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CLI MATE CHANGE AND ITS IM PACT ON VEG E TA BLE PRO DUC TION-A RE VIEW

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CLI MATE CHANGE AND ITS IM PACT ON VEG E TA BLE PRO DUC TION-A RE VIEW
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  CLI MATE CHANGE AND ITS IM PACT ON VEG E TA BLE PRO DUC TION-A RE VIEW J. Phani Kumar*, Syed Sadarunnisa, P. Syam Sundar Reddy, D. Srinivasa Reddy 1 De part ment of Veg e ta ble sci ence, COH, Anantharajupeta, DR.YSRHU-516105. 1 De part ment of En to mol ogy, HRS, Anantharajupeta, DR.YSRHU-516105. *E-mail: phani515202@gmail.com  ABSTRACT Agriculture is a climate dependent activity. So, it is going to be affected by climate change largely.Vegetables are verygenerally sensitive to environmental extremes, and thus high temperatures and limited soil moisture are the majorcauses of low yields as they greatly affect several physiological and biochemical processes like reduced photosyntheticactivity, altered metabolism and enzyme activity, thermal injury to the tissues, reduced pollination and fruit set etc.,which will be further magnified by climate change. Climate is traditionally defined as the mean and variability of relevantatmospheric variables viz., temperature, precipitation, humidity, sunshine hours, cloudiness, pressure, drought, salinity, flooding, light, sea level rise, soil erosion, wind velocity etc. Any change in one of the parameter affects the other eitherdirectly or indirectly. Climate change influences the severity of environmental stress imposed on vegetable crops. Theresponse of plants to environmental stresses depends on the plant developmental stage, the length and severity of thestress. Changes in climate parameters especially temperature and precipitation in particular, have a very stronginfluence on the insects’ physiology and behaviour, particularly development, reproduction and survival. Hot summerresults in soaring insect number,where as milder and shorter winters mean that warm weather pests will start breedingsooner. With every degree of global temperature rise, the life cycle of each bug will be shorter. The quicker the life cycle,the higher will be the pest population. In bell pepper Sclerotium, Rhizoctonia  and Pythium   root rot will be more prevalentif crop is grown under high temperature stress. In cabbage the excess rainfall may cause incidence of soft rot anddecreased seed yield. Global climate change is emerging as one of the major constraints for world food security and willbecome more prevalent in the coming years. There is urgent need for scientific research to improve our understanding of the interactions of rising temperature, precipitation as wellas with biotic factors such as pests and diseases. Key words :  Cli mate change, Pest and dis ease, Veg e ta ble crops. Vegetables are an important components of human dietas they are source of nutrients, vitamins and minerals.They are also good remunerative to farmers as they fetchhigher price in the market. Likewise, other crops they arealso being hit by the consequences of climate changesuch as global warming, changes in seasonal andmonsoon pattern and biotic and abiotic factors. Underchanging climatic situations crop failures, shortage ofyields, reduction in quality and increasing pest anddisease problems are common and they render thevegetable cultivation unprofitable.India is the secondplace in productivity of vegetables (17.3t/ha) after China(22.5 t/ha). In past two decades the vegetable productionin India has been increased 2.5 times from 58.5 Mt in1991-92 to 146.6 Mt in 2010-11 (Kumar et al.,  2011).Climate change is affecting our agriculture due to 0.74 0 Caverage global increase intemperature in last 100 yearsand atmospheric CO 2 concentration increase from 280ppm in 1750 to 400 ppm in 2013. Such changes will havedrastic effect on the growth and cultivation of the differentcrops on the Earth. Simultaneously, these changes willalso affect the reproduction, spread and severity of manyplant pathogens, thus posing a threat to our food security.The changes in climate may include fluctuations intemperature, increases in soil salinity, water logging, highatmospheric CO 2 concentration and UV radiation.Climatic parameters which will affect the crop productionare :1. Temperature 2. CO 2  concentration in atmosphere3. Relative humidity4. Moisture5. Precipitation6. Drought Temperature : Fluctuations in daily mean maximum andminimum temperature is the primary effect of climatechange that adversely affects vegetable production. Asmany plant physiological, bio-chemical and metabolicactivities are temperature dependent.Climate changeresulting in increased temperature could show impact oninsect