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1426 CROPSCIENCE, VOL. 47, JULYAUGUST2007
RESEARCH
Breeding strategies o vlop hh-yl o-yp o wh (Triticum aestivum L.) xvly b o
ppoch h volv l umb o co ubquly lc mo wh popul-o. To , wh b ou h wol h b bpmly o mpcl lco c (yl p ) o ylmpovm (Au l., 2002). Sc yl chcz bylow hbly hh oypvom co,mpcl lco my b uf c o chv c (Jcko l., 1996).
Iy pom oyp b pom wllb cl yl c b pc bo h cop h-v. Th ly pco woul lo b vy hlpul h op-pom ml coul b om oup o hu
Potential Use o Spectral Ref ectance Indices
as a Selection Tool or Grain Yield in Winter
Wheat under Great Plains Conditions
B. P, B. F. Cv, M. L. So, M. A. Bb, W. R. Ru, A. R. Kl*
ABSTRACT
Selection criteria that would acilitate increased
genetic gain or grain yield would be considered
advantageous in plant breeding programs. We
evaluated the potential o spectral refectance
indices (SRI) or assessing grain yield variability
in winter wheat (Triticum aestivum L.) genotypes
under Great Plains conditions. One experiment
was conducted at two locations on the Okla-
homa State University research arms or 1 yr,
and two experiments were conducted or 2 yr at
a single location. The rst experiment included
25 winter wheat cultivars rom the Great Plains,
and the other two experiments contained two
groups o 25 F4:6
and F4:7
recombinant inbred
lines. Six reported SRI (red and green normal-
ized dierence vegetation index, RNDVI, GNDVI;simple ratio, SR; water index, WI; normalized
water indices 1 and 2, NWI-1 and NWI-2), and
two new normalized water indices (NWI-3 and
NWI-4) were calculated at booting, heading,
and early grain-lling stages using a FieldSpec
UV/VNIR spectroradiometer. Signicant geno-
typic variation was observed or SRI and growth
stages, though the booting stage was least
associated with grain yield. The relationships o
grain yield with WI and NWI were stronger than
with the RNDVI and SR. The WI and the NWI
perormed better in identiying superior geno-
types, either at any individual growth stage orin a combination o growth stages. Our study
clearly demonstrated the potential o using SRI
as a selection tool or grain yield in a winter
wheat breeding program.
B. P, B.F. Cv, W.R. Ru, A.R. Kl, Dp. o Pl Sol Scc, 368 A Hll, Oklhom S Uv., Sl lw, OK 74078;M.L. So, Dp. o Boym Aculul E, Okl-hom S Uv., Sl lw, OK 74078; M.A. Bb, Dp. o Aoomy,K S Uv., Mh, KS 66506. Th ch w pllyu by Oklhom Aculul Expm So, Oklhom WhCommo, Oklhom Wh Rch Fouo. Rcv 25
July 2006. *Copo uho ([email protected]).
Abbreviations: GNDVI, omlz c vox; LAI, l x; NDVI, omlz c vox; NIR, ; NWI, omlz w c; NWI-1,omlz w x 1; NWI-2, oml z w x 2; NWI-3,omlz w x 3; NWI-4, omlz w x 4; PAR,phooyhclly cv o; RIL, comb b l;RNDVI, oml z c vo x; SR, mpl o;SRI, pcl cc c; WI, w x.
Publh Cop Sc. 47:14261440 (2007).o: 10.2135/copc2006.07.0492 Cop Scc Socy o Amc677 S. So R., Mo, WI 53711 USA
All h v. No p o h pocl my b pouc o m yom o by y m, lcoc o mchcl, clu phoocopy, co,o y omo o vl ym, whou pmo w omh publh. Pmo o p o p h ml co hh b ob by h publh.
Published online July 30, 2007
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CROPSCIENCE, VOL. 47, JULYAUGUST2007 WWW.CROPS.ORG 1427
o hou o populo b po-m (Royo l., 2003). Ryol l. (1999) ch mopholocl chc uch umb o p u hv x c b u h vullco o b l , bu ho f cul omu l umb o mll plo ly -o u o lbo v m.
Yl v vom cly cly
uc by mopholocl, phyolocl, vo-ml co. Slco o b l o yl vc u o po o mk lco co bcu commoly u cl po-cu omm l o pouc uf cly ccuul o y upo oyp (Bll Ko-zk, 1993). A lycl b y lvb ppoch h qu b uo h co pobl o vlopm, owh,
yl (Rch, 1982). Th y co mopho-phyolocl lco c h hv pol o mkmpcl lco mo f c (Ryol l., 2001).
Th lm pplco o h lycl ppoch pob-bly u o h lck o ppop u o hphyolocl pm, h mo, h uoco wh yl (Rch, 1996). Commolyu phyolocl lco c clu oml co-ucc, copy mpu po, C
13oop
cmo o (Ryol l., 1999). Spclpop o h pl cm o ocu pol lc-o ool o yl mo c y (Apco l., 2002; Royo l., 2003; Bb l., 2006).
Th bc pcpl ov copy pcl c-c h pcc pl oc wh h
bopo o pcc wvlh o h pcum (Ry-ol l., 1999). Fo xmpl, l pm lk chloo-phyll, xhophyll, coo oly bob lh h phooyhclly cv o (PAR) poo oh pcum, bu o h (NIR) o.Th pm uc cc o PAR, bu o NIRwh h mu o cc uc by hc uo o lh by l u(Kpl, 1970). Spcl cc by cop copy l o h ovll o lv oh phooyhco h copy, pm coco, ohphyolocl co (Au l., 2001). Thu, h m-um o h pcum c om pl povomo h c b u o m l umbo pm (Au l., 2001), uch bom oh copy, phooyhc , mou o PAR bobby h copy, phooyhc pol (Ryol l., 2001). Oh pm l o h phyoloclu o h copy h m o mum, uch lv w co, u cc, voml, pm coco, phooyhc -o u f ccy, hv b by pcl c-
c mum (Au l., 2001; Ryol l.2001). Svl ch hv u h ylc b m u pcl cc u - cop owh (Au l., 2001; Apco l.2002; Obo l., 2002; Bb l., 2006).
