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Allelopathy in two durum wheat (Triticum durum L.) varieties
Agriculture, Ecosystems and Environment 96 (2003) 161–163
Short communication
Allelopathy in two durum wheat (Triticum durum L.) varieties Oussama Oueslati∗ Ecole Supérieure d’Agriculture du Kef (ESAK), Le Kef 7100, Tunisia Received 8 April 2002; received in revised form 24 September 2002; accepted 3 October 2002
Abstract Two varieties of durum wheat (Triticum durum L.), ‘Karim’ and ‘Om rabii’ commonly used in northern Tunisia were grown to maturity. Their allelopathic effects were measured in terms of germination rate and radicel length of a barley variety ‘Manel’ (Hordeum vulgare L.) and a bread wheat variety ‘Ariana’ (Triticum aestivum L.). Diluted extracts of roots, leaves and stems of durum wheat were applied to seeds of the test varieties. Leaf extracts of durum wheat depressed the germination rate, radicels also being susceptible to durum wheat extracts. The allelopathy of durum wheat varied with the source of extracts, leaf extracts being the most active. Results suggest that durum wheat allelopathy takes the form of heterotoxicity, depressive to crops in a sequence. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Allelopathic potential; Heterotoxicity; Durum wheat; Barley; Bread wheat
1. Introduction Allelopathy was defined as a process involving secondary metabolites produced by plants, micro-organisms, viruses, and fungi that influences growth and development of biological systems (Torres et al., 1996). The allelopathic effect may be so striking that competition for resources does not explain why, in plant communities, many species appear to regulate one another through the production and release of chemical attractants, stimulators or inhibitors (Putnam and Tang, 1986). Several crops are known to have allelopathic effects on other crops, e.g. Beet (Beta vulgaris L.), lupin (Lupinus lutens L.), maize (Zea mays L.), wheat (Triticum aestivum L.), oats (Avena sativa L.) and barley (Hordeum vulgare L.) (Rice, 1984), whereas allelopathic activity of wheat straw has been demonstrated under field conditions ∗ Tel.: +216-78-223-086; fax: +216-78-223-137. E-mail address: [email protected] (O. Oueslati).
(Shilling et al., 1985). Growers need to be aware of allelopathic interactions between plant species to adapt their crop sequence. The avoidance of allelopathic effects between crops, or the exploitation of beneficial interactions in a rotation or a mixed cropping system may have direct bearing on the crop yield (Rizvi et al., 1992). Research on durum wheat allelopathy has been undertaken to: (i) test the heterotoxicity of durum wheat on bread wheat and barley, and (ii) study the allelopathic potential of various parts of durum wheat.
2. Materials and methods Two durum wheat varieties ‘Karim’ and ‘Om rabii’ were sampled in July 1999. Whole plants were pulled out of the field at the stage of grain development. The plants were gently washed with distilled water, dried between two paper towels and separated into roots, leaves and stems. The three components were
0167-8809/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 8 8 0 9 ( 0 2 ) 0 0 2 0 1 - 3
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O. Oueslati / Agriculture, Ecosystems and Environment 96 (2003) 161–163
chopped into 1 cm long pieces and dried at 50 ◦ C for 24 h. The components were soaked in distilled water for 24 h at 200 rpm at the rate of 5 g fresh weight per 100 ml distilled water. Each extract was filtered through four layers of cheese cloth, Whatman filter paper under vacuum and stored at <5 ◦ C. Dilutions were made of the original extracts adding four parts of distilled water to one part of water extract. The growth medium used was agar (1.2%) amended with diluted extract. A 1.2% distilled water–agar was used as control. The agar solutions were placed in 10 mm × 150 mm Petri dishes containing 15 ml of growth medium. Extracts of durum wheat were tested for phytotoxicity on seed germination and radicel growth of bread wheat (cultivar Ariana) and barley (cultivar Manel), two cereal varieties commonly cultivated in Tunisia. Seeds of each variety were surface sterilized with a 5% aqueous solution of sodium hypochlorite for 2 min, rinsed five times with distilled water and dried between two paper towels. Twenty-five seeds were placed in each Petri dish containing agar and placed in the dark at 25 ◦ C. Three days after seeding, germination counts and central radicel length were measured and recorded. Seeds were considered germinated when the radicel extended through the seed coat. The experimental design was a complete randomized design with four replications. All experimental data were subjected to analysis of variance by using SAS (1985) and Fisher’s protected least significant difference (LSD) at the 5% level of probability (Steel and Torrie, 1980).
