Allelopathic Effects of Aqueous Extracts of Sorghum (Sorghum bicolorL. Moench) on the Early Seedling Growth of Sesame (Sesamum indicumL.) Varieties and Selected Weeds

J C Murimwa,R Mandumbu,J T Rugare,S Mabasa

doi:10.1155/2019/5494756

Abstract

Sesame (Sesamum indicumL.) production is lucrative to resource poor farmers in marginalised areas of Zimbabwe, although most farmers have reportedly been failing to derive maximum economic benefits from sesame production due to poor productivity. Low productivity has been attributed to several factors including challenges of weed control due to absence of registered herbicides for use in sesame in Zimbabwe. Laboratory enzyme assays were conducted using different sorghum aqueous leaf and stem extract concentrations at 0, 2.5, 5.0, 7.5, and 10.0% wv−1to determine the effect of sorghum aqueous extracts on plant defense enzymes polyphenol oxidase (PPO), peroxidase (POD), and phenylalanine ammonia lyase (PAL) in sesame and selected weeds. Greenhouse experiments were conducted to assess the effect of sorgaab or sorgaab-Agil postemergence sprays on the seedling growth and physiology of sesame and weeds. The exposure of sesame, black jack, and goose grass to sorghum aqueous extracts caused a significant (p<0.05) concentration-dependent increase on the activity of antioxidant enzymes PAL, POD, and POD. Similarly, postemergence sprays of sole sorgaab, herbicide, and sorgaab-herbicide combination significantly (p<0.05) increased sesame and black jack seedling growth, chlorophyll content, and fluorescence but not of goose grass. From this study, it could be concluded that the allelochemicals in sorghum aqueous extracts were not effective at inhibiting the growth and physiological processes of sesame and the weeds. Therefore, resource-poor farmers cannot rely on sorgaab to control weeds in sesame but there is a need to integrate weed control options to form an effective integrated weed management program.

Highlights

Sesame (Sesamum indicum L.) is one of the world’s oldest cultivated oilseed crops, and it belongs to the Pedaliaceae family [1]. e place of origin of this crop is not clearly known to one place because it is thought to be either Africa or Asia which together contribute to 96% of the total global sesame production [2]
In Zimbabwe, sesame is currently grown in areas that receive low to moderate rainfall (
Inhibition of seedling growth and physiological parameters was observed in goose grass seedlings treated with a sorgaab-herbicide combination. e results suggest that the sole herbicide and sorgaab-herbicide treatments effectively controlled goose grass and had no effect on sesame or black jack. is result contradicts the findings reported by Uddin et al [27, 28] who stated that broadleaved plant species were susceptible to sorgoleone, an allelochemical produced by sorghum roots as compared to grass weeds

Summary

Introduction

Sesame (Sesamum indicum L.) is one of the world’s oldest cultivated oilseed crops, and it belongs to the Pedaliaceae family [1]. e place of origin of this crop is not clearly known to one place because it is thought to be either Africa or Asia which together contribute to 96% of the total global sesame production [2]. E place of origin of this crop is not clearly known to one place because it is thought to be either Africa or Asia which together contribute to 96% of the total global sesame production [2]. In. Zimbabwe, most farmers in dry land areas such as Gokwe, Guruve, Chiredzi, and Nkayi have abandoned cotton (Gossypium hirsutum L.) production and have since adopted commercial sesame production for export to Mozambique [4]. Most farmers in dry land areas such as Gokwe, Guruve, Chiredzi, and Nkayi have abandoned cotton (Gossypium hirsutum L.) production and have since adopted commercial sesame production for export to Mozambique [4] In areas such as Guruve and Chiredzi, farmers are growing sesame on contract farming arrangements. In 2014/15 Sidella, a company which is promoting widespread adoption of this crop, contracted 2820 smallholder famers which resulted in total production of 1,474,860 kg [5]

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