Effect of Pollination and Different Amendments on Seed Oil, Phenolics and Antioxidants of Sesamum indicum L. Grown in Southern Chad

Abstract

Sesame (Sesamum indicum L., Pedaliaceae) is a one of the earliest oilseed plants highly prized in tropical and subtropical countries. In Chad, its yield remains low, averaged 500 kg.ha-1 and organic and/or mineral fertilization are used to increase its grain yield. The low production would be linked ether to lack of crop knowledge, changing agronomic conditions and probably to the lack of pollination services. The seeds contain very high oil contents and are rich in total phenolic compounds and antioxidants which give it unprecedented stability for its oils. Thus a two-year experiment (rainy season 2022-2023) was conducted at Bébédjia in Chad to assess the effect of different types of amendments and pollination by entomophilous insects on the oil content, total phenols and antioxidant activity of sesame seeds. The study was based on a split plot design with three replications. The two studied factors were studied: fertilization with six types of amendments (control, 0.050 t.ha-1 of mineral NPK fertilizer , 5 t.ha-1 and 10 t.ha-1 of compost, 5 t.ha-1 and 10 t.ha-1 of cow-dung manure) and pollination with two modalities (free pollination plot and insects protected plot. The results of the combined analysis of variance showed that fertilization highly (p < 0.001) affected all the three studied biochemical parameters while the effect of pollination was significantly only for the antioxidant potential (p < 0.05). The effect of the interaction between fertilization and pollination was significant only for polyphenols content (p < 0.05). Among treatments, the highest seed oil contents were obtained for compost 10 t.ha-1 (52.77%) and cow manure10 t.ha-1 (51.34%). Highest rates of polyphenols and antioxidants were recorded for unfertilized control indicating that amendments reduced these biochemical traits. This study showed that insect pollination had little effect on these biochemical traits in contrast organic fertilizers at 10 t.ha-1 increased the seed oil content of sesame but reduced the polyphenols rates and the antioxidant potential.