An experiment was conducted to determination of effect of resistance inducing agents (chemicals and plant extracts) on the mineral contents of induced/un-inoculated and induced/inoculated plants with Ascochyta rabiei in three chickpea cultivar 7 and 14th day time interval. The result revealed that all the mineral content were increased after the induction of resistance but this increase was more significant (p=0.05) upon inoculation with the pathogen after 14th day time interval by the application of chemical but it was not significant in case of plant extract expect neem. Only Na content was decreased in Bion applied plant in the cultivar C-44 and Pb-98 further more Cu content was also decreased in salicylic acid, Bion and neem leaf extract treated plants in the cultivar C-44. The over all results showed that resistance induction increases the mineral both macro and micro nutrient which prevent the spread of the pathogen by strengthening host physiological and biochemical process.
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Diseases are among the major constraints in the successful production of crop through out the world (El-Khallal, 2007). Most the diseases are controlled by the application of chemicals which causes health hazards and also resistance developed in the pathogens. Plants have developed different mechanisms to defend themselves and there understanding against pathogens may lead to novel strategies to enhance disease resistance in crop plants (Pozo et al., 2005). Plant defence responses against the pathogen are regulated by a complex net work of signal molecules and transcriptional regulators. Biological control and chemical (hormonal) inducers are two of the promising approaches to the control of plant diseases (Yu and Zheng, 2006).
Chickpea (Cicer arietinum L.) is prone to several biotic and abiotic factors under the field condition which affect the production of the crop, the diseases being one of them. The chickpea blight disease, caused by Ascochyta rabiei (Pass) Labr. fungus, upsets the production statistics of the crop under environmental conditions conducive for the disease and may result in 50-70 percent crop losses (Malik and Bashir, 1984) or complete failure of the crop (Nene, 1984). The disease can be managed by some cultural practices (Sattar, 1933, Lutra & Bedi, 1935) and use of chemotherapentants (Tripathi et al., 1987; Singh and Singh, 1990) but the cultivation of cultivars resistant to blight disease is the most effective and economical practice (Nene and Reddy, 1987). The resistance of an organism is governed in many cases by biochemical metabolites and enzyme catalyzed biochemical reactions (Tanhaken and Barz, 1991) which in turn depend on the availability of certain anions, cations and enzymes (Chen and Strange, 1991). Nutrients play very important role for growth and development of plants and at the same time for microorganisms, they are considered as important factors in disease control (Agrios, 2005). The severity of the disease is affected by all the essential nutrients (Huber and Graham, 1999) and the balance nutrition is necessary for any host plant to be resistant or susceptible to pathogen (Filippi and Prabhu, 1998). However, no general rule exist that how, a particular nutrient can decrease or increase the severity of a disease or incidence of other diseases and it may have a completely opposite effect under different environment (Marschner, 1995; Graham and Webb 1991: Huber, 1980). The importance of nutrients in disease control has been recognized for many years but for some of the most severe diseases, the correct management of nutrients for the control disease in sustainable agriculture and successful disease management program has received little attention (Huber and Graham, 1999).
The physiology of the plant is impaired when it is under the attack of the pathogen which results in the disturbance in nutrient uptake, assimilation, translocation from the root to the shoot and also its utilization (Marschner, 1995). Due to the activity of some pathogen, the nutrients in the rhizophere become immobilize, surrounding plant roots, or in infected tissues such as roots, that ultimately results in interfere with translocation or utilization efficiency and can cause nutrient deficiency or hyperaccumulation and nutrient toxicity (Huber and Graham, 1999). At the same time, other organisms may utilize a significant amount of nutrients for their growth, causing a reduction in the availability of nutrients for the plant and increasing the chance of its susceptibility due to nutrient deficiency (Timonin, 1965).
