Effects of management practices and plant growth regulators on the allelopathic potential of rye (Secale cereale)

Effects of management practices and plant growth regulators on the allelopathic potential of rye (Secale cereale)

Summary

Different cover crop management practices demonstrated significant effects on allelochemical levels in rye. Five different rye varieties, including Hancock, Spooner, Abruzzi, Rhymin, and Wheeler were planted in the Fall. Management treatments included Spring mowing, with and without N (30 lb/a) applications. Shoots were harvested on four different dates (4/01 to 5/12) and measurements were taken including total shoot dry weight, total benzoxazinone content (ug/g.d.w.), and Feekes growth stages. At the final harvest, the growth stage of the rye plants was slightly delayed in the +N treatments. The N treatments also increased the leaf tissue biomass at the final harvest, while the stem and flower biomass did not increase. The impact of N and no-N treatments on benzoxazinones (DIBOA) levels in the re-growth shoot tissue varied with rye variety. In addition to the field trial, preliminary greenhouse experiments were conducted to determine the effect of plant growth regulators on allelochemical levels in Aroostook rye. Experiments included a dose response to determine the most effective concentration of BTH (analog of salicylic acid), ethephon (ethylene), and methyl jasmonate (MeJA). The effect of these plant growth regulators over time was examined, as was the effect of mowing in combination with chemical application. Measurements taken included both fresh and dry weights. PGRs were found to decrease the biomass when compared with the control.

Objectives/Performance Targets

Field cover crop management treatments will include different Fall planting dates and Spring mowing dates. The impact of N fertilization at mowing will also be considered. The research will also determine if Spring planting of different varieties, particularly late maturing varieties, will affect allelochemical potential of the cover crop mulch.
The research will also evaluate different rye varieties at different developmental stages for responses of allelopathic potential to plant growth regulators, including MeJA, BTH, and ethylene.

Accomplishments/Milestones

A field study was conducted, looking at the effect of Spring mowing and N fertilization on five rye varieties. After mowing, N fertilization delayed the maturity of all the rye varieties, except Abruzzi. For example, the Feekes stage for Spooner treated with N was 10.1, while the stage for untreated plants was 10 to 10.1. While N fertilization slightly delayed the growth stage, leaf tissue biomass was dramatically increased. For two varieties, the leaf dry weight was double that of the nonfertilized treatment. Stem dry wt and flower dry wt/stem for the most part showed no significant difference between the +N and the –N treatments. Total benzoxazinone (BX) content (ug/g.d.w.) in response to N fertilization varied. For example, BX content in Wheeler and Spooner was higher in the +N treatment, but in Hancock +N treatment decreased BX content.
In addition to the field study, several preliminary experiments were carried out in the greenhouse, using the plant growth regulators BTH, Ethephon, and MeJA. These included a dose response experiment, the effect of the plant growth regulators over time, and the combination of mowing and chemical application. A slight decrease in both fresh and dry weights was observed with chemical application, although this decrease is most likely not statistically significant. Remaining work to be done includes GC analysis of the preliminary greenhouse experiments, as well as conducting additional plant growth regulator experiments on other rye varieties.

Impacts and Contributions/Outcomes

This project thus far has examined the effect of Spring mowing and N fertilization on allelochemical levels in Fall planted Winter rye. Results suggest that Spring mowing with N fertilization will elevate the leaf tissue component of the biomass, the location of the greatest levels of allelochemicals. Also, preliminary work into the effect of plant growth regulators on allelochemical production has been conducted. The research will benefit growers by providing insight into cover crop management options that will result in enhanced for weed suppression when using rye as a cover crop. Various cultural methods are being tested to determine which will increase the allelochemical content in rye, which will increase the cover crop’s ability to provide weed control.

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