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Three‐lobe morning glory (Ipomoea triloba L.) is an annual weed, which presents vigorous growth, long cycle, and tolerance to glyphosate. Thus, knowledge of aspects related to germination and behavior in the seed bank of this species are essential for the adoption of appropriate management practices to reduce the population in agricultural fields. Therefore, the objective of this work was to characterize the requirements for three‐lobe morning glory germination, perform field emergence modeling using thermal and hydrothermal time models, and determine the longevity of the seed bank. Eight temperatures and 10 water potentials were tested in the laboratory to determine the base temperature and water potential for seed germination. For the modeling of the emergence, field experiments were conducted between the years 2014 and 2018 considering three sampling times (10/20, 11/10, and 12/01), which coincide with the sowing times of summer annual crops. To evaluate the longevity and persistence of the seed bank, a factorial experiment was conducted in which factor A consisted of three burial depths and factor B consisted of five harvesting times. Base values for three‐lobe morning glory emergence are base, optimum, and maximum temperatures of 12.32, 29.82, and 43.31°C, respectively, and base water potential of −0.80 MPa. Both models are adequate to predict the emergence of three‐lobe morning glory in the three sampling times. The species has a persistent seed bank, in which the greater the depth of seed burial, the greater the longevity of the seed bank, and can remain viable for up to 16 months. [ABSTRACT FROM AUTHOR]

Weedy rice (Oryza sp.) is one of the most troublesome global weeds in cultivated rice. Its troublesome status is associated with characteristics such as seed shattering and dormancy, allowing for long‐term reinfestation and persistence in rice fields. However, the role of rising carbon dioxide levels (CO2) and other climate variables on these characteristics has not, to date, been assessed. The current research objectives were to evaluate two aspects related to climatic change, increased CO2 concentration (400 ± 50 μmol mol−1 and 700 ± 50 μmol mol−1) and water management (continuous and alternate‐wetting drying), to assess plant development, seed shattering and seedbank longevity of weedy rice. Our results indicated that elevated CO2 (700 ± 50 μmol mol−1) increased weedy rice growth and biomass, seed shattering and lengthened viability within the seedbank. Water management did not affect weedy rice growth, seed shattering and seed dormancy. These results suggest that in areas where weedy rice is dominant, its seed bank persistence and potential competition may be exacerbated with rising CO2 levels, with negative consequences for rice production. [ABSTRACT FROM AUTHOR]

Italian ryegrass (Lolium perenne spp. multiflorum Lam.) is a troublesome weed commonly found in winter cereals. Winter cover crops represent an alternative for weed suppression, reducing weed soil seed banks, and future infestations. The aim of this study was to evaluate the suppression of winter cover crops on reducing the soil seed bank and infestations of Italian ryegrass in fields managed under no‐tillage system. Field experiment was carried out during three consecutive years, in a strip‐plot design with four blocks, containing the winter cover crops. Wheat (Triticum aestivum), canola (Brassica napus), barley (Hordeum vulgare), common vetch (Vicia sativa), cereal rye (Secale cereale), feral radish (Raphanus sativus), and black oat (Avena strigosa) were sown in each strip (block) under no‐tillage system and compared with weedy fallow. Seed bank was quantified at 0.0‐ to 0.05‐ and 0.05‐ to 0.10‐m depths, whereas Italian ryegrass infestations were measured with a sample frame of 0.0625 m2. Greater suppression and lower soil seed bank were reported in plots managed with cereal rye, common vetch, black oat, and feral radish, reducing up to 80% in the first year, and up to 96% after 3 yr of continuous management in comparison to weedy fallow. Italian ryegrass infestations increased four‐ to six‐fold when managed with canola. High suppressor potential of Italian ryegrass occurred for cover crops with biomass dry accumulation greater than 8.7 tons ha−1, especially to plants with a height upper to 1 m, plant characteristics essential to reduce strongly Italian ryegrass infestations and ensure weed‐free fields throughout the time. Core Ideas: Winter cover crops reduce up to 97% the Italian ryegrass infestations and soil seed bank.Cover crops with greater biomass dry accumulation exhibit higher weed suppression.Cereal rye, black oat, feral radish, and common vetch have higher potential suppressor.Suppression with cover crops is a tool to manage herbicide resistance Italian ryegrass. [ABSTRACT FROM AUTHOR]

Jointvetch (Aeschynomene spp., Fabaceae) is considered a problematic broadleaf weed for rice production in Brazil, the United States, and Asia. Seed dormancy is particularly important for the perpetuation of annual weeds, representing the only link between different generations and thus the source of all future weed infestations. Seed dynamics in annual species are complex and related to many biotic and abiotic factors. The objectives of this study were to determine whether dormancy occurs in Aeschynomene denticulata and Aeschynomene indica seeds, and, if so, what is the most efficient method to break it. In addition, the persistence of seeds in soil also was investigated for both species. Three experiments were conducted, two in lab conditions and one in field conditions. The first experiment consisted of germination tests conducted in controlled conditions to determine whether seeds have dormancy. The second experiment tested the effectiveness of preheating, precooling, potassium nitrate, gibberellic acid, water soaking, chemical scarification, and mechanical scarification as dormancy breaking methods. Finally, the third experiment evaluated seedbank longevity for 1‐year period in the rice‐cultivated soil during which seeds were buried and recovered every 3 months. Variations in physical dormancy are present at different levels in both species due to seed‐coat impermeability to water absorption. Meanwhile, A. denticulata can persist over a year in soil seed bank but A. indica seeds only persisted for half a year. [ABSTRACT FROM AUTHOR]

Herbicides are stressors that can have negative effects on plants. In Oryza sativa (L.), differential gene expression may be evaluated through real-time reverse transcription quantitative polymerase chain reaction (RT-qPCR). The aim of this study was to evaluate the stability of candidate reference genes and to quantify the relative expression of oxidative stress genes at different times (12, 24, 48, and 96 hours after treatment [HAT]) with penoxsulam, cyhalofop-butyl, and bentazon herbicides. Norm- Finder, BestKeeper, and GeNorm software and the comparative Ct method were used to assess expression stability and to determine the RT-qPCR threshold values of the candidate reference genes. The UBQ5 gene was the most stable among the reference genes analyzed. The gene expression results showed upregulation of OsCAT and OsMnSOD1 genes at all times after herbicide application. The OsAPX2 and OsGST3 genes showed increased gene expression at 12 and 96 HAT for all herbicides. The OsHO-1 gene had the most significant expression changes, with maximum expression levels at 24 HAT with bentazon and at 96 HAT with penoxsulam and cyhalofop-butyl. Overall, antioxidant system gene expression increased after the application of bentazon, penoxsulam, and cyhalofop-butyl in rice. [ABSTRACT FROM AUTHOR]