University of Nigeria Virtual Library

Serial No

Author 1 OKEZIE, C. E. A.

Author 2 CHIKWENDU, V.E.

Author 3

Title

Report on Wild Yam Domestication

Experiment

Keywords

Description

Report on Wild Yam Domestication

Experiment

Category

Biological Science

Publisher

Publication Date

Signature

Gainin;; insiglil inro tllc origin:; ol' yam dmnicslic:!~ion 11;::; cngagcd 11ic alLcnl.ion oC scliol:us, cspccinlly ;\rcl~xologi:i\s, bo~misrs, linguists, ctllnogreplicrs and his~oi.ians. Arc11;lco- cthnokmtai~icnl nnu linguistic cvidcnccs lc~itl 10 assi!;n xi-cat anliqui~y LO ll~cdom,.:;tication or yam i n M'cs~ACricn, c:;pcci;illy i l l 111c ai-ca lyinl; casi of tlic Bandaix: !t i \ i l . iii ~ l ~ c Ivory C o a s ~ ant1 wcsrorlhc C:r,l?crou~i rangc (illcxrr~rdcr 1975). I

Choice oi' Expcrixncnt;~i Farm Siie W h c ~ w c npplicd lo clrc Lantlscapc Office for a prr ion of l a ~ d for r t~c cxpcrimcnt. thc nu~hor i~ics rcfcrrcd us lo ~ I l c Agricul- tural Farrn I\liar~agc~-ncnt to ricgc~tiilte lor. a portion of I;:n(l. This sq ; ip t ion wxs nor scccprablc ro us bccuusc artiricial fcriilizcrs 11;ivc been Iieavily applicrl lo t l ~ c Inrid. We nccdctl land wntlul- ~crarcti will1 ariificial chemicals as ihcsccnn Iring aboirt radical ctlangcs in t l ~ e cxpcl-inlcnlal spccimcns.

C Q ~ ! l r ( ~ i ~ j I'oi tlonicsric;lrctl ynnys, tl~crc x c sc\~cr:il aponon~ic pracriccs in\!olvccl in lllcii cuI~ivii[ion. Such prxticcs wo111ti incliiclc

, , clc;!riri~: o!' 1 1 1 ~ : la1~1, ~ill : i j ;c, ~ x S ~ ; l n ~ or. m o ~ ~ ~ ~ d i r i ~ , sswin: o[ sccd yams or sctts, inulcl~ing, watcring if ncccssnry, sl;i!::r:~, wccdinl:, : I I I ~ fcrlilixi- npplica;ion. Such practices arc abscr~r ['or wilt1 yalrir; or o~licr rosrlis j:i.owirlg i l l v i r ~ i r l rorcsls.

I n o ~ i r sl~~tl ics oil wiltl T)io:;r:or'ca pl;in;:;, v~: , Iinvc illc:i-cl'orc dc.vk! i iiic I'ollowin~; co~lrrol!;: - d

2. Loctrli~!!~ cf .E,vpei.i;.mntc!i' Sr'ics WIliIc S O I ~ I C pmp:ig:liion niatcrial:; (scctl yams ant1 sctts) wcr-c planted i!! o!:cr~ ikltis prclxirul tl~csarjic \\?y as for tlorncsticatcd I_)ioscorca species, sonlcorllcrs v/cr.c pl;tn~ctlriclit in tlic foscs~from wllicii sonic of rhc. wilt1 yam:; wcrc :ccovcrcd, and sliil othcrs wcsc. ph !cd ill nil opcn c;lvi~.onmi:ni wi!.ii no prcvioos !iislory I;: culiiv:i~ior~. I'lnn~ing in ;In opcn ficld cxposcs the yams Lo ihc same conditions as tlon~csticatcd forms while those planlccl h;xk in tile ~oscs t :c~n;~iri in an environment in wllicli they hay-, Lo con1l)cic \villi oihcr f'orcsr plant.? lor ~ 1 . 1 1 1 l i ~ i l t ns wzll as cl.hc: rcso:irccs of the forcsl cnvironmcnl.

