How Many Ways Can Nature Kill the Goose That Laid the Golden Egg? – The Many Mechanisms of Evolved Glyphosate Resistance

Weeding has been the bane of humanity since the dawn of agriculture. For about 70 years, synthetic herbicides have removed much of the drudgery of this onerous task. Glyphosate was introduced as a non-selective herbicide in 1974. Its ideal properties made it a very popular herbicide, and the introduction of glyphosate-resistant (GR) crops allowed its use as a selective herbicide, greatly expanding its use to become the most used herbicide on earth. For farmers who used glyphosate in GR crops, it was the golden age of weed management, as this technology significantly improved the efficacy and reduced the cost of weed management. Weed management was also simplified, an asset that was particularly valuable to part-time farmers. Furthermore, this technology provided the environmental benefits (reduced soil loss and fossil fuel use) of significantly reducing tillage. Farmers saved billions of US$, and weed management became more effective and simple. Indeed, to many farmers, glyphosate with GR crops became the goose that laid the golden egg. After more than 20 years of use, the first cases of GR weeds were reported in the latter 1990s. After a lag period of less than 10 years after the first GR weed was reported, the number of species reported to have evolved glyphosate resistance began to increase in a linear fashion, reaching 53 species in 2021, third only to atrazine (66 species), a much older herbicide and to ALS inhibitors (168 species), which include several different herbicides used in numerous crops since the 1980s. The long lag phase before any resistance was detected led some to believe by the mid-1990s that evolution of resistance was improbable. By this time, glyphosate use was greatly increasing, especially in GR crops, an ideal situation for the evolution of resistance. After this, the number of glyphosate-resistance cases exploded, and the mechanisms of resistance to many of these cases of resistance were determined. A recent, short commentary detailed these mechanisms after a new mechanism of resistance was reported. The number of mechanisms for resistance to no other herbicide comes close to those of glyphosate. In the present paper, we briefly describe the many evolved mechanisms by which weeds have evolved resistance to glyphosate.

Physiological Responses of Wheat Seedlings to Soil Waterlogging Applied after Treatment with Selective Herbicide

Waterlogging impairs crop development and considerably affects plant productivity worldwide. Wheat is sensitive to waterlogging. Serrate® (Syngenta) is a selective herbicide controlling annual grass and broadleaf weeds for use in wheat. To extend the existing information about the physiological effects of selective herbicides (Serrate® in particular) and subsequent waterlogging in wheat, we monitored phenotype alterations and examined key enzymatic and non-enzymatic antioxidant defense systems together with typical oxidative stress biomarkers. Seventeen-day-old wheat (Triticum asetivum L., cv. Sadovo-1) plants were sprayed with Serrate®; 72 h later, waterlogging was applied for 7 days, and then seedlings were left to recover for 96 h. The herbicide did not alter plant phenotype and increased antioxidant defense, along with H2O2 content, confirming the wheat’s tolerance to Serrate®. Evident yellowing and wilting of the leaves were observed at 96 h of recovery in waterlogged wheat, which were stronger in plants subjected to Serrate® + waterlogging. Waterlogging alone and herbicide + waterlogging gradually enhanced the content of stress markers (malondialdehyde, proline, and H2O2), non-enzymatic antioxidants (low-molecular thiols and total phenolics), and the activity of superoxide dismutase, guaiacol peroxidase, and glutathione reductase. The effects of herbicide + waterlogging were stronger than those of waterlogging alone even during recovery, suggesting that Serrate® interacted synergistically with the subsequently applied flooding.

EFFECTS OF SELECTIVE HERBICIDE, ATRAZINE ON THE RHIZOBIUM POPULATION AND NODULATION OF GROUNDNUT (ARACHIS HYPOGEAE)

Atrazine is a selective herbicide used to control weeds in farm operations. The effect of different concentrations of atrazine on Rhizobium population and nodulation in groundnut (Arachis hypogeae) was investigated using Yeast Extract Mannitol Agar (YEMA). The test crop was planted for 90 days after the soil was treated with the various concentration of atrazine. The following parameters; Rhizobium count, nodule count, plant height and germination percentage were observed. The total Rhizobium count obtained at 0% atrazine treatment has 3.0 x 108, 0.1% has 2.9 x 108, 0.5% has 2.5 x 108, 1% has 2.0 x 108, and 3% has 1.4 x 108 all in cfu/ml while the number of root nodules formed was also counted after uproot which was; 0% atrazine treated has 50 nodules, 0.1% has 50 nodules, 0.5% has 30 nodules, 1% has 23 nodules and 3% has 19 nodules. The study revealed that the higher the atrazine concentration the lower the population of Rhizobium, the numbers of root nodules increased with decrease in atrazine concentration and Plant height, root length and germination percentage was also affected adversely by increased in atrazine concentrations.

