inter.ctj,ons utthin sol1 plant atDosphera continuuh Tt ihplov

Dracossrox
a co:d:rlex phenoh€non involvlhq ilvnailc
inter.ctj,ons utthin sol1 plant atDosphera continuuh Tt
ihplov€ dlouqbt r66tst.!cr., tt is lnportant to knov htt
th€se factors inter.ct :o tead to rater stres6 in pl'at
ti.3u6.!d hd tbe Flan! retpondE and atlapt6 to this 5t"3s
in ters of groeth .nrt productivltv. E35cni1a1 to tl'
Fredictlor of genettc tlprovesent ln drvland plants i5 an
qnderEl;andlns of lype or valet lirttauions encount€led in
t6hs of tihlng, dtrration and intenslty.
Dtought' i.
!to6! ol tha .tudl63 r.ported on rlter stress and lts
elrect on plant gloFth have d€Fended on natural cycles of
stre5. anil in Dany of such 6tudi€3 no atlerpt uas .ade to
leasura th6 actual soll v3tei 6tatu3 aa extsted durlnq t.he
coa!3. o! study. !is.l,€! antl sanche.r (1919) and Roar
€t al. (tee1) Etuci€ir th. .alsct of v.rio{. p€riod of
drought on g!.!n yleldr d:y !.tte! produclton and harvest
index blt di<l sot pro,, r d€ any infollation ol soil eate!
content. Tarukde. et al. (1e39) dld glve detalls of BoiI
,at€! deplotion ulch tlhj, Ih n sirtY loa$ 3oil tith A fleld
c.paclty of 35: and v.ilting polnt of 16'at (bv leight). The
only tteatneDt in q:'i.1 lvallable v.ter rerli.€rl |telcq
elttlng pol.t (tr5 dayli oa6 uh.!e no trrlgatlon laa applred.
a tfeatDe.t sifrilar to one of the tleatnents apptied tn tne
pr.seht 6tudy. the dip!€sEion in grain yield obtained by
Talukde! e! al. (1939r ra6 4e.3t a3 against 14.31 to 56.7*
oblalned ,1th .ev.n relotypea ln lho plesent Etudv. ihe
et aI. (1939) is rithin the
rang€ found in the pre:ent Etudy. It lay be noted that the
dlratton ot sater str+is belov rilting point uas abcut
69 alays as agathst 35 ia/r on a rhole 6oil profilE basls
calculated floD r:he pir:! by Talqkder et at. (re8e). the
valiation in yielit 3,)pres6ion Eeehs to be genotype
d€pendent. In addltlon croi ph..ology and duratton of stress
beyonrl ,ilting point r.,a, ptay a !ore in ylerd depressicr.
Ritchle (1s31) conrenled that ,ater extra.tion j{ so!,e
in6tanc€E dontinues ever! beyohd -r5 bars (oitrlnq poinr),
Thls lay t. true ih th€ presen! stldy as €vcn th the !o6t
affec€ed E€notypes tbe green leaf area did not cobpl€tety
iltsappea! (an lndica':ion that rater vas srilr avairabre)
until 23 ttay6 afte! the 60ll leEch4d th€ virting polnt
(genotypes AzE-17 and pAv.n !t9.6), Ratliff et at. (res3)
dEfined the 1016! lihtL as the touest fleld seasured later
cont€nt of a Eo1l afte: pl.nts bad stopped extradring vate.
and u€r€ at o! nea! pr:iarore d€ath o! trcore itonant as a
r65utt of aat€r
alvel er al. (1e6s) on the basis
ot their 6tudle. suggell(d lhar in rh6!r about
of uater ls present b€Lr,:en rhe upper atlained Iinit and the
depr66sion obtained by lalrhder
In th. pr4rent studv aboui 1t4 nE vater tas
present b€treen li€ld czpacity and tiltt.g point (Fig. 3), a
fiqu!€ fa! 6ho!t of r )c e the loter lange grven by
va. R.vel et a1. (1e53), il flsure6 of 1eo_2r0 b gtvet bv
va. Bav6l 6t al, (1963) are lssuf,ed to be colrect then in
th€ preao.t study dtlcas{: 36 hn (t9o-154)
{210-15a) of sate! ?as ',till availnbl6 to p1anr. uhtir tb4
lover llnit eas reached- Dtre to placticat itlfflcll,tl6s uater
content beyond vilting !,urr't could not be !e;sured in the
p!€s€nt 6tudy. A recent €tudy !y cutfortn et ar. (teel)
relnfolces the alquhoht qiven by earlier aurhols (Ritchie,
1941; Rallirt et aI. 19st). Thcl! definitioh of torer tinit
rrose. lihtt of avail.Lle uarer lep!€sents the ltnit of
transpilation ,htch 16 t.rs. rh.n rh6 lihit for groerhi atjd3
a ner illDehsjon !o th: urderEranding of vate! avatrabitity
for plant glovth- Th€ .: r.utattons hade by curforlh 6c :1.
(r99r) lndicite that trr spring rheat at teast 44 m of
eater i3 avaitabl€ b€rre:r - r.5 |r p. and - ro x ra in r20
cn l.yer of aoil, As alte.dy nention€d jn tbe presenr study
the noDe o! th€ gonotypi s u6ear het the ateft.irion of to*er
lielr of ,ai6r avajldb|ily fo! quit€ sone rtno .fter tue
soll plofile h.it r€acheit th€ r1lr1n9 potnr (-1.5 M pa) n.
thcls e€le indication3 of grorth b€yond vitti.g point.
Iover libit.
at al. (re63) rere of rh6 viee rhat for Eany
anhu.1 crops th. tok6r lrrit
of a s6lt nay
van Bav.l,
i?l
be constant. Hov.ver, Brown (1s?r) lound thst tl e
€xtlactable e!ee! vns nhou. r55 rn in n feltlllzed 30il .s
agalnst 915 bn to! tlr cnleltirized 6oil. Tho Plants 1n
fror ! gr..tc!
feltlllze.l €ol1 rera nb:c to
atepth (5o @)., h the Dr.s.nt rtudy vhen iooting p.rtern ts
tak€n thto conslder.tion the concept o! eater availabitlty
becoEB quit€ Intrtgulng. oep€ndtnq trpon tt'. 6t!.6s
t!.atiert a.il th€ g.DotypeE 9! to loo* o! root6 ver€ ptes.rt
ln tbo o-,t5 cD soll pr.fiL€ rhich reacbod t[e rlltlng point
vithin ?o daya in t'o {!o irrisation) and s4 d.),s in Tt (..e
illlgatioh at ro dnys). rr 12 (one tfrig:riur, ai 1ol dats)
th€ o-45 c. laye! sas b:.to, vilting poinr aros roth day to
102 d.ys. As the iltigiti'n
to this trearreht saa given on
1o3rd day rhe 6oit not:iura rose ab4v6 uirrlng poinr ahd
r.!atn6d atlove rc u::to 126th c.:,5. ,r'he g.orth ah.ly:.i3
sugqests thnt plllts. rer:e able to 9ro! lhtch co.fires th€
contaDtion of Ritdh,i. (re8r) and cutforth er ar. t19er) ri.ar
vater r€Eins avallabl6 Dvon b€t@ rho rllting point.
