Deployment of fine and coarse grain rice cultivars in time and space for increased productivity.

To examine the impact of mixture ratio and temporal deployment of fine and coarse grain cultivars on rice productivity and profitability, two experiments were carried out at Bangladesh Agricultural University. In both investigations, two monsoon rice cultivars viz., Binadhan-13 (a tall, late-maturing, fine-grained) and Dhani Gold (a semi-dwarf, mid-maturing, coarse-grained) were utilized. In the 1st experiment, rice cultivars were planted in different mixture ratios viz., sole Binadhan-13, sole Dhani Gold, 1:1, 2:3, 3:2, 2:4 and 4:2 ratio of Binadhan-13 to Dhani Gold. The second study included the introducing time of Dhani Gold viz., seven days before or after or same day of Binadhan-13, sole Binadhan-13 and sole Dhani Gold. Three replications of the randomized complete block design were used for both trials. In the first experiment, both cultivars produced more when grown in mixtures as opposed to solitary cultures. Even though Dhani Gold's sole culture had the greatest yield, it was statistically equivalent to combined yields when Binadhan-13 and Dhani Gold were grown together in mixtures at 2:1, 3:1, or 4:1 ratios. The maximum net return and benefit cost ratio (BCR) were achieved when Binadhan-13 and Dhani Gold were planted in mixture following a 4:2 ratio as opposed to when Binadhan-13 was grown solely. In the second experiment, a sole cultivar generated less yield than cultivars that were transplanted on the same day, before, and after another cultivar. Cultivation of sole Binadhan-13 produced the lowest net return and minimum BCR (1.37), while the highest net return and BCR (1.81) was recorded when Dhani Gold was planted seven days before Binadhan-13 in mixture. A clear economic advantage of mixed culture with temporal deployment over the sole culture of either cultivar was evident. Therefore, transplanting Dhani Gold in a 1:1 ratio seven days before Binadhan-13 may be advised for greater output and economic return.

Millets: The future crops for the tropics - Status, challenges and future prospects.

Millets are small-grained nutritious minor cereal crops that are resistant to different abiotic stresses resulting from climate change. Despite their many benefits, millets have received limited attention in agricultural research, policies, and markets. Considering the importance of millets, recently the government many tropical countries including India and Bangladesh give more emphasis to millets cultivation and improvement. Moreover, Food and Agricultural Organization of the United Nations (FAO) declared 2023 to be the "International Years of Millets". In these connections, a details and updated review of the pros and cons of millets cultivation and its improvement in this region warrant due attention. The review therefore, examines the potential and main barriers to the adoption and promotion of millet cultivation in this region. These include limited research and development efforts, inadequate infrastructure and inputs, weak market linkages and demand, and insufficient awareness and knowledge about millets' nutritional and environmental benefits. This review also highlighted the prospects and strategies for scaling up millet cultivation in this region especially in Bangladesh. These include increasing public and private investment in research and extension services, strengthening farmers' organizations and market linkages, promoting millet-based value chains and products, and integrating millets into nation's food policy. The review concludes that millets might support equitable and sustainable agricultural growth, which would contribute to global food and nutritional security and could help attain the sustainable development goals (SDGs). However, achieving this potential will require concerted efforts from multiple stakeholders, including farmers, researchers and policymakers. The review emphasizes the need for a multi-disciplinary and multi-stakeholder approach that prioritizes innovation, inclusiveness, and sustainability. Lastly, the review highlights more investigation into the socioeconomic, environmental, and nutritional effects of millet production in this region with special emphasis on Bangladesh in order to support evidence-based policies and practices.

Preliminary report on the comparative weed suppressibility of Bangladeshi Wheat varieties.

A key and ecologically sound strategy for integrated weed management is the use of varieties of weed-competitive crops. Utilizing wheat cultivars that are weed-competitive can lessen weed pressure and inordinate herbicide usage in wheat fields by a substantial amount. To assess the weed suppressibility of Bangladeshi wheat varieties, a field test was carried out in 2018 throughout the winter season at the Agronomy Field Laboratory, Bangladesh Agricultural University, Bangladesh. Tests on a total of 18 selected Bangladeshi wheat cultivars were conducted in both "weedy" and "weed-free" environments. Additionally, weed monoculture plots (without wheat) were kept. The experiment was replicated three times using a randomized complete block design (RCBD). The results demonstrated that wheat varieties' weed interference and production capabilities differed greatly. BARI Gom 22 permitted the most weed growth (35 m-2), whereas BARI Gom 23 allowed the least (15 m-2) at 60 DAS among the wheat types under study. Grain yield ranged between 4.42 t ha-1 (BARI Gom 20) and 5.45 t ha-1 (BARI Gom 26) in weed-free settings, whereas it fluctuated from 2.48 t ha-1 (BARI Gom 21) to 3.93 t ha-1(BARI Gom 33) in weedy condition. The extent of the relative yield loss brought on by weeds ranged from 24 to 53%, with BARI Gom 33 suffering the least and Binagom-1 suffering the most. The weed competitive index varied from 0.48 to 1.47 for the examined wheat types. Among the cultivars, Binagom-1 had the lowest WCI and BARI Gom 29 had the highest. Although BARI Gom 33 was the best yielder in weedy condition and had the lowest relative yield loss, its interference against weed was moderate. Relative to the other varieties under consideration, comparatively BARI Gom 33 was the best in terms of yield and weed interference, but it is also advocated that breeders should continually focus on developing a variety that has both excellent producing potential and robust weed suppression.

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.

Phytochemical Constituents and Allelopathic Potential of Parthenium hysterophorus L. in Comparison to Commercial Herbicides to Control Weeds.