pest populations in several complex ways. Although some climate change effects might tend to depress insectpopulations, the warmer temperature in temperate climate will result in more types and higher populations of insects.Climate change also influences the ecology and biology of insect pests (Jat, 2012). Increased temperature, in somegroup of insects with short life cycles such as aphids anddiamond back moth, increases fecundity, earliercompletion of life cycle.Increased temperature causes  Progressive Research – An International Journal    Society for Scientific Development  Print ISSN : 0973-6417, Online ISSN : 2454-6003 in Agriculture and Technology  Volume 11 (Special-VIII) : 5484-5490 (2016) Meerut (U.P.) INDIA  Kumar et al., 5485 migration of insect species towards higher latitudes, whilein the tropics higher temperatures might adversely affectspecific pest species and increases insect developmentaland oviposition rates.Temperature and frost sensitivityeffect the distribution of pathogen species as irrespectiveof their huge host range the soil borne pathogens such as Sclerotium rolfsii and Macrophomina phaseolina do notoccur in temperate climates due to their high temperatureoptimum and frost Sensitivity (Termorshuizen, 2008).Higher temperatures cause faster disease cycles in airborne pathogens and increase their survival due toreduction in frost (Termorshuizen, 2008 and Boonekamp2012). Changes in temperature and precipitation regimesdue to climate change may alter the growth stage,development rate and pathogenicity of infectious agents,and the physiology and resistance of the host plant and itcould directly affect the spread of infectious diseases andtheir survival between seasons. There are indications ofincreased aggressiveness at higher temperatures of stripe rust isolates ( Puccinia striiformis  ), suggesting that rustfungi can adapt to and benefit from higher temperatures.Potato is the fourth most important and non-cereal staplefood of the mankind, it is well known for its exacttemperature and day length requirement for tuberformation as well as flowering, so it becomes the mostvulnerable crop for climate change. The effect of climatechange on potato production in India has previously beenstudied by (Singh et al. , (2009). Planting of potato crop at a new optimal date of mid November in order to minimizethe yield losses up to 8%. Increase in temperature favoursthe potato cultivation by prolonging the crop growingseason in high altitudes and temperate regions of theworld like Europe, Russia and in India, Himalayan andother mountain regions and frost prone states likeHaryana and Punjab whereas, it disfavours the potatoproduction by shortening the growing period in subtropicalplains such as West Bengal and Bihar during winterseason (Singh, 2010). Potato requires long days and lowtemperatures for its flowering. It makes possible thehybridization or heterosis breeding of potato in highaltitudes of Himachal Pradesh. Due to increase intemperature the potato breeding area is shifting towardsthe further more high altitudes. Potato is very strict to itstemperature requirement for tuber formation. Optimumtuber formation takes place at 20 0 C. An increase intemperature of above 21 0 C cause sharp reduction in thepotato tuber yield, at 30 0 C complete inhibition of tuberformation occurs (Sekhawat, 2001). In potato highharvesting index (HI) of 0.8 is recorded at 15 0 C nighttemperatures of and zero at 28 0  C in Northern IndianPunjab, Haryana, Uttar Pradesh, Bihar and Northern hills.A moderate HI of 0.4-0.6 is recorded at 20 0  C nighttemperatures in Central Indian states like Gujarat,Chattisgarh, some parts of Maharashtra and West Bengalindicating temperature stress limiting the partitioning ofphotosynthates to the tubers. A low HI of 0.2 is recorded at more than 20 0  C night temperatures in South India(Pandey et al., 2009; Singh, 2010). Potato tubers with high starch content are favoured by the processing industry. Atlow temperatures starch is converted into the sugar, which causes browning due to charring of sugar while chipsmaking there by reduces their preference by theprocessing industry. This ultimately results in increasedpost harvest losses more than the present level, which isfigured as 40-50%. This is most common problem in areas where night temperatures fell below optimum duringwinter season (Singh, 2010). Fruit colour is havingsignificant importance in assessing the marketable qualityof tomato. The optimum temperature for development oflycopene pigment in tomato is 25-30 0  C. Degradation oflycopene starts at above 27 0  C and it is completelydestroyed at 40 0  C. Similarly high temperatures above 25 0 C affect pollination and fruit set in tomato (Kalloo et al., 2001). Abnormal pollen production, abnormaldevelopment of the female reproductive tissues, hormonal imbalances and lower levels of carbohydrates and lack ofpollination are responsible for the poor reproductiveperformance of tomatoes at high temperatures (Peet et al.,  1997). Lurie  et al.,  (1996) reported high temperatureinhibits ripening by inhibiting the accumulation of ripeningrelated m-RNAs, thereby inhibits continuous proteinsynthesis including ethylene production, lycopeneaccumulation and cell-wall dissolution. In pepper,exposure to high temperature at post-pollination stageinhibits fruit set (Erickson and Markhart 2002). Hightemperature affects red colour development in ripen chillifruits and also causes flower drop, ovule abortion, poorfruit set and fruit drop in chilli (Arora et al.,  1987). Flynn et al.  (2002) found high percentage (90%) seed germinationof chilli at 20 0 C and complete inhibition at 10 0  C indicatingthat fall in minimum temperatures affect seed germinationin chilli. Germination of cucumber and melon seeds isgreatly suppressed at 42 0  and 45° C, respectively besidesgermination will not occur at 42° C in watermelon, summer squash, winter squash and pumpkin seeds (Kurtar, 2010).The temperature fluctuations delay the ripening of fruitsand reduce the sweetness in melons. Low moisturecontent in the soil effects fruit quality and development inmelons and gourds (Arora et al.,  1987). Warm humidclimate increase the vegetative growth and result in poorproduction of female flowers in cucurbitaceous vegetables like ash gourd, bottle gourd, pumpkin which causes lowyield (Singh, 2010). High temperatures will causeenhanced abscission of flower buds, flowers and youngpods and reduce pod production, mature pod size andseeds per pod. Onsets of anthesis and pod developmentstages are most sensitive to high night temperature. Podslarger than 3 cm do not abscise but usually abort andshrivel under high night temperatures (Konsens et al., 1991). Moisture stress in the months of April and May and  intense rain during flowering and fruiting stage (Jun-Jul)reduces the productivity of french bean (Singh, 2010). Inokra, high temperatures cause poor germination of seedduring spring summer season Flower drop in okra isrecorded at high temperatures above 42 0 C (Dhankhar and Mishra, 2001), whereas flower abscission and ovuleabortion in french bean occurs at temperature above 35 0 C (Prabhakara et al. , 2001). High temperature causesbolting in cole crops, which is not desirable when they aregrown for vegetable purpose. Temperatures effect on disease infestation : Temperature has potential impacts on plant diseasethrough both the host crop plant and the pathogen.Temperate climate zones that include seasons with coldaverage temperatures are likely to experience longerperiods of temperatures suitable for pathogen growth andreproduction if climates warm. For example, predictivemodels for potato and tomato late blight (caused by Phytophthora infestans  ) show that the fungus infects andreproduces most successfully during periods of highmoisture that occur when temperatures are between 45 0 F(7.2 0  C) and 80 0  F (26.8 0 C) (Wallin et al  .,1950). Effect of atmospheric CO 2  : Due to increasedanthropogenic activities, concentration of green housegases like CO 2  and CH 4  is increasing in the atmosphereday by day. They are not only responsible for globalwarming but also cause their own direct effect on growthand development of plants. Potato plants grown underelevated CO 2  may have larger photosynthetic rates up tosome extent, later on with increase in CO 2  concentrationthe photosynthetic rates will come down (Burke et al., 2001). The high atmospheric CO 2  content inhibits tomatofruit ripening. This inhibition is due to the suppression ofthe expression of ripening associated genes, which isprobably related to the stress effect exerted by high CO 2 (Rothan et al  . , 1997).In contrast, high levels of CO 2  aloneor in combination with high concentration of O 3 , increasedthe severity of Septoria leaf spots.Some workers suggestthat elevated CO 2  concentration and climate change mayaccelerate plant pathogen evolution, which can affectvirulence. Under elevated CO 2  conditions, potential dualmechanism of reduced stomata opening and altered leafchemistry results in reduced disease incidence andseverity in many plant pathosystems where the pathogentargets the stomata.Increased CO 2  levels can impact both the host andthe pathogen in multiple ways. Some of the observed CO 2 effects on disease may counteract others. Researchershave shown that higher growth rates of leaves and stemsobserved for plants grown under high CO 2  concentrationsmay result in denser canopies