Phytotoxicity and Benzoxazinone Concentration in Field Grown Cereal Rye (Secale cerealeL.)

Abstract

Winter rye (Secale cerealeL.) is used as a cover crop because of the weed suppression potential of its mulch. To gain insight into the more effective use of rye as a cover crop we assessed changes in benzoxazinone (BX) levels in rye shoot tissue over the growing season. Four rye varieties were planted in the fall and samples harvested at intervals the following spring. Two different measures of phytotoxic compound content were taken. Seed germination bioassays were used as an estimate of total phytotoxic potential. Dilutions of shoot extracts were tested using two indicator species to compare the relative toxicity of tissue. In addition, BX (DIBOA, DIBOA-glycoside, and BOA) levels were directly determined using gas chromatography. Results showed that rye tissue harvested in March was the most toxic to indicator species, with toxicity decreasing thereafter. Likewise the BX concentration in rye shoot tissue increased early in the season and then decreased over time. Thus, phytotoxicity measured by bioassay and BX levels measured by GC have a similar but not identical temporal profile. The observed decrease in phytotoxic potential and plant BX levels in rye later in the season appears to correlate with the transition from vegetative to reproductive growth.

Mycorrhiza‐mediated interference between cover crop and weed in organic winter cereal agroecosystems: The mycorrhizal colonization intensity indicator

“…The other species (i.e., S. media, P. aviculare and R. crispus), which are generally considered as non-host endomycorrhizal plants (Ronikier & Mleczko, 2006), showed in our systems intraradical structures usually formed by AMF, such as inter-radical hyphae, coils and vesicles, rarely in P. aviculare, sometimes in R. crispus and more frequently in S. media. The near absence of R. crispus in the rye treatment, regardless of environmental conditions, suggests that its lacking mycorrhization made it sensitive to the allelochemicals exuded by rye (La Hovary et al, 2016). A previous in vitro test on R. crispus seeds showed their high sensitiveness to the allelopathic activity of rye, which was not only able to reduce its rootlet elongation, but also to inhibit root fungi colonization at emergence (Trinchera, Testani, Ciaccia, Tittarelli, & Canali, 2015).…”

“…As a matter of fact, the Anagallis genus is characterized by strong allelopathic potential, particularly on gramineous plants, such as millet or wheat: this property, together with the highest weed mycorrhization recorded in field, explain its predominance in such competitive agroecosystem (Rebaz, Shaukat, & Siddiqui, 2001). The near absence of R. crispus in the rye treatment, regardless of environmental conditions, suggests that its lacking mycorrhization made it sensitive to the allelochemicals exuded by rye (La Hovary et al, 2016). The near absence of R. crispus in the rye treatment, regardless of environmental conditions, suggests that its lacking mycorrhization made it sensitive to the allelochemicals exuded by rye (La Hovary et al, 2016).…”

Plot Size and Number of Replications for Evaluation of the Yield of Grains in Cultivars and Dates of Sowing of Rye

“…When working with rye, each researcher has adopted plot size and distinct number of replications in his or her experiments, and thus there is the need for the development of experimental techniques for trials carried out with the crop, since there is a lack regarding the correct experimental design. In these studies, plots were used ranging from 5 m² (Lehmen, Fontaneli, Fontaneli & Santos, 2014) to 35 m 2 (Hovary et al, 2016), and with two (Auinger et al, 2016) to eight replications (Souza et al, 2013).…”

Tamanho de parcela e número de repetições para avaliação de caracteres vegetativos em centeio

“…Os tamanhos de parcela utilizados nos estudos conduzidos com centeio por Bortolini et al (2004), Fontaneli et al (2009), Meinerz, et al (2011), Ferrazza et al (2013), Souza et al (2013), Lehmen et al (2014), Auinger et al (2016) e Hovary et al (2016), foram superiores aos obtidos no presente trabalho, sugerindo confiabilidade nas informações 10/9 publicadas pelos autores. Este fato mostra a importância de dimensionar o tamanho de parcela na cultura de centeio uma vez que os autores citados anteriormente poderiam ter economizado recursos financeiros, mão de obra e tempo na condução de seus experimentos, sem comprometer a precisão de seus resultados com a redução do tamanho de parcela.…”

“…Experimentos com a cultura de centeio foram realizados com distintos tamanhos de parcela e número de repetições. Foram utilizados tamanhos de parcela com dimensões de 5 m² (Fontaneli et al, 2009;Lehmen et al, 2014), 5,1 m² (Bortolini et al, 2004), 5,5 m² (Auinger et al, 2016), 6 m² (Ferrazza et al, 2013), 7 m² (Fontaneli et al, 2009), 15 m² (Meinerz, et al, 2011), 25 m² (Souza et al, 2013) e 35 m² (Hovary et al, 2016). Esses estudos têm sido realizados com duas (Haffke, et al, 2014;Auinger et al, 2016), três (Bortolini et al, 2004;Fontaneli et al, 2009;Meinerz et al, 2011;Ferrazza et al, 2013;Lehmen et al, 2014) e oito repetições (Souza et al, 2013).…”