3. Results and discussion Durum wheat leaf extracts significantly affected germination, except for var. ‘Manel’ the seeds of which were tolerant to leaf extracts of var. ‘Om rabii’. Both leaf and root extracts of var. ‘Karim’ were phytotoxic to radicel length of both var. ‘Manel’ and ‘Ariana’. A maximum reduction occurred with leaf extracts, which inhibited radicel length more in barley than in bread wheat. Radicel length of var. ‘Manel’ was not affected by stem extracts, whereas that of var. ‘Ariana’ showed a slight, not significant stimulation with the same extract (Table 1).
Table 1 Effects of diluted extracts of durum wheat (var. ‘Karim’) on germination (%) and radicel growth (cm) of barley and bread wheat
Control Root extract Leaf extract Stem extract LSD (5%)
Barley var. ‘Manel’
Bread wheat var. ‘Ariana’
Germination
Radicel length
Germination
Radicel length
24.50 25.00 24.25 25.00 0.59
4.84 3.62 2.79 4.85 0.65
23.50 24.75 21.50 24.00 1.82
5.33 4.92 1.88 5.56 0.59
ab a b a
a b c a
a a b a
ab b c a
Means within a column followed by different letters are significantly different according to Fisher’s protected least significant difference (LSD) (P < 0.05).
Extracts from plant parts of var. ‘Om rabii’ were phytotoxic to radicel growth of both var. Manel and ‘Ariana’, the highest reduction being recorded for leaf extracts. Leaf extracts inhibited radicel growth in var. ‘Ariana’ more than in var. ‘Manel’ (Table 2). All extracts of durum wheat except leaf extracts showed no effect in the germination test (Ben Hammouda et al., 2001). The radicel length test detected the heterotoxic potential of durum wheat on barley and bread wheat, both being somewhat more susceptible to var. ‘Om rabii’ extracts than to var. ‘Karim’. Results showed that radicel length was more sensitive than germination test for detecting any allelopathic effect of durum wheat (Hedge and Miller, 1990), leaf extracts of durum wheat being the most phytotoxic plant part extracts in both germination and radicel tests (Guenzi et al., 1967). Leaf extracts Table 2 Effects of diluted extracts of durum wheat (var. ‘Om rabii’) on germination (%) and radicel growth (cm) of barley and bread wheat
Control Root extract Leaf extract Stem extract LSD (5%)
Barley var. ‘Manel’
Bread wheat var. ‘Ariana’
Germination
Radicel length
Germination
Radicel length
24.50 24.75 24.75 24.75 0.80
5.20 3.44 1.76 3.13 0.58
24.75 22.75 17.00 23.00 4.25
5.63 3.73 1.21 3.45 0.55
a a a a
a b c b
a a b a
a b c b
Means within a column followed by different letters are significantly different according to Fisher’s protected least significant difference (LSD) (P < 0.05).
O. Oueslati / Agriculture, Ecosystems and Environment 96 (2003) 161–163
of Artemisia princeps var. ‘orientalis’ also decreased seedling elongation of receptor plants more than root and stem extracts (Kil and Yun, 1992). The results demonstrated that durum wheat must be considered as an allelopathic species presenting risk in a crop sequence. References Ben Hammouda, M., Habib, G., Kremer, R.J., Oussama, O., 2001. Allelopathic effects of barley extracts on germination and seedlings growth of bread and durum wheats. Agronomie 21, 65–71. Guenzi, W.D., McCalla, T.M., Norstad, F.A., 1967. Presence and persistence of phytotoxic substances in wheat, oats, corn, and sorghum residues. Agron. J. 59, 163–165. Hedge, R.S., Miller, D.A., 1990. Allelopathy and autotoxicity in alfalfa: characterization and effects of preceding crops and residue incorporation. Crop Sci. 30, 1255–1259. Kil, B.S., Yun, K.W., 1992. Allelopathic effects of water extracts of Artemisia princeps var. orientalis on selected plant species. J. Chem. Ecol. 18, 39–51.