Th mo commoly u pcl cc c(SRI) mpl o (SR) omlz c v-v x (NDVI) (Au l., 2002). G bom
l x (LAI), x, l x, co o bob phooyhclly cvo povly col wh SRI (W Rcho, 1990, 1990b; B Guyo, 1991; Pc Buch, 1995). Mu SRI poclly u cop owh llow h mo o l uo h v co o olc h ol PAR bob by h copy, whch hmo mpo co o pc yl (W Rcho, 1990). S m pl o oh mpo phyolocl ool oc wh cpcl c. W x (WI) h b mo
o pc lv w co, l w pol, o-ml coucc, copy mpu wh uf -c w (Pul l., 1993). Pul l(1997) how h uul o u WI o hc o ly o bly.
Expm mulpl loco o pc yl o wh u SRI hv how h ppoxmly50 o 65% o yl vbly c b xpl by NDVI SR (Tuck l., 1980; Apco l., 2000; So l., 2000; Ru l., 2001). A LAI vlu bov 3h copy bob ll o h c lh, lv omo lh o b bob by hh vo c-
o. Hc, h commo SRI h ulz h b v o vo vo co o LAIvlu byo 3 (So l., 2000). Tho, hSRI co b u lco ool wh bpom wh oyp lc l pouc-v owh .
Th uy xplo h pcum o wvlh ocombo o wvlh h coul b u o -quly pc w wh oyp o ylvo. Spcc objcv w o h coloo wly u SRI wh yl vbly, o -y w pcl c b col wh ylvbly mo w wh oyp co vo-m, o m h opmum owh () omum o SRI.
MATERIALS AND METHODS
Experimental MaterialsTh xpm, ch co 25 w wh o-yp vlop by b pom h ouh cl G Pl, w couc u h 2003/2004 2004/2005 wh ow o. Th xpm w
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CROPSCIENCE, VOL. 47, JULYAUGUST2007 WWW.CROPS.ORG 1429
59), ly -ll (Zok 75) o ll hxpm boh y loco. Th w co 3 o 7 mo h oyp ch boo, h, ly -ll . Th cc mumw k h ml o h o u mml u-c o h . W clcul bou 200 w cu combo o vbl NIR wvb o oml z om cho wo w c b oh ovll pomc co xpm comp wh
x pvouly po c. Dcpo o h c p Tbl 2.
Data AnalysisTh lph lc ly w pom by SAS MIXEDpocu (SAS Iu, 2001) o yl pclcc c. Po colo cof c w uo m h oco bw yl pclcc c mu vul owh co owh . Gc colo bw yl SRI w clcul co owh vom by h omul (Flco, 1989)
r= (Cov
G1G2)/(V
G1 V
G2)
wh Cov c compo o covc bw yl (G1) SRI (G2), V c compo o v-c o yl SRI.
Rlohp bw SRI yl w b-lh by o ly w ccomplh by h SASow (SAS Iu, 2001). D w o mol b o h l-qu mho o pm m-o. Rul w chck o mol . Cof c o
mo w comp o mol. Roo mqu o w clcul b o wok by Kobyh Slm (2000).
Slco o h 25% hh-yl 25% low-yl oyp w o by k h oyp cco- o yl k h oyp b o h SRISc yl c bw h oyp o hwo lco oup b o h 25% hh h 25%low SRI vlu w . Th oyp w k o
SRI b o h m o h ob by comb- h cc co h owh . W lom h yl p o h 25% hh-yl 25% low-yl oyp. Th yl m b ovul SRI w clcul u h o quo oh pcc x wh yl. Pc yl cw h m bw yl p yl mb o SRI.
RESULTS
Genotypic Variation and Growth StageSc oypc c (p < 0.05) o yl
w ou ll h xpm (Tbl 3). Dc(p < 0.05) w obv o pcl bhvo cop owh , mly boo, h, ly-ll (Tbl 4). Th vlu o RNDVI, GNDVI SR c om h boo o h -ll (Tbl 4, F. 1). O h oh h WI, NWI-1NWI-2, NWI-3, NWI-4 pov wo yp o p (F. 1). I y 2003/2004, h c
Table 2. Description of the spectral reflectance indices employed in this study.
Spectral reflectance indices Estimation Function References
Red normalized difference vegetation index (RNDVI) (R780
R670
)/(R780
+ R670
) Canopy photosynthetic area Raun et al., 2001
Green normalized difference vegetation index (GNDVI) (R780 R550)/(R780 + R550) Canopy photosynthetic area Aparicio et al., 2000
Simple ratio (SR) (R900
/R680
) Canopy photosynthetic area Gitelson et al., 1996
Water index (WI) (R970
/R900
) Canopy water status Peuelas et al., 1993
Normalized water index 1 (NWI-1) (R970
R900
)/(R970
+ R900
) Canopy water status Babar et al., 2006
Normalized water index 2 (NWI-2) (R970
R850
)/(R970
+ R850
) Canopy water status Babar et al., 2006
Normalized water index 3 (NWI-3) (R970
R920
)/(R970
+ R920
) Canopy water status Newly developed
Normalized water index 4 (NWI-4) (R970
R880
)/(R970
+ R880
) Canopy water status Newly developed
R, reflectance at a specific wavelength of the light spectrum (in nm).
