600

Euphytica 22 (1973) : 600-606

GENOTYPIC DIFFERENCES IN FLAG LEAFAREA AND THEIR CONTRIBUTION TO

GRAIN YIELD IN WHEATJ. H. MONYO 1 and W. J. WHITTINGTON

University of Nottingham School of Agriculture, Sutton Bonington,Loughborough, Leics ., England

Received 12 December 1972

SUMMARY

Flag leaf areas of the wheat variety Chinese Spring, six chromosome substitution lines of the varietyHope into Chinese Spring and their hybrids were measured by the planimeter method . Data on tillernumber at ear emergence and ear number and grain yield at harvest were also obtained . Considerablevariation existed in each of the characters investigated . The inheritance of flag leaf area showed someevidence of over dominance and non-allelic interaction while ear number was mainly under additivegenetic control with partial dominance . Highly significant associations were found between flagleaf area, ear number and grain yield per plant. The importance of flag leaf area in yield determinationwas discussed in the light of the results obtained . It was concluded that despite the correlation betweenflag leaf area and grain yield, the major components of yield and grain yield itself, still offer the bestguide for selection .

INTRODUCTION

The dependence of grain yield in wheat on the area and duration of the leaf surfacebefore and after ear emergence has been well established (WATSON et al ., 1963 ;LANGER, 1967) . The relevance of leaf area to grain yield has been shown to be due toits role in radiant energy interception . THORNE (1965) showed that after anthesis inwheat the carbon dioxide fixed by the ear was equivalent to between 17 and 30 % ofthe grain weight but more than this amount was lost by respiration . Thus assimilationby the flag leaf lamina, its sheath and peduncle accounted for 10-20 % of the final grainweight . LUPTON (1966) using 14C02 was able to show that translocation from glumesand flag leaves was almost entirely towards the grain while that from the second andthird leaves was only partly towards the grain . An association between photosyntheticarea above the flag leaf node and yield in wheat was further demonstrated by SIMPSON(1968) . In all these results the flag leaf seems to play a dominant role . While varietaldifferences in flag leaf area have been indicated in various studies no attempts havebeen made to determine its inheritance . In this study the genetic control of flag leafarea in wheat substitution lines and its contribution to grain yield were investigated .

MATERIALS AND METHODS

The data were collected in Experiment 7 of Monyo & Whittington (1970, 1971) . In thisexperiment single plants of Chinese Spring, chromosome substitution lines 2A, 2B, 2D,1 Present address : University of Dar es Salaam, Faculty of Agriculture, P .O. Box 643, Morogoro,Tanzania .

5A and 5D and all F 1 hybrids between them were grown in a greenhouse in earthen-ware pipes during the summer of 1967 . A randomised block design with two replicateswas used. The spacing was 60 cm between pipes in the row and 30 cm between rows .At ear emergence the flag leaves were taken at random from each line and F 1 plant .Blue prints of the flag leaf laminae were taken and their areas measured with a plani-meter. The number of tillers for each plant at ear emergence was counted . At maturityear number and grain yield were obtained .

RESULTS

The data on flag leaf area, tiller number, ear number and grain yield showed that therewere highly significant differences between genotypes (Table 1). The correlationsbetween flag leaf area and yield per plant and between ear number and yield per plant

Table 1 . Area of flag leaf lamina per tiller, tiller number, ear number and grain yield per plant .

FLAG LEAF AREA AND YIELD IN WHEAT

Chinese Spring (CS)Line - 2A

5A2B5B2D5D

CS x 2ACS x 5ACS x 2BCS x 5BCS x 2DCS x 5D2A x 5A2A x 2B2A x 5132A x 2D2A x 5D5A x 2B5A x 5B5A x 2D5A x 5D2B x 5B2B x 2D2B x 5D5B x 2D5B x 5D2D x 5D

Standard error

Tukey test (D)

