Field Crops Research, 8 (1984) 307--313 307 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands

EFFECT OF FLAG LEAF AND AWN REMOVAL ON GRAIN YIELD AND YIELD COMPONENTS OF WHEAT GROWN UNDER DRYLAND CONDITIONS

MAHMUD DUWAYRI

Department of Plant Production, Faculty of Agriculture, University of Jordan, Amman (Jordan)

(Accepted 21 October 1983)

ABSTRACT

Duwayri, M., 1984. Effect of flag leaf and awn removal on grain yield and yield com- ponents of wheat grown under dryland conditions. Field Crops Res., 8: 307--313.

Effect of flag leaf and/or awn removal on grain yield, kernel number and single weight were investigated in nine durum (Triticum durum Desf.) and one hexaploid (Triticum aestivum L.) wheat genotypes grown under dryland conditions in Jordan. The treatments were control, removal of the flag leaf, removal of the awns, and a combination of awn and flag leaf removal. Genotypes studied differed in the traits investigated in addition to other agronomic characters. Flag leaf removal, awn removal and their combination significantly reduced grain yield by 10.7, 15.9 and 21.2%, respectively. Reduction in kernel number per plant was 11.1, 11.3 and 11.2%, respectively. Kernel weight was decreased by 5.2 and 11.3% as a result of awn removal and the combination treatment, respectively, but not by flag leaf removal. Although no genotype x treatment interaction was detected for any of the traits studied, grain yields of the local cultivars which are adapted to dryland conditions were affected more than other genotypes by awns' removal.

INTRODUCTION

Understanding of the contr ibution to wheat yield of the different plant parts such as the awns and the flag leaf should help the plant breeder in selecting plants for maximum yield. Teich (1982) concluded that yield in wheat was influenced by the presence or absence of awns and that the nature of the yield response was determined by an array of environmental factors such as moisture regime, light intensity and temperature which may interact with different stages of wheat growth. Kramer and Didden (1981) found that after mass selection for grain yield per plant the frequency of awned types increased significantly. They considered that awns did not contr ibute directly to yield, but that the effect was via linked genes. Olugbemi et al. (1976a) investigated the effect of awns on grain yield and its com- ponents in crosses, segregating for plant height and presence of awns. They concluded that under the British conditions in the absence of severe drought

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there is little advantage to be gained by breeding awned varieties of wheat. In another experiment, the same authors showed that although the awns were responsible for 9--15% of the fixation of CO2 by the canopy, overall photosynthesis was not increased by their presence. Evans et al. (1972) reported that awns were detrimental to grain yield on irrigated plots but advantageous on nonirrigated plots, the interactions between the effects of awns and irrigation being significant. Patterson et al. (1962) compared twelve pairs of lines of soft red winter wheat which were nearly isogenic except for awns vs. awnless. Generally, awned lines were superior, more distinctly so for kernel weight and test weight than for yield. The awned types showed the greatest advantage in the year most favourable for wheat production. Saghir et al. (1968) found that clipping awns at anthesis re- duced grain yield and kernel weight by 21 and 13%, respectively. Atkins and Norris (1955) showed that awned lines of wheat have been found to produce higher yields, heavier kernels and higher test weight and the effects were greater during drought years.

McDonough and Gauch, cited by Patterson and Ohm (1975), found that the percentage contribution of awns to kernel weight increased while that of the flag leaf blade decreased at soil moisture levels close to the wilting point. They concluded that this is why awned types outyielded awnless types in semi-arid regions, while they may show little or no yield advantage in humid regions. According to Olugbemi et al. (1976a), the presence of awns decreased photosynthesis in the remaining ear structures and in the flag and penultimate leaf laminae. Ears of awnless lines of T. aestivum contributed about 10% to the photosynthesis of the organs above the node of the penultimate leaf and awns increased this to about 18%. Fixation by awned ears of T. durum and T. turgidum was 21--29%, and of this 78--86% was contributed by awns. The contribution of the flag leaf to shoot photosynthesis was greater in T. aestivum than in other species (Olugbemi et al., 1976b).

