SDS-PAGE electrophoresis. Total soluble leaf protein was resolved with standard protein marker ladder with molecular weights ranging from 6-180 kDa for reference. Specific bands lying in the range of 6-50 KDa were observed in treated samples as compared to their respective control (Plate 1). In gel figure bands  in range of  PR-2 family  i.e. Beta-1,3-glucanases having hydrolytic enzyme activity on fungal cell wall lying in range of molecular weight of 25-35kDa, Antifungal PR-1 family having molecular weight of  14-17kd, and peroxidises (PR-9 family) lying in range of 35-45 kDa band can be seen. Thus indicating induction of PR-protein which induced defense against late blight of potato against P. infestans.Disease data   
Testing of SAR inducers in various combination treatments was done to have better disease control. As replacement of contact fungicide i.e only selected doses of SA, JA, BTH and BABA were used for disease control then in combination of half recommended dose contact fungicide, i.e. & Mancozeb 75 % WP (Indofil M-45) @ 350 g per acre was also done.  Selected doses of SA, JA, BTH and BABA were also tested in combination with systemic fungicide i.e. Ridomil @ 350 g per acre (Half dose than recommended). First spray of treatment was done on 21 days after the sowing of crop and followed by five sprays, at intervals of seven days. After one week of elicitor treatment; plants were challenge  inoculated with disease (Table 3 ). The data on disease severity was calculated on weekly interval. All the treatments gave 100% disease control upto seven days of challenge inoculation. Per cent disease control varied from 75 % in BTH treated plots to 94 % in standard recommended fungicide treatment. Second best treatment comes out to be three sprays BABA followed by two sprays of contact fungicide Mancozeb with 92.8 % disease control. SA singly gave 82.6% disease control whereas in combination with Mancozeb and Ridomil gave 87.7 % and 92.8% respectively, which was at par with recommended fungicide control. Therefore it can be concluded that SA treatment can be combined with half dose of systemic fungicide Ridomil for late blight control in potato even for economical reasons.

Table 3: Testing efficacy of SAR elicitors along with Ridomil gold and Mancozeb against disease severity of late blight of potato

Variety	Treatment	No. of sprays	% Disease severity				% Disease control
			Days after challenge inoculation
			7	14	21	28
Kufri Pukhraj	SA	5	0	3.80	4.56	10.23	82.62
	JA	5	0	4.57	6.25	12.25	79.19
	BABA	5	0	5.20	7.45	14.36	75.61
	BTH	5	0	8.27	9.56	14.68	75.06
	SA & & Mancozeb	3+2	0	4.21	5.32	7.21	87.75
	JA & & Mancozeb	3+2	0	4.51	5.33	8.53	85.51
	BABA & Mancozeb	3+2	0	3.54	4.11	4.24	92.80
	BTH & Mancozeb	3+2	0	7.50	8.54	10.25	82.59
	SA & Ridomil Gold	3+2	0	3.50	3.53	4.56	92.25
	JA & Ridomil Gold	3+2	0	3.60	3.5	5.23	91.12
	BABA & Ridomil Gold	3+2	0	5.10	5.12	5.42	90.79
	BTH & Ridomil Gold	3+2	0	6.50	6.66	7.35	87.51
	Mancozeb & Ridomil Gold (Recommended spray schedule)	3+2	0	3.10	3.24	3.54	93.99
	Control	DDW	9.5	34.23	43.15	58.87	0.00
CD (5%)	Treatment (A)-1.03;  Time interval (B)-0.55; Interaction (AB)- 2.07

