Keywords: Artemisia annua cropping; Multi-harvesting for high artemisinin yields; Artemisinin production in Indo-Gangetic plains; Rotationof Artemisia annua and conventional crops; Ratooning inArtemisia annua
1. Introduction
The sesquiterpene lactone endoperoxide artemisininand a variety of molecules semi-synthesized fromartemisinin are known to possess a variety of biologi-cal activities including those against certain protozoanpathogens, cancer cell lines, fungi and bacteria and
plant photosynthesis (Klayman, 1985; Woerdenbaget al., 1990; Bagchi et al., 1997; Beckman et al.,1998; Posner et al., 1999; Kumar et al., 2000a; Liet al., 2001; Borstnik et al., 2002; Kim et al., 2002;Khanuja et al., 2002; Shuhua et al., 2002).
Among the artemisinin derivatives, the compoundsarteether, artemether, artisunate, artinulate and di-hydro-artemisinin have been found to be highly potentanti-malarials (Anonymous, 1982; Jain et al., 2000,2002a,b; Bhakuni et al., 2001). Malaria is a worldwidedisease and according to World Health Organization
78 S. Kumar et al. / Industrial Crops and Products 19 (2004) 77–90
(WHO) about 2500 million people live under itsthreat. While about 300 million people get infectedwith malarial parasite, malaria kills about 2 mil-lion people each year (Anonymous, 1993). The bulkof malaria is caused byPlasmodium falciparum.Many populations ofP. falciparum in Asia andAfrica have become multi-drug resistant such thatmalarial patients infected with them do not respondto drugs such as quinine, chloroquine, mefloquineand/or pyrimithamine-sulfadoxine (Looareesuwanet al., 1992; Anonymous, 1999). Malaria caused bydrug resistant and sensitive strains ofP. falciparumand other kinds of plasmodia have been found torespond to artemisinin derived drugs; artemisinincombination therapy involving the use anti-malarialssuch as mefloquine and lumefantrine in combina-tion with artemisinin derivatives is proving effectiveagainst complicated as well uncomplicatedfalci-parum malaria in areas where multi-drug resistancemalaria is widespread (Van Vugt et al., 2000; Nostenet al., 2000; Wilairatana et al., 2002).
Artemisinins have demonstrated therapeutic poten-tial against several important infectious diseases, be-sides malaria. The patients of schistosomiasis disease,caused by the protozoan speciesSchistosoma japon-icum, Schistosoma mansoni andSchistosoma haema-tobium, which afflicts 200 million people and causes1.5 million disabilities, have been found to respondwell to artemether (Utzinger et al., 2001; Shuhua et al.,2002). �-Arteether has been found to block the func-tion of quinolone resistant DNA-gyrase inEschrichiacoli, Mycobacterium smegmatis and Mycobacteriumtuberculosis (Kumar et al., 2000b; Khanuja et al.,2002; Srivastava, 2002). In view of the applicationsarising from array of their activities, the artemisininrelated drugs would be in future required in commen-surate huge amounts.
The total chemical synthesis of artemisinin iscomplex and therefore uneconomical (Schmid andHofheinz, 1983; Avery et al., 1987; Yadav et al., 2003).The only viable resource of artemisinin is the plantspeciesArtemisia annua of the family Asteraceae.With regards to artemisinin production, theA. annuaplant has proved amenable to domestication and cul-tivation (Woerdenbag et al., 1990; Gupta et al., 2002)and several procedures for the chemical extractionof artemisinin fromA. annua herbage have been de-scribed (Jain et al., 1999; Kumar et al., 2001b; Tandon
et al., 2003). The large scale availability and cost ofartemisinin-related anti-malarials will be determinedby the economics of artemisinin yield fromA. annuacrops (Ferreira et al., 1997; Gupta et al., 2002) and ofchemical modifications on artemisinin to derive thedesired semi-synthesized antiprotozoal/anti-microbialcompounds (Anonymous, 1982; Jain et al., 2002b;Borstnik et al., 2002; Singh and Tiwari, 2002).