163
Putnam, A.R., Tang, C.S., 1986. Allelopathy: state of science. In: Putnam, A.R., Tang, C.S. (Eds.), The Science of Allelopathy. Wiley, New York, pp. 1–19. Rice, E.L., 1984. Allelopathy, 2nd ed., Academic Press, Orlando, FL, pp. 67–68. Rizvi, S.J.H., Haque, H., Singh, V.K., Rizvi., V., 1992. A discipline called allelopathy. In: Rizvi, S.J.H., Rizvi, V. (Eds.), Allelopathy: Basic and Applied Aspects. Chapman & Hall, London, UK, pp. 1–10. SAS Institute, 1985. SAS User’s Guide: Statistics, Version 6.0. SAS Inst. Inc., Cary, NC. Shilling, D.G., Liebel, R.A., Worsham, A.D., 1985. Rye (Secale cereale L.) and wheat (Triticum aestivum L.) mulch: the suppression of certain broadleaved weeds and the isolation and identification of phytotoxins. In: Thompson, A.C. (Ed.), The Chemistry of Allelopathy: Biological Interaction Among Plants. American Chemical Society Symposium Series No. 268, American Chemical Society, Washington, DC, pp. 243–271. Steel, R.G.D., Torrie, J.H., 1980. Principles and Procedures of Statistics, 2nd ed. McGraw-Hill, New York. Torres, A., Olivia, R.M., Castellano, D., Cross, P., 1996. In: Proceedings of the First World Congress on Allelopathy: A Science of the Future. SAI (University Cadiz), Spring Cadiz, 278 pp.
Short communication
Allelopathy in two durum wheat (Triticum durum L.) varieties Oussama Oueslati∗ Ecole Supérieure d’Agriculture du Kef (ESAK), Le Kef 7100, Tunisia Received 8 April 2002; received in revised form 24 September 2002; accepted 3 October 2002
Abstract Two varieties of durum wheat (Triticum durum L.), ‘Karim’ and ‘Om rabii’ commonly used in northern Tunisia were grown to maturity. Their allelopathic effects were measured in terms of germination rate and radicel length of a barley variety ‘Manel’ (Hordeum vulgare L.) and a bread wheat variety ‘Ariana’ (Triticum aestivum L.). Diluted extracts of roots, leaves and stems of durum wheat were applied to seeds of the test varieties. Leaf extracts of durum wheat depressed the germination rate, radicels also being susceptible to durum wheat extracts. The allelopathy of durum wheat varied with the source of extracts, leaf extracts being the most active. Results suggest that durum wheat allelopathy takes the form of heterotoxicity, depressive to crops in a sequence. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Allelopathic potential; Heterotoxicity; Durum wheat; Barley; Bread wheat
1. Introduction Allelopathy was defined as a process involving secondary metabolites produced by plants, micro-organisms, viruses, and fungi that influences growth and development of biological systems (Torres et al., 1996). The allelopathic effect may be so striking that competition for resources does not explain why, in plant communities, many species appear to regulate one another through the production and release of chemical attractants, stimulators or inhibitors (Putnam and Tang, 1986). Several crops are known to have allelopathic effects on other crops, e.g. Beet (Beta vulgaris L.), lupin (Lupinus lutens L.), maize (Zea mays L.), wheat (Triticum aestivum L.), oats (Avena sativa L.) and barley (Hordeum vulgare L.) (Rice, 1984), whereas allelopathic activity of wheat straw has been demonstrated under field conditions ∗ Tel.: +216-78-223-086; fax: +216-78-223-137. E-mail address: [email protected] (O. Oueslati).
