Tracing the source - do allelochemicals in root exudates of wheat correlate with cultivar-specific weed-suppressing ability?

摘要

To investigate the involvement of allelochemicals in root exudates in cultivar dependent weed-suppressing activity, over 130 cultivars of Triticum aestivum L,, T. durum Desf. and T. spelta L. were screened for their growth inhibiting ability against Sinapis alba L. and the direct release of allelochemicals by plant roots. Cultivars differed significantly in their ability to suppress the root growth of Sinapis alba in a dose-response bioassay and could be differentiated by cluster analysis into six groups, whereby cultivars of the different species were evenly distributed over the groups. The resulting dose-response curves were parallel, indicating the similarity of the growth inhibiting effect by the different species. By means of HPLC-UV-analysis of the exudates, collected at the end of the bioassay over a period of two hours, only hydroxamic acids (Diboa, Dimboa) could be detected. While in exudates of Triticum aestivum and T. spelta only Dimboa was detected, exudates of T. durum contained Dimboaand Diboa. The amount of hydroxamic acids exuded by different cultivars showed a positive correlation with their growth inhibition in the bioassay. These findings are no proof that hydroxamic acids are the primary cause of inhibition, but cultivars exuding larger amounts cause a stronger growth inhibition of the test plant.