Anothe! inteleBting teature of the ples€nt study is
that €ven in control vher€ pertodtc irli.gatioh va6 applied
the later contenl in th€ o-,{5 cn $olt taye! ienained no3tty
b€Iow field capacity abd ,.tth the Eassag€ of tltre it.
fluctuatBd vher€ sltit rarer de!icit {soil iolsture r,o:o,
ri.rd capaclty) va!teJ b,:ieeah ro nn ro 3t hh, (FIs.2) A
Bituatlon sonc rhat srr,Jlrr to the ohe obtlinable in T,l o!
lahkd€r st !1. (19s9) rhor€ ltrlgattod tas cithb€ld aft'r
65 d.ys. tloeever. In the p!.6ent Btudv tbe vl€ld6 {e!6
no!!.I uh€!a.! ln cA.€ o! €sp6!h€nt6 conducled bv faluxder
ar al. (19s9) th.r. e.E . atePr.sslon of 2ol ln grain vleld
rhlch 1. haral to €xDtain.3 the vater content in th€ soil
ploltr€ nevar r6nt b€lot lc.dilv avallabl€ ranqe'
unda! lor solt tolslur. atatus, the q€notyp:'
diita!.nc.. in grltn vt€rd !€corded In th!6e v€ars, appe"ed
ro reEult fro! . cotlrtnatlon of intafacting factols
a6€ociateal rlth a.siDir.!e paltltlonilg in both root ahd
6hoot 3y6te.s, rate! r.Iation6, glycinebetalne'ccunul'tlci.
carbon isotope di3cri!!BLion. sulvlving tlllers index and
lFlka yt.t.li 16.l ar.. ,l.v6loPDenl and aenesceDc'' harv'st
lnalax lnd yi€ld polcntra:..
r'.i|tt.t.
PrrcltioDltq
lole of earlv
vigour eluctatatad thc .ol. lt pl.v6d in incr€a'hs crv
ratte! and gr.In yl6ld ti.thout.llacting h'rv€€t t[dgx'
tloeev6r, €hay cautloh.d ihat in so!6 Eitu'tionE specilIrv
und€r telninat 5tr..s l! bav have t negative eflect ln th€
ples€Dt 6tudy evan uhder tolrlnat drotght the €tllv vtgour
{top {.!qht at 5 r6a! sta94) had a Pdsttlve effect' The
qenotype rhlch shos€d tho hlgheit early vlgour also gav€
hlqb6.! btologlc!l y,.rd, gr.lb vI'Ld 'nd h'rveEt indo'
Luallor .nd t{ucho* 11990) tllBou$tng th€
r?5
the qenotyPa qrhicb 6hoted the podr€s! elrlv vlgclr
6160 9!ve lodes! vielL :nd harvest index of the e€!'n
genotypas u6ed in r,tst ri ahe case6 th' patie'n et6 sinlrar
}Iicolns (1e3?) founit '
(rabled 24,?6).
.tgniflcant colr€latio: t€tv€en e'rly vlgo$ and grain yiei't
tn:2 genotypes of vhlat. l siDila! lelationship vas folbd
by esecar€llt (lss?) Ln .at€ of balr€v Tdrner and Ntco)as
(1es7) theorized that I hiqh tlansfer of assinilat6B r:r
glaln sould latiniss r:l'€ barvest ind'r unde! terBiinl
drought. ilirouqh :..lv vlsolr vas hiehlv correiated to
harvest inde: !n 6ll tr:rrsents used in th4 preEenE atudv
(appendlx A-D). The cont.,nllon lnat these values lete due to
high transaer ol a6slntra$s to gratn seeds to be doubtfur
aE Ih the pres€nt case the totes! balve6t tndex !16 found ln
.11 tenotypes uhder ter.inal druu'rht and th€ hiqh66t in
fulry lrrlg.te.l Plot:i eith internedl^;d valuos for rrre
antharls .nd po4t an!,l!.i! drought This is to be 6xpedt'd
a. palt c! !h€ 6..r-ri:::{ unde! etre!6 'ou1'r be n€dded to
raintatn tu.gor ad .stati' pot€nti:l and
leqllr€oentt l.r pr,r't sulvival Tne t!'nsporl of
asinllates nay be ItP:J1l due to nlrrovlnq of transpori
sy5t.6 6s a !€sult? o! st.rlss fh' ljteratnre on sucrr sliqv
could not te found t!!L tftr 6tudy conducted bY ^zni atrd Al'n
(1eeo) un.ler s.Iinitv s:resd Indic'Ees thaL tha nuhber 4r
vascular burdl€s p!t'gtt:tsiveiy dcclease uith increasrng
ehereas
sallnlty thethBr tar€ \i]}eng
studylng. An indlcrtirn th.t
asslbitat€ Plays 6o':e part in
be had !n ca.e ol g.io;t!€6
ubder drorght eould be volEh
in 5o& 'ase6 transfer tf
det€lDlninq harvest lndex crn
growing uhdcr droughr' Henti
chakr!l-36 ehlch gave s:'.Jntflcantry louer biological vrel'r
than c-22s, had sigLificantlY htgher harvest inogk
indicatlng poor Dobiij.,!,tlon of assinilales fot grain
fortr.tion in c-228(raLre 24).
lllcoias (1e37) end c6ccnrclli (le3?) did 'ot
study root palaneter z!- .n early gro*tlr stage Ho'evet'
Tulne! and nicolas rbr,l:ulated !h't eaxlv vigou! will
@xtDlse satar u5. r.d Liinloise 'at€t Ioss and deep toils
eiIl !.xlDisa vater u'.r .".llabiritv throush 6ut lha 3ol1
prollle. R6ot dlv N )ight studled in lhe Dres'nE
investtqation behav:d riDl larl) to earlv vigour in il6
associatio. sith yterd .fd har!''s' lrcex ('{ppen'rix a-D) Tr'
vl9orou6 qenotype€ I'ait higre! root drv telqht (Tabre 14)'
Turner ahd
At Daturity in all .t.ess treatDants there vas a1':
reducilon ln top ,.iqnt rhan .oot dlY reight (Tahr' 15)'
rhl6 tlndltq vnt sirilar to sh.rP anc rinvtes (1e7e' '
Passtoula (lesr) .n,l triqlrt et ar' (193r)' Oifferences in
total root dty seiqht betseen genotyFes
iloathents {e!e dpP.renL, qith Azs_4 produci'9 942' 5C2 an'l
9o4 19 rra_l no!€ root dty n:tter than Azs-1? Tot'l root dlv
signlfic.nttt co!!eI'!ed sith str€ss yI€ld
,he!6a6 tt vas non 6ignificant under nornar lrrigation
eith tbose ol
{appendl! r-D). Th€re ?€iu1tE are In asreen€nr
xlsla and chaudh.ry (1935),
The root diy rolgh! !t tratufity va6 not genelallv
higher th.n at antheei! (Tabre 10) tndicatlnq that r6ot
has been
Elor.th Etopped afte! an:h€sis. This Pheno[enon
repolt€d ty Eanv authols (Hu!'l/ ]e63; Plnthusr 1e6s and
qenotvpesr
t|ack€y, r9?3). tloreve!, root dly ueight tn fou!
hlghe!
