Allelopathic Activity and Characterization of Allelopathic Substances from Elaeocarpus floribundus Blume Leaves for the Development of Bioherbicides

To help protect the environment as well as increase agricultural production, the use of synthetic herbicides must be reduced and replaced with plant-based bioherbicides. Elaeocarpus floribundus is a perennial, evergreen, and medium-sized plant grown in different areas of the world. The pharmaceutical properties and various uses of Elaeocarpus floribundus have been reported, but its allelopathic potential has not yet been explored. Thus, we carried out the present study to identify allelopathic compounds from Elaeocarpus floribundus. Aqueous MeOH extracts of Elaeocarpus floribundus significantly suppressed the growth of the tested species (cress and barnyard grass) in a dose- and species-dependent way. The three most active allelopathic substances were isolated via chromatographic steps and characterized as (3R)-3-hydroxy-β-ionone, cis-3-hydroxy-α-ionone, and loliolide. All three substances significantly limited the seedling growth of cress, and the compound (3R)-3-hydroxy-β-ionone had stronger allelopathic effects than cis-3-hydroxy-α-ionone and loliolide. The concentrations of the compounds required for 50% growth inhibition (I50 value) of the cress seedlings were in the range of 0.0001–0.0005 M. The findings of this study indicate that all three phytotoxic substances contribute to the phytotoxicity of Elaeocarpus floribundus.

Induction, identification, and characterization of autoallo-dodecaploid barnyard grass (Echinochloa crus-galli L.) using in vitro colchicine treatment

Polyploidization is a major trend in plant evolution that has many advantages over diploid. Barnyard grass (Echinochloa crusgalli L.) has many good characteristics, but has not been fully utilized until now. In this study, we report for the first time the in vitro induction of autoallo-dodecaploid E. crus-galli by colchicine treatment. Calli derived from young panicles were transferred to liquid medium containing different concentrations of colchicine (0.01, 0.05, or 0.1% w/v) and incubated for 24, 48, or 72 h. Treatment with 0.05% colchicine for 48 h was the most effective condition for producing polyploid plants, yielding 42.9% dodecaploids. The relative DNA content of the induced dodecaploids was twice that of wild-type hexaploids. The chromosome number of dodecaploids was 2n = 12x = 108, whereas that of hexaploids was 2n = 6x = 54. Compared with the hexaploids, the dodecaploids had larger individual stomata, but a lower stomatal density. There were significant differences between dodecaploid and hexaploid plants in terms of morphological variables, such as plant height, leaf length, panicle length, and grain size. Dodecaploid plants showed the obvious “gigas” effects of polyploid organs, as well as significantly reduced seed set. The nutritional concentrations of crude protein, crude fat, crude ash, and nitrogen-free extract in the dodecaploid were higher than those in the hexaploid, whereas the concentration of crude fiber in the dodecaploid was lower. Compared with the hexaploid, the concentrations of calcium, iron and some free amino acids in dodecaploid plants were significantly higher than in hexaploids. The dodecaploid E. crus-galli had been obtained successfully by treating calli with colchicine. And E. crus-galli has the potential to be developed as a new type of high quality forage crop for cultivation under stress conditions, especially the dodecaploid with its greater nutritional value.

Allelopathic Effect of Selected Rice (Oryza sativa) Varieties against Barnyard Grass (Echinochloa cruss-gulli)

Rice has been subjected to a great deal of stress during its brief existence, but it nevertheless ranked first among cereal crops in terms of demand and productivity. Weeds are characterized as one of the major biotic stresses by many researchers. This research aims to determine the most potential allelopathic rice variety among selected rice accessions. For obtaining preeminent varieties, seventeen rice genotypes were collected from Bangladesh and Malaysia. Two prevalent procedures, relay seeding and the sandwich technique were employed to screen the seventeen rice (donor) accessions against barnyard grass (tested plant). In both approaches, only the BR17 variety demonstrated substantial inhibition of germination percentage, root length, and dry matter of barnyard grass. The rice variety BR17 exclusively took the zenith position, and it inhibited the development of barnyard grass by more than 40–41% on an average. BR17 is originated from KN-1B-361-1-8-6-10 (Indonesia) and developed by the Bangladesh Rice Research Institute (BRRI), Gazipur, Bangladesh in 1985, having a high yielding capacity of more than 6 t/ha. Our study suggested that the usage of the allelopathy-weed inverse relationship to treat the weed problem can be a fantastic choice in the twenty-first century.

A, The Allelopathic effects of Papavare somniferum on germination and initial seedling growth of Echinochloa cruss-galli

Weeds are unwanted plants in crop that can be control by different methods among them use of aqueous extract of crop is an imperative method. To investigate the allopathic potential of aqueous extract of winter crop Papavare somniferum (opium) on summer weed Echinochloa cruss-galli (barnyard grass) laboratory experiments were conducted. The experiment coomprised seven concentrations (0, 0.25, 0.50, 1, 2, 4, and 8%) of different plant parts i.e., leaves, stem and flower of P. somniferumwere. All the tested concentrations and plant parts of P. somniferum significantly reduced mean emergence time, germination index, germination percentage, time to 50% germination as well as well growth of E. cruss-galliweed. However, maximum mean emergence time (9.07 days), time to 50% germination (3.67 days) was noted at leaves and stem extract, respectively. Application of aqueous extract of stem at 8% concentration resulted in greatest time to complete 50% germination (5.42 days) and lowest fresh weight (6.28 g), dry weight (1.00 g) and root length (0.33 cm) of E. cruss-galli. Whereas leaf extract at 8% concentration produces less shoot length (1.13 cm) and more emergence time (9.18 days). Lowest emergence percentage (6.67%) and germination index (0.89) were produced by aqueous extract of fruit at 8% concentration. On the basis of this experiment, it can be concluded that higher concentration (8%) of stem extract of P. somniferumwas used to biologically control the infestation of E. cruss-galli weed.