The artemisinin yield fromA. annua crops is ex-pected to depend on the inherent artemisinin contentof the cultivated genotype and agronomy of culti-vation. The artemisinin content of the variousA.annua genetic resources has been reported to varyfrom ≤0.01 to >1.0% (Liersch et al., 1986; Singhet al., 1988; Charles et al., 1990; Woerdenbag et al.,1994; Kawamoto et al., 1999; Gupta et al., 2002).The maximum reported yield of artemisinin from thefield grown crops ofA. annua is about 25 kg ha−1 (deMagelhaes et al., 1999). To improve the economicsof production of artemisinin and anti-malarials oranti-microbials semi-synthesized from artemisinin,there is need to increase the yields of artemisininfrom the field grownA. annua.
Earlier, we have reported upon the developmentof a artemisinin-rich cultivar ofA. annua calledJeevanraksha (Kumar et al., 1999) and organ-, de-velopment stage- and season-wise variation in thecontent of artemisinin in the cultivar Jeevanraksha(Gupta et al., 2002). It has been shown that the cul-tivar Jeevanraksha ofA. annua takes about a yearto complete its life cycle in the subtropical agrocli-mate and sandyloam soils of the kinds that occurin the Indo-Gangetic plains area. The seeds sown inDecember/January produce seedlings which can betransplanted in the field from February/March throughJuly/August. The field grown plants come to flowerin late September/October and mature seeds becomeavailable in November/December. In the vegetativelygrowing 20–30 weeks old plants, leaves are the prin-ciple organs for the synthesis and accumulation ofartemisinin; stems have artemisinin in about 10-foldlower amount. Usually, the younger leaves havemore artemisinin than the older leaves. The leavesof young rosette plants during their growth in thewinter season (December through March) have verylow concentrations of artemisinin. The expression ofartemisinin synthesis and accumulation in the leavesprogressively increases with the onset of summer in
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March/April and becomes high by May/June (sum-mer) and peaks during rainy season (July–September).The flowering plants accumulate bulk of their totalartemisinin in leaves (30%) and capitula (40%). Rootslack artemisinin at all stages of plant growth. Sincethe presence of lipids (oil) in the achenes of capitulamakes artemisinin extraction cumbersome, the plantsharvested in their vegetative state, when≥90% of theartemisinin is in the leaves and fine stem, offer thebest economy in chemical extraction of artemisinin.The harvested crop needs to be dried to about 5–10%moisture content before its chemical extraction. Whilethe crops harvested in the summer (May/June) andwinter (October/November) seasons can be economi-cally shade dried, those harvested in the rainy season(July–September) may require the use of speciallyaerated drying chambers/suitable alternate equipment,making the post-harvest drying process relatively ex-pensive. TheA. annua cultivation practices thereforeneed to be designed so as to match with the innatefeatures of cv Jeevanraksha and agro-ecology of thegeographical area of cultivation.
Here, we report on the results of an agronomicstudy over 3 years onA. annua cv Jeevanrak-sha, in the Indo-Gangetic plains geographic area,which allows two conclusions: (1) The artemisininyields could be very significantly increased bymulti-harvesting/ratooning of its annual determinatecrops over seasons. The preliminary results of such astudy are reported in a patent (Kumar et al., 2002a).(2) A. annua crop can be rotated with seasonal foodgrain and vegetable crops.
2. Materials and methods
2.1. Agroclimate and soil quality
The CIMAP experimental farm situated at Lucknowwhere the field crops were raised, has subtropicalagroclimate and sandy loam soil. During 1999–2001,the temperature at the location ranged from 8.5to 24.5◦C in winter (October/November–March),from 23 to 44◦C in summer (April–June/July)and from 21 to 33◦C in monsoon rainy season(July–September/October). On average, 115± 12 cmof rainfall was received, 21± 2 cm in winter and94± 7 cm in monsoon season; rainfall in the summer
season was infrequent. The relative humidity variedfrom 55 to 71% in winter, from 35 to 52% in sum-mer and from 65 to 76% in monsoon. The soil pHwas 7.5–8.5 and it contained 0.013 % N, 0.002% P,0.006% K and 0.3% organic carbon (C).