Nitrogen is among the most important macronutrient which is required for the normal growth and development of plant (Chandra and Mishra, 1991) Nitrogen is indispensable elementary constituent of many metabolites like proteins, amino acids, phyochrome, nucleic acid and chromosomes (Marschner, 1995). The deficiency of nitrogen results in impaired growth, lead to reduction in proteins synthesis in plants and photosynthetic rate is inhibited indirectly (Stitt and Krapp, 1998). Phosphorus is an integral part of many organic molecules of the cell DNA (deoxyribonucleic acid), RNA (ribonucleic acid), ATP (adenosine triphosphate) and phospholipids) and is also involved in many metabolic processes in the plant and also in the pathogen but its role in resistance is unpredictable and seemingly inconsistent (Kiraly, 1976). Other nutrients also induce systemic acquired resistance which involved in the suppression of plant diseases. (Dordas, 2007).
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Since minerals play significant role in biochemical reactions yielding such metabolites that are involved in resistance/susceptibility of a crop against its pathogens, the objective of this study was to determine the influence of induction and inoculation of three susceptible chickpea cultivars, with Ascochyta rabiei, on their mineral contents.
Materials and Methods
Plant samples (comprising of shoots) of induced/un-inoculated and induced/inoculated of three chickpea cultivars, were collected from the field from the pervious experiment, when the symptoms were fully developed on the plants in control row. They were washed in 0.2 percent detergent solution in order to remove any dirt from them followed by washing in 0.8 percent HCl (to remove metallic contaminants from them) and deionized water (to remove the previous two solutions). The samples were air-dried in the shade on paper towels and then placed in paper bags. The samples were dried in an oven at 70ï‚°C for 72 hours to get constant weight. These samples were ground with the help of Buhler sample grinder and afterwards processed for the determination of N. P, K, Na, Ca, Mg, Zn, Cu, and Fe following (Bhargava and Raghupathi ,1995: Karla and Mynard 1991)). Nitrogen and phosphorus content was recorded as percentage of dry weight whereas content of rest of the elements were recorded as ppm (parts per million).
6.3 Results and Discussion
There is significant increase (P=0.05) in the amount of nitrogen 2.95 percent by the application of salicylic acid (Fig. 1a). This increase was observed after induction of resistance inducer and inoculation with A.rabiei in the cultivar C-44 while in case of Pb-91 and Bitter-98, this increase was 2.65 (Fig. 2a) and 2.51 percent respectively (Fig. 3a). In all the three cultivars, the increase in nitrogen contents was more after the induction with highest dose rate of salicylic acid and inoculation with pathogen. Bion application increases the nitrogen contents with 2.86 percent in C-44, 2.76 percent in Pb-91 and 2.48 percent in Bitter 98 14th day after induction and inoculation with 1.2mM dose rate (Fig. 1a, 2a, 3a). In case of KOH application, not significant increase was observed and all the three cultivars showed almost small increase (1.5, 1.3 and 1.3 percent) in nitrogen contents in C-44, Pb-91 and Bitter-98 respectively (Fig. 1a, 2a, 3a). The application of plant extracts also increased the nitrogen content but this increase was not significant. The neem leaf extract at the dose rate of (15% v/v) in all the three cultivars increases the content but this increase was (1.0, 0.9 and 0.8 percent) after 14th day. There is no difference in the increase of nitrogen content after 7th day after induction and inoculation with A.rabiei and similar trend was followed in case of induced and un-inoculated chickpea plants. Extracts of Datura and Gralic also caused small increase but no difference was observed among the three cultivars with highest nitrogen content was recorded (0.55 percent) in case of Pb-91 at (15% v/v) dose rate 14th day after the application of inducers and inoculation (Fig. 1a, 2a, 3a). On over all bases it was concluded that application of resistance inducing chemicals increased the nitrogen contents as compared to plant extracts but this increase was more pronounced by salicylic acid with least by KOH in cultivar C-44 at maximum dose rate.
