Allelopathic Potential of Three Oil Enriched Plants against Seedling Growth of Common Field Crops

Current study aims to investigate into the allelopathic potential of the different parts (leaf, bark, stem, twig and root) of three oil-enrich plant species of Bangladesh viz., Jatropha curcus, Ricinus communis and Aphanamixis polystachya. The aqueous extract of those plant parts were diluted into four different concentrations viz., 1:5, 1:10, 1:15, 1:20 (w/v) and tested against the seedling growth of jute, rice, wheat, radish, tomato, mungbean and mustard under control laboratory condition. A control (distilled water without extract) was also maintained in every cases and the bioassay experiment was replicated thrice. The results of this research showed that the shoot and root growth inhibition of rice, wheat, jute, tomato, radish, mungbean and mustard by leaf, bark, stem, twig and root extracts of J. curcus, R. communis and A. polystachya varied significantly. Compare to the shoot growth, the root growth of the test species inhibited more except J. curcus. The leaf and root have higher allelopathic potential than any other parts of the studied plants. Finally, it can be concluded here that J. curcus plant extracts has higher allelopathic potential than other two plants R. communis and A. polystachya. Therefore, J. curcus can be used as a candidate plant for isolation and identification of allelopathic substances for the development of new natural herbicides

Efficacy and Economics of Herbicidal Weed Management in Monsoon Rice of Bangladesh: Weed Management in Monsoon Rice of Bangladesh

Weed management is a challenging task in sustainable rice production. Physical and cultural methods of weed control are laborious and expensive, whereas chemical control is cheaper and less time consuming despite of some detrimental effect on environment with its inappropriate application. Considering these points, an experiment was conducted at the Agronomy Field Laboratory of Bangladesh Agricultural University, Mymensingh, Bangladesh during July–December 2015 to find out appropriate weed management practices for inbred and hybrid rice. The experiment comprised of four rice varieties (two inbred; BRRI dhan49 and Binadhan-7, and two hybrids; Dhani gold and Agrodhan-12); and eight herbicidal weed control treatments (season-long weedy or weed free, Pretilachlor fb Penoxsolum or 2,4-D dimethyl amine, Pendimethalin fb Penoxsolum or 2,4-D dimethyl amine, Pretilachlor or Pendimethalin fb one-time hand weeding). Eleven weed species belonging to five families were observed in the experimental plots. The highest weed density and dry weight were found in season-long weedy treatment and the lowest one was found in Pretilachlor fb one-time hand weeding. The highest above ground crop biomass (9.7 t ha-1) and harvest index (46.3%) were obtained from the hybrid variety Agrodhan-12 and the lowest biomass (8.3 t ha-1) was obtained from the inbred variety Binadhan-7. Season long weed free condition resulted the highest above ground crop  biomass (10.9 t ha-1), harvest index (48.7%), highest yield increase over control (213.8), weed control efficiency (100%) and gross return (BDT 141480 ha-1) and the lowest values for all those parameters were obtained from season-long weedy treatment. Season-long weed free treatment combined with Pretilachlor or Pendimethalin fb one-time hand weeding showed the best performance in reducing weed density and increasing above ground crop biomass, but gross return was higher because of high labour wages in these treatments. The highest BCR (2.5) was observed in Pretilachlor fb Penoxsolum. Therefore from economic view point Pretilachlor fb Penoxsolum is the best combination. But from sustainability view point Pretilachlor or Pendimethalin along with one-time hand weeding may be recommended for effective weed management in inbred and hybrid rice during monsoon season

Exploring 55 tropical medicinal plant species available in Bangladesh for their possible allelopathic potentiality

The current research was conducted to investigate the allelopathic properties of 55 medicinal plant species of Bangladesh representing 32 different families. The aqueous leaves or whole plant extract of those plant species was diluted into four different concentrations viz., 1:5, 1:10, 1:15, 1:20 (w/v) and tested against the seedling growth of Raphanus sativus. A control (distilled water without extract) was also maintained in every cases and the bioassay experiment was replicated thrice. The aqueous extract of all these species inhibited both shoot and root length of R. sativus at concentration greater than 1:15 (w/v) except Delonix regia (Fabaceae) and Leucas aspera (Lamiaceae). The inhibitory activity was concentration dependent and root growth was more sensitive than their shoot. Among the plant species, Citrus aurantifolia (Rotaceae), Moringa oleifera (Moringaceae), Annona muricata (Annonaceae), Aegle marmelos (Rutaceae), Cinnamomum tamala (Lauraceae) and Azadirachta indica (Meliaceae) completely (100%) inhibited the shoot and root growth of R. sativus at concentration 1:5 (w/v). Other than this six plant species, 15 out of 49 medicinal plants showed more than 95% shoot and root growth inhibition at the same concentration. The least allelopathic potential plant was Garcinia mangostana (Clusiaceae) that showed on an average 36% growth inhibition followed by Schleichera oleosa (Sapindaceae). Based on these results it can be concluded that among the tested plant species, C. aurantifolia, M. oleifera, A. muricata, A. marmelos, C. tamala, and A. indica are strongly allelopathic and therefore, could be used as potential candidates for the development of eco-friendly natural herbicides

