Evidence for an Allelopathic Interaction Between Rye and Wild Oats

Abstract

Allelopathy is a biological phenomenon in which an organism produces one or more biochemicals that influence the growth, survival, and reproduction of other organisms. Allelopathy has been the subject of a great deal of research in chemical ecology since the 1930s. The characterization of the factors that influence this phenomenon has barely been explored, mainly due to the complexity of this area. The main aim of the research carried out to date has been to shed light on the importance of these interactions in agroecosystems, especially in relation to the interactions between crops and weeds. Herein we report the characterization of a complete allelochemical pathway involving benzoxazinones, which are known to participate in allelopathic plant defense interactions of several plants of high agronomic interest. The production of the defense chemicals by a donor plant (crop), the route and transformations of the chemicals released into the environment, and the uptake and phytotoxic effects on a target plant (weed) were all monitored. The results of this study, which is the first of its kind, allowed a complete dynamic characterization of the allelopathic phenomenon for benzoxazinones.

Plants Release Precursors of Histone Deacetylase Inhibitors to Suppress Growth of Competitors

“…The presence of these allelochemicals in the rhizosphere depends on factors such as species, cultivar, or plant density (Huang et al, 2003;Belz and Hurle, 2005;Macías et al, 2014). Maybe the best estimate for naturally occurring APO concentrations can be gained from studies of exudation of the APO precursor DIBOA from roots: In hydroponic cultures, DIBOA released from rye (Secale cereale) and durum (Triticum durum) roots accumulated to concentrations of 300 and 30 µM, respectively (Belz and Hurle, 2005;Macías et al, 2014). Given the equimolar conversion of DIBOA to BOA, and a conversion rate of 10:1 of BOA into APO (Gents et al, 2005;Understrup et al, 2005), this would result in APO concentrations of 30 and 3 µM, respectively.…”

“…The resulting product APO is a highly potent phytotoxin, which is also the case, although to a lesser extent, for AMPO (Macías et al, 2006(Macías et al, , 2009. The allelochemicals APO and AMPO as well as their precursors have been detected in plants in proximity to DI(M)BOA donor plants (Macías et al, 2014).…”

“…The resulting benzoxazolinone metabolites are much more stable, and in particular, the aminophenoxazinone compounds 2-amino-3H-phenoxazin-3-one (APO) and 2-amino-7-methoxy-3H-phenoxazin-3-one (AMPO) are highly potent phytotoxins (Macías et al, 2006(Macías et al, , 2009. The precursors DIBOA and DIMBOA as well as their degradation products APO and AMPO have been detected in target plants (Macías et al, 2014). As they exert physiological effects on a variety of plant species, it has been surmised that these allelochemicals act on highly conserved central cellular pathways or structures (Duke, 2007;Dayan et al, 2009).…”

Allelopathy: driving mechanisms governing its activity in agriculture

“…Recently, scientific progress and new equipment and experimental protocols have helped to reveal parts of this complex problem. Some allelochemicals, such as benzoxazinones and their derivatives, which can cause weed suppression, have been already characterized from their production in the donor plant (Secale cereale L.) to their action on the target plant (Avena fatua L.) (Macías et al 2014). Up to 20 kg ha -1 benzoxazinones can be released from rye residues and after degradation, up to 5 kg ha −1 was recovered from the soil .…”

Allelochemicals of the phenoxazinone class act at physiologically relevant concentrations

“…Experiments on durum wheat and rye showed that DIBOA accumulated in the leachate at concentrations of 30 mM and 300 mM, respectively. 7,8 Taking into account a 10:1 conversion rate of DIBOA to APO, 9,10 the resulting APO concentration reaches 3 mM to 30 mM. In our previous experiments we had determined the half-maximal-effect concentration (EC 50 ) of APO to be 75 mM, 2 and thus slightly above the concentrations found in the root leachates.…”