The temporal expression of gene sor1 and the inhibitory effect of Sorghum bicolor L. Moench against weeds were studied by semiquantitative polymerase chain reaction and intercropping management, respectively. To quantify sor1 expression, seeds were sown in pots and RNA was collected from the roots at 5, 10, 15, 20 and 30 days after emergence (DAE). In the inhibition assay, cotton and three weeds were evaluated during single cropping and during intercropping with S. bicolor. The assay was completely randomized, with eight replications. We found early expression of sor1 in most S. bicolor accessions by 5 DAE, and a gradual reduction thereafter. Only one of the accessions showed sor1 expression up to 30 DAE. In the inhibition assay, the most significant effects were related to the dry matter production (shoots and roots) of the weeds Cenchrus echinatus and Cynodon dactylon. The intercropping of cotton and S. bicolor had no apparent deleterious effects.
Allelopathy; semiquantitative PCR; sorgoleone; weeds
