Exploitation of allelopathic properties for weed control in grain production -

1. Exploitation of allelopathic properties for weed control in grain production - is that an environmentally sound strategy? Inge S. Fomsgaard, Solvejg Mathiassen, Per Kudsk, Lars M. Hansen

2. 300 BC, Theophrastus: reported inhibitory effects of pigweed on alfalfa 81 BC, Plinius Secundo : desribed allelopathic effects from walnut trees 1832, De Candolle: proposed that exudates from plants could be the reason for soil sickness History of allelopathy

3. 1881, Hoy and Stickney: reported deleterious effects of walnut on plants nearby 1907, Screiner and Reed: isolated organic acids released by plant roots that suppressed the growth of other crops History of allelopathy

4. 1937, Molisch: coined the word ”allelopathy” from Greek ”allelo” and ”pathy”, meaning ”mutual” and ”suffering” 1966, Muller: defined the phenomenon of plant-plant interaction as ”interference”, involving both competition and allelopathy History of allelopathy

5. Research in allelopathy: adverse effects of living plants or their residues upon growth of higher plants and crop yields, interactions among organisms, ecological significance of allelopathy in plant communities, replanting problems, autotoxicity, problems with crop rotations, the production, isolation and identification of allelochemicals in both natural and agroecosystems. History of allelopathy

6. 1996, Torres et al: Allelopathy was defined as: Any process involving secondary metabolites (allelochemicals) produced by plants, microorganisms, viruses, algae and fungi that influence the growth and development of agricultural biological systems Allelopathy - definition

7. secondary plant metabolites alkaloids phenolics flavonoids terpenoids glucosinolates benzoxazinones cyanogenic compounds Allelochemicals

8. Allelochemicals Reigosa et al, 1999

9. Use of pesticides in agriculture Exploitation of allelopathic effects Synthetic transformation of natural substances Isolated natural substances Pure synthetic products

10. Organic crop rotations for grain production - an example http://www.agrsci.dk/pvj/plant/croprot/indexuk.shtml

11. Wheat, rye and maize contain 4-hydroxy-1,4-benzoxazin-3-ones (hydroxamic acids) as glucosides Allelochemicals in selected cereals Wheat: DIMBOA, DIBOA Rye: DIBOA Maize: DIMBOA. DIM2BOA

12. From 1.4 to 10.9 mmol DIMBOA/kg fresh weight in 52 Chilean cultivars (young seedlings) Worldwide screening of 37 cultivars: from 0.99 to 8.07 mmol DIMBOA/kg fresh weight Triticum speltoides: 16 mmol DIMBOA /kg fresh weight (10 days seedlings) Concentration levels of DIMBOA in wheat

13. Biological activity of4-hydroxy-1,4-benzoxazin-3-ones • Increase the resistance of cereals to insects, fungi and bacteria • trigger the reproduction of grass-feeding mammals • influence the growth of weeds • are involved in the detoxification of pesticides • are mutagenic agents

14. Biological activity of4-hydroxy-1,4-benzoxazin-3-ones, examples • Increase the resistance of maize to the European corn borer • increase the resistance of cereals to aphids • inhibit root and coleoptile growth of wild oats

15. Molecular structure of4-hydroxy-1,4-benzoxazin-3-ones

16. Mechanism for decomposition of4-hydroxy-1,4-benzoxazin-3-ones to benzoxazolinones, ex. DIBOA decomposed to BOA DIBOA BOA

17. Further decomposition of benzoxazolinones in soil Kumar et al, 1993: BOA  2-amino-3H-phenoxazin-3-one Nair et al, 1990: BOA  2,2´-oxo-1,1´-azobenzene (AZOB)

18. Further decomposition of benzoxazolinones in soil R = H DIBOA-glu BOA AZOB

19. Utilization of rye as cover crop or green mulch • Barnes & Putnam, 1986 • Barnes & Putnam, 1987 • Mwaja et al, 1995 • Chase et al, 1991 • recent trials in organic crop rotation: • rye is sown in a density 3 times normal prcatice, young seedlings ploughed down, and winter crop sown afterwards

20. Concentration levels of DIMBOA in wheat • From 1.4 to 10.9 mmol DIMBOA/kg fresh weight in 52 Chilean cultivars (young seedlings) • Worldwide screening of 37 cultivars: from 0.99 to 8.07 mmol DIMBOA/kg fresh weight • Triticum speltoides: 16 mmol DIMBOA /kg fresh weight (10 days seedlings)

21. Theoretical concentration levels of DIMBOA in soil • 0.99-16 mmol/kg in young seedlings • 400 plants per m2 • weight of each seedling 0.25g • 190-3078 g DIMBOA per hectare • 105-1701 g AZOB per hectare

22. Literature search • DIMBOA or DIBOA or hydroxa* or benzoxaz* or (allelo* and (wheat or rye or maize)) • 2159 records since 1972 • 195 records since 1999

23. FATEALLCHEM Fate and toxicity of allelochemicals in relation to environment and consumer

24. WP2 • Cultivation of wheat in 2 countries • Economic evaluation Isolation and identification of allelochemicals from plants Isolation and identification of soil metabolites from allelochemicals • Quantification of allelochemicals in plants+soil • Interlaboratory evaluation of analytical results WP1 • Dev. of analytical method for allelochemicals in plants and soil • Interlaboratory evaluation of analytical results WP3 Degradation studies of allelochemicalsin soil Herbicidal effects of soil-incorporated wheat plant material Insecticidal effects of whole wheat plants Ecotoxicology of allelochemicals to soil organisms Ecotox of allelochemicals to water organisms Insecticidal effects of isolated allelochemicals Herbicidal effects of isolated allelochemicals Sorption studies of allelochemicals in soil QSAR modelling of ecotoxicology of allelochemicals Germination studies with allelochemical compounds QSAR modelling of fate of allelochemicals WP5 WP4 QSAR modelling of human toxicology of allelochemicals Fungicidal effects WP8 Allelochemicals in old Polish wheat varieties WP6

25. Expected achievements I: IF wheat varieties with well described and efficient allelopathic properties against one or or more of the most important weeds and /or pests are identified and the allelochemicals have low environmental toxicity

26. Expected achievements I: THEN commercial exploitation of isolated allelochemicals is possible and/or exploitation of the identified wheat varieties by plant breeders for production of new varieties for use in both conventional and organic farming is possible and/or exploitation of the adquired knowledge in genetic engineering is possible and/or exploitation by farmers using the known varieties with high concentrations is possible (depending on costs for production and/or obtainable yields)

27. Expected achievements II: IF the evaluation of risks to environment and humans show that the allelochemicals have a risk equal to or higher than synthetic pesticides Danish Institute of Agricultural Sciences, Sept 7-8, 2001

28. Expected achievements II: THEN new views must be put on the exploitation of allelochemicals crops and/or plant breeders must look for varieties with low concentrations and/or public authorities regulating environmental and health standards must focus on allelochemicals and/or definitions of ”organic farming” must be discussed

29. Expected achievements III: IF none of the tested varieties have well described and efficient allelopathic properties but some allelopathic effect less the the effect of synthetic pesticides and risk to environment and humans is low

30. Expected achievements III: THEN growing of the varities with ”highest” allelopathic properties might still be useful to organic farmers and development by breeding of new varities for use in organic farming is still useful (depending on economy)

31. Conclusion Toxicity? Transport to ground water? Exposure of non-target plants and other living organisms? Cheng, 1992

32. The holistic approach! Future studies