Evaluating sorgoleone herbicidal activity on weed species and wheat ( <i>Triticum aestivum</i> )

Abstract Sorgoleone, an allelochemical exuded from root hairs of grain sorghum [ Sorghum bicolor (L.) Moench], has proven herbicidal activity on several weeds and crops. Due to its hydrophobic nature and affinity for organic matter, sorgoleone can persist in the soil for a long period. Although sorghum residues are beneficial for weed suppression, growers in the southeastern United States have raised concerns that these residues may negatively affect wheat ( Triticum aestivum L.) emergence in double-crop systems. Two independent laboratory studies were conducted to evaluate sorgoleone activity: (1) weed species/wheat variety study, which included four weed species, Italian ryegrass [ Lolium perenne L. ssp. multiflorum (Lam.) Husnot], large crabgrass [ Digitaria sanguinalis (L.) Scop.], sicklepod [ Senna obtusifolia (L.) Irwin &amp; Barneby], and velvetleaf [ Abutilon theophrasti Medik.], and two wheat varieties, ‘USG3251’ and ‘Shirley’; and (2) wheat variety and group study, which included a total of 20 varieties distributed in four wheat groups. In both studies, sorgoleone was applied at 0.025, 0.05, 0.10, 0.15, 0.20, and 0.30 g L −1 to seeds grown in petri dishes under laboratory conditions. In Study 1, sorgoleone activity had a stronger effect on grass weeds than on broadleaf weeds. Lolium perenne ssp. multiflorum was the most susceptible weed, showing 77% growth reduction at 0.3 g L −1 of sorgoleone. At the same concentration, D. sanguinalis showed the second-highest response, with a 32% growth reduction, followed by A. theophrasti and S. obtusifolia , with reductions of 23% and 20%, respectively. No effect of sorgoleone was observed on wheat varieties. In Study 2, growth reduction was only observed for six wheat varieties at the highest sorgoleone concentrations. Furthermore, in between group comparisons, Hard Red wheat presented higher response to sorgoleone. These findings demonstrate strong herbicidal activity of sorgoleone on grass weeds, particularly L. perenne ssp. multiflorum , while having minimal effects on most wheat varieties.