The effect of nitrogen on disease development is inconsistent and contradicts and causes of this inconsistency are poorly understood (Hoffland et al., 2000). Earlier studies by Sati and Grewal (1982) reported that the level of N was higher in a susceptible cultivar (G-24) compared to resistant one. The studied under taken by El-Khallal (2007) found that treatment with AM fungi plus jasmonic acid have higher nitrogen content. In our experiments this increase in amount of nitrogen is attributable to fungal mycelia in inoculated and induced plants similarly the results presented here are in line with studies of Randhawa (1994) reported an increase in nitrogen content was recorded in chickpea cultivars resistant to Ascochyta blight while there was a decrease in the susceptible cultivars, although the varieties under study were susceptible to Ascochyta blight but by application of resistance inducers they showed reduction in the disease with increase nitrogen content. There was increase in the nitrogen content and this increase was relatively higher in the susceptible group as compared with the resistant one (Sahi et al, 2007). The application of N to the cereal crop reduces the take-all disease caused by (Gaeumannomyces graminis). Cahill et al., (1987) found that adequate nitrogen level reduce the disease severity of red thread disease by enhancing its vigor. Contrary to these results increase level of nitrogen level make the plant more susceptible to the attack of pathogen and it was proved in different host pathogen interaction as reported by (Nam et al., 2006: Umemoto, 1991).
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The mean comparison of data regarding the phosphorus content (Fig. 1b, 2b, 3b) of induced/un-inoculated and induced/inoculated in the three chickpea cultivars exhibited significant difference (p>0.05) There is general trend of increased in the content of phosphors in all the cultivars by the application of chemical and plant extracts after inoculation at higher dose rate 14th after application of treatment, expect KOH application where the induction and un-inoculation showed higher (0.51, 0.62 and 0.77 percent) phosphors content as compared to induced and inoculated plants (0.35, 0.45 and 0.48 percent) in cultivar C-44 but opposite to this trend was followed in Pb-91 and Bitter-98.
The plant extracts did not show appreciable change in the amount of phosphorus in three chickpea cultivars with maximum (0.35 percent) being produced by the application of neem leaf extract in cultivar C-44, while the least (0.17 percent) is shown by garlic at the same dose rate in the cultivar Pb-91. The disease resistance inducing chemical salicylic acid, Bion and KOH also increased which was more pronounced by the application of Bion in the cultivar C-44 with (1.05 percent), Pb-91 (0.79 percent) and (0.59 percent) in Bitter-98.
Present studies demonstrated that P level increased in both the induced/un-inoculated and induced/inoculated chickpea plant but more upon inoculation with A.rabiei. The increase in phosphorus content in induced/inoculated cultivar of chickpea indicates intact and consistent uptake and translocation of this mineral as phosphorus is consumed by the plants in the formation of different cell constituent's like phospholipids, nucleic acids, the coenzymes NADP, NAD and ATP and other energy yielding compounds (Devlin & Witham, 1983). Similar results were obtained by (Sahi et al, 2007) regarding the phosphorus content that was higher in un-inoculated plants of susceptible lentil lines than the resistant ones but upon inoculation it increased in the resistant lentil lines. Our results are in line with Randhawa (1994) who reported increase in phosphorus in chickpea cultivars of both the susceptible and resistant groups after infection with Ascochyta rabiei. The application of P as foliar treatment induces systemic protection against various pathogens like powdery mildew in roses, cucumber, mango and nectarines (Reuveni and Reuveni, 1998), which might be true in this case that increased level of P induced systemic resistance. Increased level of P reduces the intensity of disease in different host pathogen interaction downy mildew, rice bacterial blight, blue mold, Barley yellow dwarf virus, and rice blast disease (Huber and Graham, 1999: Reuveni et al, 2000) on the other hand application of P may enhance the severity of Sclerotinia in garden plants, flag smut in wheat, Bremia in lettuce (Huber, 1980).