DISCUSSION

licitor treated plants have been shown to induce defense related PR-proteins in response to late blight pathogen. The present study depicted that elicitation could be a promising strategy to control late blight of potato by priming plant own defense system with SAR inducers. The results obtained in present study are corroborated with findings of Gao and Zhang (2013) who, demonstrated that SA treatment showed the best effect on disease control in pear fruit against rot as it significantly induced activities of the enzymes β-1, 3-glucanase, PAL, PPO, and POD, which are type of PR proteins. An important common feature of most PR proteins (chitinase and glucanase) is their antifungal effect, with some also exhibiting antibacterial, insecticidal, nematicidal, and antiviral action (Van Loon etal.,2006). Thaler et al. (2012) studied the influence of SA and JA against late blight of potato and studied the evolution of jasmonate and salicylate signal crosstalk. Complete control of late blight in tomato was reported with BABA, even when applied post- infection as reported by Cohen (2002). Induction of PR proteins i.e. P14a and β-1, 3-glucanase was higher in BABA-treated tomato plants as compared with control plots. Kone et al.(2009) studied in greenhouse that SA applied as soil drench or foliar spray at 25 or 50µg ml-1 significantly reduced severity of disease caused by Phytothphora capsici, compared with control. Tian et al. (2005) demonstrated that pear fruits treated with various elicitors like SA, oxalic acid, calcium chloride etc significantly enhanced defence-related proteins activities such as β,1-3 glucanase  and reduced the disease incidence of Alternaria alternata. Olivieri et al. (2009) studied biochemical mechanisms of by which BABA increase resistance against P. infestans, as well the effect of BABA on the activity of a potential pathogenic factor of Fusarium solani. Mostafa and Gado (2007) reported that the application of  ESA and JA, reduces the disease severity compared to check against late blight of potato. The study of Aldesuquy (2015) supports our study by demonstrating that in Vicia faba, SA application increases the total soluble protein content against Botryis spp. Similar, results were observed in case of, tomato plant treated with JA and SA showed higher total soluble protein and free amino acid content compared to infected control plants with Fusarium wilt (El-Khallal 2007).

Table 4: Correlation between various enzymes activity, chlorophyll, carotenoids, protein content and disease severity in different varieties of potato

Disease Severity on variety	Total protein	b-1, 3 glucanase	Pal	Peroxidase	PPO	Chlorophyll	Carotenoids
Kufri Badshah	-0.984	-0.970	-0.932	-0.911	-0.914	-0.759	-0.942
Kufri Jyoti	-0.975	-0.861	-0.919	-0.898	-0.907	-0.705	-0.976
Kufri pukhraj	-0.992	-0.994	-0.950	-0.991	-0.990	-0.647	-0.988

There are many reports available on the accumulation of chitinases and β-1, 3- glucanases and other enzymes in many plant species in response to infection by pathogens, elicitor or chemical treatment. Kim and Hwang (2014) also observed that pepper plants showing high activity of PAL enzyme were resistant to the infection of Xanthomonas campestris pv. vesicatoria. Higher activity of peroxidases and polyphenol oxidases have been reported in  early maturing germplasm of maize when challenged by banded leaf and sheath blight pathogen, R. solani (Dahima et al., 2014). Exogenous application of SA was found to enhance the net photosynthetic rate, internal CO2 concentration, water use efficiency, stomatal conductance and transpiration rate in B. juncea (Fariduddin et al., 2003).  The maximum chlorophyll content and dry weight was recorded with 0.5 mM SA and 0.25 mM MJ application; so SA treatment increased the chlorophyll and carotenoid contents in maize plants (Khodary, 2004). Our study revealed that carotenoids were further enhanced by all the elicitors treatments with maximum increase in case of JA application. This increase may be attributed to protection of plant cells from Reactive oxygen species and other oxidations factors. However, increase in PPO and PAL was higher in resistant variety than in susceptible cultivars after treatment with the SAR elicitor, indicating that defense related proteins reach an inhibitory level to the fungus in the potato plants. Increase in ß-1,3-glucanase and peroxidase activity, after treatment, was higher in SA treated plants as compared to other elicitors. There seems to be a definite role of total phenols, peroxidase and ß-1,3-glucanase in defense against  P. infestans in potato. Therefore, it can be concluded that SA treatment can be combined in spray schedule with contact fungicide or with half dose of systemic fungicide  for control of,  late blight in potato,  which will be economical and as well as environmental friendly.

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