2.2. Cropping and sampling
2.2.1. Field techniqueThe experimental crops ofA. annua cv Jeevan-
raksha were raised in the winter–summer–monsoonyearly seasons of 1998–1999, 1999–2000 and2000–2001 calendar years. In each of the croppingyear, a nursery was developed by sowing the seeds inthe middle of December. Seedlings were transplantedto main field at a density of about 70000 plants ha−1
(Ram et al., 1997). Each crop treatment was repli-cated five times, using randomized block design. Acrop treatment in a replication occupied 5 m× 5 marea. Before transplantation, the field plots had beenapplied N, P and K at 80, 40 and 40 kg ha−1, respec-tively. The crops were irrigated as and when required.
2.2.2. Sampling of plants for artemisinin contentTo determine artemisinin content of the crops, treat-
ments were sampled replication-wise, 1 day beforeharvesting. A sample consisted of leaves in the vege-tative state and leaves and capitula in post-floweringstages, plucked from the tops of about 50 randomlyselected plants of a treatment in a replication.
2.2.3. Extraction and detection of artemisininSamples of leaves or leaves and capitula were
shade dried and pulverized. Hexane extracts wereprepared from 0.1 g of each sample. Concentration ofartemisinin was determined by HP-TLC (Gupta et al.,1996).
2.2.4. Parameters of multi-harvested cropsThe measurements made on individual harvests
were added up to estimate shoot, stem mass and leafyield of multi-harvested crops. The artemisinin con-tent (%) from samples of each of the harvests wereaveraged to estimate the parameter artemisinin (%) inleaves of such crops. However, to estimate artemisininyield, the yields of individual harvests were calcu-lated by use of specific leaf yield and artemisinin (%)and then added up to obtain multi-harvest yield.
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2.3. Transplantation and harvesting schedules
2.3.1. Treatments2.3.1.1. Experiment 1. Transplanting and harvest-ing times and harvesting frequencies were varied.The seedlings from the nursery were transferred totreatment-wise plots in the main field manually be-tween the months of February and April 1999. Thecrops transplanted on 27 February, 28 March and7 April had three kinds of harvesting schedules: (i)once harvested on 14 October; (ii) twice harvested—first cut on 15 May and second on 14 October; (iii)thrice harvested—first cut on 15 May, second on 3July and third on 14 October. The crops transplantedon 8 February and on 7 March were harvested fourtimes; the first harvest was on 15 May, second on 3July, third on 8 August and fourth cut was taken on14 October 1999. To ensure their regeneration, cropswere cut with the help of sharp secateurs, 40–50 cmabove ground level and a few twigs were left intacton each plant. The ratooned crops were irrigated thesame day, when harvest was taken.
2.3.1.2. Experiment 2. This experiment was like theExperiment 1. The seedlings were transplanted on 20February, 7 April, 23 April and on 25 May 2000. Thecrops planted on 20 February were harvested once ei-ther on 5 September, much before the onset of flow-ering, or four times—on 16 May, 23 June, 17 Julyand 5 September 2000. The crops transplanted on 7April were harvested either once on 5 September orthrice—on 16 May, 25 June and 5 September 2000.The crops planted on 23 April were harvested thrice—on 28 June, 27 July and 8 September 2000. The cropsplanted on 25 May were harvested on 8 September2000.
2.3.1.3. Experiment 3. Here the planting time wasconstant and harvesting time and frequency was var-ied. The crops transplanted on 20 February 2001 wereharvested only once on 28 May, 25 June, 25 July, 27Aug, 28 September and 20 October or three times, firston 28 May, second time on 25 June and thirdly on 28September 2001.
2.3.1.4. Experiment 4. In this experiment, the plant-ing time varied and harvesting time was kept constant.The seedlings were transplanted at different times, on
20th day of February, March, April, May, June andJuly. All the crops were harvested on 20 August 2001.
2.3.2. Post-harvest handlingFresh biomass obtained after each harvest was col-
lected, plot-wise tagged, weighed and transported forshade drying. After drying, the leaves and stems weremanually separated and weighed.
2.4. Statistical analysis
Each of the experiment, 1–4 had been laid in fieldby following the randomized block design. There were17 treatments in experiment 1, 6 in experiment 2, 7 inexperiment 3 and 6 in experiment 4, all replicated fivetimes. The analyses of variance and covariance weredone by following the statistical procedure describedby Cochran and Cox (1957)andPanse and Sukhatme(1985).
