Biochemical composition and allelopathic properties of sweet sorghum seeds [Sorghum bicolor (L.) Moench]

Abstract

Aim. To establish the main composition of allelochemicals and the activity of their aqueous extracts from sweet sorghum seeds – hybrids with high and medium sugar content ‘Sugargraze ARG’ (Argentina), ‘Sioux’ (USA) and ‘Ananas’ (Ukraine) on germination energy and seed germination of test crops (peas, clover). Methods. Allelopathic, physiological-biochemical, agrochemical and statistical methods were used. The allelopathic activity of extracts (water-soluble) from the seeds of the studied sorghum hybrids was determined by direct biotesting. The chemical component of allelopathically active substances was determined by extraction. Results. Aqueous extracts from sweet sorghum seeds of hybrids ‘Sugar­graze ARG’, ‘Sioux’ and ‘Ananas’ were found to have a high content of phytochemicals and at a concentration of 40 and 50% inhibited the germination energy and germination of pea and clover seeds by an average of 15–42%. Aqueous extracts of concentrations from 5 to 30% of the studied hybrids showed a stimulating and tolerant effect on the quality of seeds of biotest crops of clover and peas, as germination rates were at the level of control or 5–7% higher, i.e. showed the least allelopathic activity. Conclusions. Sweet sorghum seeds have a sufficient number of allelochemicals, the specificity of which depends on varietal differences in the content of phenolic compounds (glycosides), tannins, acids and carbohydrates. The activity of the allelochemicals extracted from the seeds was weak in the stimulating effect and high in the inhibitory one. For water-soluble extracts from sorghum seeds, a sharp decrease in the manifestation of allelopathic activity is characteristic when their concentration decreases to 5–20%. Studies of water-soluble extracts of seeds at a concentration of 30–50% showed their high overall allelopathic activity, which was manifested in the inhibition of seed germination of biotest crops by 42%. The species-specific action of allelochemicals must be taken into account when sowing multicomponent fields, crop rotation planning, and the use of sweet sorghum as green manure.