Azs-4, AzS-11, C-22s and chAktal_o5 'aE signlflcanlly
at natulIty than at anthesi€ und€r tsrrinal drouqht
lndicating root grocth after anthesiE (Table 10) o'tool€
r€vier alticl' nentloned the
plesence of genotype! {rrlch continued thelr !oo! grovtn
6ft€! 5nth66ig. The continuod root glouih vIIl extract tate!
frotr d€eP€r soil hy€rs and rill plovlde additional t[otrnt
and Blantl (1ess) in tiei!
of r.te! to plan! durirg EeDsltlve reploductiv€ phaE€6 to
lt
avold droughE 3t!eE3 and i,6nc€ hlqh yt'ld under drought
lay tE not€d th.! thl€ Fh..oo.enon ra5 obselved onlY ln fou!
qro{lh
genotypeE. Azs_4 va€ the only genotype ib vhich loot
alEo co.tlnuad af!€r a.ihe6i6 i' Tr' Inter'stingtv this
genotypeg is the Dost drouqht toleranr' lbeth€t conttnr':d
root groulh plavs atry !ol. ln drought tolerance is difficdlt
In nosc of th€ studi6s root selgh! is taJ<€n at a'
indieatlon of loot grovlh. lt is Euggeated that root thdex
rik6 haw€st ind.t t.'ultt defins the partttloninE of
aErilil.t€s in a torc o.lnlngfur raY' rhd !@t rndex :s
tlefin.il as tbe rallo ol too€ baes to total biologlca] iaaE
{otal blo}oglc6l
mass
rn inleraiting flc':Li.e ene'g€s {hen this c'lterla iE
!€eat to analY6€ the drtr. At 5 lcaf stage th€ varjation in
loot lndox i3 no! nr ul\ snon.Jst tlre geootvp6s' lt var'is
b€tresn 23 6nd rrti iDdicatiiq lhat at 5Ieaf stage '
/,
F{bstabltal atount of tsrintlatdgoes lhto loot deveroPrent'
tzs-a uhl.h 16 drokht tolG!.nt genotYPer had lhe hlghest
v!1ue folloved by Azs.11 vhich is llso - tol6rtnt 9enotvp6.
Azs-l? vhlch th tl,e Dre.n'nt Etudy lras been found to be !h6
llost auscep",lb]€ h:s t.€ lsast value. ths picture tnnt
.irit€ interosting (trbre lr). 'rlE
.r6r9ss at @tulitY
loot lndex aror.tc ia I .Jenoi:yp65 under no!n.1 lrrlgrtion
1€ r5.2 vhtch is ii"co-.:r all taeatnent€. rtre high€st vaLue
eer€ !o! tetnlnal anrl ,:o :n!:he$1e stre*' Those qenoivt:s
,hich tete a,tle tu lri irn ror9.a tbe a'sir'llates to :ne
loot vere th6 ones alc. ro ri-lnrta"d dtotshl.
Azs-3 and Azs-lr thich f,ad slgi,ili.antl-y hir;her rool ind:x
lL{!
ol a.e.!
lld Ltrlty
It i L.!!
't.E.
G.!otlt.. 6!ra lt!r14 Dll!.t.!t lat.t l.gh.t
CenotYP€
Tl
'..2
D
31.1
B
!
15.9
B
,
for loolnol. 5e. rob|.
5
under 5tr666 sp€cillly unle! sovere slress (Te$inal and pre
anlhesis ) gave slgnlficdntlv higt'er srain vield' The Dosi
66nsitiv. genotypq. azs-17 and Pavon <lid not shoe anv ch'nqe
in root indes und6r varloug treatDent6 {Tabl€ 33)' The
colrelatlon bet|e€. loot tndex and qraln vield tas htghrv
significant (rig.s) vith th. valuee la'ging flon o 53 to
o.93 under stre.. condition6. Ho{everr under irliglted
condition the correlation t.s negatlve indicating that
lnveshent in root grotrh lad noi cohducive to production of
The leEulls.epofted j.f conlined undcr wartous
€coloqical condltions nay provide Elngle criteria for th:
.alect1on or q€notyPgs for drouEht €olelance nnd fulfill the
neen for ,hich rany sctgntlsts have been 'o'king ror so
long, A! least flon the Fr€sent study ihele i6 €verv rE'6on
to beli€v. that th€ 9en6!vp.t vhich haae the capabilltv or
t.ansaelrtng 1016 o! th€ .sshilat' for root qroeth hlve 3n
advantago over nor tfan6felrj.n9 geno!y!6s'
v.rttcal df.trlbution o! root dry laltef 111u6!r'ted
(r19. 5) 6ufrici€nt genetlc vartatlon ahong genotvPos in
their abllity to hodify the pattern of root dlv battar
allocation und.r €tress. Frank and aaule! (1991) deterDl'ed
ibdirectlY roottng acttvitY in ciEsted and ee3i6rn
rheatgla€s dultng vegetrttve dev'Iopnent bv evaruatln'J "t
sater extraction Pattein. the late or dovnrard roottnl
plant
actlvity in both th€ sl,e':ie6 tas asdoclated sore tith
t3l
a
to r
f rlta.rtlotrt-s511.9t!t
rt , i.e!r.ot.t{rr-|rr, (isr
Ir
tY
rr9s,Otrikr{ot2.t3r!
Prhd,Y,l5r
ioor
tNo€x
rr95fir-D9o.1ror
Fig:8.th. r.torto.rnip lrtw.en.oor ind.r ond g.ca.,i.td
und.r 3tr.3, conditions,
d€voloPlent €taga thaa vlth soil ,tter conte't The
9€notype6; Azs-4, Azs-tl, c'22a and chakral-a6 6ppe'r€d ro
deeply then stressed (To) |
di6trtbut6 dly
clearly lncreas.s in den6ity and dePth of rootinq can herp
to .ustain a high rate of vater eatraction ih drvjns aoil
(shaip and Davi€g. 1135) and lay Pronot€ substantial
ihplovenent in ylqtd IrL dr/ years (Jordan et at. 1933). such
phenotypic pllsticity !r dry r.tte!.e.!6
to be{deslrab:Ie
trait. Euld (1963) in vheat, Joldan and nonk (1930) nnit
Retta et ar. (1932) in golshun leport€d plae€ic re6pon6e fo!
.leep rootlns unde! drorqirr. such ph6botypid lesponse dtd rot
tn fodd€: 9ras6€s (rrank anit Baur€rr 199tr.
I-dlor an.t tucbou (rero) ctins Ricbalds .nd caldoerr (1917)
.nl Turhar (1936) havs sogg€Ered that d€ep .oor syEr€n co)td
b€ a<lvantageous ln p.oviding ,ater !o roots in the uFp€r
layers to k66p theb allr€ ahd alloe the upra)(E ot nutrients
ehlch occur iD the upper 1ay€!s and also leduc€ the
productton of horbones signats vhictr leduce leaf grorth and
stoEtal conductalc..
Jdentiflc.tion and qtili.arion or tbts dest!.d genetic
valtatlon lay teaat to rhe developbent of loot systeh bBttpr
.ble to p.otect 6en6ltlv6 .reproducttve evonts rlon
.nvilonnahtal 6t!€6s.r .nat providinq opporrunttles fo.
lnc!.asing 6tr6E3 yl6l.d,
Dl
ElAlt X.r.r R.lrrton.
||ate! 6tr€33 at 6h@tlng to lteading 6ta9e of !l:nr
d€v€lopr€nt has the Ereate6t €ffect on rhe.! g!.in yietd.6
conpar€d to arlsss .t othe! sta9e6 {Rab €t at. 19A4 and
Talukder et at. 1939)r earor€rcnt of pl.nt ,at€r statuB at
thl6 critlcal staq€ vill b. IDportant fo! charact€rizing the
pra.t lesponse to di@ght stress. an avelagrng or
rea! fate!
potehtl.f ov6r the rhote .tresE period i6 a
bstrer e.ttDate
of cuttlv.r respons€ tbah a Elhgle Dessurehent obtain.d
at
p.ak Et!.s., atthouqh cultivar. u6u.rly
nlintain tr!€ir
lelatlv€ r.nl.ihg .s t€df vater potentlat
decrense6 sith
atress lntenstty (Btuh, 1rr74 tn sorghuni
o,Toole and roya,
re?8 ln lice ahd B1ur, 19ao in ubeat).
valiartoh in le6f
rat€! potential abolg el_:at curtivals
und€! &oi.tu!s Etress
eaB founat (tlrcher a.d saDche.,
19?9i Adjel and xi.].h.n,
r9aoi Bluh et al. t9r11 nbd agg.tual and
sihha. 19s?). a
differ€nc€ tn leaf vater por€ntial of _3.3
to _r5.1 bars
(-o-33 to -r.51 u pa) betreen extlen€
g4ot)ipes uas fouDd.