3. Results
The effects of variation in date of transplanting ofseedlings, date of harvest and number of harvests onthe yield of artemisinin and related characters wasexamined in the field grown crops ofA. annua cv Jee-vanraksha, over several cropping seasons in the sub-tropical agroclimatic environment of Indo-Gangeticplains. Tables 1–4 present the plant growth andartemisinin yield related characteristics of the singleand/or multi-harvested crops ofA. annua raised in1999, 2000 and 2001, respectively.
In the experiment carried out in the 1999 (Table 1),there were 17 kinds of crops which differed fromeach other in the time of their planting and numberof times the differentially planted crops had beenharvested. A total of seven planting times had beenused and crops obtained were harvested once, twice,thrice or four times. There were similarities as wellas differences between the various kinds of cropsstudied. When the planting time differences amongcrops were disregarded and crops were compared ac-cording to the number of times they were harvested,the four kinds of crops clearly differed from eachother in artemisinin yield and the crops could be ar-ranged in the following order in terms of artemisininyield: four times harvested (80± 15 kg artemisinin
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Table 1Effect of variation in the date of transplantation and number of harvests taken on the expression of growth and artemisinin yield related traits from the experimental cropsof Artemisia annua cultivated in the year 1999
Serialnumber
Number ofharvests
Date oftransplantation
Number of days fromtransplantation toharvest(s)
Shoot mass(t h−1)
Stem mass(t h−1)
Leaf yield(t h−1)
Leaf harvest index(leaf yield ×100/shoot mass)
Artemisininin leaves(%)
Artemisininyield(kg ha−1)
1 1 8 February 242 22.2 17.5 4.7 22 0.60 28.22 27 February 227 26.1 22.5 3.6 14 0.45 16.23 7 March 216 20.9 15.6 5.3 26 0.46 24.44 28 March 200 28.2 22.9 5.3 19 0.42 22.35 7 April 180 21.8 17.3 4.4 20 0.44 19.36 2 8 February 101, 242 16.9 11.5 5.3 32 0.55 28.97 27 February 84, 227 24.5 18.5 6.0 25 0.58 32.48 7 March 77, 216 23.7 19.6 4.0 20 0.45 18.19 28 March 123, 200 27.8 21.3 6.5 24 0.67 41.6
Table 2Effect of variation in the date of transplantation and number of harvests taken on the expression of growth and artemisinin yield related traits from the experimental cropsof Artemisia annua cultivated in the year 2000
Table 3Effect of harvest time and number of harvests taken on the expression of growth and artemisinin yield related traits from the experimental crops ofArtemisia annua cultivatedby transplantation on 20 February in the year 2001
Table 4Effect of transplantation time on the expression of growth and artemisinin yield related traits from the experimental crops ofArtemisia annua harvested on 20 August in theyear 2001
Serialnumber
Date oftransplantation
Number of days fromtransplantation towhen harvested
Shoot mass(t h−1)
Stem mass(t h−1)
Leaf yield(t h−1)
Leaf harvest index(leaf yield ×100/shoot mass)
Artemisininin leaves(%)
Artemisininyield(kg ha−1)
1 20 February 180 13.5 8.6 4.9 36 1.10 53.92 20 March 155 12.0 7.4 4.5 38 1.12 50.43 20 April 120 8.0 6.3 3.7 47 1.10 40.74 20 May 90 7.1 4.2 2.9 41 1.07 31.05 20 June 60 4.8 2.5 2.1 44 1.04 21.86 20 July 30 4.0 2.4 1.6 40 1.07 17.1
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ha−1) > three times harvested (42± 14 kg ha−1) > twotimes harvested (29± 9 kg ha−1) and once harvested(22.1 kg ha−1) crops. The three times harvested cropsgave on average 1.65-fold higher artemisinin yieldthan the crops harvested once or twice. The artemisininyield from the four times harvested crop was 1.94times higher than three times harvested crops. Therewas correspondence between the artemisinin yield,leaf yield and artemisinin harvest index (artemisinin×100/shoot mass) properties in the four kinds of crops.
It will be further seen fromTable 1 that the ex-pression of leaf yield, leaf harvest index, artemisinincontent and artemisinin yield in the crops harvestedtwo or three times was similar to the mean expres-sion of these characters in all the crops considered to-gether. However, for all these characters, expressionwas lower than the general mean in crops harvestedonce and higher than general mean in crops harvestedfour times. The crops harvested once, twice, thrice orfour times did not differ or differed marginally fromeach other in the expression of total stem and shootmass.