3. Mourli1.s crnd Ridges verslls F'lafs arld H~lc. . - Mouiid or sitlgc rn;tking is a v x y nornial prncricc i n tio1i1cs1.i~ ynnl c~ i l~ ivn~ ion . Such is abscnrin ~ i i e wild from vihicll wi: liav,: tlcrivcd our cxpcrirncntal rna~crinls. Somc o f t h c ~ n wcre lllcrc- Sorcplantcxl on mounds, cirhersingly oranuinbcrolsetooi; one iiirgc mound as tlonc in sornc parts o l so!~thcsn Nigeria. Sornc oili;;.~ vicrcplnntul o!i ridges, orhcrson fh is Ihnth:ttlbccn ;iilcc'

nnd harrowed wtiilc still otllcrs wcre plmtcd in holes (IlaLs ;hat wcn: not tilIcd or hnrrowcd).

d

4 . Tending of the Plnrrls Anolllri i ~ n ~ o l we c~nplo:~ctl was on thc method of tcndir~g Lhc plants whilc they grcw. Opcralions like mulching, manuring (hrm yard manurc only) and watcring wen: ernploycd for onc set and abscnt in anollicr sct of planls in &r to sce how thcsc wild spccics would r cx t to such normal agronomic practices.

5. Time of Planring Currcntpracticcs in yam propagatio~~ is that yams are p l m i ~ d eithcr i n thc'dry scason or a1 h e o n w of thc rainy season and, dcpnding on, thk locality, thc calc~~(l:lr dates of thcsc opcratiorls may 'vary ,Onwucmc 1978). Our observation is that in most parts olscurh-caslcrn Nigcria, yams arc normally plantcd in March at Uic onscl of thc rainy scason. For thc purposcs of this study, wc havc tlividcd our planting timcs into"carlyl, 'normal' anti 'latc'. Wc thcrcl'orc llavc threc sets of control with rcgard to tirnc or planting. Onc s c ~ was phntedbctwccn January and Fcbruary (carly planling).ano~hcr sctbetwccn march and Apri! (normal planting), and ihc third s c ~ bctwccn May and June (latc planting).

6. Sole Cropping verszts Inter-Cropping I t is normal practicc to inter-crop cultivated yams with Nlcr crops such rw; maizcand okra. Solccrapping isabscnt in i ! i ~ wild yam spc~ics and in placc of otlicr crops thc wild yam stand will be growing withothcr forcsttrccsandshrttbs. Acontrol wassct up inwhich sole wild yam wcrc allowcd Lo grow along and somc inlcr-

, cropped will1 thosc c r q x also grown wi~h culiivatcd forms. ,This was donc in order to find out thc kind of ir~rcractions hat could go o,n bctwccn fhc wild yams 'and LIK crops allowed to grow arounjl them. . . -

7 . ~ a r v e s t i n g It is normal practicc to liarvcst yarns cvcry year at t l~c cnd of the rainy sqson or duriri: thc cxly pan of thc dty season whcn vcgctativc growlh k finishcd for thc ycar (courscy 19G7). But i t is known hat wild lorim :KC Icfl lo grow pcrcnnially since lhcy ,arc not bwally liarvcslctl for food. Mic havc thcrclore dccidcd lo harvcit annually, bicnnially, q u i n - qucnnially and dcccnnially in ordcr to noticc what c l f c c ~ ~ such l~arvcst would havc on Lhc s i x anti morphology of tubcrs of such wild forms,

B m d on visual observations ~nadc ovcr thc past six ymrs of study, wc wouId want to rcport the foliowing:-

1. Leaf Morphology Lcavcs are sim!~lc, cordaleand bornc on coniparativcly long periolesas in d~mcs;icatcd forms. No compound Icavcs have bcen noticcd so far. Thc tips of thc leavcs arc usually pointcd and thcrc is variation in l ed sizcs cvcn on tllc mncplant. In somc of tl~cslantls many glands wcrc no~icctl on the lcwss. L ~ ~ f ~ l r r a n g c m c ~ ~ t o n lhc vinc(phy1lolay)

2. S t ( e ) 'l'llori~ii~css of Lhc virlc has' bccn .>

drnsliwlly rctlucctl i n Ihc third ant1 fourth ycarspxirnc!ls. Vinc Icnglh and thickrlcss is also rctli~cctl rclnlivc to purc wilt1 forms. h4or.c ~atapl~ylls iuc bonic on vincs rclativc to thc situakio~i ir: domcsticatcd lorrns but fcwcr than in purc wild forms.

blorcspcci~ncns hnvc virlcs which ~winc to rhcri~,ht sliowing I! ':icy bclong to rhc sc~tion Ena~i~iophyIlum. 011ly very f ~ w spccinlcns Ilad vincs that twiric to tlrc iclt showing hi\? Ihcy bclong lo h c olllcr sections.