The potassium content in the induced and inoculated plants of the cultivar C-44 ranged from 480.8 to 527.86 ppm by the applying all the three doses of salicylic acid which was significantly different from induced and un-inoculated plant (Fig. 1c, 2c, 3c). The cultivar Pb-91 and Bitter- 98 also showed the same trend with maximum 310.1 ppm and 158.3 ppm, 14th day after induction and inoculation. The maximum potassium content (533.0 ppm) was recorded after the application of Bion at the highest dose rate, the potassium content in Pb-91 and Bitter-98 was also high by the application and inoculation with the pathogen. Lowest amount of (79.16 ppm) was recorded in cultivar Bitter-98 which was significantly different in case of Pb-91 and C-44 by the application of KOH and inoculation with A. rabiei while in case of induced and un-inoculated plant this increased was also followed. The plant extracts also influenced the K contents of the plant tissue but that was not appreciable as compared to the chemical. Neem leaf extract in the cultivarc-44 with (174.89 ppm) was the maximum 14th day after induction and inoculation at the same time the induced and un-inoculated plant of cultivar exhibited (69.4 ppm) potassium content (Fig. 1c). The smaller amount (29.2 ppm) was produced in the cultivar Bitter-98 by the application of garlic extract at maximum dose rate.
The finding of the present research is in line with that of (Shehu and Aliero, 2010) reported that increase in the P content in the disease infected leaves as compared to healthy one. Similarly Sahi et al., (2007) found that potassium contents, increased invariably in both the resistant and susceptible group of lentil lines. These results are also in line with those of Randhawa (1994) and Reddy & Khare (1984). These results comply with (El-Khallal, 2007) reported high potassium level was found in salicylic acid treated plants. This noticeable increase in the potash content of induced/inoculated susceptible lines of chickpea may be attributed to due to change in the physiological and biochemical defence system of the plant by the application of resistance inducers. Application of potassium at proper rate and balanced with other nutrient decreases the susceptibility of host plants (Huber and Graham, 1999). It is involved in different metabolic function in plant physiology (respiration, photosynthesis and chlorophyll) and synthesis of high molecular weight compounds (proteins, starch and cellulose), potassium deficiency in plant to parasitic disease is due disturbance into that metabolic functions. Almost 2450 references were reviewed by Perrenoud (1990) on the use of potassium (K) and describe that 70% fungal disease incidence was decreased, 69% in the bacterial pathogen, mites and insect 63% and virus 41% further application of K increased the yield of fungal , bacterial and viral pathogen. The other draw back of K deficiency result impaired protein synthesis and accumulates simple N compounds such as amides which are used by invading plant pathogens (Dordas, 2008). There were no differences in the response of the crop with different sources of K further the balance between nitrogen and potassium affects disease susceptibility of plants. The examples of disease reduction in obligate and facultative parasites by the application of K included Helminthosporium leaf blight disease severity and increase wheat yields, stem rot, sesamum leaf spot in rice, black rust in wheat and seedling rot caused by Rhizoctonia solani (Sharma and Duveiller, 2004; Sharma et al., 2005).
The sodium content of both the group induced/un-inoculated and induced/inoculated with Ascochyta rabiei was significant. The increase in the Na content was observed by the application of salicylic acid in three chickpea cultivars at higher dose rates, the maximum (335.99 ppm) was in C-44 followed by (271.91 ppm) and (198.37 ppm) in Pb-91 and Bitter-98 respectively (Fig. 1d, 2d, 3d). The same trend was followed in case of un-inoculated plants. The application of Bion decrease the sodium content which was (282.35 ppm) as compared with (340.6 ppm) in un-inoculated induced plants at dose rate of 1.2mM after 14th day while in case of Pb-91 the higher dose reduce the sodium content. KOH application also increased the sodium content and plant extracts exhibited an increased in Na content with maximum (111.53 ppm) in case of neem leaf extract 14th day after induction and inoculation. Datura and gralic extracts showed increased but that was not significant. Only very few report are available regarding the role of Na in resistance and susceptible response in host pathogen interaction except for Sahi et al., (2010) reported that upon inoculation with the pathogen, the sodium content increased in both the groups, being more prominent in case of susceptible lentil lines. Due to lack of literature on this aspect, the role of sodium in resistance/susceptibility to Ascochyta rabiei could not be justified.