In the year 2000 (Table 2), the artemisinin yieldwas highest (62 kg ha−1) from A. annua crops that hadbeen raised by transplanting of seedlings in the fieldearly, in late February, and harvested intermittentlyfour times for shoot mass. Crops of comparable agebut which had been harvested for shoot mass only oncegave about 2.5-fold less artemisinin yield. The yieldof artemisinin was very low (16.1 kg ha−1) from cropsraised by transplanting of seedlings in the field late, inlate May, and harvested only once, coinciding with theend of growing season. The crops transplanted in thefield in early or late April and harvested two or threetimes gave about the same average yield (22.7 kg ha−1)as the early planted and once harvested crops. Theleaves of crops harvested twice, thrice or four timeshad on average lower artemisinin content than that inleaves of crops harvested only once. High artemisininyield giving crops yielded more leaves and/or leavesricher in artemisinin.
The observations of an experiment carried out in2001 (Table 3) showed that the three times harvestedcrop gave marginally higher yield than certain cropsharvested once; its yield was about 95% higher thanthe average yield of once harvested crops of the ex-periments. This experiment also showed that amongthe transplanted crops that were harvested once, those
that remained in the field for 18 weeks or more gavesignificantly more yield of artemisinin than that har-vested earlier. This latter observation was confirmedby the results obtained in the second experiment of theyear 2001 (Table 4). Here, the crops that remained inthe field for 30–180 days from the time of transplanta-tion to the first and last harvest were compared. It wasfound that the crops that were in the field for 22 ormore weeks yielded about 1.5-fold more artemisininthan the average yield of all the crops. The 22 weeksold crop gave about 3.0-, 2.3-, 1.6- and 1.2-fold moreartemisinin yield than the crops that grew in the fieldfor about 4, 9, 13 and 17 weeks, respectively. The av-erage yield of artemisinin from crops that remainedin field from the time of transplantation to harvest forabout 17, 22 and 26 weeks was 48.3 kg ha−1 and thatfor the crops which were in field for about 4, 9 and13 weeks was 23.3 kg ha−1. The corresponding leafyield for the two sets of crops was 4.4 and 2.3 t ha−1
respectively. Apparently, high artemisinin yield in ma-ture crops was related to higher component of leaf inthe shoot mass.
The large majority of the crops included in the twoexperiments carried out in 2001 (Tables 3 and 4) wereonce harvested. Such crops included inTable 3wereall transplanted in the field on 20 February but wereharvested at different times from May to October. Onthe other hand, the crops included inTable 4 weretransplanted in field at different times from Februaryto July but harvested altogether on 20 August. Thecomparison of results given inTables 3 and 4showthat yield differences among the crops of similar ageare related to the differences in the yields of leaves andpercent content of artemisinin in the leaves. It appearsthat artemisinin content (%) of leaves is high in Julyand August.
All the treatments covered inTables 1–4wereincluded in an analysis of correlations between thevarious plant characters included in the study andnumber of harvests. The coefficients of correlationsbetween all the pairs of variables are presented inTable 5. It will be seen that the artemisinin yield inA. annua crops was positively correlated with leafyield and number of harvests. Besides, the leaf yieldhad positive correlations with shoot and stem massand number of harvests. The number of harvests wasalso positively correlated with shoot and stem masswhich were themselves highly correlated. Thus, it
86 S. Kumar et al. / Industrial Crops and Products 19 (2004) 77–90
Table 5Coefficient of correlations between pairs of variables related to expression of growth and artemisinin yield in crops ofArtemisia annuaplanted at different times and harvested one or more times
∗ Significant with 95% confidence.∗∗ Significant with 99% confidence.
appears that multiple harvesting led to higher yield ofartemisinin via high levels of leaf yield accompaniedby increased stem and shoot mass. The leaf yield hadnegative correlation with artemisinin content in leaves,which in turn was also negatively correlated with stemmass and shoot mass. This indicates that proliferatedplant growth did not favor artemisinin accumulationin the leaves. The highly significant negative correla-tion between leaf harvest index on one hand and shootor stem mass on the other hand and positive correla-tion of the former character with artemisinin contentof leaves indicate that high yields of artemisinin wererealized when crops produced artemisinin-rich leavesaccompanied by least possible growth of stem tissue.