(Shilling et al., 1985). Growers need to be aware of allelopathic interactions between plant species to adapt their crop sequence. The avoidance of allelopathic effects between crops, or the exploitation of beneficial interactions in a rotation or a mixed cropping system may have direct bearing on the crop yield (Rizvi et al., 1992). Research on durum wheat allelopathy has been undertaken to: (i) test the heterotoxicity of durum wheat on bread wheat and barley, and (ii) study the allelopathic potential of various parts of durum wheat.
2. Materials and methods Two durum wheat varieties ‘Karim’ and ‘Om rabii’ were sampled in July 1999. Whole plants were pulled out of the field at the stage of grain development. The plants were gently washed with distilled water, dried between two paper towels and separated into roots, leaves and stems. The three components were
0167-8809/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 8 8 0 9 ( 0 2 ) 0 0 2 0 1 - 3
162
O. Oueslati / Agriculture, Ecosystems and Environment 96 (2003) 161–163
chopped into 1 cm long pieces and dried at 50 ◦ C for 24 h. The components were soaked in distilled water for 24 h at 200 rpm at the rate of 5 g fresh weight per 100 ml distilled water. Each extract was filtered through four layers of cheese cloth, Whatman filter paper under vacuum and stored at <5 ◦ C. Dilutions were made of the original extracts adding four parts of distilled water to one part of water extract. The growth medium used was agar (1.2%) amended with diluted extract. A 1.2% distilled water–agar was used as control. The agar solutions were placed in 10 mm × 150 mm Petri dishes containing 15 ml of growth medium. Extracts of durum wheat were tested for phytotoxicity on seed germination and radicel growth of bread wheat (cultivar Ariana) and barley (cultivar Manel), two cereal varieties commonly cultivated in Tunisia. Seeds of each variety were surface sterilized with a 5% aqueous solution of sodium hypochlorite for 2 min, rinsed five times with distilled water and dried between two paper towels. Twenty-five seeds were placed in each Petri dish containing agar and placed in the dark at 25 ◦ C. Three days after seeding, germination counts and central radicel length were measured and recorded. Seeds were considered germinated when the radicel extended through the seed coat. The experimental design was a complete randomized design with four replications. All experimental data were subjected to analysis of variance by using SAS (1985) and Fisher’s protected least significant difference (LSD) at the 5% level of probability (Steel and Torrie, 1980).
3. Results and discussion Durum wheat leaf extracts significantly affected germination, except for var. ‘Manel’ the seeds of which were tolerant to leaf extracts of var. ‘Om rabii’. Both leaf and root extracts of var. ‘Karim’ were phytotoxic to radicel length of both var. ‘Manel’ and ‘Ariana’. A maximum reduction occurred with leaf extracts, which inhibited radicel length more in barley than in bread wheat. Radicel length of var. ‘Manel’ was not affected by stem extracts, whereas that of var. ‘Ariana’ showed a slight, not significant stimulation with the same extract (Table 1).
Table 1 Effects of diluted extracts of durum wheat (var. ‘Karim’) on germination (%) and radicel growth (cm) of barley and bread wheat
Control Root extract Leaf extract Stem extract LSD (5%)
Barley var. ‘Manel’
Bread wheat var. ‘Ariana’
Germination
Radicel length
Germination
Radicel length
24.50 25.00 24.25 25.00 0.59
4.84 3.62 2.79 4.85 0.65
23.50 24.75 21.50 24.00 1.82
5.33 4.92 1.88 5.56 0.59
ab a b a
a b c a
a a b a
ab b c a
Means within a column followed by different letters are significantly different according to Fisher’s protected least significant difference (LSD) (P < 0.05).