Allelopathic Properties of Lamiaceae Species: Prospects and Challenges to Use in Agriculture

Herbicide resistance due to the increasing reliance on herbicides is a near-term challenge for the world’s agriculture. This has led to a desire to develop new herbicides with a novel mode of action, to address resistance in weed species. Lamiaceae, a large dicotyledonous plant family, is very well known for the multitudinous pharmacological and toxicological properties of its member species. Moreover, many species of this family are significant for their allelopathic activity in natural and laboratory settings. Thus, plants in Lamiaceae have the potential to be sources of alternative herbicides. However, gaps in our knowledge need to be addressed prior to adopting these allelopathic activities in agriculture. Therefore, we review the existing state of knowledge about the Lamiaceae family, the reported allelopathic properties of plant extracts, and their isolated allelochemicals under laboratory, greenhouse, and field conditions. In addition, we offer a perspective on existing challenges and future opportunities for adopting the allelopathic properties of Lamiaceae plant species for green agriculture

Agricultural Uses of Juglone: Opportunities and Challenges

Application of conventional synthetic pesticides and agrochemicals has boosted the yield and productivity of crops by reducing pest infestation and promoting crop growth yet increasing reliance on many of these products poses serious environmental threats. This has led to growing interest in obtaining more environmentally friendly alternatives to conventional pesticides and agrochemicals. Allelochemicals produced by plants, fungi, and microbes offer options for developing novel natural product-based pesticides and agrochemicals that are effective but with lower environmental half-lives. Here, we review the current state of knowledge about the potential use of juglone (5-hydroxy-1,4-naphthoquinone), the allelochemical produced by black walnut trees (Juglans nigra), which has been investigated for applications across a range of different agricultural purposes. We then offer our perspective on what opportunities and challenges exist for harnessing juglone as a component of sustainable agriculture

Phytotoxic Activity of Ocimum tenuiflorum

Phytotoxic activity of Ocimum tenuiflorum (Lamiaceae) plant extracts was investigated against the germination and seedling growth of cress (Lepidium sativum), lettuce (Lactuca sativa), alfalfa (Medicago sativa), Italian ryegrass (Lolium multiflorum), barnyard grass (Echinochloa crus-galli), and timothy (Phleum pratense) at four different concentrations. The plant extracts at concentrations greater than 30 mg dry weight equivalent extract mL−1 reduced significantly the total germination percent (GP), germination index (GI), germination energy (GE), speed of emergence (SE), seedling vigour index (SVI), and coefficient of the rate of germination (CRG) of all test species except barnyard grass and GP of lettuce. In contrast, time required for 50% germination (T50) and mean germination time (MGT) were increased at the same or higher than this concentration. The increasing trend of T50 and MGT and the decreasing trend of other indices indicated a significant inhibition or delay of germination of the test species by O. tenuiflorum plant extracts and vice versa. In addition, the shoot and root growth of all test species were significantly inhibited by the extracts at concentrations greater than 10 mg dry weight equivalent extract mL−1. The I50 values for shoot and root growth were ranged from 26 to 104 mg dry weight equivalent extract mL−1. Seedling growth was more sensitive to the extracts compared to seed germination. Results of this study suggest that O. tenuiflorum plant extracts have phytotoxic properties and thus contain phytotoxic substances. Isolation and characterization of those substances from this plant may act as a tool for new natural, biodegradable herbicide development to control weeds