The inoculated plants of induced group has more (p=0.05) calcium contents as compared to those that were un-inoculated. Calcium content was significantly higher (7844.0 ppm) in plants that were applied with aqueous solution of Bion at higher dose rate after 14th day (Fig. 1e, 2e, 3e). While in case of salicylic acid at the same interval the ca content was (7837.66 ppm) which is at par with Bion in the cultivar C-44. The lowest (2549.57 ppm) was in KOH treated plant 14th days after inoculation with A. rabiei. The cultivars Pb-91 and Bitter 98 showed the same response but not significant variation in the Ca contents was observed at all the dose rates. The plant extracts also exhibited the same response with maximum calcium contents was observed in the C-44 cultivar (2549.57 ppm) which was significantly different to datura and garlic application.
Calcium is indispensable mainly due to its importance as a constituent of plant cell wall integrity and stability in the form of clacium pectate. Under the Ca deficient condition in the plants, there is leakage of sugar and amino acids from the cytoplasm to apoplast that makes the plant venerable to the attack of the pathogen secondly Ca is bound in the middle lamella if partly removed from the middle lamella, the cell plasticity is increased (Devlin & Witham, 1983: Taiz and Zeiger, 1998). It is therefore obvious that plant that are deficient in calcium would have more plastic cells, which may make them more susceptible to different stresses. Increased cell plasticity may ease the entry of the pathogen into the host cells similarly the tissues with less amount of Ca are more prone the attack of the pathogen as compared to the normal level (Dordas, 2008).
The Ca content of plant tissues affects the incidence of parasitic diseases in two ways. First, Ca is essential for the stability of biological membranes; when Ca levels are low, the efflux of low molecular weight compounds, e.g., sugars from the cytoplasm into the apoplast are enhanced. Second, Ca is bound in the middle lamella for cell wall stability (Taiz and Zeiger, 1998). The role of Ca in fungal and bacterial diseases is evident, and a close relationship between plant resistance to bacterial diseases and further calcium also sturdily restrain the activity of pectolytic enzymes released by fungi to dissolve the middle lamella of the cell wall of the host. Calcium contents in case of bean influenced the activity of polygalacturonase and pectate transeliminase by reducing them with increasing Ca content resulting in a higher resistance to soft rot disease, Erwinia carotovora (Platero and Tejerina, 1976). The lower infestation of lettuce with grey mould, Botrytis cinerea, at higher Ca contents (Krauss, 1971) or the decreasing incidence of apple decay caused by Gloesporium perennans at increasing Ca contents can also be related to the control of pectolytic enzymes by Ca. A putative mechanism by which Ca is believed to provide protection against Sclerotinia sclerotiorum is by binding of oxalic acid or by strengthening the cell wall. The results of (Filippi and Prabhu, 1998: Sahi et al, 2010) are in line with the present study as the out come of the indicated that calcium content of chickpea cultivars after induction of resistance and inoculation was significantly higher, which supports the above hypothesis that increased Ca contents makes the host resistance to the attack of pathogen. Same response in the lentil cultivars has already been reported against rust (Reddy & Khare, 1984).
The data regarding the Mg content of both the group induced/un-inoculated and induced /inoculated is given in (Fig. 1f, 2f, 3f). Application of disease resistance inducer chemical significantly (p=0.05) increase the Mg contents in both the group but this increase was more pronounced by the application of Bion (1197.28 ppm) as compared to all other chemicals. Application of salicylic acid also increase the content in the cultivar C-44 but it was less (1189.99 ppm) as compared with Bion application at the highest dose rate 14th day after induction and inoculation with A.rabiei however there was less increase (594.49 ppm). The plant extract also increase the Mg content which was more in the neem leaf extract treated plants (387.47 ppm) while the increase (251.94 ppm) in case of datura and (202.88 ppm) by garlic extract.
