Fate of Benzoxazinone Allelochemicals in Soil after Incorporation of Wheat and Rye Sprouts

Abstract

Growing cereals (especially rye), which are incorporated into the soil to increase soil fertility or organic matter content, is a common practice in crop rotation. The additional sanitizing effect of this incorporation has often been appreciated and is said to be due to leaching of benzoxazinones and subsequent formation of benzoxazolinones. In this study wheat (Stakado) and rye (Hacada) sprouts were incorporated into soil in amounts that simulated agricultural practice. By extraction and subsequent LC-MS analysis the disappearance and appearance of benzoxazinones, benzoxazolinones, and phenoxazinones in soil were followed. In the wheat experiments 6-methoxybenzoxazolin-2-one (MBOA) was detected as the main compound. 2-Hydroxy-7-methoxy-1,4-benzoxazin-3-one (HMBOA) and 2-hydroxy-1,4-benzoxazin-3-one (HBOA) were detected as well. No phenoxazinones were detected. For the rye experiment the picture was more complex. In the first 2 days of incubation MBOA and 2,4-dihydroxy-1,4-benzoxazin-3-one (DIBOA) were detected as the main allelochemicals along with HBOA, HMBOA, and benzoxazolin-2-one (BOA), in decreasing order. Later in the incubation period some 2-amino-3H-phenoxazin-3-one (APO) was detected and the amount of HBOA increased considerably and decreased again. The profiling of the benzoxazinone metabolites and their derivates in soil was dynamic and time-dependent. The highest concentrations of most of the compounds were seen at day 1 after incorporation. A maximum concentration was reached at day 4 for a few of the compounds. This study is the first of its kind that shows the dynamic pattern of biologically active benzoxazinone derivates in soil after incorporation of wheat and rye sprouts. Methods for organic synthesis of HBOA and HMBOA were developed as part of the study.

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

“…The formation of APO from root-exuded DIBOA as well as the absorption of APO by exposed plants has been confirmed (Krogh et al, 2006;Rice et al, 2012), but little is known about the rate of synthesis and the availability of APO and AMPO in the soil under natural conditions. 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).…”

Interactions of Bacillus mojavensis and Fusarium verticillioides with a Benzoxazolinone (BOA) and its Transformation Product, APO

“…Knop et al (2007) reported that F. verticillioides could utilize APO as a C-source, but indicated that its growth was reduced by 14% when cultured with 1 μM of APO. This concentration was considerably less than that used here and elsewhere (Macias et al 2005;Martyniuk et al 2006;Krogh et al 2006), which are concentrations reported to occur naturally (Martyniuk et al 2006). Perhaps the growth reduction observed in F. verticillioides by Knop et al (2007) is reflective of the small amount of APO used.…”

Benzoxazolinone Detoxification and Degradation – A Molecule ́s Journey

“…Also Bacon et al (2007) take APO for a stable compound. In contrast, Krogh et al (2006) determined 1.4x10 -11 M APO as the highest concentration in sandy loam soil after incorporation of one rye seedling 300 mg 1-soil. The APO concentration decreased rapidly during 10 days to about 30%.…”