CHANGES OVER TIME IN THE ALLELOCHEMICAL CONTENT OF TEN CULTIVARS OF RYE (Secale cereale L.)

Abstract

Published studies focused on characterizing the allelopathy-based weed suppression by rye cover crop mulch have provided varying and inconsistent estimates of weed suppression. Studies were initiated to examine several factors that could influence the weed suppressiveness of rye: kill date, cultivar, and soil fertility. Ten cultivars of rye were planted with four rates of nitrogen fertilization, and tissue from each of these treatment combinations was harvested three times during the growing season. Concentrations of a known rye allelochemical DIBOA (2,4-dihydroxy-1,4-(2H)benzoxazine-3-one) were quantified from the harvested rye tissue using high performance liquid chromatography (HPLC). Phytotoxicity observed from aqueous extracts of the harvested rye tissue correlated with the levels of DIBOA recovered in harvested tissue. The amount of DIBOA in rye tissue varied depending on harvest date and rye cultivar, but was generally lower with all cultivars when rye was harvested later in the season. However, the late maturing variety 'Wheeler' retained greater concentrations of DIBOA in comparison to other rye cultivars when harvested later in the season. The decline in DIBOA concentrations as rye matures, and the fact that many rye cultivars mature at different rates may help explain why estimates of weed suppression from allelopathic agents in rye have varied so widely in the literature.

In situ validation of fungal N translocation to cereal rye mulches under no-till soybean production

“…It is understood that cover crop mulches suppress weeds physically and chemically (Teasdale and Mohler, 2000;Reberg-Horton et al 2005;RebergHorton et al 2012). Physically, cover crop mulches provide a restrictive barrier that reduces temperatures and light at the soil surface, thus inhibiting the germination and emergence of small-seeded summer annual weeds.…”

“…Physically, cover crop mulches provide a restrictive barrier that reduces temperatures and light at the soil surface, thus inhibiting the germination and emergence of small-seeded summer annual weeds. Cover crop mulches also suppress the germination of weeds through the release of phytotoxic allelopathic chemicals (Reberg-Horton et al 2005).…”

Weed Management Systems for No-Tillage Vegetable Production

“…Furthermore, Chase et al (1991) indicated that large-seeded weed species or those species that have deeper seed placement in the soil profile were less affected by allelochemicals produced by winter rye, which was most likely due to higher concentrations of allelochemicals near the soil surface where small-seeded species typically germinate. The decline in DIBOA concentrations as winter rye matures, and the fact that many winter rye cultivars mature at different rates, may partially explain the discrepancies observed in previous studies from weed suppression from winter rye (Reberg-Horton et al 2005). Although the allelopathic potential of hairy vetch and other legume cover crops have been documented, weed suppression by legumes is generally less compared to grass cover crops.…”

Allelopathy, an alternative tool to improve cropping systems. A review

“…Its known effective allelochemicals include phenolic acids [beta-phenyl-lactic acid (PLA) and beta-hydroxybutyric acid (HBA)], hydroxamic acids [2,4-dihydroxy-1,4(2H)-benzoxazin-3-one (DIBOA), 2(3H)-benzoxazolinone (BOA) and 2,2'-oxo-1,1'-azobenzene (AZOB, which is a compound formed by the microbial transformation of rye residues)]. Hence, a variety of natural products can contribute to the herbicidal activity of rye residues (Chase et al, 1991;Kruse et al, 2000;Reberg-Horton et al, 2005). Reberg-Horton et al (2005) identified seasonal changes in the production of allelochemicals that varied depending on the cultivar and harvesting time, with lesser production at the end of the harvest.…”

“…Hence, a variety of natural products can contribute to the herbicidal activity of rye residues (Chase et al, 1991;Kruse et al, 2000;Reberg-Horton et al, 2005). Reberg-Horton et al (2005) identified seasonal changes in the production of allelochemicals that varied depending on the cultivar and harvesting time, with lesser production at the end of the harvest. Chlorosis was a symptom of damage from rye residues on several indicators and may be related to the effect of DIBOA and BOA on photophosphorylation and electron transport (Barnes and Putnam, 1987).…”