Allelopathic effects of Chenopodium album L. and Chenopodium polyspermum L. on another weed and two crop species

Abstract

Chenopodium album L. and Chenopodium polyspermum L. are cosmopolitan weeds that often cause serious crop yield losses. Although it is well known that both species compete strongly with crops, nothing has been published on their relative allelopathic potentials. Experiments for assessing the allelopathic effects of C. album and C. polyspermum on three indicator species were conducted under controlled conditions. The indicator species were sunflower (Helianthus annuus L. cv. SO 222), tomato (Lycopersicon esculentum Mill cv. Heinz 1370) and the cosmopolitan weed Indian goosegrass (Eleusine indica subsp. indica (L.) Gaertn.). Top growth of mature C. album and C. polyspermum plants was freeze-dried, milled to a coarse powder and gamma-irradiated. Steam-sterilized soil was mixed with the powdered material to reach a concentration of 1% for each donor species. The control treatments consisted of an untreated soil and the same soil containing 1% extracted material of the donor species. Only sunflower and tomato showed significant growth reduction in soil containing C. album material. The emergence of tomato was significantly poorer on soil containing C. album material. C. polyspermum inhibited the growth of only sunflower seedlings. In another experiment the effects of three concentrations of each of hexane, ethyl acetate and MeOH:H₂O extracts of C. album and C. polyspermum on tomato seed germination were investigated. A concentration of 8 mg ml¹ of the 50:50 MeOH:H₂O extractable fraction from C. album material significantly inhibited germination. Extracts of C. polyspermum did not affect germination of tomato seed significantly. Results showed that C. album, and to a lesser extent C. polyspermum, have growth-inhibiting allelopathic effects.