By Shaina Eagle, Global Disease Biology ’24
Feeding the world’s 8 billion– and growing– people [2] is an Augean task that requires cooperation between farmers, scientists, government agencies, and industry stakeholders across the globe. Agriculture and climate are deeply intertwined and climate conditions play a critical role in determining agricultural productivity and have a significant impact on global food security. The climate crisis poses immense challenges to food security and the farmers whose livelihoods depend on crop production. As the consequences of the climate crisis increase and intensify, developing resilient agricultural systems is essential to ensuring that our food and those who grow it can adapt without further depleting carbon and water resources.
Climate-smart agriculture identifies technologies that can best respond to the impacts of climate change, such as increasing temperatures and heat waves, changing rainfall patterns, severe storms, drought, and wildfires that adversely affect crop yield and quality [1]. Agronomists, plant biologists, and farmers are working to develop crops that will increase sustainable production and better withstand a changing climate via various genetic techniques.
Clonal Seeds
A team including a UC Davis Assistant Professor of Plant Sciences, Imtiyaz Khanday, genetically engineered rice seeds that reproduce clonally, or without sexual reproduction, in order to maintain the desirable traits found in the F1 generation (Vernet et al. 2022). They developed a breeding technique that allows for high-frequency production– or the ability to produce a large quantity in a short amount of time in a cost-effective manner– of hybrid rice using synthetic apomixis. Apomixis, a type of asexual reproduction in plants, allows for the production of seeds without fertilization, which can be useful in hybrid breeding programs. The study used CRISPR/Cas9 gene editing to introduce mutations in the genes responsible for sexual reproduction in rice. These seeds were planted and produced the F1 generation of plants, which were genetically stable and had high yield potential. Subsequent generations were clonally propagated from the F1 plants. In agriculture, high-frequency production has the ability to produce a large number of crops or seeds using advanced breeding techniques. High-frequency production is important for meeting the increasing demand for food and other agricultural products, as well as for improving the efficiency and profitability of farming operations.
The study suggests that this technique could be a valuable tool for plant breeders to produce high-quality hybrid rice seeds with more efficient and cost-effective methods. Clonal propagation can help maintain desirable traits as the climate crisis threatens agriculture, such as disease resistance, yield potential, or drought tolerance that might otherwise be lost through sexual reproduction. It is a faster alternative to sexual reproduction methods such as cross-breeding, which can take several generations and require extensive testing to identify desirable traits.
De Novo Domestication
De novo is a Latin term that means “from the beginning” or “anew”. In the context of genetics and plant breeding, de novo refers to the creation of something new or the starting point for the development of a new organism or trait. De novo domestication, for example, refers to the process of identifying and selecting wild plants with desirable traits and developing them into new crops that are better adapted to agricultural use. This approach differs from traditional domestication, which involves selecting and breeding plants that have already been used by humans for thousands of years. Eckhardt et al. highlight the potential benefits of de novo domestication, including the creation of new crops that are better adapted to changing environmental conditions, and the conservation of genetic diversity by using previously unexploited wild species.
A study by Lemmon et al. (2021) aimed to create a domesticated tomato variety with desirable traits by introducing mutations into genes related to fruit size and shape via CRISPR-Cas9. While there are many tomato cultivars available, they often have limitations in terms of yield, quality, or other traits that are important for consumers and growers. Therefore, there is a need to develop new tomato varieties with improved characteristics, and the de novo domestication of a wild tomato variety using genome editing offers a potential solution to this challenge. The domesticated variety has several desirable traits, including larger fruit size, smoother fruit shape, reduced seed count, and prolonged fruit shelf life. Additionally, the domesticated tomato plants have increased branching and produced more fruit per plant compared to the wild-type tomato plants.
Kaul et al. (2022) conducted a de novo genome assembly of rice bean (Vigna umbellata), a nutritionally rich crop with potential for future domestication. The study revealed novel insights into the crop’s flowering potential, habit, and palatability, all of which are important traits for efficient domestication. Flowering potential refers to the crop’s ability to produce flowers, which is important for seed production and crop yield. Understanding the genetic basis of flowering potential can help breeders select plants that flower earlier or later, depending on their needs. Habit refers to the overall growth pattern of the plant, such as its height, branching, and leaf morphology. Understanding the genetic basis of habit can help breeders select for plants that are more suitable for specific growing conditions or cultivation methods. Palatability refers to the taste and nutritional value of the crop, which are important factors for its acceptance as a food source. Identifying genes involved in carbohydrate metabolism and stress response can help breeders develop crops with better nutritional value and resistance to environmental stressors. Overall, these traits are desirable because they can contribute to the development of a more productive, nutritious, and resilient crop. The researchers also identified genes involved in key pathways such as carbohydrate metabolism, plant growth and development, and stress response. Climate change is expected to have a significant impact on crop yields, water availability, and soil fertility. One NASA study found that maize yields may decrease by 24% by 2030 [3]. Understanding the genetic basis of stress response and carbohydrate metabolism can help breeders develop crops that are more resilient to environmental stressors, such as drought, heat, and pests. Furthermore, identifying genes involved in plant growth and development allows breeders to introduce desirable traits, such as earlier flowering or increased yield. This is important for domestication because it can help accelerate the process of crop improvement and make it easier to develop new varieties with desirable traits. Overall, the genes identified in the study provide a foundation for developing crops that are better adapted to changing environmental conditions and more suitable for cultivation, which is crucial for ensuring food security in the face of climate change.