The Need for New Directions on Conservation Agriculture towards Weed Management: Review

Agriculture conservation practices such as minimal soil disturbance, permanent soil covering by crop residues or cover crops, and crop rotations leads to higher farm productivity. Although conservation agriculture has been adopted in India since its inception, it has now been successfully used in Indo Gangetic Plains irrigated rice-wheat cropping systems and has recently been made known in parts of central India. In conservation agricultural system, cover crops play an important role in weed control, but their adoption level is still limited Changes in tillage practices, planting schemes, and other management techniques can change the soil environment and trigger a significant change in weed flora In intense tillage operations early season weed control could be obtained by turning the soil, which disrupts the germination of weed seeds and the growth of seedlings through burial. In addition, soil-administered herbicides that do not need to be manifested can have less persistence and efficacy in the presence of plant residues that can hinder and bind the chemical before it reaches the soil surface. Selective herbicide compounds that are effective on weed species and not on a specific crop, conferring non-selective herbicide tolerance on a crop may be enormously effectual for potent weed control.

Under-seeding potato with nurse crops in eastern Canada: challenges and opportunities

Soil erosion can be a serious issue in eastern Canada during the 3–5 wk that it takes for potato (Solanum tuberosum L.) to emerge under the cool, humid climatic conditions with frequent heavy rainfall events. Seeding a fast-growing nurse crop at the same time as the potato crop can hold the soil particles in place, reduce surface crusting, and increase water infiltration. The objective of this study, conducted in Prince Edward Island and in New Brunswick in 2017, was to evaluate the effects of under-seeding potato with barley (Hordeum vulgare L.) and winter rye (Secale cereale L.) on marketable potato yield, nitrate dynamics during the growing season, and soil moisture content. Nurse crop growth was terminated mechanically (hilling), with a selective herbicide, or with a nonselective herbicide. Yield increases ranging from 9% to 91% were observed when nurse crop growth was terminated using a nonselective herbicide at both sites. Inconsistent results were obtained when a mechanical method or a selective herbicide were used, with marketable yield reduced at one site and no effect on yield at another site. There was a trend toward higher soil nitrate contents under the control than under the nurse crop treatments, though it was not consistent across sampling times. Results demonstrated that there are circumstances under which nurse crops can be successfully integrated into a potato-based system and provided future hypotheses to test. Potential confounding factors that can impact the nurse crop efficiency are discussed.

Cardiogenic shock with first-degree heart block in a patient with glyphosate-surfactant poisoning

Glyphosate is a commonly used non-selective herbicide in agriculture and aquafarms. Gastrointestinal, respiratory and cardiovascular symptoms are predominant manifestations of glyphosate poisoning. Cardiac dysfunction should be kept as a possibility in patients presenting with shock, and the treatment is mainly supportive. We present such a case.

Phyto-toxic Influence of an Atrazine-based Selective Herbicide – Arda-force® on Onions (Allium cepa L)

Introduction: The constant impact on the environment occasioned by pollution, indiscriminate application of agricultural chemicals, security challenges and crisis in the Niger Delta ecological area of Nigeria has caused severe damage to plants, soil organisms and humans. Aim and Methodology: In this research, onions (Allium cepa L) was exposed to varying concentrations of an atrazine-based selective herbicide Arda-force® to estimate the phyto-toxic effects on the plant species using the Organization for Economic Co-operation and Development, (OECD) protocol #208. Results: The mean effective concentration (EC50) using root growth inhibition produced indications of phyto-toxicity to the exposed species at a concentration of 0.55 ± 0.06 mg/L. Similarly, the maximum root growth inhibition efficiency relative to the control was 65% as recorded in the highest test concentration of 1.25 mg/L. Discussion: The study indicated that constant application / indiscriminate use of the herbicide Arda-force® could cause deleterious influence on these plant and vegetable species, daily consumed by humans as a rich source of anti-oxidants. Conclusion: This study concluded that atrazine-based herbicide Arda-force® used in this assessment resulted in phyto-toxic effects to Allium cepa L. At the exposed concentrations of the herbicide to non-target specie – Allium cepa L. that are integral parts of the ecosystems, the ‘‘harmless’’ status of atrazine acclaimed by the United State Environmental Protection Agency (USEPA) is still very much in doubt.