The allelopathic effect of various concentrations (0, 6.25, 12.5, 50 and 100 g L-1) of Parthenium hysterophorus methanol extract on Cyperus iria was investigated under laboratory and glasshouse conditions. No seed germination was recorded in the laboratory when P. hysterophorus extract was applied at 50 g L-1. In the glasshouse, C. iria was mostly injured by P. hysterophorus extract at 100 g L-1. The phytochemical constituents of the methanol extract of P. hysterophorus were analyzed by LC-ESI-QTOF-MS=MS. The results indicated the presence of phenolic compounds, terpenoids, alkaloids, amino acids, fatty acids, piperazines, benzofuran, indole, amines, azoles, sulfonic acid and other unknown compounds in P. hysterophorus methanol extract. A comparative study was also conducted between P. hysterophorus extract (20, 40 and 80 g L-1) with a synthetic herbicide (glyphosate and glufosinate ammonium at 2 L ha-1) as a positive control and no treatment (negative control) on Ageratumconyzoides, Oryzasativa and C. iria. The growth and biomass of test weeds were remarkably inhibited by P. hysterophorus extract. Nevertheless, no significant difference was obtained when P. hysterophorus extract (80 g L-1) and synthetic herbicides (glyphosate and glufosinate ammonium) were applied on A.conyzoides.

Physiological and Biochemical Responses of Ageratum conyzoides, Oryza sativa f. spontanea (Weedy Rice) and Cyperus iria to Parthenium hysterophorus Methanol Extract.

The current study was designed to investigate the effect of Parthenium hysterophorus L. methanol extract on Ageratum conyzoides L., Oryza sativa f. spontanea (weedy rice) and Cyperus iria L. in glasshouse condition. Here, Parthenium hysterophorus methanol extract at 20, 40, and 60 g L-1 concentrations was applied on the test species to examine their physiological and biochemical responses at 6, 24, 48 and 72 h after spraying (HAS). The phytotoxicity of P. hysterophorus was strong on A. conyzoides compared to weedy rice and Cyperus iria at different concentrations and exposure times. There was a reduction in photosynthesis rate, stomatal conductance, transpiration, chlorophyll content and carotenoid content when plants were treated with P. hysterophorus extract concentrations. Exposure to P. hysterophorus (60 g L-1) at 24 HAS increased malondialdehyde (MDA) and proline content by 152% and 130%, respectively, in A. conyzoides compared with control. The activities of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD)) were also increased in the presence of P. hysterophorus extract. Present findings confirm that the methanol extract of P. hysterophorus can disrupt the physiological and biochemical mechanism of target weeds and could be used as an alternative to chemical herbicides.

Suaveolic acid: a potent phytotoxic substance of Hyptis suaveolens.

Hyptis suaveolens (Lamiaceae) is an exotic invasive plant in many countries. Earlier studies reported that the aqueous, methanol, and aqueous methanol extract of H. suaveolens and its residues have phytotoxic properties. However, to date, the phytotoxic substances of this plant have not been reported. Therefore, the objectives of this study were isolation and identification of phytotoxic substances of H. suaveolens. Aqueous methanol extract of this plant was purified by several chromatographic runs through bioassay guided fractionation using garden cress (Lepidium sativum) as a test plant. Final purification of a phytotoxic substance was achieved by reverse phase HPLC and characterized as 14α-hydroxy-13ß-abiet-8-en-18-oic acid (suaveolic acid) by high-resolution ESI-MS, (1)H-,(13)C-NMR, CD, and specific rotation. Suaveolic acid inhibited the shoot growth of garden cress, lettuce (Lactuca sativa), Italian ryegrass (Lolium multiflorum), and barnyard grass (Echinochloa crus-galli) at concentrations greater than 30 µM. Root growth of all but lettuce was also inhibited at concentrations greater than 30 µM. The inhibitory activities were concentration dependent. Concentrations required for 50% growth inhibition of suaveolic acid for those test plant species were ranged from 76 to 1155 µM. Therefore, suaveolic acid is phytotoxic and may be responsible for the phytotoxicity of H. suaveolens plant extracts.

Phytotoxic activity of Ocimum tenuiflorum extracts on germination and seedling growth of different plant species.

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 (T 50) and mean germination time (MGT) were increased at the same or higher than this concentration. The increasing trend of T 50 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 I 50 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.

Two novel phytotoxic substances from Leucas aspera.

Leucas aspera (Lamiaceae), an aromatic herbaceous plant, is well known for many medicinal properties and a number of bioactive compounds against animal cells have been isolated. However, phytotoxic substances from L. aspera have not yet been documented in the literature. Therefore, current research was conducted to explore the phytotoxic properties and substances in L. aspera. Aqueous methanol extracts of L. aspera inhibited the germination and growth of garden cress (Lepidum sativum) and barnyard grass (Echinochloa crus-galli), and the inhibitory activities were concentration dependent. These results suggest that the plant may have phytotoxic substances. The extracts were then purified by several chromatographic runs. The final purification was achieved by reversed-phase HPLC to give an equilibrium (or inseparable) 3:2 mixture of two labdane type diterpenes (compounds 1 and 2). These compounds were characterized as (rel 5S,6R,8R,9R,10S,13S,15S,16R)-6-acetoxy-9,13;15,16-diepoxy-15-hydroxy-16-methoxylabdane (1) and (rel 5S,6R,8R,9R,10S,13S,15R,16R)-6-acetoxy-9,13;15,16-diepoxy-15-hydroxy-16-methoxylabdane (2) by spectroscopic analyses. A mixture of the two compounds inhibits the germination and seedling growth of garden cress and barnyard grass at concentrations greater than 30 and 3 µM, respectively. The concentration required for 50% growth inhibition (I50) of the test species ranges from 31 to 80 µM, which suggests that the mixture of these compounds, are responsible for the phytotoxic activity of L. aspera plant extract.