Table 3. Statistical parameters for grain yield in three experiments presented as individual year/location.
ParametersExp-1 Exp-2 Exp-3
STW 03/04
LCB 03/04 LCB 03/04 LCB 04/05 STW 03/04 STW 04/05 Yield (kg/ha) Min. 3920 4229 3566 2482 3294 3381
Max. 6460 6620 6576 3512 5808 5498
Mean 4950 5383 4989 2980 4667 4271
SE 530 430 589 249 437 361
LSD (5%) 1125 912 1250 527 927 765
CV (%) 10.2 7.8 11.7 7.9 8.6 8.5
Significance level * ** * * ** **
*Significant at the 0.05 probability level.
**Significant at the 0.01 probability level.
STW, Stillwater site; LCB, Lake Carl Blackwell site.
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1430 WWW.CROPS.ORG CROPSCIENCE, VOL. 47, JULYAUGUST2007
c om boo o h, h c h -l l (F. 1, b), bu 2004/2005, hyhow couou c om h boo o h-ll (F. 1c, ). I ll c, h vluo h w-b c w hh h -ll comp o boo (Tbl 4, F. 1).
Interaction between Genotypes,
Growth Stages, and Years/Locations
Th ANOVA o Exp-3 (Tbl 5) vl h oyp owh m c w c, wll h owh by oyp co. Th h-wyco w c o ll h w-b NIR
Table 4. Statistical parameters of different spectral reflectance indices estimated at different growth stages, presented for
three experiments across different years and locations.
Indices ParametersExp-1 Exp-2 Exp-3
Booting Heading Grain-filling Booting Heading Grain-filling Booting Heading Grain-filling
WI Minimum 0.810 0.784 0.891 0.824 0.843 0.866 0.806 0.794 0.869
Maximum 0.876 0.906 0.964 0.866 0.910 0.980 0.871 0.870 0.953
Mean 0.842 0.849 0.935 0.847 0.865 0.915 0.835 0.833 0.903
SE 0.012 0.013 0.015 0.015 0.013 0.012 0.008 0.013 0.015
Significance level ** ** ** * ** ** ** **
RNDVI Minimum 0.928 0.779 0.524 0.841 0.757 0.518 0.886 0.869 0.612Maximum 0.945 0.943 0.834 0.941 0.900 0.828 0.948 0.933 0.837
Mean 0.870 0.887 0.651 0.900 0.851 0.680 0.931 0.904 0.724
SE 0.016 0.028 0.046 0.018 0.028 0.036 0.009 0.016 0.051
Significance level * ** * ** ** ** **
GNDVI Minimum 0.755 0.660 0.564 0.768 0.680 0.620 0.773 0.776 0.606
Maximum 0.846 0.858 0.736 0.830 0.810 0.741 0.869 0.849 0.746
Mean 0.808 0.780 0.633 0.799 0.757 0.668 0.835 0.811 0.672
SE 0.018 0.023 0.026 0.016 0.020 0.021 0.01 0.015 0.027
Significance level ** ** ** * * ** ** **
SR Minimum 18.2 8.5 3.15 11.45 6.54 2.83 17.07 14.65 4.15
Maximum 34.9 33.1 11.22 32.35 21.82 9.49 38.59 28.04 11.36
Mean 27.8 19.9 5.12 21.49 13.44 5.52 29.07 20.49 6.81
SE 3.86 2.665 1.013 4.043 2.48 0.911 3.417 2.91 1.42
Significance level * ** ** * ** ** **
NWI-1 Minimum 0.105 0.121 0.058 0.096 0.085 0.072 0.108 0.115 0.070
Maximum 0.067 0.049 0.019 0.072 0.047 0.010 0.069 0.07 0.024
Mean 0.086 0.081 0.034 0.083 0.072 0.044 0.09 0.09 0.051
SE 0.007 0.007 0.008 0.009 0.008 0.007 0.005 0.008 0.008
Significance level ** ** ** * ** ** ** ** **
NWI-2 Minimum 0.107 0.118 0.040 0.095 0.079 0.061 0.105 0.105 0.056
Maximum 0.066 0.027 0.015 0.066 0.022 0.035 0.053 0.056 0.007
Mean 0.084 0.072 0.005 0.081 0.063 0.02 0.087 0.080 0.032
SE 0.008 0.009 0.011 0.010 0.01 0.009 0.006 0.009 0.011
Significance level ** ** ** * * * ** ** **
NWI-3 Minimum 0.102 0.118 0.061 0.094 0.084 0.072 0.105 0.111 0.071
Maximum 0.067 0.054 0.026 0.071 0.052 0.022 0.070 0.070 0.031
Mean 0.084 0.082 0.041 0.082 0.073 0.049 0.08 0.089 0.054
SE 0.006 0.007 0.007 0.008 0.007 0.006 0.004 0.007 0.007
Significance level ** ** ** * ** ** ** **
NWI-4 Minimum 0.017 0.125 0.055 0.101 0.087 0.073 0.111 0.113 0.070
Maximum 0.068 0.043 0.010 0.074 0.041 0.004 0.066 0.067 0.015
Mean 0.087 0.082 0.027 0.086 0.073 0.040 0.092 0.090 0.048
SE 0.008 0.008 0.009 0.01 0.008 0.008 0.005 0.008 0.009
Significance level ** ** ** * * ** ** ** **
*Significant at the 0.05 probability level.
**Significant at the 0.01 probability level.
GNDVI, green normalized difference vegetation index; NWI-1, normalized water index 1; NWI-2, normalized water index 2; NWI-3, normalized water index 3; NWI-4, normal-ized water index 4; RNDVI, red normalized difference vegetation index; SR, simple ratio; WI, water index.
