Document Type : Research Article
Authors
1
Department of Genetic and Plant Production, Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil, Iran
2
Research Assist. Prof., Plant Protection Research Dep, Ardabil Agricultural and Natural Resources Research and Education Centre, AREEO, Moghan, Iran
10.22067/jpp.2026.95300.1250
Abstract
Introduction
Abstract
Wild mustard is a common and competitive weed in global agricultural systems. Its high ecophysiological adaptability and ability to form a persistent seed bank make it a serious threat to crop production. In the autumn of 2023, an experiment was conducted to investigate the emergence and establishment indices of wild mustard seedlings. The study was arranged as a factorial experiment in a completely randomized design with three replications. The factors included wild mustard biotype at 2 levels (susceptible and resistant to the herbicide tribenuron-methyl), soil type at 2 levels (clay and silt texture), and sowing depth at 8 levels (0, 1, 2, 3, 4, 5, 6, and 7 cm). According to the findings, although the resistant biotype demonstrated superiority under optimal conditions (shallow depths and clay soil) with a high emergence index of 24.5, this genetic advantage proved entirely fragile when confronted by a determining factor: seed burial depth. The identification of a critical physiological threshold at a depth of 4-5 cm is considered crucial for controlling this weed. At this depth, even the most resistant biotype expends its energy reserves in darkness and under the mechanical pressure of the soil before reaching the light, ultimately failing to emerge. At the 1 cm depth, the mean emergence percentage in clay soil was 98.66% for both biotypes, while in silt soil it reached 84% for the resistant biotype. At the 6 cm depth in silt soil, the survival percentage of the susceptible biotype was 0%, indicating the destructive interaction of depth and unsuitable soil texture. The decrease in emergence percentage from over 90% at shallow depths to below 20% at depths greater than 4 cm clearly indicates the depletion of seed energy reserves before reaching the soil surface. By implementing targeted tillage operations (such as plowing) to bury weed seeds at critical depths, its population can be fundamentally controlled without reliance on herbicides or concerns about resistance.
Materials and Methods
In the autumn of 2023, a factorial experiment arranged in a completely randomized design (CRD) with three replications was conducted to investigate the emergence and establishment indices of wild mustard seedlings. The factors included wild mustard biotype at 2 levels (susceptible and resistant to tribenuron-methyl herbicide), soil type at 2 levels (clay and silt textures), and sowing depth at 8 levels (0, 1, 2, 3, 4, 5, 6, and 7 cm). Seeds of both susceptible and resistant biotypes were collected in the spring of 2023 from fields around the University of Mohaghegh Ardabili greenhouse, where they had been cultivated. To break physiological dormancy, seeds were pre-treated with Gibberellic acid (GA₃) at a concentration of 1500 parts per million (ppm).
Results and Discussion
Findings revealed that although the resistant biotype demonstrated its superiority under optimal conditions (shallow depths and clay soil) with a high emergence index (24.5), this genetic advantage is entirely fragile against the determining factor of seed placement depth. Identifying a critical physiological threshold at 4-5 cm depth is considered the key to controlling this weed; this is the depth where even the most resistant biotype, in an unequal battle against darkness and soil mechanical pressure, exhausts its energy reserves before reaching the light and fails to emerge. The resistant biotype achieved the highest survival percentage (98.61%) and the highest emergence rate (emergence index 16.50) at 1 cm depth in clay soil. At 1 cm depth, the mean emergence percentage in clay soil was 98.66% for both biotypes, while in silt soil it reached 84% for the resistant biotype. At a 6 cm depth in silt soil, the survival percentage of the susceptible biotype was 0%, highlighting the detrimental interaction of depth and unfavorable soil texture.
Conclusion
In response to increasing depth, the plant allocates its resources primarily to the rapid elongation of the hypocotyl to escape darkness, rather than to radicle development and biomass production. Furthermore, a strong positive correlation between germination speed and final emergence percentage/seedling survival clearly demonstrated the decisive role of speed in the ultimate success of establishment. Considering the advantage of the resistant biotype at shallow depths, particularly in clay soils, it is recommended to use competitive crops with high shading ability to neutralize this biotype's germination speed advantage. Additionally, careful monitoring of fields for the presence of resistant biotypes and selecting seedbeds with appropriate texture can be effective in designing integrated weed management programs. Ultimately, integrating these ecology-based strategies, founded on the findings of this research, can significantly contribute to reducing reliance on herbicides and achieving a more sustainable agricultural system.
According to the findings, although the resistant biotype demonstrates its superiority under optimal conditions (shallow depths and clay soil) with a high emergence index (24.5), this genetic advantage is entirely fragile against a determining factor called seed placement depth. The identification of a critical physiological threshold at a depth of 4-5 cm is considered the key to controlling this weed, where even the most resistant biotype, in an unequal battle against darkness and soil mechanical pressure, exhausts its energy reserves before reaching the light and never succeeds in emerging. The resistant biotype achieved the highest survival percentage (98.61%) and the highest emergence rate (emergence index of 16.50) at a depth of 1 cm in clay soil. At the 1 cm depth, the mean emergence percentage in clay soil was 98.66% for both biotypes, while in silt soil it reached 84% for the resistant biotype. At the 6 cm depth in silt soil, the survival percentage of the susceptible biotype was 0%, indicating the destructive interaction of depth and unsuitable soil texture. The decrease in emergence percentage from over 90% at shallow depths to below 20% at depths greater than 4 cm clearly indicates the depletion of seed energy reserves before reaching the soil surface. By implementing targeted tillage operations (such as plowing) to bury weed seeds at critical depths, its population can be fundamentally controlled without reliance on herbicides and without concerns about resistance issues.
Keywords
Subjects