-r.s to -2,0 b6r. (_0.r5 to -0.2o ,,r !a]
^
allfleiehce is
gufftcl€nt to 3lgnlflcan!:ry
dlflorentlate cuftrvarE. In !r€
ple5€nt study a dtlference of _15.5
ba!6 (-1.55 M !a, Tabl€
l?) ea5 found.rong 6.ven senotyp€E indrcating
rhat planrs
rare frcing
c.norypes h.ving lover leaf vater
potentlal rhorod h19h grrth yleld
{Table 2a). fhe6e lesults
ar. .lbitar to thos6 of llllnr€! €r at. (less).
leaf eater potenttal and leat
turgor potentt.l 13 d€picted ln Flg.g. rcaf {.ter poLertlal
decrsaE.d as the s!!€ss progreEs€d. Turgor potenlial f€lt
lith thq l@ellng o! leaf rater Potential bui the rata of
fall eas half to that of lea! rat.r poteDtial ihdlcatjr,s
Gnotic adjustb6nt {al6:her aDd sanche2, 1e7e) If there oa6
no lccunulatioh ot scluree and the ahount of solur:€s
r.ialned constantt turq.r potential vould be expected to
ral1 coDcurrant to la6f uaie! Potentlat. Zelo tui(lo!
potghtlal at -3.57 x Pa leaf r.tet potehtial i6 predicted in
thls study vhereas rlolqan (1931) and Xorg.n antl cond.n
(1e36) !€polt€d a vilues of -3.3 M Pa in hlsh ostotic
adrustlhg rlnes. und.r stress treatrents A?s-4 h.d h!gr-€!
tutgor potenttal at lorr!! Ieaf vate! potential as coupared
to oth€! ge.otypes. The ability ot Azs-4 to haintain higher
turgor pot€ht1al seeDs to be a. iDpoltant adaptation to
vate. deficit. olr result :re ln as!€enent uith thoF. 6f
Fischer aDd sahchez {1979). fhele ls need lor fuither srudy
to flnd 9.Dotypr6 valiation lor hish€r turgo! poten€ial nt
lore! leaf pater pot€ntI.t, Thls ibfolhation nay b€ use:lrl
for breedlng drought tole:ant genotypeg
Th€ !€ratlonehiP betr6en
ln the ples€rt 3tu:ly genotypJ6 varlation in lDaa
osnollc potential anorg sev€n eheat genotypes ua6 found.
I!€af osnotlc potertial C.creas.6 as the str€ss lntehsity
.rlff.r.nc. oa -9.. ba!! (-o.9,{ r r! t.bl. 1')
r35
.fi,1'*, "'r,r
Fie:
e
.r,.;-:Ii;il:i*-fffi
rr r nrai ror€trq!
t&,.,
.rh. r.rdrionship
i";;
;"i;.;""nrior ond r.o,
rurgor pot.ntiol und.. 3lr.ss ond
non .rr.s, co.dirio.s,
r.,".-
iD t€.f osnotic potaltiat vls found betreen tbe host 6n.ll
l.ast tol€i.nt 9€notype6. rzs-,t had the louest reaf os[otic
potential vhereas AZS-17 th€ highest. These ale the
g.notypeg Bho{l.g tol€rant a.d .o. to16!ant !.sponse
lespectlvery to vallous tralta related io droughl loleranc€,
F13che! and sa.chez (19?9) found a dtff€!€nc€ of -13.1 bars
(-1.31 x Pa) bet{e€n ettr€no genotypes of sprlng rhea!
sb€r€as xeiD and Kronstad (1931) and schonf€rd et a1. (1933)
found -16.5 bars (-1.55 x P6) and -s.r bals (-o.31 x ra)
difference lospectlvely in rinte! rheats, hspite of th€
large dM.r6nces ln the llIgheat aDd tbe lores! reaf oEDollc
potentlal x€iD anC Xror'Etad (1931) did not ftnd any
dl!f.!.ncsa In qraih y:erd. th. lelatioDshlp b€tseen ognotlc
potentlal and s!.in yj.rlil does not seee to foltou any
.on6l6tent patt€rn. P€rn.ps this Is th. rea6on vhy ogDottc
adJu.tlent i3 conBlateEeit hole applopriare para!.t€r
8p€clalry tn vheat ehere it orlelate6 ,erl lith halvesr
tntlex (Xccosan €t al. 1934; uolgaD and condon, 19sG and
r{orgAn et ar. rs36). aen?t.icarry vallabltlty for thls tratt
In vheat na6 also be€i !€polted by Blun et ar. (r9s:),
rblgan (1934),.and rorgan and condon (1936). As tn rLe
preeeDt 6!udy 6shotj,c E.Uu3tre.t was not studiedi lt ,ourd
not /po6albl6 to ascertain their appttcabillty.
Inteleatlngly I'unns (1s3a) on th€ bagig or l!e! oen ,ork
and thor6 o! oth.!. h.. Eav.!.ry &tttclr€at tt!. v.Iu6 o!
osbotic adju6tuent as an tdicltion or grain vtetd und'r
6tres3. she doubts any D€chanlstlc link bet een osrottc
adjust@nt antl yi6td. she leels that vi'ld @uld b€ due to
othe! cbaracters rhich probota highet assiniratios such as
grovth. $hr pr...nt. a paladoxrrHov dan d
piocess rhich dlv.!t. solutaB fton cell expan3ion pron't6
bigh€r grorth and ylelt. I! osnotid adiustnett occurE lh
loot as {ellrthe pa!.ilo} 13 6v.n etlaDqer_i
cly.inebatatr.
Instead of
neasu.inq ,6te!
status to
e6tin'ts
atehydlatlon avoidanc., llln6on (1930) proposed Donltoling of
accDulation of .n hert r€tabotile (behrne) it an
integlated functlo! ot tLtsu. sate! dericitf. Betaina has
been rePotted to accsulat€ 1n chetopo& and several gras6eE
Ln le6ponse to uats! or E.It- s€r€66 (llvn JoneE and Slor€y,
19?s and Eitz at al. 1es2)' vlllatio. in b€taine lev6l haE
llEo been !€Po!t6d aDong 9.notyp63 oa balley t'oth qhd'r
ilriqate.t and notr 1!!jEat€d cotrditions (Ladvnan et al '
1933). In the present Etudvr genetlc differences foi betal'6
level vere obtaln€d aboig o.ven Epring vheal qenotypes under
stless and non 6tres6 condltiona (Tabre 19)'
lncreas€ in betaln. c(ntentd ln alr ule qenotvp$ 'as
Daturity' azs-4 had an
recorded onde! tsrtrtn.I s!r.53.t
elevateit leval oa b€taln., a?.2? n Dol g-1 as conparea to
d rol 9-1 dry vt. !nd€! non stlest condition rzs-'l?