Estimates based on two locations in year 2003/2004.
Estimates based on 2 yr (2003/2004 and 2004/2005).
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CROPSCIENCE, VOL. 47, JULYAUGUST2007 WWW.CROPS.ORG 1431
c. Th ly o vc o h oh wo xp-
m w ml ( o p). Th colocof c bw h h -ll o ch vul x vlu w c o moxpm co loco y (Tbl 6). O hoh h, h colo cof c o h x vlubw boo h , wll bwh boo -ll , w oc mo c (Tbl 6).
Correlation between Spectral
Reflectance Indices and Grain YieldAmo h c, x hv b pvouly u(WI, RNDVI, GNDVI, SR, NWI-1, NWI-2), wo w c (NWI-3 NWI-4) hv b clcu-l. Th po c hv b pvouly u om phyolocl pm yl, molywh uum wh (Triticum turgidum L. ubp. durum) uM - coo o p wh (Triti-cum aestivum L.)u o. Th c (RNDVI,GNDVI, SR) pov pov oco wh
yl, wh, h oh v how v oco(Tbl 7). Almo ll h c how low colo
wh yl h boo hh col-
o h -ll wh ylTh c c b cl o wo oup. O oupclu h vbl NIR wvb, oh oupclu oly h NIR wvb, pclly h mow bopo b o 970 m (Tbl 2). Th cb o h mo w bopo b o po-v hh colo wh yl comp o hwly u RNDVI, GNDVI, SR. I ch vuxpm, h NIR-b c xhb cov oco wh yl co y loc-o. Th vo-b c (RNDVI, GNDVI SR) v colo h w co xpm co y loco.
M c ov h h owh lwy po-v hh colo wh yl comp o yvul owh (Tbl 7), xcp o h RNDVIGNDVI, SR c c c. Th c bo h mo w bopo b lwy pov hh oco wh yl comp o h RNDVIGNDVI, SR wh h m o h h owh w u. Th p w lo v wh cw comb o h h -ll , bu
Figure 1. Changes in the pattern of different spectral reflectance indices with the advancement of growth stages: (a) and (b) represent
Exp-1 in year 2003/2004 at Stillwater, and (c) and (d) represent Exp-2 in 2004/2005 at Lake Carl Blackwell. GNDVI, green normalized
difference vegetation index; NWI-1, normalized water index 1; NWI-2, normalized water index 2; NWI-3, normalized water index 3; NWI-4
normalized water index 4; RNDVI, red normalized difference vegetation index; WI, water index. The bars indicate standard errors.
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1432 WWW.CROPS.ORG CROPSCIENCE, VOL. 47, JULYAUGUST2007
Table 5. Combined analysis of variance (mean squares) for different spectral reflectance indices across different years and
growth stages (GS) in Exp-3.
Spectral reflectance indices
Source of variation df WI RNDVI GNDVI SR NWI-1 NWI-2 NWI-3 NWI-4
Year 1 0.00091 0.000744 0.015693 7.88 0.000319 0.000109 0.000247 0.000438
Rep (year) 2 0.00523** 0.02528** 0.00965** 395.84** 0.00175** 0.002919** 0.00149** 0.002424**
Block (year rep) 16 0.00036 0.001430 0.000548 21.63** 0.000106 0.000187* 0.000092* 0.000154 *
Genotype 24 0.00175** 0.006872** 0.00355** 79.87** 0.00059** 0.000874** 0.00046** 0.000702**
GS 2 0.15693** 1.26649** 0.77409** 12608** 0.05152** 0.091245* 0.04003** 0.062720*
GS genotype 48 0.00049* 0.00322** 0.00118** 19.47** 0.000167* 0.000248* 0.000135* 0.000199*Year genotype 24 0.00029 0.001126 0.000499 15.41* 0.000097 0.000140 0.000073 0.000110
Year GS 2 0.00048 0.000281 0.00417** 9.99 0.000141 0.001964** 0.000055 0.00075**
Year GS genotype 48 0.00029** 0.000916 0.000375 9.34 0.000095** 0.000134** 0.000075** 0.00011**
Residual 132
Total 299
*Significant at the 0.05 probability level.
**Significant at the 0.01 probability level.GNDVI, green normalized difference vegetation index; NWI-1, normalized water index 1; NWI-2, normalized water index 2; NWI-3, normalized water index 3; NWI-4, normal-
ized water index 4; RNDVI, red normalized difference vegetation index; SR, simple ratio; WI, water index.
Table 6. Correlation coefficients between the estimates of spectral reflectance indices among different growth stages in three
experiments for two locations/years.