The induced/un-inoculated plant of cultivar C-44 also showed the increasing trend being more by the application of Bion (1042.44 ppm) after 7th day of application followed by (1137.37 ppm) in the salicylic acid and (518.35 ppm) in case of KOH at the lowest dose rate. The plant extracts also caused increased but that was not significant with (340.11 ppm) in neem after 14th day of application at 10% dose rate while in case of datura (218.37 to 218.81 ppm) and garlic (168.85 to 169.85 ppm) after 7th and 14th day. The same trend was followed in case of Pb-91 and Bitter-98 with maximum (1023.81 ppm) Mg content was recorded in Bion treated plant after 14th day followed by (999.0 ppm) by the application of salicylic acid in comparison very less amount (173.51 ppm) of Mg content was recorded in garlic extract. The induced and un-inoculated plant showed the increase in case of salicylic acid and Bion treated plants while KOH, neem, datura and garlic increase the small amount of Mg content with out inoculation after 7th and 14th day of induction in the cultivar Pb-91. Mg content (152.07 ppm) was exhibited by plants of cultivar Bitter-98 after induction and inoculation with pathogen while salicylic acid showed (903.13 ppm) Mg content followed by (903.13 ppm) in Bion treated plants. Similar results were also reported by Randhawa (1994) that there was increase in the Mg content upon inoculation with the pathogen but Sahi et al., (2001) reported that significant increase in magnesium content of resistant lines of lentil but on the contrary there was highly significant decrease in the magnesium content of susceptible lines. Three times foliar spray with either JA or SA significantly increased Mn contents in the tomato plant against Fusarium oxysporum but it was more with AM fungi plus JA in both leaves and roots (El-Khallal, 2007).
Manganese is considered to be the most premeditated micronutrient in the development of resistance in plants in case of both root and foliar diseases (Graham and Webb, 1991: Heckman et al., 2003). Mn also have direct role in the synthesis of lignin, biosynthesis, of phenol, photosynthesis and various other functions (Marschner, 1995; Graham and Webb, 1991). Mn also inhibits the initiation of an enzyme amino peptidase, which provides essential amino acids for fungal growth and also pectin methyl esterase that degrades host cell walls furthermore manganese controls lignin and suberin biosynthesis (Römheld and Marschner, 1991) which are biochemical barriers to fungal pathogen invasion (Hammerschmidt and Nicholson, 2000: Vidhyasekaran, 2004) by the activation of various enzymes in the shikimic acid and phenyl propanoid pathways (Marschner, 1995) as they are phenolic polymers resistant to enzymatic degradation (Agrios, 2005).
The amount of zinc content of both groups induced/un-inoculated and induced/inoculated showed the increased trend (Fig. 1g, 2g, 3g) which was significant (p=0.05), in case of Bion application (104.23ppm) followed by (99.41 ppm) in salicylic acid treated plants with least amount of Zn contents (49.70 ppm) was recorded in C-44 14th day after induction and inoculation. In case of plant extracts neem leaf exhibited significant increase (33.97 ppm) Zn content as compared to datura (24.45 ppm) and garlic (25.45 ppm) extracts. The later two showed the increased but it was at par with each other.
The Zn contents in the cultivar Pb-91 was also increased by the application of resistance inducing agents and it was more pronounced after inoculation with the A.rabiei with maximum (87.07 ppm) was recorded in Bion treated plants as compared to KOH (41.10 ppm) while salicylic acid treatment induced (82.2 ppm) Mg contents 14th days after inoculation and induction. The un-inoculated and induced plants also showed increaseed but that was significant by the application of salicylic acid and Bion but non significant in KOH treated plants.