ia.l 29,95 a nol q-l dr: {t. aE conpated t6 6 6 { nol g_r
dry rt. under nolnal lrrlgation. nanson (1930) and ashrtf
et .I. (1991) found that qenoiypes which itad low
glyclhebetatne under fully lltigated.ondttiob also had lor
10.95
glycilebetatne unde! drought conditiohs_
In th6 p.€6€nr Etudv beh6ved ih a sinirar
lashion. oreverr rhen p€rcentage incre:sa rrob control i3
coDsldeled. the EusceFtlbt6 g€not-vpe5 had higher varues/
36s.5t for Pavon and !t3.st for Azs_17 a3 conpared6331 7t
for Azs-{. In tbe Pre6ent investigation glycineb€taiie
cont6nts tete poEitlvel! co4elated vith glain yleld under
5tr€83 treatn€nts. ?erccntagg inc.ease
neq.tlvety assoctatud eith glain vie1d. It 15 cl6a' tbat li
is not ths percentag€ ircrease ehich hatt€tg but a c€ltaln
blniruD.bount IE n€€:led to bnlance llssue eat€. content/'
GruD€t et al. (19s?) lePolled that in near isogenlc
populations selection for an increas€:arevel of betaine l'd
to a decllne In yielat in barlev at the coinunitv level ln
the fi6ld. $heth€r lt t.r the €ffect of betaine per se or
concorilant tncfeaEe/dec.eas€ In factols affecting vield
ne€de to b€ sorted out. I{heth€r their flndlng holds true for
sh€!t, needs !o ba evaluat€d bv svnthesizihg i3og€nic
populalions ln dtfferent gen€tlc backgrou'd'
gebotypes us€d
In the pr€€6nt study a n€gatlve lelatlonahtP becv€€n
betai,n6 content..nd lea! vater po!€ntlal and leaf osnotlc
pot€nti.aI uas obs€rved, cleallY tndic.tinq higher betaine
cont.nts rith th6 lorest uate! lehtions tn these genotvpgs.
A€hlaf €t al. (199r) in vh.at repo!!..t Ethilar reEuItE. rt
i6 tlport.nt to note .hat betain€ .ccuiulation I nc.easaE
rh..rly vith tho leductlon iD l€a! *at€. f,ote.lial aftl
oslotlc potentlal. clunet ihd Hangon (1936) ,€!€ unable to
br€a)< lhe a53@1!llon b€treen hlgh glvcinebetalne and lo{
osrotlc polentl.l and sitilarly betve€n 10, qlvcinebetaitre
and hlEh oshottc pote.tial in closs€s bet{eeh diffeler:
isolopulation. lth.y .pe<ulat€d that the results obtainol
could t€ du6 to (i) b€tat.6 lt5elf sov.rns ostotlc Potentlal
(iI) rlnkage bets€€n gene (B) for betalne ahd gene (s) thrt
govern o6Dotlc potentlar or (lii) lndirect Eelectio! lo!
gen€6 thlclt control both betaine level atrd osrotlc
potentlal. cenotlc .nalysis rade by thetr provld.d evid€nc.
fo! osroregulatoly genes llth neaBurable effec!3 ln bailey.
Pelh3ps a s!!ira! lechanls! i3 oper.ttwe tn uheat also.
Llt.r.ture surv€y tndicales thal no such tork hrs been dona
in rh6at. It vould be lorthuhile to Produce isogenic line$
and .ee if svldence ior o$oreEulation gene6 could b.
catbon r.otoP.
Di3ariri6tloD
A in respons€ to raler stre63 lppears to be a
comon obg€lvation t. the v.llous crop sPecl€s both under
field and grorth chahler condltlols (ralquhar .nd Rlchards!
1944; Condon et a1. rr3? and 199O, Read et al. 199r aod
Ehd.i€ al .1. 1991 in rh.ali ltubicx et al. 1934 1n peanut;
Xaltin and Thor6tensen, r9tB ln todatoes and virgona et ar'
1990 th .qnllor€r). I! tlr€ praseht study drought stresE ars.
cauged r.ductton in a (rabl€ 20) . under tehinal stress tne
range o! A ts 1.r3 s lo3 rlth a nean valu6 of 26'04 x ro3
antl undes nomal trrtgatton 16 1.29 t 103 vlth a nean value
of 2?,{9 x ro3. The genotypa. variation in A und6! teoin:r
6t!.€. i. posttively corr.lat.d sithAof Dorral lrrigatl.n
(r-o..91s*). R6ad et a!. {1991} obtained a r.hqe of Aof
0.9 t 103 and 0.5 x 103 ln lou and hlgh aBA 11nes under
fi€Id t.ulDal stre66 .nd llrlgated condlttons.
dilfer€nceg ve!€ non 6lgnMcant. condon et ar. (1ee0)
obtain€tl a range of 1.5 x !o3 and l.s x 1o3 uhder teminar
and rell ,at.ted con.ritions in the gro,th chaDber' Under
terninal 6t!€3 neatr 4 tao 3.9 r 103 le3s lhan nean value
neasuled in retl water.!l .ondltlohs. Genetlc varlation in
Aof telhlnal stress va: strongly correlated vllh A ieasure<t
in r€1t vatered conditt.ts (!=o.?e"). rhe dlEPalltv nav b€
due to DLant parts u.trrd for A analysiE and severity ot
R€duc€d
In th3 present ihv6Btlgatlon A
correlated rlth bloloqlcal yield and grain yield under
temin.l str6s6 anl pt€ anthesis et!€ss (Appendix
A-c) suggesting a potentlal, incohpatibllltv beteeen vate!
w€ qlflci€ncy and dry ratter productlvitv under t'hese
('.ee1) obse.ved po6itivc
.nvironDents. Read et .r.
correl.tlon b€tuee.6.nd grain yierd under flsld tlllqated
lnd t€lDlnal .tr43 condltlons thereas cohdon et al (19e0)
shosetl no correlatloo bett.en gr.in yield of stless€d plants.
and a of €1th6r 6t!es6dd or vell ,atered ptantE unde!
glovth charber condiriors. undEr the6e conditioh6 the
relationEhip betr€€n ao.v6 q.ound drv natte. productrot rn
,ate! 6tlesE€d p1.nt5 and A of ,erl eat€red blonass
(!=o.45') {ar 6iqnlftcant. condon et a1. (1937) Bv.luated
g€notypes und€r lield conditiong rhere ,at€r uaE not
lllittng. They repolt6d poEltive lelatlon6hip bstveen a and
yield (bioloslcar anil gr.In). rdhata et at. (1991) obtained
poEttlvg corr.ralion betv.6n a and bloroslcal vi.ld aid
gEain yield undar fiald dlougbt 3t!.aa onlv. studt€3 .of
A In relatton !o yleld (btoloEical lnd graiD) hav6 6hovn
variabt€ results.
sufficient senotvpes
variation in A . Th€r€ i3 sttll need ro! flrlh€r
exploitalion of varia!ion in 1ocal !s vBll a6 €xotlc
g.npr..r for carbon I'oLoP. ltl.c!ttln'troh
The p!e36nt 6tqdy has denohstrat€d
.nei!6nnent.. Inthenca of planti,ng denEity on the
6ipr.ssion of carbon l.otope discrinination 6ee6 to be also
awlvlaq rtrr.ls lia6r
aDt
aplt. yl.til
The flnal nunbe! ,f €alE proituc€d i6 obviously rhe
nurbei of till.rs vhlch survive ro bear ears. rr.e6p6cttve
of qenotyp€s the plopcrtio^ of ttllels rhich di€, increas€s
und€r drought conparg.t 1.. nolnat illigarton. Hou€verr th€
Eevelity ot reduction iE leE*in thoEe genotypes,hich ale
ror€ droushr toler.nt (Trble 22 ). rn the plesent study
rarer EtrqBs cauEed abortion of v6g€tarive tillgls and
tba survlvinE tilt€rg ihd6x. Th€ lo*e.t ,.6 un.te!
telDln.1 st!6s! (29*), pr. an€hasts 6tr€gs (2tt) ahd po.r
anthe6ls 6tr€s6 (17t) fh€ ph€noDonon ls perhaps dep.ndeDt
on 9.norype6. kelD (1e.r4) tound dedle6se rn rhe nuhbe!
or
productive rillers in rJre g€Dotypes under te!trinat
drouqht.