3. Flo~vering a ~ r d Prrdirfg bIorc pro fusc !lower- ing and fruiting occurrul in t l~c wild I;l;~nts grown i n tl~c opcn Cicld than would IIC cxpcctctl for clo~ncs~icatcd forms. 1,Vc counlcd ovcr lwo Ilundral l n ~ i ~ ~ on onc sr;mtl.

5. finlorn~logictr! Data Cnrc has bccn ~llkcil to obscrvc thc kinds of insccts which y k i r tt.tcsc plants right from thc ~ i n ~ c thcy xcplantcd unlil lhcy arc harvcstcd. Thecommon- cst pcsts arc tllc snlclling grasslwppcr (.Zcno.rorilrs var i cgu i !~~) thc pading snail (Lirnicolaria) and various typcs of bectlcs. A prcy ing m a d s nest is lotlgcd i l l thc foliagc, whilc 11ic ncsl ol'a bird (wrcn) adorns thc top of onc of thc yaln stands. Wc :lope that sincc thc llard parts of lhcsc insccts havc grcatcr chances of prcscrvation, Lhc prcscncc o l a nurnbcr ol' thcir rcniains in archncologicd conlcxt may bc arl indicator of Lhc prcscncc of yarn.

This rcport isdcsigncd to gcncmtccomnlcnrs, criticismsantl suggestions which will cnablc thc rcnppmisal of thc ~ncthods and aims in thc rcsc.arch.

Pattern of Tu bcr Dormancy I1 is known hat lrcshly harvested yam tubcrs cannot bc madc lo sproul i~nrncdiatcly (Onwucmc, 1975). Thcy go Lhrou::h 3 pcriotl oldomancy during which they ~anr~o~~pr~t~t(Cai~ij~I)clI, Chuk~icke, Tcriba and I-Io-A-Shu 19G2; Cottrscy 1967), with lllc dormancy gctling progrcsr;ivcly Icss with time aftcr harvcst- ing. As such, if tukrs ha t wcrc harvcstcd at the samc time are plantctl at dilfcrcnt timcs, h e earlicst planting wilt rcquirc a vcry long time bcforcitcan sprout, whilc latcr pl~t i r~gsrcquirc progrc:;sivcly shorlcr timcs to sprout (Onwucmc 1975). ,

Thc period of dormancy may bc only a 111011th or two wlli forcst spccics conditioned to a shorr dly scason such r;s 1) cuyc.nouis and U , watiii, ~ h c r x w stein bcgiiis to grow alnro:,l as soon as thc old onc has d ~ u l down. At Ihc otllcr cxwme, the mcm bcrs of Tcstudinz ria arc irtiaotcd LO sci~li-dc~crt conditior~s

4

a'nd arc dormant for morc than half the ycar. thc gi.owth of thc stcm? and lcavcs bcing coiuparalivcly ~nnsic~lt(Cour.wy 1967).

It is clear d~crcforc ihat thc lor mancy pcriod Is onc in wlllch thc tubcr stays without spioullng durhg the dry pcriods o l thc ycar which usirdly comcidc with thcpst-hxvcst pcriod. If thc yam tuber werc to overcomc dormancy, s;,routing of vincs would cxposc: them to thc post-harvcst dry srnson pcriotl which might bc so hot and dry as to scorch the vlncs and Icad to thc evcntual dcah of thc plant. Tubcr dormancy sliould Lhcrclorc bc scen as a natural way by which he plants Lidcovcr thc season, wh~ch is unfavournblc to yam gro~vth.