Simpson (1968) reported significant correlations between flag leaf area and grain weight and grain number. He cited a study by Fischer and Kohn (1966) indicating high correlation between grain yield and leaf area index at flowering. Patterson and Ohm (1975) reported that leaf rust, leaf rust plus stem rust and removal of flag leaf each greatly reduced yield, test weight and kernel weight and had much greater effects on these character- istics than did the presence or absence of awns. Awns appeared to have a more consistent advantage for kernel weight than for yield but compensated little for removal of the flag leaf or its impaired function by rust as com- pared with the awnless condition. Awned types showed the greatest advan- tage under severe rust conditions.

Ibrahim and Abo Elenein (1977) found that the flag leaf contributed 41--43% to the grain weight due to increase in kernel weight and number per spike since the flag is photosynthetically the most active leaf during the grain formation stage.

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The objectives of the present investigation are to study the effect of the removal of awns, flag leaf or both on grain yield, kernel number and kernel weight of several wheat genotypes grown under dryland conditions.

MATERIALS AND METHODS

Ten wheat genotypes were selected for this s tudy from a screening nursery which included 50 genotypes each grown in two-row plots 2.5 m long and 30 cm apart with three replications. The nursery was planted on 23 Decem- ber 1981 in Jubeiha, the site of the campus of the University of Jordan. The soil was clay loam and was fertilized with 60 and 30 kg/ha of N and P2Os, respectively. The average rainfall for the period 1971--1980 was 506 mm, whereas it was 491 mm for the 1981--1982 growing season. Nine of the genotypes utilized for this s tudy were tetraploids (Triticum durum Desf.) including the local cultivars F8, Hourani, Deiralla 2, Stork and other promising lines. Pavon 76 was the only hexaploid wheat (Triticum aestivum L.) included in the study. Data on some of the agronomic characters of these genotypes are listed in Table I.

TABLE I

Agronomic characteristics of the wheat genotypes grown under dryland conditions in Jubeiha in 1981/1982 season

Genotype Origin Days to Plant Awn length Spike length heading height (cm) (cm)

(cm)

1. Pavon 76 Mexico 128 71.9 6.6 9.4 2. Wascana Canada 136 96.1 12.7 6.6 3. Yamuna Syria 135 77.5 14.0 7.2 4. C r ' S ' (T.Pol.185.309xTP) Jordan 134 69.8 14.8 5.7 5. Deiralla 2 Jordan 135 94.3 12.3 6.1 6. F 8 Jordan 133 79.0 11.2 5.5 7. Stork Jordan 131 65.4 10.4 6.3 8. Hourani Jordan 136 82.5 11.1 5.3 9. Palestinian Palestine 128 85.9 11.9 6.5

10. JNK India 128 69.2 13.0 6.9

The plants in each plot were thinned to a density of 50 plants per row and 20 of those plants were randomly selected and tagged. Five adjacent plants were chosen to comprise one of the following four t reatment repli- cates: (1) control; (2) flag leaf removal, where the blade was cut at the collar for each tiller at heading; (3) awn removal, where the awns were clipped at the top of each lemma on every tiller ear at heading; (4) both awns and flag leaf were removed at heading.

At maturi ty the plants in each treatment were pulled and the main tiller

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and other tillers were threshed separately. Grain yield (g), grain number, and kernel weight (rag) were determined for the main tiller, other tillers and the whole plant. Statistical analyses were carried out for a split plot design considering the genotypes as main plots and the treatments as sub- plots.

RESULTS AND DISCUSSION

Data on the traits studied for the ten wheat genotypes are presented in Table II. Plant yield ranged from 4.71 to 9.40 g for Wascana and Yamuna genotypes, respectively. Pavon 76 produced the highest number of kernels in the main stem ears (50) and the lightest kernel weight (36.0 rag), while the local cultivar Hourani had the lowest number of kernels (27.8) and the heaviest kernel weight (59.8 rag) was in cv. Yamuna.

TABLE II

Comparison of several wheat genotypes grown in 1981/1982 season and averaged over different flag leaf and awn removal in relation to grain yield, kernel number and kernel weight

Genotype Grain yield (g) Kernel number Kernel weight (mg)

main tiller main tiller main tiller

Pavon 76 1.81 bc* 50.1 a 36.0 f Wascana 1.60 bc 34.8 b 45.5 de Yamuna 3.01 a 49.7 a 59.8 a Cr 'S ' (T.Pol. 185.309xTP) 2.09 b 39.3 ab 53.4 bc Deiralla 2 2.01 b 34.8 b 56.3 ab F8 1.98 b 38.8 ab 50.6 bcd Stork 2.03 b 39.6 ab 51.2 bcd Hourani 1.25 c 27.8 b 43.9 e Palestinian 1.58 bc 31.2 b 47.8 cde JNK 1.86 bc 36.0 b 53.5 bc

Mean 1.92 38.2 49.9

*Values within the same column followed by the same letter are not significantly dif- ferent at the 5% level of probability using Duncan's Multiple Range Test.