InheE and Blnckrell {r9sr) fouDd increased nunber
of
productive rillels ih r,)jt .nthesis drought ih spring
uhe.t
g€notypel fiighbuly but J,e oppoelto ih Tn 26e. stnltarly
Innee et a1. (lea1) ro!n.t Increa6ed nuhbe. of productive
tiUers LD high tlfleltrq vinter rhear type Dut opposlt€ 1n
ro* tilrerlnE type. rhey shoreat thar lines havtng targe
nunbe! of ea!6 o-2 uni,:r norEat irDgarron had higher
raductton In €ar. h-: lhder pr€ anthesis drought where.6
reduc€d
6hoeed non slgnitlcant
auiference6. tnn€6 and Blacku€ll (1931) tolking tith 3P!i.s
rrt€at obtaine<l results rhlch reie contlaty to rasultg
obtaln€d vith wlnt.r rheat. In Euch studies a nurbe! of
factors can eafect the !€6ult includlng the genotype6 and
In the ir€s€nt Etudy Pavon rrehaved lik€ rin€er
uheat. uhereaa !e6t or the gsnotypeg behaved lik6 6p!i.s
rheat genotyp€. of rnne. and Blackrcrt (1931).
rIne. h.vinq loH 6ptr.es
D-2
The r€lattohship betreon sulvj,vlng tiltels inales d.d
E!.in yt6lil a6 r€aluction pelcentage of non Etre6s under
t€hlnat lnd pre aDth€.j6 €tress i, depicted lr Fts. 10. ,rr:
rinl!6 sulvlvlng till(fs index as *age or non stless ihi.x
ua. ls.oclateat rtth tn.: rorest g!!in yt€ld d.pres6lon ard
vice v.rea. tzs-r? an., pavon had the highest leductton tn
Eqlvtving titl€r€ lnthx. a6sociar6at vlth tb€ htghesr
deF!€$lon ln slaln y.r.61d. r.rele6tinsty survlvinq ttlle!6
lndex ghoeed no corr.lar.,on vlrh 9r.in yr€rd unale! nob,r,t
trfigatlon. Thls D.y t., dre ro a very hlqh !rllers sqrvi.ql
1n thergenotypos.
It has been Euglresteal th.t productive spikes per unit
6r.a 4rit- an llportrn! t!.1t cohtllbutllg ro srreEs 9ra1h
yierd (xetn and xronstad, rest). selecrion of genorypes rith
htgh plastlctty for ploducrive splkes can allevtate tte
adveiEe €ffect of strrlss ror st.nd estabt ishnenr. XeiD ar.d
"""'(,,,
-
suivlvtNo
lt!!!nt
rNoEt A5 nEoucTlox'rr
5TiE59 lxDEr.
inder qs reduction '/.
nm stross indar ond groin yield os r€duction'/. ol non
Fi9:10. R.lql ion ship b.tween slrviving
of
of xorl
slress yield.
till.rs
KlonEtad (19s1) ln {ln'ce. theat and EdneadaE €t al
(rss9)
ln spring rrleat i.dlc.tad that productiv€ sptkes (tir!€r
vlablt1ty) can be uE.l as 6el6ctlon crltelia unde! 6tre'!
6hvilonhsntE. R€cent ,tudt€E bv Hucl a.d Ba&r (re39) ara
lnte!€5tlng and Day h.te f.r_re.chlng consequenc€s in futu'o
E€udi.6. rccordlng to ahel! studles no! all the till€r6 Dake
of fact in the
aqual .ontributton to the vield.
t€n g.notyp.s !h.y strdied on lbe av€raqa tbout 2/3rd of the
!tnal grrh yl.tit ta! contiibuted by th!6e tlIl€!! (Maln
3ten, 11 and T2). r! r.ht6 13 trla tben th. eff€ct of ilrouqht
oh lhe tltree tlrrer6 )8y Provide so!€ clue to the rechanlEn
of yteld <lepres€ion thd evorvlng Etrateqies lo! bteedlnq
drought tololance.
spike yi€Id I. at. irport.nt vield coDPon€n!. the
1nc!..6e ln splka yie)d can contllbuta to hlgh vield
provldsd there i6 no d.,ct:€ase in other yield corponeita.
Dus:yrt (193,t) rateit Iavon a5 a very seneitivE genotvPe to
vat.r FltaEe du6 to tre lou€gt 6Pil6 vi€ld. In th€ Plee.ht
EtDdy Pavo! shos€d afto sinlla! re3ponse
tr6.trents ( Tabr€ ,5). azs-l? eas the lo6t s€nsltlve
genotype lnd produced tb. lore.i 3pik6 y16ld. Azs-4 gave the
highest spi.xe yielit. 6enotyp6 having htgh spike v!€rd also
had hlgt! flou! yield splke ylald vas th6 hai6r conponent
vhlch explain€d s6* and 941 vallation in qrain vield under
Don.r lrrls.tton an(i pro anth..i. .tr... (fabl. 3or2e)'
tlousvs' ite contrlbutlor' va3 not gignLftc'nt under !'h!nal
and post .nth€3i. .trD6s. Although 6pI*€ vlerd under
tami.a! and po6ts antlresj.E drought Etre3s Ehotsd poslt:le
slgntflcant dorrelatlon 'lth grain vl.ld (Appendlx A,a) blt
sh6n Btepvlg€ bultlpl. regreEElon vaa done contlibutton tl
spike yterd toralds !ield e.s lound to bs insigntflcant
(app€ndir To, T1 Etepvls€ t.tultipl. Reqresslon). Pathak
(1es5) shored that srlke yield unde! space Ptanting vas an
irport.nt tlait in salacting lor dlought r€st8iance. lrhethe!
thls holds tru6 fo! c(rnercial planting 1. eolth rtu<lyinq.
Ii.rf rr.a D.v.lop!.nt
Bru. (r9s5), dnd
and Muchoe (re;o) in th€ir
',udld
revt€, artlcle6 r€nt1oi:l th. !€ductlon ln leaf alaa unier
eate! at!.6s dua to .r:,rih retardatlor and s€nescence o!
te.v€s. R.b et ar. (r9r,) shoued that glorth of l€lves Las
r€tluceal unale! all t!. srlesE treatDents, The [axirrD
reilu.tlon as calculat€li i!6n the graph va6 about 42t. rn ir,e
pf6seht study ln alt thE st!€ss tr€atnenrs rhe cuiutatlle
gleen leaf ar€a ens :e.lucedr the hlghest !€ilucrioD beihg
under tenlnal stres8 (12!). (table 2r). It lay b6 noted
th.t R.b €t .t. (1e3r) dld not use telDlnal stresg. lheir
r6aulta a!€ dlfficur: to expraln a6 in th6 tlllering to
Ehoocing (long6! period o! dlouqht), the reductlon ln teaf
alea vas l6ss than ti)lerihg to loibtrhg (sho!re! p€riod of
dlouqht), In the pre:.hc inveEiigal:jo" rh' reructton rn
gre6n Ieaf ared {as dne t. s}ot lcat:rea dev€tophenE aril
srtess (Firi 5,?) - se'en
tncr€as€d lcaf
g6n6tYp€E .tudie.t shov.,i q.t'!ivPl'{-dlfrerances tn 1e3l alea
lggrrval and siDha
developnent ahd r.t€ ir
(1es4) studie.l lcaf .!.r d4v€ropnent in teo 5prlng eh!.ts
varleties; c-106 (tole!.!,t) and xaryanson: (non tor€rart;
under irriqat€d and slnulated ternin.l drought conditlo!:s
c-lo6 attained high6! i€af area at 60 <lay6 boLh undet str!(,s
abd no. stless condition3 rher€as kalyansona ras slov un.lc!