Wc arc not awarc of any rcport on tubcr dormancy of wild Dioscorea spccics. Wc havc thcrcforc cmbarkctl on scrial planting of wild tubers. Such a study will hclp us rnonltor thc lcngth of timc bctwccri tubcr planting and sprouting of vincs as thcy rclatc to diffcrcnt nlonllis and seasons of thc ~ G N . T h ~ s

.should give an indication of thc pattern of tubcr dormancy (if .,any) in such wild spccics. In thc future we hopc that available

1 .data will cnable us to comparc tllc tubcr dormh.,cy patkrns in , thc wlId and domesticatcc! spccics.

Results Thc resulW we arc rcporling in this study so far arc bascd on visual observation of thc morphological changcs h a t wc have monitored in our various planting locations. &!ore deta~lcd biochemical and physiolog.ca1 analyses arc going on in our various laboratories In the Univcrsity of Nigc .ia, Nsukka and such will bc rcporlcd in subsequent papers.

References Alcxandcr, J. (1975). "Yam domestication and farming in

Africa" JOAS Sc~runar LOWSOhT. Alcxandcr, J. and Courscy, D.G. (1969). Thc origins of yam

domestication. . In The domeslicalion and' Exploirafion of Plan(s and Aninuzls. P.J. Ucko and G.W. Dimblcby (ed.),

. ' London.

Aycnsu, E.S. (1972). "Anatomy of the nionocotylcdons. VI ' Dioscoreales. London, 0.cI.P.

Burkill, 1.1~1. (1960). " Thc Organogmphy and tllc evolution o l ! : thc Dioscorcaccac, thc Family of thc Yams." J. Linn. Scc. (Bot.) 56 (367): 319-412.

Camptlcll, J.S., Chukuckc, V.O., Tcriba, FA. and Ho-A-Shu, I

I-1V.S. (1962). "Sornc Physiological invcstigaticr:; thc ! Whitc Lisbon Yam (Dioscorea,alala L.) ." ThcBrcxkagc of I I . I !. thc Rcst Pcriod in 't'ubcrs by Chcmical Mcans. Emp. J . Exp. Agric. 30: 108-1 14.

Chikwcndu, V.E. (1979). "The Occurrcncc of M'aistctl Stonc Axcs/Adzcs in Eastern Nigcria. Nyarne A k u m 14. ! i

Courscy, D.G. (1967). Y a m , Longmans. London. Davics, 0. (1957). Wcsr Africa hcfore(heE~rropcws. Mcthbcn.

:I I . ,

Harris, D.R. (1969). "Agricult!lral Sys~crns,Ec'osystcm and rhc I

Origin of Agriculture. In The Dorncslica~ion and Ex~~loila- , lion of Planls and Animals. P.J. Ucko and G.W. Dimblcby :.lj I , (cds.), London. I

Okiglm, B.N.(1980). F'l,u~lsandFoodinIgboCultiuc. Ahinjiokrr ;:I ' Lcclrrre Govt. Prirlicr, Owcrri; 11; Okonwo, S.N.C. 91983). "Thc Botany of thc Yam Plant and ils g

Exploitltion in Enhanccd Productivity of thc Crop. In Osuji :I .

G. (d.), Advances in yarn research. i \ I Onwucmc, I.C. (1975). "Influence of Storagc Time on Exli- '! i

ncss o l Sprouting and Tubcxing in-@oscorea Rofundato ;I ,I ;!I Yaks. J . Agric. Sci. Cnmb. 84: 503-505.

, ' , +,j Onw~~cmc, LC. (1978). Thc Tropical Tubcr Crops. Yatrrs, : ,)1 I

Cusscivt~, Swcer P o ~ a ~ o , Cocoyams. John Wilcy and Sons. ';;I Chiccstcr, Ncw York, Brisbanc, Toronto. ,!:I ' i

Sharma, A.K. and Dc, D.N. (1956j.. ','Polyploidy in Dioscorca. . .

:!/

Gene~ica 28, 1-2: 1 112- 120. , , , , ,

I !

Sowutni, M.A. (1978). "Thc Pdynblogy bf tile Nigcr D c h . : I ! { : Palm rcad at Seminar, Dcpt, of I-Iist.,Univcrsity of Nigcria, ':,:I ,;I