The total phenolic compound and sorgoleone content as possible indirect indicators of the allelopathic potential of sorghum varieties ( Sorghum bicolor (L.) Moench)

Sorghum produces allelopathic compounds, including total phenolic compounds and sorgoleone, which exhibit a phytotoxic effect on weeds. The field study, carried out in 2016-2017, was designed as an one-factor experiment, in the randomized block design, in four replications, with Sucrosorgo 506, Rona 1, KWS Freya, KWS Juno, and KWS Sam-mos, to assess the impact of allelochemicals on weeds. Weed infestation was determined at the beginning of July. Individual weed species were collected from two random places in each plot and weighed. The aim of the laboratory study was to evaluate the total content of phenolic compounds, and sorgoleone in the early stages of plant development (5, 10, and 15 days after emergence) in varieties Rona 1, KWS Freya, KWS Juno, KWS Sammos, Farm-sorgo 180, GK Aron, PR 845F, Sucrosorgo 506 and PR849F. The total content of phenolic compounds was determined using the colorimetric method, and the sorgoleone HPLC technique on a Flexar chromatographic set. The highest value of sorgoleone was observed in 15-day-old seedlings of KWS Juno, the lowest in 5-day-old seedlings of Sucrosorgo 506, the highest levels of total phenolic compounds in 5-day-old seedlings of PR 845F, the lowest in 15-day-old seedlings of Farmsorgo 180. The results do not fully confirm the beneficial effect of allelopathic compounds on reducing weed infestation, however, it is important to emphasize the diversity of cultivars used. The statistically insignificant results indicated that most varieties of sorghum plants do not exhibit a significant decrease in yield.