telninal Etress. Althouqh the reduction in leaf area ras
faster tb c-306 than Iolylnsona und.r stress, but c-t06
6tllI had hi9her cunulatlve leat atea anl higher grain
A26-rl h.d high(r cunurative green Ie:f
lsaf nr,:r 6t rc.sc*' tko s€€!:. t
area
a,rd
Ar!-
??rhan
17 anil Pavon (hon torerr"t qenotyp.s). Th€ abitlty to retu jn
! lareer s5*y',ve re.t area under srress ln Azs,4 secFs io
be the na.ifestition of dehydlatlon avoid.nce (John!.n
el al. 1933) ! thu6 r)b.oting lt to larion vate! nrre
efrlciently fot coni.:nu.d phot.synthctic autivtry. r'f.
gr€ate! qleen l6af tDn9evity presuhably contlibuted extra
dayg of c.rbon gaIn (iorins the critical glain filling
Pe!lod. TirIs ls up!!r!lht fron the positivc assoclatiob df
cunurattv. g.€en leaf ar€. ard gr^in yi6ld. It iE 6uqsesr€d
lhat exc6ssiv€ gleen li.f Ioss and leaf senescenc€ 8hould rre
s€lect€d aqalnst In tne geqreqatlng poPulations to dev€:op
rllqh yialdinq s.notYPar Jor drought p!on' areas'
Hov€tr (19e0) defined harv'6t Inde{ as th€ slop€ of
jn xq hn-1
Itnear lolatlon6hip b.:endn cv (prant grain vlerd
ha_r)
on dry veight basi€) an:r Dt4 (aeriat drv natter in I'tq
fh contrast to th€ ttad.iltonal dafinitlon of harvest lndex
as the latio of GtlDIi. 8€ eDPhaslzed sone uininun Plant stze
to p-oaluce gr.tn vl6ld In th6at. H€ suggested the us€ of
.Ither halvest index o! hlgh dly h'lter ploduction a€ a
bleeding seledtion r:ritarla for uh€at. Boukerrou
(1990)
for hitlr blohast to increase h'rv€st 1nd€x
in balley. Ir the present 6tudv lraditional definition of
h*vast lndex has bo.n uset.
ploposed breeding
llalveFt lhdet ha.; be':n consideled an Inportant t!{rt
lor ytel,d iDProven€nt .n celeats (shana anal sDlth, 1934)'
cereal breed.r6 h.ve nged yleld aa a criterla h the
bleedlng proglaMe for jnprover€nt. Horever/ durtng the Past
d€cade5, th.re has :)e.n re^e,ed lnt;rest in Eer6cir"q
lhdilectly !o! yi€ld cohponents lor yield lnprove[er:'
Br@dlng tor yleld colponents has produced Dixed result6 (iue
to €ha pleeenc€ of .orpohen€ conpen6ation and atlon€trlc
!.lation.htP. in c.!eal. (abd*ad6r €t 'l' 1ea4)' und'!
dr.ugbt. the )'ijv.:!. in.:.x 1s hfcl: bc1.v thc q-n.t ic
r'ot.n!ial (Richards aD. -ov^le!-5dirh! Its?). grrvesL ihc:x
unLle! nomal i;riiati.r .ia3 f6r:.c to bc o.u ny o,t,Jlii1
(1!35) vhich de.r.,ared iD t.l5 url.:! gr.esr cor:lttiorr. rn
€he present stuilt in none of i:he stre.iEes .nd qenoryp:s
Etud1ed th€ harves! 1r,1e). va3 higho! than o.31 (tar,I. 24).
rhir Ey be nor.d thar tte htghcst |n.vest index ortain:J
condition ,rs o.,t2 6s ccipa.ed t. o.5 reir.rl ,l
by o,le.ryr (19s51. azs-3 producert the hiqhest ha.vest lndex
(0,4?) 9,riter .oriial t.!r garior vhlrea6 c-22s ah olr! ra11
varlety( rae ro"esr (0.2s). rr ro.n6 of tnsc .cducrlon Azrj_
1? abor€c the hlqhest depreEsioh in .ll tha strers
*.arDenrs. pavon atso lelraved silitarty.
Ttrese tro
g€noiypo. !l3o had the l]tghest :!aqi leductjon iD th€11
btologlcal yielir. The tcrc.! balvesr iDdex appelrs to b€ .rr:
t. th: touest r,j6ro.lt..:l yteid. ro hcrc,se halve!r jnn!,unoer stless, it si€,J: esRerEial
production in thes€ 96\,,j:,,_es. Non r.lclarr
Eenoty!r':s; i..
AZs-r? ahd ?avon llad thr 1:rc.t sorrce s i2e,.;l.vtd,:nr fr:m
th.ir cuhu)attve gr..r :u!t !rea. li)err fr.r thisr th.:e
g.notyF"s !r.trar'!y hr\r Jrrfflcilhr syct.n fj. rransF..r
rf
pborosyhthar.c. ptretnr i9 and st.r.ri.t!. (1e91) sngs.:r?:d rbritriqh h.rvest index Es rr. to gre:tc. ure o!.rah stluctur.i
dry Datter f.r graii:::tirg
c.,o:e r:oraq€ of this dry
natt.. before and .cor. a!:r.r anthesls, Nhen grajn dprand ls
Ior. Thie hay b€ true ir: tn6 pre6.Dr
The
study.
hish corr.laticn 5f harv€st i.dex rith gratn yi{::.d
and biological yl€ld uj€r stresr indicate6 that Lroth
biolo9ical yi€Id .nd li:.!. est index ar€ beihg effectivr:Iy
explott.d !o! lncr€]sing grain yletd.
contrlbutioh of hdivc; i ind€x to 6tress gratn ylerd is
evralent froh stepu_lE. ,:erJression analysis. under telnthr1
stlesa 97t and post altltrsis 6treEs ss* valiatloD in grnin
yield i6 attributabl.j to harvest index {fables 2?,2{ r.
Agsalvar et al. (1es6) o:re.ved 56t variatio. in glain ylord
due to ev.potlan6piraqion. Hovever, the tnctusion
of hlrvest
index 1nc!€a6sd the value to alt u.der lernrnal stress.
Based on legre6slon analyses ( Tabtes 27,23)
it .is clear
that of the giv€n ird€pendent vari.bt6s, harv€st
Ind6x ts
ro!€ i&poltanr in reg rrallDg srress yteld.
Th. stqaly 6u99estj tlat halv€6t iDdex can be
used.n a
a€lecttoh criterirn f(, enhancing graln
Yisld tn et!r:$6
eDvlrohretrts. Ir ts ei:y to ieasure .n.l does
not !.qu:re
sophtaticatett insrruner I n.iohs.