with higher humidity thatfavour pathogens. Lower plant decomposition ratesobserved in high CO 2  situations could increase the cropresidue on which disease organisms can overwinter,resulting in higher inoculum levels at the beginning of thegrowing season, and earlier and faster diseaseepidemics. Pathogen growth can be affected by higherCO 2  concentrations resulting in greater fungal sporeproduction. However, increased CO 2  can result inphysiological changes to the host plant that can increasehost resistance to pathogens (Coakley et al 1999).Increases in CO 2  from 0.03 to 0.07% may have aslightly stimulatory effect on growth of pathogens(Manning and Tiedemann 1995).Under elevated CO 2 ,increased partitioning of assimilates to roots occursconsistently in crops such as carrot ( Daucus carota ),sugar beet ( Beta vulgaris  ), and radish ( Rhaphanus sativus  ). If more carbon is stored in roots, losses from soilborne diseases of root crops may be reduced underclimate change (Coakley et al.  1999). The inoculumpotential of nonbiotrophs, from more abundant cropdebris, would increase (Manning and Tiedemann 1995).Evidence indicates that high- CO 2  leaf litter decomposesat a slower rate (Coakley  et. al 1999). In recent studies onhost-pathogen interactions in selected fungalpathosystems, two important trends have emergedrelated to the effects of elevated CO 2 . Effect of Relative humidity : Relative humidity and COcan potentially affect pest and disease occurrence(Hamilton et al., 2005). Moreover, insects feed more onleaves with lower nitrogen content in order to get morenitrogen for their metabolism (Coviella and Trumble, 1999; Hunter, 2001). High atmospheric CO 2  increases foodconsumption by caterpillars, reproduction of aphids anddecreases the nitrogen based plant defence, thebeneficial effects are increased predation by predators,effect of foliar application of Bt., carbon based plantdefence and decreased insect development rates asreviewed by Das et al. (2011). Effect of Moisture : Moisture can impact both host plantsand pathogens in various ways. Late blight and severalvegetable root pathogens are more likely to infect plantswith increased moisture content because forecast modelsfor these diseases are based on leaf wetness, relativehumidity and precipitation measurements (Coakley et.al. 1999). Other pathogens like the powdery mildew speciestend to thrive under conditions with lower (but not low)moisture.Several diseases are less severe when available moisture is limited. Reduced root growth under moisturestress conditions diminishes the possible chance ofinfection by soil borne micro organisms as the chances ofbecoming contact of roots with pathogen propagules insoil will become less (Pertot et al., 2012). Effect of Precipitation : Precipitation washes someinsects like whiteflies and thrips from fields, but highhumidity due to high precipitation favors some insects like 5486 Kumar et al.,  Kumar et al., 5487 Tomato and legume pod borer Helicoverpa armigera andokra and egg plant leaf hopper Amrasca biguttulabiguttula. However, high humidity also favors the fungalpathogens of insects.Increased precipitation and humidconditions obviously favor the development and survivalof pathogens there by helps in increasing diseaseseverity. Risk of pathogen infection will increase with hostplants having holding high leaf wetness or having highcanopy moisture content (Coakley et al., 1999). Effect of Drought : Drought and salinity and are the mostimportant side effects of global warming. The prevalenceof drought conditions adversely affects the germination ofseeds in vegetable crops like onion and okra andsprouting of tubers in potato (Arora et al., 1987). Potato ishighly sensitive to drought. A moderate level of waterstress can also cause reductions in tuber yield (Jefferiesand Mackerron, 1993). As succulent leaves arecommercial products in leafy vegetables like amaranthus,palak and spinach, the drought conditions reduce theirwater content thereby reduces their quality (AVRDC,1990). Drought increases the salt concentration in the soiland affects the reverse osmosis of loss of water from plantcells. This leads to an increased water loss in plant cellsand inhibition of several physiological and biochemicalprocesses such as photosynthesis, respiration etc.,thereby reduces productivity of most vegetables (Penaand Hughes, 2007). Salt stress causes loss of turgor,reduction in growth, wilting, leaf abscission, decreasedphotosynthesis and respiration, loss of cellular integrity,tissue necrosis and finally death of the plant (Cheeseman,1988).Onions are susceptible to saline soils, whilecucumber, eggplant, pepper, and tomato are moderatelysensitive to saline soils (Pena and Huges, 