Indices
Exp-1 STW 03/04 LCB 03/04
Boot-Hd Boot-Gf Hd-Gf Boot-Hd Boot-Gf Hd-Gf
WI 0.217 0.043 0.076 0.122 0.183 0.699**
RNDVI 0.043 0.317 0.373 0.273 0.133 0.602**
GNDVI 0.310 0.135 0.071 0.389 0.296 0.667**
SR 0.003 0.218 0.324 0.106 0.035 0.792**
NWI-1 0.208 0.031 0.074 0.133 0.185 0.694**
NWI-2 0.258 0.102 0.057 0.005 0.272 0.679**
NWI-3 0.257 0.078 0.096 0.148 0.118 0.725**
NWI-4 0.297 0.154 0.090 0.099 0.202 0.690**
Exp-2 LCB 03/04 LCB 04/05
Boot-Hd Boot-Gf Hd-Gf Boot-Hd Boot-Gf Hd-Gf
WI 0.289 0.041 0.664** 0.717** 0.367 0.656**
RNDVI 0.016 0.104 0.804** 0.690** 0.185 0.482*
GNDVI 0.258 0.279 0.791** 0.748** 0.415* 0.604**
SR 0.197 0.320 0.842** 0.683** 0.048 0.363
NWI-1 0.295 0.037 0.665** 0.716** 0.386 0.652**
NWI-2 0.130 0.181 0.695** 0.646** 0.173 0.528**
NWI-3 0.353 0.106 0.674** 0.691** 0.459* 0.705**
NWI-4 0.205 0.168 0.666** 0.668** 0.286 0.593**
Exp-3 STW 03/04 STW 04/05
Boot-Hd Boot-Gf Hd-Gf Boot-Hd Boot-Gf Hd-Gf
WI 0.505** 0.105 0.614** 0.126 0.128 0.804**
RNDVI 0.196 0.244 0.623** 0.746** 0.489* 0.771**
GNDVI 0.388 0.119 0.589** 0.707** 0.430* 0.813**SR 0.288 0.137 0.648** 0.836** 0.522** 0.765**
NWI-1 0.485* 0.097 0.619** 0.127 0.140 0.802**
NWI-2 0.464* 0.081 0.609** 0.216 0.199 0.762**
NWI-3 0.506** 0.085 0.605** 0.110 0.140 0.798**
NWI-4 0.425* 0.107 0.616** 0.173 0.203 0.770**
*Significant at the 0.05 probability level.
**Significant at the 0.01 probability level.GNDVI, green normalized difference vegetation index; NWI-1, normalized water index 1; NWI-2, normalized water index 2; NWI-3, normalized water index 3; NWI-4, normal-
ized water index 4; RNDVI, red normalized difference vegetation index; SR, simple ratio; WI, water index.Correlation between booting and heading stages.Correlation between booting and grain-filling stages.Correlation between heading and grain-filling stages.
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CROPSCIENCE, VOL. 47, JULYAUGUST2007 WWW.CROPS.ORG 1433
h colo cof c w low h h cof cu h owh combo ( o how).
Th w-b NIR c (WI NWI) lwypov hh c colo wh ylcomp o h wly u c (RNDVI, GNDVI, SR) (F. 2). Th p w lo obv whvul owh vul y/loco
yl w co ( o how). I mo c, h
pomc o h mo w bb c (WI NWI) w uhbl om ch oh, buco h ovll pomc, NWI-3 NWI-4how b colo wh yl h - xpm y loco.
Functional Relationship between Spectral
Reflectance Indices and Grain Yield
Th ucol lohp bw yl h SRI o h h owh vully combo w blh houh o l-
y. Fu 3 how h ucol lohp o NWI-3wh yl h owh o wo xpmTh NWI-3 xpl mo o h yl vbl y
h -ll comp o h boo- (F. 3). Th lohp o h -c (NWI-2, NWI-3, NWI-4) wh yl p F. 4 o h xpm, bo h m o h h owh
Table 7. Correlation coefficients between spectral reflectance indices and grain yield at three growth stages (GS) for
three experiments.
Indices GS EXP-1 EXP-2 EXP-3
STW 03/04 LCB 03/04 LCB 03/04 LCB 04/05 STW 03/04 STW 04/05
WI Boot 0.374 0.272 0.105 0.358 0.588** 0.139
Hd 0.674** 0.733** 0.643** 0.512** 0.686** 0.569**
GF 0.516** 0.672** 0.657** 0.752** 0.571** 0.685**
Mean 0.814** 0.763** 0.676** 0.653** 0.785** 0.623**
RNDVI Boot 0.081 0.266 0.029 0.372 0.319 0.402
Hd 0.401* 0.481* 0.499* 0.400* 0.259 0.525**
GF 0.129 0.474* 0.567** 0.522** 0.150 0.591**
Mean 0.183 0.567** 0.570** 0.574** 0.232 0.605**
GNDVI Boot 0.130 0.295 0.210 0.473* 0.397* 0.469*
Hd 0.622** 0.557** 0.680** 0.475* 0.494* 0.509**
GF 0.108 0.387 0.512** 0.478* 0.058 0.567**
Mean 0.312 0.524** 0.624** 0.559** 0.341 0.571**
SR Boot 0.107 0.312 0.112 0.348 0.313 0.484*
Hd 0.445* 0.554** 0.604** 0.464* 0.367 0.594**
GF 0.052 0.535** 0.606** 0.533** 0.224 0.608**Mean 0.381 0.618** 0.471* 0.533** 0.435* 0.595**
NWI-1 Boot 0.364 0.268 0.097 0.366 0.579** 0.135
Hd 0.673** 0.730** 0.650** 0.515** 0.682** 0.600**
GF 0.518** 0.663** 0.662** 0.750** 0.577** 0.684**
Mean 0.819** 0.758** 0.671** 0.653** 0.788** 0.618**
NWI-2 Boot 0.429* 0.278 0.069 0.334 0.598** 0.172
Hd 0.668** 0.690** 0.617** 0.522** 0.650** 0.614**
GF 0.442* 0.596** 0.652** 0.645** 0.511** 0.670**
Mean 0.759** 0.702** 0.690** 0.657** 0.741** 0.622**
NWI-3 Boot 0.423* 0.260 0.106 0.348 0.560** 0.132
Hd 0.704** 0.740** 0.678** 0.522** 0.666** 0.581**
GF 0.514** 0.703** 0.742** 0.729** 0.579** 0.698**
Mean 0.865** 0.798** 0.776** 0.666** 0.777** 0.668**
NWI-4 Boot 0.499* 0.281 0.089 0.335 0.581** 0.164
Hd 0.707** 0.727** 0.649** 0.516** 0.658** 0.598**
GF 0.478* 0.646** 0.721** 0.670** 0.551** 0.689**
Mean 0.845** 0.810** 0.753** 0.673** 0.761** 0.684**
*Significant at the 0.05 probability level.
