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Evaluation of Allelochemical Effects of Hordeum Vulgare Extracts

Md. Azharul Islam
BARI, Gajipur & Postdoctoral Researcher, Tokyo University of Agriculture and Technology, Fuchu, Tokyo, Japan

Shahanara Begum
BARI, Gajipur & Postdoctoral Researcher, Tokyo University of Agriculture and Technology, Fuchu, Tokyo, Japan

Abstract/ Executive Summary:

There is increasing interest in the development of allelopathic crop varieties for weed suppression. The study was conducted to investigate the allelopathic potential of Hordeum vulgare varieties namely, BARI Barley-1, BARI Barley-2, BHL-3 and BL-1 that were collected from Bangladesh Agricultural Research Institute (BARI) and grown in control condition at Research Field of Tokyo University of Agriculture and Technology, Japan in 2010. The importance of allelopathy in nature and in agroecosystem has attracted researcher’s attention with the main goal of using the phenomenon in biological control of weeds. Screening accessions of allelopathic crops and natural vegetation for their ability to reduce weeds is the basic approach for utilizing the phenomenon. Extracts of examined plant on annual ryegrass (Lolium rigidum L.) was investigated. Water extracts of 4 studied varieties were bioassayed on germination and seedling growth of Lolium rigidum such as, a) to test the heterotoxicity of barley on Lolium rigidum; b) to study the dynamics of allelopathic potential over three growth stages; c) to identify the most allelopathic plant part of barley; d) to indicate which variety has the highest allelopathic potentiality. Stems, roots, and leaves were extracted at three growth stage separately. Results of seedling growth bioassays demonstrated that Lolium rigidum responded differently to the allelopathic potential of H. vulgare. For L. rigidum radicle growth and germination were more depressed than coleoptile growth. The allelopathic potential of investigated plant parts was not stable over its life cycle for L. rigidum. Leaves were the most phytotoxic part of H. vulgare for L. rigidum in the all stages. The leaves extract of BHL-3 variety had the highest inhibition on radicle growth of L. rigidum. Results suggested that the response by L. rigidum varied depending on the source of allelochemicals (plant part) and the growth stage of the H. vulgare plant. The findings may be driven by the recognition that agro-ecological applications of allelopathy may provide alternatives to synthetic herbicides for weed control.

Keywords: Allelochemicals, autotoxicity, Hordeum vulgare L., Heterotoxicity, Lolium rigidum

Location: Field laboratory of Tokyo University of Agriculture and Technology, Japan

Start Date: 00-01-2010

End Date: 00-10-2010

Program Area: Variety and Species

Commodity: Barley

Objectives:

1. Record the accompanying changes in levels of phytotoxicity by bioassay against root and shoot growth of annual ryegrass, 2. To investigate the allelopathic potential over three growth stages on Lolium rigidum, 3. To explore the parts of plant sensitivity to allelochemicals and 4. To select the more responded variety for allelopathocity.

Methodology:

Plant material - Seeds of four barley (Hordeum vulgare L.) varieties namely BARI Barley-1, BARI Barley-2, BHL-3 and BL-1 were collected from Bangladesh Agricultural Research Institute (BARI) in 2010. The collected varieties were gown under controlled condition at the field laboratory of Tokyo University of Agriculture and Technology, Japan. Lolium rigidum L. seeds were collected in October 2010 from Bangladesh Agricultural Research Institute, cleaned and stored at 350C for further research works. Sterilization and pre-germination - The pretreatment of barley and ryegrass seeds has been followed a method which previously reported. Barley seeds were surface sterilized by soaking them in 70% ethanol for 2.5 min, followed by four rinses with sterilized distilled water. Seeds were soaked in 2.5% sodium hypochlorite solution for 15 min, followed by five rinses with sterilized distilled water. The surface-sterilized seeds of barley and ryegrass were each soaked in sterilized water for imbibitions in light at 250C for 24 hrs and then rinsed with fresh sterilized water. Finally, barley seeds were incubated in light at 250C for another 24 hrs, and ryegrass seeds incubated in light at 250C for 48 hrs. Before the start of experiments for the determination of allelopathic effect, the Lolium rigidum seeds were surface sterilized in a 1:10 (v/v) dilution of commercial hypochlorite bleach for 10 min and rinsed several times with distilled water. These sterilized seeds were placed on a paper towel for about 2h. Then Lolium rigidum seeds were placed on a filter paper in sterilized 9cm diameter petridishes. Experimental sampling - Sampling of barley plants were made at its three growth stages like, stage 8: last leaf just visible, stage 10: in boot, stage 11: grain development. At stage 8 and 10, roots, stem and leaves of barley plants were used to prepare water extracts and at stage 11 roots, stem, leaves and panicles were used to prepare water extracts. Water extracts prepared. All of the water extracts were used to determine the allelopathic effect on seed germination, root length (cm) and shoot length (cm) of Lolium rigidum. Bioassay of barley exudates - The method described previously was slightly modified to assess the allelopathic activity of barley seedling exudates. Glass beakers (500 ml) containing 30 ml of 0.3% agar-water (non-nutrients) were autoclaved. Twenty four pre-germinated barley seeds were uniformly selected and aseptically sown on the agar surface in each beaker. Beakers were wrapped with parafilm to prevent contamination and evaporation from the agar surface and placed in a controlled environment growth cabinet with an L/D cycle of 13 hrs and a temperature cycle at 25/13⁰C. Seedlings were allowed to grow for 2, 4, 6, 8, 11, and 15 days. Seedlings were carefully removed from agar, and 10 pre-germinated seeds of ryegrass (L. rigidum) were aseptically sown onto each of the respective agar surfaces. Ryegrass sown on agar-water-with no barley before hand was used as a control. Ryegrass containing beakers were wrapped with parafilm and placed back into the growth cabinet, and the seeds were allowed to grow for 7 days. At the end of this period, the lengths of ryegrass roots and shoots were determined as the means of the three replicates. Statistical analysis - The experiment was designed under Completely Randomized Design (CRD) with 4 replications. A non-amended treatment was included as a control. For germination bioassays, 20 seeds were placed in Petri dishes. Each experiment unit consisted of two Petri dishes. For radicle or coleoptile bioassays, an average across a cluster of 10 growths with one pre-germinated seed each was used as a single observation for each treatment. Analysis of variance was conducted using Dunkan program of MSTAT-C.

Source of Information: BANGLADESH RESEARCH PUBLICATIONS JOURNAL; ISSN: 1998-2003, Volume: 5, Issue: 4, Page: 295-305, May -June, 2011

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Achievement/Findings:

Interaction effect of growth stages and different varieties of barley significantly inhibited germination of Lolium rigidum. With regarded to seed germination percentage significant allelopathic effect of barley was recorded in stage 8. BARI Barley-1 showed minimum weed seed germination and BARI Barley-2 and BHL-3 varieties showed statistically similar weed germination. In stage 8 of barley plant, BL-1 variety has limited inhibition on the germination of annual ryegrass. In stage 10, almost four varieties of barley have similar germination inhibition of ryegrass. In case of stage 11, the maximum germination inhibition recorded for BHL-3 followed by BARI Barley-2 and BL-1 varieties, but statistically significant weed germination reported among three varieties. BARI Barley-1 variety showed similar germination effect in stage 10 and stage 11.

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