As the agricultural world continually seeks to balance crop cultivation with weed management, scientists have recently made remarkable progress in understanding how resistant weeds thwart herbicidal effects. A breakthrough study led by Daniel R. Kohlhase of the Department of Agronomy at Iowa State University, along with colleagues from the U.S. Department of Agriculture (USDA)-Agricultural Research Service (ARS), sheds light on the molecular responses of waterhemp (Amaranthus tuberculatus) to a class of herbicides that interfere with a key plant enzyme, 4-hydroxyphenylpyruvate dioxygenase (HPPD). The study, published in BMC Plant Biology, employs RNA-sequencing (RNA-seq) technology to explore the genomic mechanisms behind waterhemp’s remarkable resilience. This article delves into the study’s findings and implications for the future of weed management and agricultural practices.
Digital Object Identifier (DOI): 10.1186/s12870-019-1795-x
Introduction
Waterhemp poses a significant challenge to farmers, especially in the Midwestern United States, by competing with crops like maize (Zea mays L.) and soybean (Glycine max L. Merr.) and causing substantial yield losses. Herbicide resistance in waterhemp, particularly to HPPD inhibitors like mesotrione, has been documented as early as 2011 in some populations, leading to even greater challenges in controlling this robust weed.
More recent studies have described the genetic mechanism and heritability of herbicide resistance, but the whole-plant molecular response to herbicide exposure had yet to be elucidated before Kohlhase and colleagues embarked on their investigative journey.
Study Overview
The team worked with HPPD-herbicide resistant and susceptible waterhemp genotypes to examine their gene expression profiles at multiple time points following herbicide application. By employing a de novo transcriptome assembly approach, the study identified transcripts unique to a particular genotype, herbicide treatment, or temporal snapshot post-exposure, paving the way for an unprecedented look into the weed’s adaptive capabilities.
Key Findings
Kohlhase’s team discovered that the herbicidal response in both resistant and susceptible waterhemp genotypes manifested rapidly, within as little as 3 hours after treatment. Additionally, the gene expression patterns between the two genotypes showed minimal overlap, indicating that each employs a distinct strategy to confront the herbicide’s mode of action.
The identification of candidate single nucleotide polymorphisms (SNPs) provided a genetic fingerprint for distinguishing between resistant and susceptible populations, offering an invaluable tool for future studies.
Implications for Agronomy and Plant Science
The insights gained from the study’s transcriptome and SNP data serve multiple purposes. For the field of agronomy and plant science, they promise to reinforce weed management strategies by unraveling the genetic intricacies of herbicide resistance and accelerating the development of next-generation herbicides.
For crop science, they underscore the importance of harnessing similar adaptive traits in crops, which could vastly improve agricultural resilience.
Research Significance and Further Applications
This pioneering investigation is significant not only for its practical applications but also for the technological triumph it represents in the world of plant genomics. The deployment of RNA-seq technology provided a clear resolution of the genome-wide response of waterhemp to HPPD inhibitors, opening new avenues for understanding herbicide resistance.
Future studies can utilize these findings to design herbicides that target specific pathways or to enhance crop defenses against a variety of biotic and abiotic stresses.
Keywords
1. Herbicide Resistance Waterhemp
2. RNA Sequencing Weed Management
3. HPPD Inhibitors in Agriculture
4. Genomic Adaptation in Weeds
5. Amaranthus tuberculatus Herbicide Response
References
1. Kohlhase, D. R., O’Rourke, J. A., Owen, M. D. K., & Graham, M. A. (2019). Using RNA-seq to characterize responses to 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor herbicide resistance in waterhemp (Amaranthus tuberculatus). BMC Plant Biology, 19(1), 182. https://doi.org/10.1186/s12870-019-1795-x
2. Hausman, N. E., Singh, S., Tranel, P. J., Riechers, D. E., Kaundun, S. S., Polge, N. D., et al. (2011). Resistance to HPPD-inhibiting herbicides in a population of waterhemp (Amaranthus tuberculatus) from Illinois, United States. Pest Management Science, 67(3), 258–261.
3. Oliveira, M. C., Jhala, A. J., Gaines, T., Irmak, S., Amundsen, K., Scott, J. E., et al. (2017). Confirmation and control of HPPD-inhibiting herbicide-resistant waterhemp (Amaranthus tuberculatus) in Nebraska. Weed Technology, 31(1), 67–79.
4. Délye, C., Jasieniuk, M., & Le Corre, V. (2013). Deciphering the evolution of herbicide resistance in weeds. Trends in Genetics, 29(11), 649–658.
5. Heap, I. The International Survey of Herbicide Resistant Weeds. [Internet]. [cited February 19, 2019]. Available from: http://www.weedscience.org