The rice (Oryza sativa L.)–wheat (Triticum aestivum L.) cropping system (RWCS), recognized as the world’s prime agricultural system, plays a pivotal role in global food security by providing employment for millions and ensuring a steady income, thereby serving as a cornerstone for farmers’ livelihoods and attracting numerous investors. However, the sustainability and efficiency of this critical system face momentous threats due to climate change, which affects both the quantity and quality of wheat and rice crops. Currently, the growth frequency of the RWCS has declined, principally due to evolving challenges such as weed infestation, delayed wheat sowing after rice harvest, soil salinity, and the prevalence of various diseases. Among these challenges, weeds pose a considerable threat to the cultivation of both rice and wheat. Seed germination, a crucial stage in the plant life cycle, is influenced by various factors, including dormancy, temperature, moisture, oxygen, and light. A comprehensive understanding of weed ecology is essential for identifying vulnerabilities that can be targeted for improved weed management. Population-based threshold models, including hydro-time and thermal time, provide insights into germination patterns, contributing to the overall fitness of weed species. The ability to predict species’ responses to climate change is paramount, and these models are effective in comprehending and controlling weed emergence behavior across diverse environments. Hence, this review paper emphasizes the reevaluation of current weed management practices, focusing on investigating ecologically sustainable approaches for efficient weed control.

Wide diversity in plant adaptive traits, such as seed size and dormancy, is generally linked to the rapid spread, invasiveness, and adaptative potential of a weed species. Italian ryegrass [Lolium perenne L. ssp. multiflorum (Lam.) Husnot] is a significant weed species in winter crops such as wheat (Triticum aestivum L.) and summer crops such as corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and peanut (Arachis hypogaea L.) in Alabama. In this study, diversity in seed morpho-physiological traits—such as seed length, awn length, seedling length, 100-seed weight, and seed dormancy—was assessed in 65 L. perenne ssp. multiflorum populations collected from Alabama in 2023. Significant diversity was observed among the populations for 100-seed weight (61.8 to 295.8 mg), seed length (3.5 to 6.43 mm), awn length (0 to 7 mm), and seedling length (0.5 to 38.6 cm). Germination speed was significantly lower in the populations with high initial seed dormancy (>30%) compared with medium (15% to 30%) and low dormancy groups (<15%) at 0 and 3 mo after harvesting. Additionally, the relationship between herbicide-resistance status and seed morpho-physiological traits in these populations was explored. A significant positive association was observed between seed dormancy and the number of survivors following glyphosate (P < 0.01) and clethodim (P < 0.01) treatments. The observed diversity in morpho-physiological traits could be the reason for enhanced adaptability of L. perenne ssp. multiflorum, and its correlation with herbicide resistance indicates directional selection or coexistence of specific seed morpho-physiological traits with herbicide resistance under the repeated use of similar modes of action.

American sloughgrass [Beckmannia syzigachne (Steud.) Fernald] is a troublesome weed in wheat (Triticum aestivum L.). We tested the germination of B. syzigachne seeds under different temperatures in growth chambers (12-h dark/12-h light, 12,000 lx), simulating temperatures during the winter wheat sowing periods: early (25/15 °C), standard (20/10 °C), late (15/5 °C), and very late (5/0 °C). We also tested the accumulated temperatures required for seedling growth to the 2- to 5-leaf stages, using 225 populations collected from wheat fields in eastern China. The average 1,000-seed weight of the 225 populations was 1.2 ± 0.01 g. Overall, the populations tested did not show seed germination after 21 d of treatment (DAT) at 5/0 °C or constant 30 °C. At 14 DAT with 25/15, 20/10, and 15/5 °C, the mean germination rates were 85.4%, 6.4%, and 0.1%, respectively. These rates increased to 99.9%, 58.6%, and 21.7% at 21 DAT. Populations collected from lower-latitude regions germinated significantly faster (P < 0.05) under optimal conditions. Accumulated temperatures required for growing the second, third, fourth, and fifth leaves were 139.0 ± 1.0, 127.8 ± 1.0, 115.6 ± 1.0, and 98.9 ± 0.7 °C, which showed a significant decreasing trend. The narrower optimal temperature range for B. syzigachne seed germination and higher thermal requirements for early seedling growth constrain its distribution, while the heterogeneous seed germination facilitates its infestations in wheat-planting areas in eastern China.