**Significant at the 0.01 probability level.
Boot, booting stage; GF, grain-filling stage; GNDVI, green normalized difference vegetation index; Hd, heading stage; NWI-1, normalized water index 1; NWI-2, normalized
water index 2; NWI-3, normalized water index 3; NWI-4, normalized water index 4; RNDVI, red normalized difference vegetation index; SR, simple ratio; WI, water index.
Correlation between yield and mean spectral reflectance indices across three growth stages.
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vul y o loco. Th lohp o h ohc wh yl w lo ( o how), l l c h mol b wh l l-ohp hv h hh cof c o mocomp o oh mol. Ic o xpl moo h yl vbly wh m w u,o xmpl, comb owh , comb y/loco, o comb boh. Ou ly b o com-b owh vl h upoy o NWI-3
ov h oh c pc yl, xpl- 74% o h yl vo o loc-o 63% o h vo h oh locoo Exp-1 (F. 4). Th lohp o mu yl pc yl b oNWI-3 p F. 5. Th lohpw blh o h b o ll h xp-m u h m vlu o h h owh
co loco y. Alhouh omc w obv bw h xpm o yl pcl bhvo,h lohp vl h c lpcbly o yl b o NWI-3.
Selection of GenotypesSc c bw oypc
yl o h wo lco oup b o h25% hh h 25% low SRI vlu wobv o ll h w-b SRI ( ohow). Th w x h NWI how
ccucy y boh h hh-yl h low-yl oyp com-p o h RNDVI, GNDVI, SR (Tbl8). Sml w lo obv wh -vul owh w co ( ohow), bu h combo o owh lwy wok b. Th c h cluh mo w bopo b 50 o83% o boh h 25% hh-yl oyp h 25% low-yl oyp llh xpm. Amo h NIR-b -c, NWI-3 NWI-4 coly pom
b. Th w lo v wh h m oh wo loco o 2-y w comb ovul xpm, lo wh h hxpm w co oh (Tbl 8).
Yl p yl m o h 25% hh--yl 25% low-yl oyp oh h xpm b o h l -o quo o h SRI p Tbl 9. Th pc c bw h h-v pc yl xpmw clo 0.9% o h hh-yl o-yp u NWI-3 Exp-1. Th l cbw cul pc yl w 21.1% o h
RNDVI Exp-3. I mo c, h pc yl cw 10% o l, wh h w-b NIR c com-moly hv c o 1 o 5%. Th wly u -c (RNDVI, GNDVI, SR) how cocy co
y loco y h hh-yl low-yl oyp, whl h NIR c howmkbl ccucy cocy pc h l-v pomc o h oyp o yl co y loco.
Figure 2. Phenotypic and genetic correlation coefficients between different
spectral reflectance indices (mean of different growth stages across year/
location) and grain yield (mean of two locations in Exp-1 and 2 yr in Exp-
2 and Exp-3). GNDVI, green normalized difference vegetation index; NWI-1,
normalized water index 1; NWI-2, normalized water index 2; NWI-3, normalized
water index 3; NWI-4, normalized water index 4; RNDVI, red normalized
difference vegetation index; SR, simple ratio; WI, water index.
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DISCUSSIONGenotypic Variation and Growth StageSc oypc vo o yl pc-l bhvo owh , mly boo,h, -ll, com h xc o u-c vo mo h oyp. Th xp-m (Exp-1) clu wly u w wh culvvlbl houhou h G Pl o h USA. Thoh wo xpm co uf c v o h pcv RIL populo. Sml vo w
lo obv by oh ch wok wh pclcc wh, clu Bb l. (2006) wok- wh p wh, wh o- p wh (Guz-Rouz l., 2004)wh uum wh h M o (Apco l., 2000, 2002), wh uum wh u - coo (Royo l., 2003).Th pmy oo h c o RNDVI, GNDVI, SRom boo o -ll h uc cc h NIR o u o lo o u owh
Figure 3. Functional relationship between grain yield and normalized water index 3 (NWI-3) at three growth stages for two experiments. Top
Exp-1; bottom: Exp-2. *Significant at the 0.05 probability level; **significant at the 0.01 probability level. RMSE, root mean square error.
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po om boo o -ll, wll c cc h vbl o (Apco l.,2000). Th NIR c (WI NWI) b o hmo w bopo b (970 m), hy muh w u o h copy (Pul l., 1997; Bb l., 2006). I 2003/2004, h xpm h oow u u h (71.474.9 mm ll) h c w low h boo , wh, 2004/2005, h occu u w c
coo (9.910.7 mm ll) hc w hh h compo boo (F. 1), c h v lohp bw w -u c vlu. Th occ mo h oyp o hSRI om c h boo w u o h homoy o h LAI
mo h oyp, whch omllych mxmum h boo (Apco l., 2000). Bu, h lowh , h c hhlyuc by h poucv uc-u uch pk mopholoy, wll h c h LAI, cc h c vo moh oyp (Hl, 1981; Apco l., 2000). Th commoly u c(NDVI SR) uully u LAI> 3, whch u o h lck o v-
y o lh h hh voco. Wh, h NIR b o hw-b c (WI NWI) cp o h hh vo c-o o h copy h wu o h copy wll h mouo bom (Bb l., 2006).
Interaction Effect of
Genotypes, Growth Stages,
and Years/LocationsW obv c co bw
owh h oyp o c (Tbl 5). Th m hpcc owh vy mpocoo wh mu h pclcc. Sml obvo w m h u o Bb l. (2006) wh p wh by Apco l. (2002) wh - uum wh. Wlo obv vy low oco o yvul x bw owh, pclly bw h boo h h , bw h boo- h -ll , wh w
xcpo. Th c oyp w k lyo c vlu owh , whch mlo obvo po by Bb l. (2006) Royo l. (2003). Colo bw h h -ll- o vul c w c o ll cxcp Exp-1 Sllw 2003/2004. Sc h -ll h wo mo mpo owh o pcl cc mum, w comm m-u pcl cc h wo owh .