Herbicidal weed control in drill sown spring wheat under Bangladesh condition

Weeds are considered as one of the major factors responsible for current low wheat yield in Bangladesh. Although chemical weed control is well established in many wheat growing countries, in Bangladesh, the herbicides are typically not used by farmers to manage weeds in wheat. Hence, to evaluate the efficacy of pre- and post-emergence herbicides in mechanized drilled sown wheat, a two-year field study was conducted in southwest Bangladesh. The study evaluated the performance of four pre-emergence herbicides (oxadiargyl 80g, pendimethalin 850 g, pyrazosulfuron 15 g, and mefenacet + bensulfuran methyl 550 g a.i. ha-1) applied at 2 days after sowing (DAS) and four post-emergence herbicides (2,4-D 1400 g, ethoxysulfuron18 g, penoxsulam22.5 g, and fenoxaprop 56 g a.i. ha-1) applied at 20 DAS, on weed control efficacy. A season long weed-free and a season long weedy plots were also maintained to compare the results. The weed control option using a single pre- or post-emergence herbicide was not adequate to control weed effectively when weed infestation was relatively higher. The best yield provided by pre-emergence (pendimethalin and oxadiargyl) and post-emergence (2,4-D and ethoxysulfuron) herbicide treatments were respectively 13-15% and 12-17% lower than the yield (4.1-4.2 t ha-1) of weed-free treatment. Post-emergence herbicides fenoxaprop was the best in controlling weeds; however, due to phytotoxic effects on wheat plants, the plots applied with fenoxaprop produced very low yield (2.6-2.8 t ha-1). Similarly, even after good weed control by the post-emergence application of penoxsulam, phytotoxicity on wheat resulting in low yield. The study suggested that the best weed control option for wheat is to use a pre-emergence (pendimethalin or oxadiargyl) followed by (fb) a post-emergence (2,4-D or ethoxysulfuron) herbicides depending upon weed species which would benefit the farmers by providing high weed control efficacy at lower cost compared to manual weeding. [Fundam Appl Agric 2019; 4(2.000): 839-848

Allelopathic Properties of Lamiaceae Species: Prospects and Challenges to Use in Agriculture

Herbicide resistance due to the increasing reliance on herbicides is a near-term challenge for the world’s agriculture. This has led to a desire to develop new herbicides with a novel mode of action, to address resistance in weed species. Lamiaceae, a large dicotyledonous plant family, is very well known for the multitudinous pharmacological and toxicological properties of its member species. Moreover, many species of this family are significant for their allelopathic activity in natural and laboratory settings. Thus, plants in Lamiaceae have the potential to be sources of alternative herbicides. However, gaps in our knowledge need to be addressed prior to adopting these allelopathic activities in agriculture. Therefore, we review the existing state of knowledge about the Lamiaceae family, the reported allelopathic properties of plant extracts, and their isolated allelochemicals under laboratory, greenhouse, and field conditions. In addition, we offer a perspective on existing challenges and future opportunities for adopting the allelopathic properties of Lamiaceae plant species for green agriculture

Bioherbicidal properties of Parthenium hysterophorus, Cleome rutidosperma and Borreria alata extracts on selected crop and weed species

Natural product-based herbicides could be the effective alternatives to synthetic chemical herbicides for eco-friendly weed management. This research, therefore, was conducted to identify the phytotoxic properties of Parthenium hysterophorus L., Cleome rutidosperma DC. and Borreria alata (Aubl.) DC. with a view to introducing them as a tool for natural herbicide development. The methanol extracts of these plants were examined on the germination and growth of Zea mays L., Oryza sativa L., Abelmoschus esculentus (L.) Moench and Amaranthus gangeticus L., Oryza sativa f. Spontanea Roshev. (Weedy rice), Echinochloa colona (L.) Link., Euphorbia hirta L., and Ageratum conyzoides L. under laboratory and glasshouse conditions. A complete randomized design (CRD) with five replications and randomized complete block design (RCBD) with four replications were laid out for laboratory and glasshouse experiments, respectively. In the laboratory experiment, three plant extracts of 0, 6.25, 12.5, 50, and 100 g L−1 were tested on survival rate, hypocotyl, and radicle length of eight test plant species. No seed germination of A. conzyoides, E. hirta, and A. gangeticus were recorded when P. hysterophorus extract was applied at 50 g L−1. C. rutidosperma had the same effect on those plants at 100 g L−1. In the glasshouse, similar extracts and concentrations used in the laboratory experiments were sprayed on at the 2–3 leaf stage for grasses and 4–6 for the broadleaf species. Tested plants were less sensitive to C. rutidosperma and B. alata compared to P. hysterophorus extract. Among the weeds and crops, A. conyzoides, E. hirta, A. esculentus and A. gangeticus were mostly inhibited by P. hysterophorus extract at 100 g L−1. Based on these results, P. hysterophorus was the most phytotoxic among the tested plant extracts and could be used for developing a new natural herbicide for green agriculture