2007). Salinitycauses a significant reduction in germination percentage,germination rate, and root and shoots length and freshroot and shoot weight in cabbage (Jamil and Rha, 2004).Salinity tends to reduce the tuber yield in potato. Thecombined stress of salinity and heat results in failure ofvegetative growth recovery and a consequent reduction inthe leaf area index and canopy functioning due to thedamage of salt accumulation avoiding mechanism inyoung expanding leaves of potato (Bustan et al., 2004).Salinity reduces dry matter production, leaf area, relativegrowth rate and net assimilation rate but increases leafarea ratio in chilli. The no. of fruits per plant is moreaffected by salinity than the individual fruit weight (Lopez et al., 2011). High salt concentration causes a reduction infresh and dry weight of all cucurbits. These changes areassociated with a decrease in relative water content andtotal chlorophyll content (Baysal et al., 2004). Salt stresscauses suppression of growth and photosynthesis activityand changes in stomata conductivity, number and size inbean plants. It reduces transpiration and the cell waterpotential in salt-effected bean plants (Kaymakanov et al., 2008). The high salinity levels of soil and irrigation waterare known to affect many physiological and metabolicprocesses, leading to cell growth reduction (Gama et al., 2007). Impact of Climate Change on Insect pests : The threelegs of the triangle host, pathogen, and environment mustbe present and interact appropriately for plant disease toresult. If any of the 3 factors is altered, changes in theprogression of a disease epidemic can occur. The majorpredicted results of climate change increases intemperature, moisture and CO 2 can impact all three legs of the plant disease triangle in various ways. Preciselypredicting the impact of climate change on plant disease is tricky business.Insects are cold blooded organisms the temperatureof their bodies is approximately the same as that of theenvironment. Therefore, temperature is probably thesingle most important environmental factor influencinginsect behaviour, distribution, development, survival, andreproduction. Insect life stage predictions are most oftencalculated using accumulated degree days from a basetemperature and bio fix point. Some researchers believethat the effect of temperature on insects largelyoverwhelms the effects of other environmental factors(Bale  et al 2002). It has been estimated that with a 2 0 Ctemperature increase insects might experience one to five additional life cycles per season (Yamamura & Kiritani1998). Other researchers have found that moisture andCO 2  effects on insects can be potentially importantconsiderations in a global climate change setting(Hamilton 2005, Coviella and Trumble 1999, Hunter2001).The temperature increase associated with climaticchanges could impact crop pest insect population inseveral complex ways like (1) extension of geographicalrange 2) increased overwintering 3) changes inpopulation growth rate 4) increased number ofgenerations 5) extension of development season 6)changes sin crop pest synchrony 7) changes ininterspecific interactions 8) increased risks of invasions by migrant pests 9) and introduction of alternative host andover wintering hosts. But all these effects of temperatureon insects largely overwhelms the effects of otherenvironmental factors. Impact of climate change on plant diseases : Climatechange is predicted to have a direct impact on theoccurrence and severity of diseases in crops, which willhave a serious impact on our food security. Climatechange will result in rise in temperature and carbondioxide levels and will also have a varied effect onmoisture. In many cases, temperature increases arepredicted to lead to the geographic expansion of pathogen and vector distributions, bringing pathogens into contact  with more potential hosts and providing new opportunitiesfor pathogen hybridization. Pathogen evolution rates aredetermined by the number of generations of pathogenreproduction per time interval, along with othercharacteristics such as heritability of traits. Temperaturegoverns the rate of reproduction for many pathogens.Longer seasons that result from higher temperatures willallow more time for pathogen evolution. Pathogenevolution may also be more rapid when large pathogenpopulations are present, so increased overwintering andover summering rates will contribute as well.While physiological changes in host plants mayresult in higher disease resistance under climate changescenarios, host resistance to disease may be overcomemore quickly by more rapid disease cycles, resulting in agreater chance of pathogens evolving to overcome hostplant resistance. Fungicide and bactericide