Echinochloa crus-galli (barnyard grass).

E. crus-galli is a grass species included in the Global Compendium of Weeds (Randall, 2012) and which is considered one of the world's worst weeds. This species has the capability to reduce crop yields and cause forage crops to fail by removing up to 80% of the available soil nitrogen. E. crus-galli is considered the world's worst weed in rice paddies and has been also listed as a weed in at least other 36 crops throughout tropical and temperate regions of the world (Holm et al., 1991). The high levels of nitrates it accumulates can poison livestock. It also acts as a host for several mosaic virus diseases. E. crus-galli is also considered an environmental weed that has become invasive in natural grasslands, coastal forests and disturbed sites in Asia, Africa, Australia, Europe and America (FAO, 2014; USDA-ARS, 2014).

Synthesis Candidates Herbicide Through Optimization Quinclorac Containing 3-Methyl-1H-pyrazol-5-yl

To enhance quinclorac potency, twenty-five derivatives were synthesized containing 3-methyl-1H-pyrazol-5-yl by intermediate derivatization methods (IDMs). These compounds were confirmed by melting point (mp), 1HNMR, 13CNMR, and HRMS. The compound 1,3-dimethyl-1H-pyrazol-5-yl 3,7-dichloroquinoline-8-carboxylate (10a) was determined by X-ray diffraction. The activity of these compounds substituent on the phenyl was: electron-drawing group > neutral group > donor-drawing group, the results was like that of substituted benzyl group on pyrazole. The herbicidal activity assays showed that compounds 1-(2-fluorophenyl)-3-methyl-1H-pyrazol-5-yl 3,7-dichloroquinoline-8-carboxylate (8l, EC50 = 10.53 g/ha) and 10a (EC50 = 10.37 g/ha) had an excellent inhibition effect on barnyard grass in greenhouse experiment. Greenhouse safety experiment of rice exhibited almost no difference in plant height and fresh weight treated 10a at stage 1∼2-leaf of rice after 14 days but 8l had a detrimental effect. Two season field assays showed 10a herbicidal activity on barnyard grass at 150 g/ha as equal as 300 g/ha quinclorac in fields in 2019 and 2020. The study demonstrated that 10a could be further researched as a potential herbicide to control barnyard grass in fields.

Enantioselective and Synergistic Herbicidal Activities of Common Amino Acids Against Amaranthus tricolor and Echinochloa crus-galli

Amino acids have a wide range of biological activities, which usually rely on the stereoisomer presented. In this study, glycine and 21 common α-amino acids were investigated for their herbicidal property against Chinese amaranth (Amaranthus tricolor L.) and barnyard grass (Echinochloa crus-galli (L.) Beauv.). Both d- and l-isomers, as well as a racemic mixture, were tested and found that most compounds barely inhibited germination but moderately suppressed seedling growth. Various ratios of d:l-mixture were studied and synergy between enantiomers was found. For Chinese amaranth, the most toxic d:l-mixtures were at 3:7 (for glutamine), 8:2 (for methionine), and 5:5 (for tryptophan). For barnyard grass, rac-glutamine was more toxic than the pure forms; however, d-tryptophan exhibited greater activity than racemate and l-isomer, indicating the sign of enantioselective toxicity. The mode of action was unclear, but d-tryptophan caused bleaching of leaves, indicating pigment synthesis of the grass was inhibited. The results highlighted the enantioselective and synergistic toxicity of some amino acids, which relied upon plant species, chemical structures, and concentrations. Overall, our finding clarifies the effect of stereoisomers, and provides a chemical clue of amino acid herbicides, which may be useful in the development of herbicides from natural substances.

Potencies of Justicia adhatoda L. for its possible phytotoxic activity

The phytotoxic effects of Justicia adhatoda L. were investigated on cauliflower, broccoli, tomato, foxtail millet and barnyard grass. The experiments were carried out under laboratory and in pot experiments. Six different aqueous methanol extract concentrations (control, 0.001, 0.003, 0.01, 0.03 and 0.1 g DW equivalent mL-1 extract) were tested in the laboratory and six aqueous extract concentrations (control, 1.0, 2.0, 3.0, 4.0 and 5.0 g DW mL-1 extract equivalent) were evaluated in the pot experiment. Results showed a reduction in germination and growth (shoot length, root length and biomass weight) at higher extract concentration compared to control. The leaf extracts from J. adhatoda showed that the foxtail millet and barnyard grass are germinating below 50 % both in the laboratory condition and in the pot experiment at their maximum concentration. When maximum extracts have been applied, we have found less than 0.5 cm of shoot and root of foxtail millet and barnyard grass. Maximum dry weight reduction was observed in foxtail millet and barnyard grass at the same concentration. The findings show that J. adhatoda may have phytotoxic potential and thus contains phytotoxins. Therefore, J. adhatoda can be used in sustainable crop production as a mulch or soil additive to suppress weeds.