Genetically enhancing common crops
Molero et al. (2023) identified exotic alleles (germplasm unadapted to the target environment) associated with heat tolerance in wheat through genomic analysis and conducted breeding experiments to develop new wheat with improved heat tolerance. The exotic alleles were obtained from wheat lines that originated from diverse regions around the world, including Africa, Asia, and South America. The identified alleles increased heat tolerance in wheat under field conditions, and the effect was consistent across multiple environments. The authors obtained these lines from the International Maize and Wheat Improvement Center (CIMMYT) and used genomic analysis to identify the specific exotic alleles associated with heat tolerance. These alleles were then incorporated into breeding programs to develop new wheat varieties with improved heat tolerance.
The authors used genomic analysis to identify these alleles, which had diverse functions, including regulating heat shock proteins, osmotic stress response, and photosynthesis. The study provides evidence that the use of multiple exotic alleles could lead to the development of wheat varieties with improved heat tolerance under field conditions. The authors crossed the heat-tolerant lines carrying the exotic alleles with local commercial varieties to develop new breeding populations. They then evaluated the heat tolerance of these populations under field conditions to identify the lines with improved heat tolerance. The selected lines were further evaluated in multiple environments to confirm their performance and stability. Heat tolerance was measured by exposing the plants to high temperatures under field conditions and evaluating their performance. Specifically, they conducted experiments in three different environments, including a dry and hot irrigated environment, a semi-arid rainfed environment, and a temperate irrigated environment, all of which are known to impose high-temperature stress on wheat. The authors evaluated multiple traits related to heat tolerance, including yield, plant height, spike length, and the number of spikes per plant.
They also measured physiological traits such as chlorophyll fluorescence, canopy temperature, and photosynthetic activity. By evaluating these traits, they were able to identify the wheat lines with improved heat tolerance. By combining both phenotypic and genomic analyses, they were able to identify the wheat lines and alleles with the greatest potential for improving heat tolerance in wheat under field conditions. This demonstrates the potential for the use of exotic alleles in plant breeding to improve crop performance and address the challenges of climate change.
Porch et al. (2020) report the release of a new tepary bean germplasm (seeds or plant parts that can be passed onto the next generation and are helpful in breeding efforts) called TARS-Tep 23, which exhibits broad abiotic stress tolerance, as well as resistance to rust and common bacterial blight. Tepary bean (Phaseolus acutifolius) is a drought-tolerant legume crop that is native to the southwestern United States and northern Mexico. Tepary beans are generally grown in arid and semi-arid regions of North America, including the Sonoran Desert, Chihuahuan Desert, and the Great Basin. They are also grown in parts of Central and South America. According to FAO statistics, the total world production of tepary beans in 2019 was around 4,000 metric tons. Rust and common bacterial blight are two diseases that can affect the growth and productivity of tepary beans. Rust is a fungal disease that causes orange or brown spots on the leaves and stems of plants, leading to reduced photosynthesis and yield loss. Common bacterial blight is a bacterial disease that can cause wilting, necrosis, and reduced yield in affected plants.
The researchers conducted field trials and laboratory experiments to evaluate the performance and traits of TARS-Tep 23 under different conditions. Laboratory experiments involved inoculating TARS-Tep 23 with rust and common bacterial blight pathogens, then comparing the performance and traits with other tepary beans under these conditions. Field trials were carried out under conditions such as normal rainfall, drought, and heat stress. The results showed that TARS-Tep 23 had higher yields and better growth under drought and heat stress compared to other tepary bean varieties. It also showed high resistance to rust and common bacterial blight. The release of TARS-Tep 23 provides a valuable resource for breeding programs and can contribute to enhancing the productivity and sustainability of tepary bean cultivation. Developing climate-resistant germplasm is a critical resource for crop improvement and biodiversity cultivation, and it is used by plant breeders and researchers to develop new varieties with desirable traits such as disease resistance, stress tolerance, and improved yield.
Conclusion
The urgent need to address the challenge of climate change and its impact on global food security cannot be overemphasized. The world is already experiencing food shortages due to the adverse effects of climate change, and this problem is likely to worsen in the future unless appropriate measures are taken. Significant strides are being made in the research and development of new agricultural and genetic technologies that can engineer crops for climate resiliency. These technologies offer hope for a more sustainable future by enhancing food production, increasing resilience to extreme weather conditions, and mitigating the impact of climate change. However, it is essential to recognize that research and development efforts should not only focus on genetic engineering but should also involve all levels of the food production process, including better management practices, more efficient use of resources, and improved supply chain management. Only by taking a comprehensive approach can we hope to achieve a sustainable and resilient food system that can withstand the challenges of climate change.
References
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