4. Discussion
The objective of the field plot experiments carriedout in this study on theA. annua medicinal/industrialcrop plant was to examine the effect of planting andtime of harvesting on the artemisinin yield determiningtraits. The overall aim was to use the results to designfield practices for high yields of artemisinin per unitarea of cultivation ofA. annua cv Jeevanraksha and tofit this annual and determinate crop in the conventionalgrain, vegetable and industrial crop rotations in voguein the Indo-Gangetic plains. The results are discussedbelow in terms of the objectives.
4.1. Multiple harvesting of crops
The artemisinin yields reported from field experi-ments on the genetic resources ofA. annua carried out
in many countries round the world, have varied from<5 to∼25 kg ha−1. In the presently reported field cropexperiments onA. annua cv Jeevanraksha carried outin the subtropical agroclimate of the Indo-Gangeticplains over a 3-year period, the average artemisininyields from once, twice, thrice and four times har-vested crops were 28.5±2.8, 27.6±3.5, 39.1±5.4 and74.2± 8.9 kg ha−1, respectively. The average yield ofartemisinin from the once or two times harvested fieldcrop of the present study was more or less equal tothe highest yields of artemisinin obtained from experi-mental field crops reported upon earlier (Liersch et al.,1986; Woerdenbag et al., 1994; Ferreira et al., 1997;Kawamoto et al., 1999; de Magelhaes et al., 1999).Significantly, the four times harvested field crops ofthis study yielded about 2.8 times more artemisininthan the highest artemisinin yielding field crops of ear-lier studies. The results obtained in the present studyhave on the whole clearly demonstrated that the inter-mittently four times harvested crops ofA. annua givemore yield of artemisinin than those harvested onlyonce, twice or thrice. These results mean that in theIndo-Gangetic plains area if a field is exclusively de-voted for a year toA. annua cultivation throughrabi(winter season)–zaid (summer season)–kharif (mon-soon season) a total of about 74 kg of artemisinin couldbe harvested from 1 ha of land.
The expression of the growth properties and cor-relation analysis among the various characters exam-ined in the present field experiments showed that acommon feature among the several times harvestedA. annua crops was higher yield of leaves as com-pared to once or two times harvested crops. Since
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the intermittent harvesting led to crop regenerationby production of new branches, the ratooning ofA.annua plants favored preponderance of nascentlydeveloped artemisinin-rich leaves among those avail-able for harvest and avoidance of losses arising fromsenescence and drop of leaves from old branches.Apparently, theA. annua cv Jeevanraksha crops aresuitable for ratooning because of their long life spanin spite of their life cycle being annually determinate,vigorous root formation, profuse stem branching, highlight use efficiency enabled by alternate phyllotaxyof leaves consisting of highly lobed compound leafblades and stipules and avoidance of leaf shading,competitiveness against weeds, high level of diseaseand pest resistance, and presence of high degreeof regenerability and maintenance of fertility in themulti-ratooned crops.
The commercial procedures described for the chem-ical extraction of artemisinin prescribe the use of driedherbage ofA. annua as the feed stock/starting ma-terial (Jain et al., 1999; Kumar et al., 2001a). Thepost-harvest logistics therefore include drying of vo-luminous above ground crop produce under ambientconditions, separation of herbage feed stock in theform of leaves and attached thin stems and storage ofherbage in moisture proof containers/packages. Theadoption of multi-harvestA. annua cultivation proce-dure will allow spread of post-harvest operations overmany months and extraction of the herbage in batchesof convenient volume, thus allowing many fold sav-ings, including those in terms of field space, energy,manpower and solvents.