t!.dlttona1 Jt eiplrical or agrononic approach has
been u6€d In blaeding ffr blqh
9!a1n yleld In ,ater_linttld
€nvlronent6. It lel ies on glaih yi€ld as ! s6lect:
Jn
The
c!1te!1on.s lt intoglltes the eff€ct of drought streEE in
(le:,:r and Richards (Ie32) in eh€at a:t
x€delaki ahd refrers (t!rt) in soytean provjded expcribe.tar
evldenco thar rrlgb ,.nrldlng cultivars unde! optihuh
conarlttons gave higb.4i€rd3in sr!.ss €nvilonlents. selectton
ts e.sl€r th favourabl., condltions, has high qeDetic
variatioh and hertt.bllity. Rosletle ahd Hanbrin (19sr)
theollz€al that aef.ctlJD for tol€rance to Etless 1s exFected
to ploduce .sqrtiv6 dorf,etated lesponEe on Dean yielil in
non-stre.s €nvilonn€nr:s, Lanser 6t al. (1e?9) ha<r €allt6r
cone to the EaE€ conctuslon based on their expgriuental
.lata. they concludsd that dilect selection i. stless
.nv1!oD!ots utlt ateoeas€i yletd tn non
unless g€netic vartr.ce6 in stle6s environnentE are
consitlerably bigh€! thln those in non 3t!es6 €nvlroDb€nte
and g€n€tic collelatio.rJ :.e posit-|ve and crcse to
l. r,he
alr.olut€ plant yt€ld r:ttrr 3t!eE3 t6 a poor 63t1iar€ ot
drolght !6Bistahc€. On .lr other hand FiEch6r and laurer
(1973) lnd BIur, (leSo beri6veat th.t yi€t.l unde! srrsss
is
aflected by the gen)rypes, yield potentiat. rt Day be
alr€cted by a.y given nln stless envllonhehral factors,
raskirg th€ genotypes i 6tr€s6 lnteractton. kter studles :y
Brur (1e33) !ad. h:r tc conctud€ that droughr !€sistancc
.xl.t. aFil t. t.d.F.nd.nt ot th. yt.td por.hrl.l a.d rhc
Roy ahrt xur€y
inprovene.t of dlougtt losl3t.ncs by selectinq fo! yierd
under 6t!.63 i3 possiti,e. clalke et al. (1934) shoe€d that
selectlng for yield und€! dry condilions alon€ should b€ a
iote
ploductiva aveoue for
inplovebent ol
drought
Th. controversy fJr using yield cs a Eelecrion crireriri
anil the infhence ol ..nhdrent high yierd poteneiat rolards
6tr€EE yisld can be lesolved through studyinq th€ senorytes
x 6tre6r rnr.!.ct1on- Bake! (1933) suggested that th6 oniy
int€lactiohs o! sishlfacaDce sele tho.e rhich invorved
slun and pnuet (1eeo) arso enphlsized rb€
scleenlns o! gerupt.sn for cro6sove! yi6td levEr for the
target envi.oneent befo!. 6ny artebpt is hade to inprove
dtought to1€rance bt s€lection for yi€ld unde! dlought
3tr66s, rD the pleqrt rtudy thotrgh stqniftcanr genotype x
3tre6s intelactions s€r€ observed for all the tratts
(App€tralix Fl tet thele las
occurrence ,1th rtre
increaElng 6tr€ss. jtn the absence of genotype x str€ss level
itteractions of cros.cre! typer yielat und€r dlouqht is
positive ahd glqblftcarrry corr€lated,ith yt€rd porentiar
(rEo.3159r 0.3334 and ).8{6{ for the y€ar 198a_s9 and !, :
fo! 1oa9-9o under terbinal, post
anth€slE a.at p!€ .lth€Ei. st.ess respectively). yietd
potehtlal nay be . uslfut ..tectlon crtterla, rn rhts cas€
hlgh.! glatn yi.ld under 3tr.r. .nvtronD.nr. Day b€
cdrid||t|.r ! r!.sldu.lr .ft.at ot ltlgh yl.Iil FotdtlAl.
ac !o
MtL.
.t !1. (19ret .to toi|lel .IrlL!...ult.
*d6ovs tl|P o! g.DotyF r mvLlonrnt tnta.ctlo.
It l. @nctrd.al th.! th. getlc lrt rov€!6nt ol yt.ld
potdtL.I ellr, .le r..ull ln i&Frovsd yi.1d un l.! .tt.!..
6@tyD.. .hdtiq hll! tt.Id unalc .!r{. rry b€ du€ to h4Lrr
yi,.Id tFtottll .!d drougirt tol.ra@ .E lndlcatod by hilh
st-rs! li.Lx qlcul.t.d through 16916..l(!l
tsltlE
.Nly.la. Ih. g.ln ln 9..1n y1€ld uhiLr ilrought ApF.a!. to
re.ult r|lnly tror .n lllra3€il lErtitlonlng o! dty :[|!t r
to th. d.v6lo9l,n9 .r! 1.., incr.ls.d hArv..r lbat6x, tuthc
t€.tlnt ol th€.. l.rlotyD6e ln atrought Fron€ !!e!. uoutd
t,t@ld. 6dr.1||alE .vl.Ls. { to ,h.th.! rh€ EaIs !.ao!dlt
.n .utrltFd d bt.
G.nettcE
o! Dlought Rll.tsd t!.ltg
Dlal1e1 ahalvgls provl<les infornation of the choice ot
auitable pareht6 to b€ included in a hvbridlzation plogi'Me
and th€ nalur. ol qenc 6ctlon lnvorved in the etperEtioh 'r
quantltatlve traits ar1 iEPortant to th' breeder' Additive
sene actlon 16 destr.(l lartlcurarlv in the crops vhere
hyb.ld varletles .!e n.,i leaslbl€. on the other hsnd, non
additive gen€ actlor ii, irrportaht in th€ crops sh.re hyblid
vigour can be [email protected] explotteal.
The .Etinates o! CcA and SCA effects provldc a ba.i.
lor s€16ctin9 tha p.rentt rith hlgh ge.erar .nd ep€cif:c
coDltlning ability. The ectlhates o! geneial coDbinig at'Ilir.y
6ffects {Tabl,e 32) lddlcal:ed clea! genotyplc dlffelghces fo!
.ll the traits und6r jrrigated and non iEigated conditlons.
In Fl tro q€notyp€3 azs-{ and azs-l! ghored po6i.tiv€ qeneral
coDbining ability eff€cts fo! biologlc.l yierd. sratn yield
halveEt lndex aDd 6pit: yield rhile th€ tro Azs-r? and Pavon
ghoded n€sativ€ €ffacts. speclfic conbining abllity e!!e.ts
ra!€ highly con6picuo:s in azs-11-Azs-4 cro3e for grain
yield and spiko yiel. under both tie environnents. Tfj.
cro3e also exhibiteat 9.{-d effects for biological ylefd rnd
harvest lndex uhder trr jq|ted and non ir!igated conditlohs
lespcctivety. Anong ::,! closses, Pavon-azs-1? waa the
poo!€3t for spikc yiel(l and blologlcal yield vhereas Pavon-
Azs-11
to! 9!aln Yl.Iil, biologlcal
and harves! rndei und:r
lioth tb. envrlonnenlg.
It is cl€ar fr([ th6 data that both genelal a"
ro
Bp€ciftc conbintns .br'11!1€3 cont!tbuted 6lsntticallrv
tne
!ot.l gen€tlc variat: on anong th' croEses fo! all
it
charact€ts. But coBlderlhg thelr relativ€ uasnilude'
preponderant ln these
app.ar6 thal addltiv€ gen' 'ction v's
q€'€r!]
population. aor all th€ chalact€!6 as levealed bv
va!iarce
coibi.ins abtltt'v/spt)ciftc corbintns abllitv
€arlier
ratios. rhet. rssults 'te ln agreoent 'lth those
et ar (1935)
!6porte.t ln sprlng,h€.t b/ Bhatt (r9?1)' Xha^
hiib
genotvPee
and xall* €t ar (r9s€) usuallv tb€
'!th
productil
g.n.ral cdblning .bi1!:Y for thcs€ traits
rere also
€xcellen! hvbrids, tho!9n sore d6ei!ab1€ crosses
cotbtning
obtaln€d fr@ th€ Prrants vith lo' general
ability, lndlcat€d tr.neqre6slv€ ef fects'
uEed in
rhs .63!lts tnPlt thtt Azs_' lnd azs-1l nay I'e
fhese cros3€s are
coDblnatlon brsedlng ,rr b€tter r€sults
conbinations of
expectoat to yield segre(rrteE e!!h deFired
etf6ctive fo!
valious tfaits. si[pI. aelection apPeats to b€
bv addltive
the tnPlovaient of tl,e characte!6 t€ rev6aled
gena acllon involved {n thelr 6xpr€66ion'