Extracts from plant parts of var. ‘Om rabii’ were phytotoxic to radicel growth of both var. Manel and ‘Ariana’, the highest reduction being recorded for leaf extracts. Leaf extracts inhibited radicel growth in var. ‘Ariana’ more than in var. ‘Manel’ (Table 2). All extracts of durum wheat except leaf extracts showed no effect in the germination test (Ben Hammouda et al., 2001). The radicel length test detected the heterotoxic potential of durum wheat on barley and bread wheat, both being somewhat more susceptible to var. ‘Om rabii’ extracts than to var. ‘Karim’. Results showed that radicel length was more sensitive than germination test for detecting any allelopathic effect of durum wheat (Hedge and Miller, 1990), leaf extracts of durum wheat being the most phytotoxic plant part extracts in both germination and radicel tests (Guenzi et al., 1967). Leaf extracts Table 2 Effects of diluted extracts of durum wheat (var. ‘Om rabii’) on germination (%) and radicel growth (cm) of barley and bread wheat
Control Root extract Leaf extract Stem extract LSD (5%)
Barley var. ‘Manel’
Bread wheat var. ‘Ariana’
Germination
Radicel length
Germination
Radicel length
24.50 24.75 24.75 24.75 0.80
5.20 3.44 1.76 3.13 0.58
24.75 22.75 17.00 23.00 4.25
5.63 3.73 1.21 3.45 0.55
a a a a
a b c b
a a b a
a b c b
Means within a column followed by different letters are significantly different according to Fisher’s protected least significant difference (LSD) (P < 0.05).
O. Oueslati / Agriculture, Ecosystems and Environment 96 (2003) 161–163
of Artemisia princeps var. ‘orientalis’ also decreased seedling elongation of receptor plants more than root and stem extracts (Kil and Yun, 1992). The results demonstrated that durum wheat must be considered as an allelopathic species presenting risk in a crop sequence. References Ben Hammouda, M., Habib, G., Kremer, R.J., Oussama, O., 2001. Allelopathic effects of barley extracts on germination and seedlings growth of bread and durum wheats. Agronomie 21, 65–71. Guenzi, W.D., McCalla, T.M., Norstad, F.A., 1967. Presence and persistence of phytotoxic substances in wheat, oats, corn, and sorghum residues. Agron. J. 59, 163–165. Hedge, R.S., Miller, D.A., 1990. Allelopathy and autotoxicity in alfalfa: characterization and effects of preceding crops and residue incorporation. Crop Sci. 30, 1255–1259. Kil, B.S., Yun, K.W., 1992. Allelopathic effects of water extracts of Artemisia princeps var. orientalis on selected plant species. J. Chem. Ecol. 18, 39–51.
163
Putnam, A.R., Tang, C.S., 1986. Allelopathy: state of science. In: Putnam, A.R., Tang, C.S. (Eds.), The Science of Allelopathy. Wiley, New York, pp. 1–19. Rice, E.L., 1984. Allelopathy, 2nd ed., Academic Press, Orlando, FL, pp. 67–68. Rizvi, S.J.H., Haque, H., Singh, V.K., Rizvi., V., 1992. A discipline called allelopathy. In: Rizvi, S.J.H., Rizvi, V. (Eds.), Allelopathy: Basic and Applied Aspects. Chapman & Hall, London, UK, pp. 1–10. SAS Institute, 1985. SAS User’s Guide: Statistics, Version 6.0. SAS Inst. Inc., Cary, NC. Shilling, D.G., Liebel, R.A., Worsham, A.D., 1985. Rye (Secale cereale L.) and wheat (Triticum aestivum L.) mulch: the suppression of certain broadleaved weeds and the isolation and identification of phytotoxins. In: Thompson, A.C. (Ed.), The Chemistry of Allelopathy: Biological Interaction Among Plants. American Chemical Society Symposium Series No. 268, American Chemical Society, Washington, DC, pp. 243–271. Steel, R.G.D., Torrie, J.H., 1980. Principles and Procedures of Statistics, 2nd ed. McGraw-Hill, New York. Torres, A., Olivia, R.M., Castellano, D., Cross, P., 1996. In: Proceedings of the First World Congress on Allelopathy: A Science of the Future. SAI (University Cadiz), Spring Cadiz, 278 pp.