Euphytica 22 (1973) 601

Genotype Mean flag Mean tiller Mean ear Grain yield (g)leaf area (cm') number at ear number at

emergence harvest

21 .8 32 .5 33 .5 32 .341 .7 14 .0 21 .5 15 .352 .0 17 .5 19 .5 22 .436 .0 42 .5 41 .0 32 .229 .4 20 .5 36 .0 28 .927 .9 45 .0 41 .5 41 .028 .2 88 .0 58 .0 27 .541 .4 20 .0 21 .0 20 .340 .9 17 .0 28.5 26 .120 .7 31.0 35 .0 30 .824 .5 26 .5 32 .5 29 .121 .0 37.5 36.5 33 .040 .3 47 .0 54.0 44 .236.4 17 .0 20.0 21 .646 .3 18 .0 23 .0 23 .224 .5 17 .5 23.5 21 .637 .4 16 .5 33 .5 23 .731 .0 44.5 45 .5 41 .944 .8 20 .0 26 .5 21 .429 .6 18 .0 28 .0 27 .233 .7 34 .5 42.0 31 .739 .9 21 .0 32 .0 26 .920.6 30 .0 38 .5 28 .919 .3 38 .0 42.0 42 .638 .1 63 .5 52 .0 48 .219 .9 35 .0 37 .0 30 .826 .7 33 .0 38 .5 38 .931 .8 67 .0 56 .5 44 .9+2.65 -x-5 .18 +4.02 +3.2013 .28 20 .72 22 .03 17 .94

were 0.60 (P<0.001) and 0.80 (P<0.001), respectively . The flag leaf area rangedfrom 19.3 cm2 per tiller in the F l hybrid between lines 2B and 2D to 52.0 cm2per tiller in line 5A . Line 5A had more than twice the flag leaf area of ChineseSpring . There was considerable variation amongst the F l hybrids for flag leaf area .Some showed negative heterosis, others were intermediate between the values ofthe parents and some showed positive heterosis . Most of the negative heterosis wasobtained in crosses with lines 5B and 2D . In all, eight F I values showed negativeheterosis, and four showed positive heterosis . In a diallel analysis a significant regres-sion was obtained between the array variances and covariances and a Wr Vr graphwas plotted (WHITEHOUSE et al . 1958). The slope of the regression line (Fig . 1) deviatedsignificantly from 1 thus indicating that non-allelic interactions were mainly deter-mining the expression. The line cut the Wr axis just below the origin suggesting thatoverdominance was involved .

A highly significant regression was obtained on the Wr Vr graph for ear number(Fig . 2). The gene system was highly additive . There was evidence of non-allelic inter-action and partial dominance . Estimates of additivity and within-chromosome inter-action (Table 2) and between-chromosome interaction (Table 3a) using the methodof LAW (1966) confirmed the results obtained from the pictorial diallel .

In view of the uncomplicated pattern of inheritance for ear number it was surprisingto find that there was no significant association between the array variances and co-variances for grain yield per plant . The slope of the regression of Wr on Vr was 0 .24 +0.16. The estimate of the additive and dominance effects showed that only the Agenome had significant additive chromosome effects for yield (Table 2) . Chromosome5D had significant dominance effects for yield . Between-chromosome interactionestimates showed that there were marked interactions between genome A chromo-

Fig. 1 . Variance (Vr), Covariance (Wr)graph for mean area of flag leaf pertiller at ear emergence.

602

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Euphytica 22 (1973)

Wr

Fig. 2 . Variance (Vr), Covariance (Wr) graph for140

mean ear number per plant at the final harvest.

51

2A

•

5D

FLAG LEAF AREA AND YIELD IN WHEAT

somes and the effects of chromosome 5D and between chromosomes 2B and 2D(Table 3b) .

The data were re-analysed using the method proposed by MORLEY JONES (1965) forhalf diallel tables (Table 4) . Component (a) was very highly significant indicating thepresence of additive chromosome effects in the genetic determination of ear number,grain yield and flag leaf area . The dominance component (b), which is the summationof components (b 1 ), (b 2) and (b3 ), was highly significant for grain yield and very highlysignificant for flag leaf area . Component (b 1) was not significant for any of the charac-ters studied implying that there was no epistasis to mean dominance . Component (b 2 )was very highly significant for grain yield and flag leaf area indicating asymmetry in thegene distribution. Component (b 3 ) was just significant for grain yield and very highlysignificant for flag leaf area suggesting the presence of residual dominance effects .There was good agreement between the analyses based on the methods of LAW

(1966) and MORLEY JONES (1965). The pictorial diallel results for ear number indicated

Table 2 . Estimates of additivity and within-chromosome interaction for yield and ear number .