Figure 4. Functional relationship between grain yield and normalized water index 2
(NWI-2), normalized water index 3 (NWI-3), and normalized water index 4 (NWI-4)
(estimated as the mean of the three growth stages). Top: Exp-2; middle: Exp-1; bottom:
Exp-3. STW and LCB denote Stillwater and Lake Carl Blackwell sites, respectively.
**Significant at the 0.01 probability level. RMSE, root mean square error.
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Correlation between Spectral
Reflectance Indices and Grain Yield
D u hv po h uul o pclcc c o pc yl u - voml coo. Mo u co hvy o h vom oyp,clu w m uum wh (Ap-co l., 2000), ly c bly (Pul l.,
1997), lz w m co (Obo l., 2002), pl populo y oyb (M l., 2001). Th umu h voml uc c h vbly h xp-m h h h c vblyo yl u o oyp. Howv,Bb l. (2006) blh olohp bw NIR-b c yl wh p whoyp. I co, h h b llch u pcl cc -
c pc w wh oypo yl u G Pl -coo. Ru l. (2001) pvoulypo h u o NDVI pch yl o w w wh culvu v o lvl.
W u x publh SRI (RNDVI,GNDVI, SR, WI, NWI-1, NWI-2), wo w c (NWI-3 NWI-4) w clcul (Tbl 2). Mo ck h boo how o-c colo wh yl h
xpm, wh w xcp-o. Th lohp bw SRI
yl bcm o h owh po ow h poucv ph.Bb l. (2006) lo po lowcolo bw h pclcc c yl hboo . M l. (2001) wh oy-b Royo l. (2003) wh uumwh lo po h h SRI co-l b wh yl h poucvowh h h ly v-v owh . Apco l. (2000)ou c colo bw yl SRI h ouh (Zok 87) wh uum whu - coo.
W x h NWI vhh colo wh yl com-p wh h RNDVI, GNDVI, SR h -ll (Tbl 7).Pul l. (1993) po c
lohp bw WI lv w co, lw pol, oml coucc, copy m-pu. Th mo w bopo b (970 m) oh NIR b u h clculo o WI NWImk h c mo v o hh co o vo h h -ll owh comp o NDVI SR (Bb l., 2006). Thhh colo cof c o h NIR-b c
wh oypc yl comp o NDVI SR Table 8. The percentage of 25% highest-yielding and 25% lowest-yielding (values
in parentheses) genotypes selected by different spectral reflectance indices.
Experiments Spectral reflectance indices
WI RNDVI GNDVI SR NWI-1 NWI-2 NWI-3 NWI-4
EXP-1
STW 03/04 83 (83) 17 (33) 50 (33) 50 (50) 83 (67) 67 (67) 83(83) 83 (67)
LCB 03/04 83 (50) 50 (50) 50 (50) 50 (67) 67 (50) 83 (50) 67 (83) 83 (67)
Mean 67 (50) 50 (33) 50 (50) 50 (33) 67 (50) 67 (50) 83 (83) 83 (83)
EXP-2
LCB 03/04 67 (50) 67 (50) 67 (50) 67 (50) 67 (50) 67 (50) 83 (67) 83 (67)
LCB 04/05 67 (50) 67 (50) 50 (50) 50 (50) 50(50) 67 (50) 83 (67) 83 (67)
Mean 50 (50) 50(33) 33 (67) 50 (50) 50 (50) 67 (33) 67 (67) 67 (67)
EXP-3
STW 03/04 50 (67) 33 (17) 33 (33) 50 (50) 50 (67) 67 (50) 67 (67) 67 (67)
STW 04/05 67 (50) 50 (50) 50 (50) 83 (50) 67 (50) 83 (50) 83 (50) 83 (67)
Mean 67 (50) 67 (17) 83 (33) 83 (33) 67 (67) 67 (67) 83 (83) 83 (83)
Overall mean 61 (50) 56 (28) 55 (50) 61 (39) 61 (56) 67 (50) 78 (78) 78 (78)
GNDVI, green normalized difference vegetation index; NWI-1, normalized water index 1; NWI-2, normalized
water index 2; NWI-3, normalized water index 3; NWI-4, normalized water index 4; RNDVI, red normalized
difference vegetation index; SR, simple ratio; WI, water index.
Selection based on mean spectral reflectance indices across three growth stages and mean grain yield
across locations/years for each individual experiment.
Selection based on mean spectral reflectance indices across three growth stages and mean grain yield
across locations/years for all three experiments.
Figure 5. Relationship between measured grain yield and predicted grain yield based on the
linear equation using normalized water index 3 (NWI-3) as the predictor, estimated using the
mean values of three growth stages for all three experiments across two locations/years
**Significant at the 0.01 probability level. RMSE, root mean square error.
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u o b o o h oyp h -ll. I h b lo po h WI c pclv w co, oml coucc, l wpol (Pul l., 1993). Th colo cof c
o w-b c wh yl w - bu lbl, whch w u o h u o NIR wvb o omlz h 970-m w b NIR c. Ic w co h plcopy c h cc o h w b, coquly, w ob v colo o hc wh yl. Bb l. (2006) po m-l obvo.