Application of plant extracts, garlic (19.78 ppm) and datura (19.91 ppm) exhibited the increased Zn content but that was not statistically different from each other on the other hand the neem leaf extract enhances the Zn contents (26.62 ppm) which was different from all the other extract in case of Bitter-98. Application of KOH resulted in (33.77 ppm) Za content which was significantly lower than that of Bion (72.92 ppm) and salicylic acid (67.54) at the highest dose rates after 14th day of induction and inoculation.
The results of the present findings are in line of Sahi, et al (2010) found that Zinc content of susceptible lentil lines was higher than that of the resistant ones prior to inoculation with the pathogen and it even increased in both the groups, increase being more pronounced in case of susceptible group. These results are similar to those recorded by Randhawa (1994) in case of chickpea-Ascochyta rabiei interaction but opposite to those obtained by Reddy & Khare (1984) in lentil Uromyces fabae interaction. Zinc has also been reported to completely inhibit the mycelial growth of Aspergillus carneus and A. ellipticus at 500 mg L-1 (Moslem & Parvez, 1992).
Zinc as an activator of Cu/Zn-SOD, is involved in protection against oxidative damage by the detoxification of superoxide radicals (Cakmak, 2000). There is invariable response to the level of Zn in decreasing or increasing or no effect toward plant susceptibility to disease (Grewal et al., 1996). The application of Zn reduced disease severity due to reason its toxic effect directly to pathogen and not through the plant's metabolism (Graham and Webb, 1991). Zinc also plays role in the synthesis of protein and starch (Römheld and Marschner, 1991). Application of Zn to the soil reduced infections by Fusarium graminearum (Schwabe) and root rot diseases, e.g. caused by G. graminis (Sacc.) in wheat (Grewal et al., 1996).
The amount of copper content varies in all the three chickpea cultivar which was significantly different (Fig. 1h, 2h, 3h) in induced/un-inoculated and induced/inoculated plants. The highest increase was found in the Bion treated plants applied @ 1.2mM which was (126.2 ppm) in induced/un-inoculated while upon inoculation with A.rabiei there is decrease in the contents that was (90.99 ppm). KOH treated plants showed (61.73 ppm), however application of salicylic acid at highest dose rate decreased (86.033 pmm) the Cu contents which was high with out inoculation (122.13 ppm) at 1.5mM dose rate 14th day of inoculation and induction of resistance in the cultivar C-44. The neem leaf extract decrease the Cu content 42.02 to 39.99 ppm) after 7th and 14th day, on the other hand application of datura and garlic extract was almost the same (29.53 ppm) and (28.74 ppm) in the cultivar Pb-91. The trend of increased Cu content was continued in the cultivar by the application of salicylic acid (71.66 ppm) and Bion (77.19 ppm) while the lowest was recorded in KOH (35.83 ppm) The plant extracts showed the change in the Cu content with maximum produced by the neem (35.63 ppm) and lowest by the garlic (16.25 ppm) In case of un-inoculated plant Bion after 7th and 14th days produce Cu content range (34.47 to 37.47 ppm) at 0.8mM dose rate. The cultivar Bitter-98 (p=0.05), increased was exhibited by the application of Bion (53.29 ppm) after 14th day of induction and inoculation with A.rabiei which was different with treatment where KOH was applied. The plant extract of datura showed maximum (18.41 ppm) followed by neem (17.78 ppm) and garlic (15.02 ppm). This was most likely due to the involvement of Cu cations in the formation of phytotoxins as already reported (Chen and Strange, 1991). The results reported by YardÄ±mcÄ± et al., (2007) showed that healthy alfalfa plant leaves contains more (48.50 ppm) Cu contents as compared to infected one. Wheat var. Kenya was less susceptible to mildew, E. graminis grown on copper deficient sand culture as compared to more susceptibility when grown on boron deficient and fairly resistant to infection when grown upon a balanced nutrient solution (Schutte, 1967).