*P<0.05 ; **P<0,01 ; ***P<0.001 .

Euphytica 22 (1973) 603

Chromosome Grain yield Ear number

2A

additive chromo-some effects

-8.50***

within chromo-some interaction

- 3.52

additive chromo-some effects

- 6.00*

within chromo-some interaction

-6.505A -4.95* - 1.25 - 7.00* ±2.002B -0.06 - 1 .46 + 3.75 -2.255B -2.20 - 1 .50 4- 1 .25 -2.252D +4.37 - 3.63 4.00 -1 .005D -2.39 +14.27*** +12.25*** - 8 .25Total -13.73 + 2.91 + 8.25 -1 .74

Table 3 . Estimates of between-chromosome interactions for ear number (a) and grain yield (b).

604

* P < 0.05 ; ** P < 0.01 .

Table 4 . Analysis of variance of the half diallel tables for ear number, grain yield and flag leaf area .

*P<0.05 ; **P<0.01 ; ***P<0.001 .

presence of partial dominance which was lacking in both numerical analyses . TheMorley Jones's method showed evidence of additive gene effects for flag leaf area butthis could not be detected in the pictorial diallel .

DISCUSSION

Heritable variation was observed for the two characters ear number and area of flagleaf. The mode of inheritance was mainly by additive gene action for ear number whilethe inheritance of flag leaf area showed evidence of non-allelic interaction in the pic-torial diallels . Flag leaf area varies considerably from tiller to tiller and it is possiblethat the evidence for interaction was due to chance effects in the selection of the mate-rial. An analysis based only on measurements of flag leaves from specified tillers e .g.the main shoot might show more evidence of additivity. The inconsistency between the

J . H. MONYO AND W. J. WHITTINGTON

Euphytica 22 (1973)

2A 5A 2B 5B 2D

5D Total

(a) Ear number5D +4.0 -17.0** - 3.5 -14.5* -0.5 -31.52D +9.5 +10.5 + 4.0 + 1.5 +25.05B +3.5 + 0.5 + 4.5 +11.02B +0.5 - 3 .5 + 2.05A +4.0 - 5.52A +21.5

Grand total +87.84

(b) Grain yield5D +9.78* -11 .02* + 6.34 + 0.90 +0.02 + 6.222D +2.75 + 4.88 +11 .12* + 1.02 +19.795B +3.51 + 4.27 + 1 .36 +11.062B +4.42 - 3.17 +20.275A +7.54 + 2.502A +28.00

Grand total +87.84

Component df Ear number Grain yield Flag leaf area

a 6

M.S.

463 .94

F

28.71***

M.S .

206 .98

F

20.29***

M.S .

221 .59

F

31.61**b, 1 0.58 0.04 40.32 3 .95 21 .20 3 .02b2 6 14.36 0.89 64.89 6.36*** 48.50 9.62***b3 14 27.27 1 .69 22.03 2.16* 42 .61 6.08***

b (b,-b3) 21 22 .31 1 .38 35 .15 3 .45** 43.27 6 .17***

Error 27 16.16 10.20 7 .01 (df=252)

results from the pictorial diallel and those based on the analysis of variance of the halfdiallel table supports this view . It is also probable that the very high degree of asym-metry in the gene distribution and the residual dominance effects affected the slopeof the regression line .