The effects of the treatments on the traits investigated are presented in Table III. Grain yield per plant was significantly reduced by the removal of flag leaf, awns or their combination. Removal of flag leaf, however, did not significantly reduce the grain yield of either main tiller or other tillers.

Grain yield was reduced by 18.6, 15.6 and 15.9% for the main tiller, other tillers and whole plant, respectively, fol lowing awn removal compared

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with reductions of 9.1, 11.3 and 10.7% following flag leaf removal. Removal of both flag leaf and awns led to reductions in the grain yield of the main tiller, other tillers and the whole plant by 23.2, 20.2 and 21.2%, respectively. These results suggest that awns and flag leaf were not able to compensate for each other.

The number of kernels produced by the main tiller and the whole plant were significantly reduced by the removal treatments. The effect on the main tiller was more prominent than on the other tillers. The reductions in kernel number of the main tiller and of the whole plant due to awn and flag leaf removal treatments were 15.3 and 10.6%, respectively.

Kernel weight was reduced only by the awn removal t reatment and its combination with the flag leaf removal. The effect of these treatments was greater on the other tillers than on the main tiller, reducing kernel weight by 4.2 and 8.4% for the main tiller, and by 5.8 and 12.2% for the other tillers due to the awn removal and the combined treatment, respec- tively. Flag leaf removal did not cause any decrease in kernel weight, bu t its combination with awn removal resulted in a significant decrease.

Though significant interactions were not detected between genotypes and the traits studied, it is of interest to observe that flag leaf and awn removal caused grain yield in the short early heading genotype Pavon 76 to fall by 9.8 and 26.3%, respectively. For the genotype Stork (S) the reduc- tions were 5.4% for flag leaf and 13.5% for awn removal. Deiralla 2, F8 and Hourani are adapted tall varieties grown in Jordan and head later than either Stork (S) or Pavon 76 (Table I). The average grain yield per plant for the three cultivars obtained from the control, flag leaf removal, awn removal treatments and their combination were 6.1, 5.8, 5.4 and 4.2 g, respectively, the reductions from the control being 4.9, 11.5 and 31.2%, respectively. This suggests that the contribution by the awns of the local cultivars, which are adapted to the local dryland conditions, is greater than that of the flag leaf.

ACKNOWLEDGEMENTS

The author wishes to thank Mr. M. Zouq)i, Mr. G. Shaladeh and Miss H. Kakish for their technical assistance and Dr. M. E1 Fawal for his review of the manuscript.

REFERENCES

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Evans, L.T., Bingham, J., Jackson, P. and Sutherland, J., 1972. Effect of awns and drought on the supply of photosynthate and its distribution within wheat ears. Ann. Appl. Biol., 70: 67--76.

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Ibrahim, H.A. and Abo Elenein, R.A., 1977. The relative contr ibution of different wheat leaves and awns to the grain yield and its protein content. Z. Acker Pflanzen- ban, 144: 1--7.

Kramer, Th. and Didden, F.A.M., 1981. The influence of awns on grain yield and kernel weight in spring wheat (Triticum aestivum L.). Cereal Res. Commun., 9: 25--30.

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Olugbemi, L.B., Bingham, J. and Austin, R.B., 1976b. Ear and flag leaf photosynthesis of awned and awnless Triticum species. Ann. Appl. Biol., 84 : 231--240.

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Patterson, F.L. and Ohm, H.W., 1975. Compensating abili ty of awns in soft red winter wheat. Crop Sci., 15: 403--407.

Saghir, A.R., Khan, A.R. and Worzella, W.W., 1968. Effects of plant parts on the grain yield, kernel weight and plant height of wheat and barley. Agron. J., 60: 95--97.

Simpson, G.M., 1968. Association between grain yield per plant and photosynthet ic area above the flag leaf node in wheat. Can. J. Plant Sci., 48 : 253--260.

Teich, A.H., 1982. Interaction of awns and environment on grain yield in winter wheat (Triticum aestivum L.). Cereal Res. Commun., 10: 11--15.