Differential allelopathic potential of sorghum hybrids on wheat.

摘要

The differential allelopathic potential of sorghum hybrids (Sorghum bicolor L.) on wheat (Triticum aestivum L.) was identified and characterized on the basis of (1) grain yield response of wheat planted after selected sorghum hybrids in the field; and, (2) wheat seedling growth response to water extracts from sorghum plant parts determined in laboratory bioassays. Field results showed that sorghum hybrids can be allelopathic but that their allelopathic potential varied from one year to the next, suggesting that the allelopathic potential is not a highly inherited trait. When wheat parameters were ranked by sorghum hybrid which wheat following in the cropping sequence, no consistency in ranking was found between wheat yield and the other parameters measured. When sorghum residues were chopped and left on the soil surface, wheat yield, seed density, and test-weight were higher than when sorghum residues were incorporated into soil or removed from the field.; Laboratory bioassays revealed that seeds, glumes, leaves, stems, and roots of sorghum were allelopathic to wheat seedling growth. Leaves, stems, and roots had allelopathic potentials that varied among sorghum hybrids and years with stems, in general, being the most allelopathic component. Bioassays could be used to predict the relative effect of a previous sorghum crop on grain yield of wheat.; Chemical analyses of water extracts from sorghum plant parts demonstrated a positive association between phenolic content of water extracts and their allelopathic potential. Also, the allelopathic potential of sorghum plant parts was positively associated to p-hydroxybenzoic (POH), vanillic (VAN), syringic (SYR), p-coumaric (PCO), and ferulic (FER) acids individually with VAN showing the highest association to the allelopathic potential. Three phenolic acids (POH, VAN, and SYR) were found in sorghum root exudates and may enhance the overall allelopathic potential of sorghum.