Abstract
Controlling black-grass in winter wheat production in northern Europe is an increasing problem because of more frequent winter crops and development of herbicide resistance in weeds. Alternative weed management strategies are needed, e.g., use of more competitive cultivars. Factors that increase cultivar competitiveness include early vigor and straw length, but also allelopathy. Therefore, the allelopathic properties of wheat cultivars included in the Swedish national list or in the release pipeline were investigated using a bioassay with herbicide-resistant and herbicide-sensitive black-grass as receiver plants. Wheat-rye translocation lines were also included in this screening to identify possible sources of high allelopathic activity. The bioassay results were followed up in two-year field trials. The results revealed large variations in allelopathic activity between cultivars. Most cultivars showed interference with both herbicide-sensitive and herbicide-resistant black-grass, although the allelopathic effect was lower on the herbicide-resistant biotype. Cultivars with high allelopathic activity gave only half the black-grass biomass of low allelopathic cultivars. Dinaro, a triticale (wheat-rye hybrid) cultivar and the new wheat cultivar Nimbus showed the highest allelopathy and inhibition of black-grass growth. Only a few wheat lines with rye chromatin, all or part of a rye chromosome, showed high allelopathy. Use of cultivars with high allelopathic activity can thus be important in integrated weed management of black-grass.
Highlights
Black-grass (Alopecurus myosuroides Huds.) is the most important herbicide-resistant weed in Europe, followed by ryegrass (Lolium), poppy (Papaver rhoeas L.) and wild oats (Avena fatua L.) [1].Black-grass is mainly a problem in western and central Europe, but in recent years in northernEurope, due to milder winters and more frequent autumn-sown crops
The triticale cultivar Dinaro followed by the new wheat cultivar Nimbus showed the highest activity against both herbicide-sensitive and herbicide-resistant black-grass
Rye is known to be allelopathic [19], but in this study, the rye cultivar Amilo showed only medium allelopathic activity. The reason for this finding, as noted in previous studies, may be that the bioassay used is not adapted to rye [13]. This is because maximum allelopathic activity occurs much later in rye than in wheat and the plants were only observed for 10 days in the bioassay [20,21]
Summary
Black-grass (Alopecurus myosuroides Huds.) is the most important herbicide-resistant weed in Europe, followed by ryegrass (Lolium), poppy (Papaver rhoeas L.) and wild oats (Avena fatua L.) [1].Black-grass is mainly a problem in western and central Europe, but in recent years in northernEurope, due to milder winters and more frequent autumn-sown crops. Black-grass (Alopecurus myosuroides Huds.) is the most important herbicide-resistant weed in Europe, followed by ryegrass (Lolium), poppy (Papaver rhoeas L.) and wild oats (Avena fatua L.) [1]. Black-grass is mainly a problem in western and central Europe, but in recent years in northern. 10 plants m−2, yield decreases linearly with black-grass density and at a density of 100 plants m−2 the yield loss can be 1 t ha−1 or more [2]. The strong negative effect on wheat yield is a combination of competition and inhibition of wheat root growth by allelochemicals from the black-grass [3]. Neither aqueous leaf leachates nor shoot and root residues of black-grass retarded growth in their study of winter wheat. Naylor [5] found that wheat was more competitive to black-grass than vice versa when the fertilizer level was sufficiently high
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