Phenolic Compounds with Allelopathic Potential of Secale cereale L. and Raphanus sativus L. Grown Under an Agroecological No-Tillage System

Abstract

The identification of compounds with allelopathic potential produced by cover crops can assist in selecting species for weed management purposes in no-tillage systems. This study aimed to identify the main phenolic compounds with allelopathic potential in the shoot of rye (Secale cereale L.) and oilseed radish (Raphanus sativus L.) cover crops, as well as evaluate whether the cultivation system and phenological stage may influence secondary metabolite production and weed emergence. Samples of the shoot of these cover crops were collected at 60, 80, and 100 days after sowing (DAS) and 15 and 30 days after lodging (DAL) under field conditions. Weed emergence was evaluated at 45, 75, and 100 DAL of cover crops. The main compounds in rye were 6-methoxy-2-benzoxazolinone (MBOA) and 2-benzoxazolinone (BOA) under monocropping and intercropping, while flavonoid quercetin was found in oilseed radish at all evaluated times. During the growing cycle, the highest contents of phenolic compounds were found at the elongation stage (60 DAS) of rye under monocropping and intercropping systems (9.33 and 8.22 mg g-1 DM, respectively) and at grain filling stage (100 DAS) for oilseed radish intercropped with rye and black oat (3.24 and 3.83 mg g-1 DM, respectively). No differences were found in the contents of the main compounds when the species was grown under monocropping or intercropping systems. A reduction in the contents of MBOA, BOA, and quercetin was observed after lodging. Weed dry matter production was lower at 45 DAL in all treatments with rye and oilseed radish residues when compared to the control. The intercropping of rye with oilseed radish is an alternative management for weed control in agroecological systems due to the physical barrier created by these species and the presence of phenolic compounds with allelopathic potential.

Microbial activity in soil with onion grown in a no-tillage system with single or intercropped cover crops

“…(Table 1). This can probably be explained by the higher shoot dry mass produced by these species when intercropped (SOUZA et al, 2019), as compared to the other single-crop treatments. An abundance of plant tissue stimulates K accumulation Table 1 -Soil chemical attributes (0-10 cm layer) and onion bulb yield in area with residues of winter cover crops single or intercropped in no-tillage system, 2010, Santa Catarina, Southern Brazil.…”

“…According to CZELUSNIAK et al 2012, metabolite production in plants varies according to their development, including leaf development, emergence of new organs, biochemical, physiological, and ecological and evolutionary processes. OR plants were in the early stage of vegetative development, as they bloom 70-80 days after emergence, while barley and rye, which have shorter cycles, were in the stem elongation stage (SOUZA et al, 2019). Therefore, the species were probably producing high rates of root exudate during this period, a carbon source for microorganisms (GARCIA et al, 2005).…”

Exploratory and discriminant analysis of plant phenolic profiles obtained by UV–vis scanning spectroscopy

“…The overlapping of samples collected at different periods at the score plot PC2(+) indicate similarity between those and distinction from the samples collected at 30 DAR, which segregated at PC2(−) ( Figure 5B ), suggesting that black oat, rye and oilseed radish phenolic profile at 60, 80 and 100 DAS share more similarities then the profiles of these plants after rolling. This result due to the changes in the chemical composition of the plant material after longer time for sampling, 30 days after rolling, when plant material have longer period of degradation and the releasing of phenolic compounds [ 36 ]. Secondary metabolites profiles, such as phenolic compounds, vary in quality and quantity depending on many factors, including weather condition, plant age, and methods for extractions and analysis [ 37 ].…”

“…Due to its lower C/N ratio and higher mineralization rate, the oilseed radish is broken down within 15 days after rolling. In contrast, rye and black oat, due to their higher fiber content, take around 20 days to be broken down [ 36 ], [ 38 ], [ 39 ]. On the whole, the three species have started breaking down 15 days after rolling.…”

Methods of preparing aqueous extract and bioactivity of Mentha spicata L. on Raphanus sativus L. seeds

“…Approximately 10,000 secondary compounds with allelopathic action are known, and the allelochemical action tends to occur more through the synergic interaction of different substances than the activity of an isolated product (Pires and Oliveira, 2011). The main compounds with allelopathic actions are those of phenolic nature, which are released in the environment in many different ways such as leaching, volatilization, plant residue decomposition and root exudation (Favaretto et al, 2018;Souza et al, 2019).…”