Indigo as a Plant Growth Inhibitory Chemical from the Fruit Pulp of Couroupita guianensis Aubl.

Kohinoor Begum,Takashi Motobayashi,Mashura Shammi,Kwame Sarpong Appiah,Yoshiharu Fujii,Nazmul Hasan

doi:10.3390/agronomy10091388

Abstract

Weed management is an important issue since weeds directly compete with crop plants for space, nutrients; serve as habitat for insect pests and diseases, and can create a significant annual reduction in crop productivity. This study focused on evaluating the contribution of the secondary metabolites of the fruit pulp of Couroupita guianensis Aubl. for its potential growth inhibitory effect. Crude extracts of C. guianensis fruit pulp were collected with different solvents and applied to test plants in petri dishes. The crude extracts of methanol and 1% dimethyl sulfoxide (DMSO) showed potential growth inhibitions with the 50% effective concentration (EC50) of 223 and 229 µg/mL in the bioassay experiment. In the greenhouse pot experiment, soil incorporated with oven-dried fruit pulp of C. guianensis was evaluated on cultivated plant species including Lactuca sativa L., Trifolium repens L., Medicago sativa L., Lolium multiflorum Lam., and Phleum pratense L. The incorporation of dried fruit pulp of C. guianensis into soil reduced shoot and root lengths and the germination percentage of test plants. It was observed that the monocot plants were more affected than the dicot plants. The fruit pulp of C. guianensis was subjected to reversed-phase high-performance liquid chromatography (HPLC) analysis to identify the active compounds. Indigo, identified as one of the candidate compounds of the C. guianensis, had high specific activity (i.e., strong inhibitory activity) in a phytotoxicity bioassay and could explain through the total activity concept the growth inhibitory effect of the C. guianensis on test plants. The results suggested that indigo has plant growth inhibitory effect, indicating the allelopathic potential of C. guianensis, which could be exploited in sustainable weed management.

Highlights

Weed management is one of the most fundamental concerns in crop production
Five crude extracts with different solvents were evaluated on the test plant to understand the inhibitory effect of the extraction of C. guianensis fruit pulp
Identification of new plant growth inhibitory species and compounds might provide the possibilities for new natural herbicide development that could be exploited in sustainable weed management

Summary

Introduction

Weed management is one of the most fundamental concerns in crop production. The interference of weeds with field crops is responsible for multibillion dollars of annual yield loss in crop cultivation [1,2,3].In the USA and Canada, the total loss in corn and soybean due to weed infestation was estimated to be USD 43 billion per annum [1]. Weed management is one of the most fundamental concerns in crop production. The interference of weeds with field crops is responsible for multibillion dollars of annual yield loss in crop cultivation [1,2,3]. In the USA and Canada, the total loss in corn and soybean due to weed infestation was estimated to be USD 43 billion per annum [1]. In Australia, the cost was estimated to be AUD 3.3 billion [2] and USD. 11 billion in India annually [3]. The excessive application of various weedicides for weed management globally has to lead to an increase in herbicide-resistant weed species [4]. Allelopathic species have been considered as valuable sources of bioactive substances for managing weeds to increase crop

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Conclusion