Colo o h m m o h SRI coh owh wh yl w hh compo y vul owh (Tbl 7). Th w lopo by Bb l. (2006) Apco l. (2000).Th NIR-b c lwy v hh coloh h RNDVI, GNDVI, SR wh ccmum w comb co owh. I mo c, h m o h c h h h -ll lo v hh colowh yl h y vul owh , bulow h h colo cof c ob houhcomb h owh ( o how). Wblv h m c co owh m-um o ovll pl hlh u c cl m
pl vlopm. Rp cc mum o oyp om owh h ovll o h oyp wh m. Tho, h cy h oyp h m hlh co-
o houhou h ow o , ul, vhh colo wh l yl. W obvhh c colo bw h w-b NIRc yl comp o h wly u v-o b c (F. 2). Th obvo ch h w-b c hv hh pcbly h oypc lvl o yl vo compo h vo b c u - coo.
Functional Relationship
between the SRI and Grain YieldTh ucol lohp bw h SRI
yl w l (F. 3 4). Bb l. (2006) Guz-Rouz l. (2004) lo po llohp bw h SRI yl.Ou ul c h h SRI c b u o p-c yl pcv o h yl pol o hoyp. Th NIR-b c lwy how bpcbly wh mo w clu h mol( owh , y/loco). Thc lo pc yl wll wh vulowh uch h o -ll w
Table 9. Comparison between measured grain yield (kg ha1) and predicted grain yield (kg ha1) of the 25% highest-yielding and
25% lowest-yielding (values in parentheses) genotypes in each experiment using spectral reflectance indices.
Yield per se Predicted grain yield by spectral reflectance indices
WI RNDVI GNDVI SR NWI-1 NWI-2 NWI-3 NWI-4
EXP-1
STW 03/04
5678 (4207)5620 (4386) 5071 (4797) 5170 (4963) 5228 (4677) 5624 (4380) 5595 (4379) 5627 (4333) 5622 (4352)
Difference 1.0 (4.2) 10.7 (14.0) 9.0 (11.6) 7.9 (11.1) 1.0 (4.1) 1.5 (4.1) 0.9 (3.0) 1.0 (3.4)
LCB 03/04
6248 (4758)
6006 (4837) 5852 (5029) 5764 (4983) 5852 (4994) 5993 (4845) 6001 (4865) 6000 (4857) 6005 (4843)
Difference 3.9 (1.7) 6.3 (5.7) 7.7 (4.7) 6.3 (5.0) 4.1 (1.8) 4.0 (2.2) 4.0 (2.1) 3.9 (1.8)
EXP-2
LCB 03/04
5995 (4157)5621 (4337) 5504 (4455) 5573 (4383) 5567 (4439) 5628 (4327) 5585 (4358) 5662 (4280) 5631 (4302)
Difference 6.2 (4.3) 8.2 (7.2) 7.0 (5.4) 7.1 (6.8) 6.1 (4.1) 6.8 (4.8) 5.6 (3.0) 6.1 (3.5)
LCB 04/05
3317 (2611)3205 (2725) 3147 (2765) 3139 (2770) 3177 (2753) 3211 (2728) 3208 (2739) 3197 (2744) 3203 (2739)
Difference 3.4 (4.4) 5.1 (5.9) 5.4 (6.1) 4.2 (5.4) 3.2 (4.5) 3.3 (4.9) 3.6 (5.1) 3.4 (4.9)
EXP-3
STW 03/04
5642 (3511)5407 (3809) 4931 (4450) 5042 (4324) 5157 (4272) 5410 (3804) 5388 (3873) 5402 (3791) 5396 (3853)
Difference 4.2 (7.8) 12.6 (21.1) 10.6 (18.8) 8.6 (17.8) 4.1 (7.7) 4.5 (9.3) 4.2 (7.4) 4.3 (8.8)
STW 04/055008 (3640)
4728 (3800) 4686 (3857) 4653 (3844) 4758 (3864) 4728 (3802) 4742 (3799) 4723 (3807) 4747 (3802)
Difference 5.6 (4.4) 6.4 (5.9) 7.1 (5.6) 5.0 (6.2) 5.6 (4.4) 5.3 (4.4) 5.7 (4.6) 5.2 (4.4)
STW, Stillwater site; LCB, Lake Carl Blackwell site.
GNDVI, green normalized difference vegetation index; NWI-1, normalized water index 1; NWI-2, normalized water index 2; NWI-3, normalized water index 3; NWI-4, normal-
ized water index 4; RNDVI, red normalized difference vegetation index; SR, simple ratio; WI, water index.
Difference between measured grain yield and predicted grain yield, expressed as percentage.
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co, hu mk hm ubl lco ool b pom o yl mpovm. Co- h ovll pomc, NWI-3 NWI-4 howb pomc ov h oh NIR-b c.
Selection of GenotypesTh f ccy o lc upo oyp pmycoc wh u c lco ool o pcc
. Sc yl c bw h wo oupo oyp b o h hh low x vluo h w-b c c h h c cpoply cm h oyp o yl. Ouul how h h w-b NIR c - mjo popoo o h hh-yl wll h low-yl oyp h xpm.I o, h clo ppoxmo o cul ylvl h pow o h c o pco o h o-yp yl. U o h NIR-b c, pcllyNWI-3 NWI-4, how pom lc oyp o hh yl.
CONCLUSIONSTh pol o SRI o pc w wh oypo yl vbly mo ou uy. Thomly v comb b l blh hc b o h lohp bw h SRI
yl. Th c w l o yl l h-o com h cv o y h hh-
yl oyp pcv o h yl pol.Comb h cc mum om h owh pov h b lohp bw SRI
yl, bu o pccl coo, w comm k-
pcl cc mum h h h-ll o pc h oypc ylpol. Ic b o h mo w bopo bcoly pov h b lohp wh yl, mo hm NWI-3 NWI-4 how b po-mc y h hh-yl oyp - w wh c bckou h G Pl.
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