Autotoxic response of barley to hordenine and gramine

Details

Supervisors

Draye, Xavier

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en sciences agronomiques, à finalité spécialisée

Abstract

Weed management is one of the biggest issues in agriculture. While the use of synthetic herbicides is still one of the most common ways to manage weeds, alternative, more sustainable methods to counter these pests have gained the interest of scientists and farmers over the past years. One promising approach would be to exploit allelopathic crops, i.e. crops capable of influencing the growth and development of neighbouring organisms through the production and release of chemically active compounds called “allelochemicals”. Barley (Hordeum vulgare) is one of such crops. It produces two allelochemicals, hordenine and gramine, that have potent effects on a wide range of organisms, including plants. However, barley also exhibits autotoxicity, a special case of allelopathy in which the allelochemicals released by an allelopathic organism inhibit the growth of its own species. In the present work, we conducted three assays using seedling pouches in order to assess the detailed manifestation of this autotoxic response on the root elongation of barley seedlings exposed to hordenine or gramine. Because allelochemicals are known for having high-concentration inhibition and low-concentration stimulation relationships with sensitive species, our first assay aimed at establishing the dose-response curves for hordenine and gramine on a single barley cultivar. We tested 14 concentrations from 10mM to 1µM for the two alkaloids and observed a stimulation at concentrations ≤ 2.5mM and ≤ 1.25mM for hordenine and gramine, respectively. Since variation in the autotoxic response has been reported between barley varieties, we characterised the response of 10 barley landraces to four concentrations selected from the first assay. We observed a variation of the response curve between the 10 landraces that involve changes in the range of concentration and in the sensitivity, so that complete dose-response curves would be needed in further genetic experiments. Our third assay investigated the reversibility and the systemic nature of the response to the two alkaloids by applying the same four concentrations locally and transiently. We could not conclude on the reversibility of the response but showed that hordenine and gramine may have a systemic effect on the root growth at high concentrations. Breeding for high yields crops with enhanced allelopathic potential to help manage weeds is a promising prospect for a more sustainable food production system. However, allelopathy is a dynamic and complex phenomenon and, as long as our knowledge of its processes is not strengthened, allelochemicals should be used carefully.