efficacy maychange with increased CO 2 , moisture, and temperature. Case study of different vegetable cropsTomato : Vegetative and reproductive process intomatoes are strongly modified by temperature alone or inconjunction with other environmental factors (Abdalla andVerderk,1968). High temperature stress disrupts thebiochemical reactions fundamental for normal cell function in plants. It primarily affects the photosynthetic functions of higher plants (Weis and Berry, 1988).High temperaturecan cause significant losses in tomato productivity due toreduced fruit set and smaller as well as lower productivitydue to reduced fruit set and smaller as well as lowerquality fruits. Over all productivity is reduced by hightemperatures due to bud drop, abnormal flowerdevelopment viability, and reduced carbohydrateavailability (Hazra et al,. 2007).Symptoms of hightemperature stress on tomato are sunburn, disruption oflycopene synthesis, appearance of yellow areas in theaffected tissues (Kader et al,. 1974). Cucumber : In cucumber, rise in temperature duringsummer months has detrimental effect on sex expression,flowering, pollination, and fruit setting. High temperatureand long day tend to keep the vines in male phase whileencouraged more female flowers in short day lowtemperature condition. Fruit yield of cucumber decreasedunder high temperature (Meng et al., 2004).Extremelyhigh temperatures can even cause early flowerdrop in cucumber (Kumar et al., 2011). Exposure ofcucumber plants to heat stress during fruit developmentstage causes bitterness of fruits (Kumar et al., 2011). CONCLUSION Though the changes in climate is a continuous process, ithas become recognizable in agricultural field from the past few years when it has started significant and lasting effecton crop production. The reasons for climate change arenot completely known today, but as per the availableinformation anthropogenic activities like industrializationand mechanization may contribute up to some extent.Global climate change is emerging one of the majorconstraints for world food security and will become moreprevalent in the coming years. Average globaltemperature has become more prevalent in the comingyears. Average global temperature has increased by0.74 0 C between 1906-2005 and a further increase of0.2 0 C to 0.4 0 C in the next 20 years is expected.Atmospheric CO 2  will increase from the currentconcentration of 360 ppm to 400-750 ppm by 2100 (IPCC,2007). Effects of temperature generated by globalwarming on crop plants are the major among all theclimate change effects. It is again responsible for otherstresses like drought or moisture stress, salinity and floods and water logging in coastal areas due to melting of polarice and increased sea levels. There has been only limitedresearch on impact of climate change on plant diseasesunder field conditions or disease management underclimate change. However, some assessments are nowavailable for a few countries, regions, crops and particularpathogens which concern with food security. Now,emphasis must shift from impact assessment todeveloping adaptation and mitigation strategies andoptions. First, there is need to evaluate under climatechange the efficacy of current physical, chemical andbiological control tactics, including disease-resistantcultivars, and secondly, to include future climate scenarios in all research aimed at developing new tools and tacticsDisease risk analyses based on host pathogeninteractions should be performed, and research on hostresponse and adaptation should be conducted to under-stand how an imminent change in the climate could affectplant diseases. REFERENCES 1.Abdalla, A.A and Verderk, K. (1968). Growth, flowering andfruit set of tomato at high temperature.  The Netherlands Journal of Agricultural Sciences. 16:   71-76.2.Arora, S.K., P.S. Partap, M.L. Pandita, and I. Jalal. (1987).Production problems and their possible remedies invegetable crops. Indian Horticulture 32(2):   2-8. 3.AVRDC. (1990). Vegetable Production Training Manual.Asian Vegetable Research and Training Center. Shanhua, Tainan, Pp:447. 4.Bale, J.S., G.J. Masters, I.D. Hodkinson, C. Awmack, T.M.Bezemer, V.K. Brown, J. Butterfield, A. Buse, J.C.Coulson, J. Farrar, J.E.G. Good, R. Harrington, S. Hartley,T.H. Jones. R.L. Lindroth, M.C. Press, I. Symrnioudis, A.D. Watt, and J.B. Whittaker. (2002). Herbivory in globalclimate change research: direct effects of risingtemperatures on insect herbivores. Global Change Biology 8:   1-16. 5.Baysal, G., R. Tipirdamaz, and Y. Ekmekci. (2004). Effectsof salinity on some physiological parameters in threecultivars of cucumber ( Cucumis sativus  ). Progress in 5488 Kumar et al.,
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