# Elicitation of the Allelopathic Potential of Rice by Methyl Salicylate Treatment
## 1 Introduction  
Weeds are one of the major threats to farm productivity and their management is an ever-present challenge. Chemical approach is becoming increasingly problematic, both in terms of environmental pollution and herbicide resistance. Among the alternative strategies, allelopathy integrated with the existing agronomic solutions can be a tool to give greater sustainability to agro-production systems. Allelopathy is defined as the beneficial or detrimental influence of one organism on the growth and development of other organisms by the production of chemical compounds known as allelochemicals [1]. They are mainly plant secondary metabolites (e.g., alkaloids, flavonoids, glucosinolates, hydroxamicacids, phenols, salicates, terpenoids) released by leaching, decomposition, volatilization, and root exudation or microbe decomposition products [1; 2]. Allelopathy is a natural survival process and has been used to reduce the competition from neighboring plants in agriculture since ancient times for its positive effects such as weed control, crop protection, and crop re-establishment [1].  
In sustainable agriculture, the possibility of incorporating allelopathic traits into genotypes to enhance their competitiveness is worth exploring [3]. The competitiveness provided by allelopathic genotypes could reduce the burden of using conventional herbicides, thus reducing the inputs of agrochemicals [4]. Rice is one of the most important crops in the world and its allelopathy has attracted great attention, as the allelopathic potential of some genotypes against one or more paddy needs has been demonstrated [5]. Since then, the selection of allelopathic rice germplasm has been carried out in many countries [6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16]. Several main and epistatic quantitative loci have been identified responsible for allelopathy in rice [17]. However, instead of developing new competitive genotypes, allelopathy can be more useful to screen the existing germplasm for allelopathic crop genotypes [18]. It was shown that some rice cultivars were able to suppress the growth of various paddy common weeds, including the _Echinochloa_ species that cause severe yield losses, showing greater allelopathic potential than others [19; 20; 21; 22; 23; 24; 25].  
Previous works hypothesized that allelopathy is an actively inducible defense mechanism and that plant signaling compounds are potentially valuable in its regulation [26]. Among them, salicylic acid (SA) plays a key role in plant defense [27]. It can activate many stress-related genes and the release of allelochemicals [26; 28]. The application of SA to different plant species was sufficient to invoke disease resistance [29]. However, it has been shown that its methyl ester, i.e., MeSA, is more effective when applied exogenously [30]. MeSA is an organic ester naturally produced by many plants, particularly wintergreens. It can be manufactured synthetically and it is used as a flavoring agent in foods, beverages, and liniments [31].  
In this study, 10 rice genotypes were screened for their allelopathic potential. Then, two competitive and one non-competitive genotypes were selected and further investigated for the changes in their allelopathic potential after the exogenous application of MeSA.