Copper cations were found to be involved in the synthesis of solanapyrone A, B and C along with other mineral elements. After having the information about the involvement of Cu cations in the formation of phytotoxins and ultimate disease condition, it would be easy to deduce that the induced plant upon inoculation had higher content of Cu in Pb-91 and Bitter-98 but was less in C-44, would easily be in a position to spare the required amount of cations for the formation of phytotoxins. At the same time, it would be having enough of the cations to be utilized for the performance of its own life functions and hence would not suffer from disease.
Increase in the iron content upon induction/un-inoculation and with induction/un-inoculation with the pathogen was highly significant (P=0.05), in all the chickpea cultivars (Fig. 1i, 2i, 3i) at all the dose rates The maximum Fe contents (998.13 ppm) was recorded in Bion treated plant in C-44, (615.24) in Pb-91 and (371.87 ppm) in the cultivar Bitter-98 14th day after induction/inoculation plants. On the other hand in case of un-inoculated plant (639.06, 440.1 and 366.31 ppm) was recorded at the same time interval. Salicylic acid exhibited (960.58 ppm) Fe content in C-44, (603.76 ppm) in Pb-91 and 360.29 ppm in of Bitter-98 14th day after induction/inoculation with the pathogen. The lowest (180.14) was recorded in the cultivar Bitter-98 after treatment with KOH at the highest dose rate.
The plant extracts also showed an increase in the Fe content which was maximum (326.97 ppm) in C-44 followed by (200.56 ppm) in Pb-91 and (120.43 ppm) in case of Bitter-98 14th day after induction/inoculation with A.rabiei. Extract of datura was able to induce less Fe content in all the three cultivars (160.16, 99.94, 63.24) in C-44, Pb-91 and Bitter-98 respectively.
Iron (Fe) is a critical micronutrient which plays a role in the vital processes such as photosynthesis, DNA replication, and respiration in the plant (Rehman and Punja, 2006). It is also significant important micronutrients for animals and humans as its deficiency resulted in the induction of anemia however, the role of Iron in resistance to diseases is not well documented therefore Fe differs from the other micronutrients such as Mn, Cu and B, for which microbes have lower requirements. Several plant pathogens, e.g. Fusarium, have higher requirements for Fe or higher utilization efficiency compared with higher plants therefore addition of Cu, Mn and B to deficient soils generally benefits the host, whereas the effect of Fe application is not as straight forward as it can have a positive or negative effect on the host. Fe is a component of peroxidase and stimulates other enzymes involved in the biosynthetic pathway. Fe can activate enzymes that are involved in the infection of the host by the pathogen or the defense, which is why opposite effects were found (Graham and Webb, 1991). Fe can control or reduce the disease severity of several diseases such as rust in wheat leaves, smut in wheat and Colletotrichum musae in banana (Graham, 1983). Foliar application of Fe can increase resistance of apple and pear to Sphaeropsis malorum and cabbage to Olpidium brassicae (Graham, 1983).
As far as the estimation of findings towards mineral content of induced/un-inoculated and induced/inoculated of three chickpea cultivars is concerned, only one paper was available with more relevant study (El-Khallal, 2007). Other studies like (Sahi et al., 2007. 2010) although related with this type of study but induce resistnace by the use of chemical and plant extracts were not properly explored. This is first attempt toward the management of chickpea blight by the application of resistance inducers. Moreover, there is a general feeling (founded or not) among the researchers that susceptible lines possess better uptake capacity of nitrogen compared to resistant lines. Hence, these become more prone to various hazards.
The other relevant information that deals with the activity of mineral elements is about the role of divalent metal cations of Zn, Mn, Ca and Cu (Chen and Strange, 1991). These cations were found to be essential constituents in the production of solanapyrones A, B and C in the presence of aqueous extract of chickpea.