VOLDENG & SIMPSON (1967) and MONYO & WHITTINGTON (1971) have shown thatleaf area is an indicator of potential grain yield in wheat and since the flag leaf plays apredominant role, its size may be important . SIMPSON (1968) found a correlation coeffi-cient of 0 .53 between the area of flag leaf and yield per tiller which is comparable to theestimate obtained in this study of 0 .41 . This raises the possibility that it may be worth-while to consider flag leaf area in selection programmes particularly since BREMNER(1967) found that the removal of all or part of the flag leaf resulted in yield reductionOn the other hand, it is likely that a relative deficiency in flag leaf area due either togenetic causes or to the direct removal of tissue may be compensated for by increasedmetabolic activity, increased leaf area duration or by increased translocation from thelower leaves. The results of BREMNER (1967) showed that removal of the flag leafresulted in a 17 and 7 % reduction for the varieties Heines VI I and Thor respectively .Removal of half the flag leaf at anthesis reduced yield only by 8 and 5 % in thesevarieties . These results which suggest very considerable compensation by other partsof the plant or by the remaining flag leaf raise the possibility, judged purely on physio-logical grounds, that varieties might be found with low flag leaf areas but with highyields thus making it unnecessary to give particular consideration to the flag leaf.

In the absence of severe effects from water deficit or disease attack the plant largelysucceeds in developing the grain within the ear and the correlation between flag leafarea and yield is likely to be determined not by physiological activity but by the correla-tion in development of large flag leaves and large ears . EVANS & DUNSTONE (1970)have shown that there has been a parallel increase in leaf and grain size in the evolu-tion of wheat and the relation between the flag leaf area and yield may be viewed aseither due to parallel selection of separate gene systems or pleiotropic effects at lociwhich determine the sizes of cells, meristems and organs . Because a genetic control offlag leaf size and an association with yield has been demonstrated it is possible to useflag leaf area as a guide to potential production by the ear. In general, however, themain consideration must continue to be given to the individual yield components andtotal grain yield .

REFERENCES

BREMNER, P . M., 1967 . Some aspects of the relationship between growth and yield in wheat . Ph . D .Thesis, University of Nottingham .

EVANS, L. T. & R. L . DUNSTONE, 1970. Some physiological aspects of evolution in wheat . Aust . J.biol . Sci . 23 : 725 .

LANGER, R. H. M., 1967 . Physiological approaches to yield determination in wheat and barley .Field Crop Abstr . 20 : 101-106 .

LAW, C. N ., 1966. Biometric analysis using chromosome substitutions within a species . In : R . Rileyand K. R. Lewis . (Ed.), Chromosome manipulations and plant genetics, p . 59-85 . Oliver, Edin-burgh and London .

LuPTON, F. G. H., 1966 . Translocation of photosynthetic assimilates in wheat . Ann . appl . Biol . 57 :355-364 .

FLAF LEAF AREA AND YIELD IN WHEAT

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MONYO, J. H . & W . J. WHITTINGTON, 1970. Genetic analysis of root growth in wheat . J . agric. Sci .Camb. 74: 329-338 .

MoNYO, J. H. & W. J . WHITrINGTON, 1971 . Inheritance of plant growth characters and their relationto yield in wheat substitution lines . J . agric . Sci ., Camb . 76 : 167-172 .

MORLEY JONES, R ., 1965 . Analysis of variance of the half diallel table . Heredity 20 : 117-121 .SIMPSON, G. M ., 1968 . Association between grain yield per plant and photosynthetic area above the

flag leaf node in wheat. Can . J . Plant Sci . 48 : 253-260.THORNE, G. N., 1965 . Photosynthesis of ears and flag leaves of wheat and barley. Ann. Bot. 29 :317-329.VOLDENG, H. D. & G. M. SIMPSON, 1967 . Leaf area as an indicator of potential grain yield in wheat .Can. J . Plant Sci . 47 : 359-365 .

WATSON, D . J., G . N. THORNE & S. A. W. FRENCH, 1963 . Analysis of growth and yield of winter andspring wheats. Ann. Bot . 27 : 1-22.

WHITEHOUSE, R . N . H ., J . B. THOMPSON & M. A. M. VALLE RIBEIRO Do ., 1958 . Studies on the breedingof self-pollinating cereals. 2 . The use of a diallel cross analysis in yield prediction. Euphytica 7 :147-169 .

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