It is perceived from the pattern of variation inartemisinin yield observed among the differentiallytransplanted and harvested crops of this study andquantitative accumulation of compounds proximaland/or distal to artemisinin in the concerned path-way noted in earlier work (Woerdenbag et al., 1994;Kumar et al., 1999; Wallaart et al., 1999a,b, 2000)that A. annua plants’ inherent potential for the syn-thesis and accumulation of artemisinin is perhaps fargreater then that rendered possible for exploitationby the multi-harvested crops of the cultivar(s) suchas Jeevanraksha. The following two approaches maybe pursued to obtain still higher yields of artemisininfrom A. annua crops: (a) genetic improvement ofA.annua for (i) higher levels of artemisinin accumu-lation in stem and leaves, (ii) greater regenerability
under multi-harvest/ratooning conditions, and (iii)larger leaf/stem ratio; (b) tight matching of each har-vest time with artemisinin accumulation peak, undermulti-harvest conditions of cultivation.
4.2. Rotational cropping
The land in the Indo-Gangetic plains is beingcultivated annually with three different crops in thethree seasons of the area (Kumar et al., 2001a). Thepreferred rotations are:→ rice/pigeonpea in mon-soon season→ wheat/lentil/Bengalgram/Brassica/potato in winter season→ mint/moongbean (green-gram)/uradbean (blackgram) in summer season→.The A. annua plant is now known to be well adaptedto all the seasons subtropical agroclimates, includingthose of Indo-Gangetic plains. The Jeevanraksha vari-ety ofA. annua sown in December at Lucknow locatedin the Indo-Gangatic plains area completes its life cy-cle in about a year. Its seedlings could be transplantedin the field any time from January to June so that20–30 weeks old reasonably productive crops couldbe obtained from any of these plantings. This prop-erty of A. annua cv Jeevanraksha allows developmentof several kinds of new crop rotations for the area.
In the Indo-Gangetic plains area, harvesting of Bras-sica and potato crops is completed by the middle ofMarch and that of wheat, Bangalgram (chickpea) andlentil by first week of April (Kumar et al., 2002b). Thecrops ofA. annua transplanted in the field on 20 Marchand 20 April in this study (Table 4) gave 50.4 and40.7 kg ha−1 yield of artemisinin. These observationsshow that wheat/Brassica/Bengalgram/lentil/potato(late harvested seed crop)–A. annua rotation couldbe practiced in the Indo-Gangetic plains and in areaswith similar subtropical agroclimates. It is also notedthat crops ofA. annua transplanted in the field on 20February and harvested on 25 July (Table 3) yielded31.9 kg ha−1 artemisinin in the present study. Theseresults reveal that rice–potato (early harvested veg-etable crop)–A. annua rotation will also be successfulin the subtropics/Indo-Gangetic plains.
In view of the relative profits from the crops ofwheat, rice andA. annua, it appears that the crop-ping of A. annua in rotation with food grain andvegetable crops will help improve the profits of farm-ers, while only marginally affecting the overall foodcrop production from a given area. The artemisinin
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manufacturer(s) could contract seasonal farming ofA.annua herbage to farmers who will make larger over-all profits as well as be able to save grains/vegetablesfor their own use, as is the practice on account ofsmall size of<1 to 2 h holdings with most farmers inthe Indo-Gangetic plains.
5. Summary and conclusions
The following important conclusions have beenarrived at about the field cropping of the annual de-terminate medicinal plantA. annua, the only viableresource of the much needed anti-malarial compoundartemisinin: (a) The intermittent harvesting of earlyplanted full time crops allows development of rela-tively large sized leaf mass at the expense of stem massand thereby high yield of artemisinin. Crops grown for≥30 weeks and harvested four times gave an averageyield of 74 kg ha−1, almost three times higher thanthe earlier reported maximum yield of 25 kg ha−1.(b) The short duration crops planted on one hand inApril and harvested in August and on the other handplanted in February and harvested in July yielded onaverage about 40 kg ha−1 artemisinin. This could verywell fit into wheat/Brassica/Bengalgram/lentil/seedpotato–artemisia and rice/vegetable potato/Brassica–artemisia rotations.
Acknowledgements
Grateful thanks are due to the Department ofBiotechnology of the Government of India for provid-ing partial support for the development of artemisinintechnology, the directors of CIMAP for the facilitiesprovided at Lucknow, and to the Council of Scien-tific and Industrial Research and director NCPGR forproviding facilities for the work done at New Delhi.The help of R.K. Verma, D.C. Jain, M.P. Darokar,J.R. Bahl, S.P.S. Khanuja and Suchi Srivastava is alsogratefully acknowledged.
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