Agricultural yields of major crops have risen over the past years, keeping up with the growing food and nutrition demands. Advances in classical breeding and agronomic approaches are helpful but year on year increase in yields of crops in many countries have plateaued. To maintain the global supply of food, new technological solutions need to be explored to create higher-yielding varieties and several studies have provided strong support that improving the plants’ photosynthetic processes can help improve yield potential.
Photosynthesis and crop yield
The efficiency by which plants harness energy from sunlight and convert it into carbon dioxide, minerals, and water is an important determinant of final yield. This inspired a team of scientists from Cornell University to engineer a key plant enzyme called Rubisco and introduce it to e.coli bacteria to create an optimal environment for studying how to speed up photosynthesis. The team believes their finding is a holy grail to improve crop yields.
Their paper, which appeared in Science Daily and journal Nature Plants, detailed that crop yields would improve if plants would accelerate their photosynthesis process. This is because they can speed up converting carbon dioxide, light, and water into oxygen. Eventually, the crop will turn it into sucrose, which the crop will use for building new plant tissue and for energy.
The Rubisco enzyme
For their study, they focused on the Rubisco, a slow enzyme involved in the first major step of carbon fixation. It is a process where the atmospheric carbon dioxide is converted by photosynthetic organisms to energy-rich molecules. Sometimes, Rubisco interacting with Co2 cause a reaction with oxygen from the air and when it happens, it wastes energy and creates a toxic byproduct. Thereby, it makes photosynthesis inefficient.
Maureen Hanson, professor of plant molecular biology at Cornell, explained that it is better if Rubisco would work faster and not interact with oxygen. This is their goal for the study. So, they took the Rubisco enzyme from tobacco plants and engineer it into e.coli bacteria. Most varieties of e.coli are harmless or may cause relatively brief diarrhea but a few strains can cause vomiting, bloody diarrhea, and severe abdominal cramps.
In plant studies, tobacco plants are commonly used as a model. Hanson said that their team wanted to make mutations to enhance the Rubisco enzyme. After that, they want to test it in e.coli bacteria.
Since the e.coli reproduce so rapidly, the researchers find it easy to test an altered Rubisco and get results the following day. Normally, it would take a few months to get the results if you introduce a new Rubisco into a plant. Initial work was conducted by another team that engineered the enzyme into e.coli bacteria led to very weak expression of Rubisco. In plants, the enzyme is composed of eight small and large subunits. The presence of multiple versions of the enzyme and its complex process in plants made it difficult to experiment with Rubisco, the team added.
The present study managed to break down that complex process. It was likewise able to express a single type of small subunit and a single type of large subunit together in e.coli to understand the properties of Rubisco. By achieving this, the researchers were able to attain an expression of the enzyme in e.coli that matched what is found in plants. As the team discovered how to engineer new versions of Rubisco in e.coli, this means they can also determine whether the properties of the said enzyme are better. After that, they can take the improved enzyme and put it into a plant to improve crop yields.
The Organisation for Economic Co-operation and Development, an inter-governmental economic organization founded to stimulate economic progress and world trade, explains that crop production depends on the availability of arable land in an area and is affected by macro-economic uncertainty, yields, and consumption patterns. It likewise has a great incidence of the prices of agricultural commodities.
OECD countries with the highest wheat production in 2019 include New Zealand (8.8 tons/hectare), United Kingdom (8.2), Egypt (6.6), Saudi Arabia (6.4), and Chile (6.2). For maize crop, Israel ranks first with 29.3 tons production per hectare, followed by Chile (12.2), New Zealand (10.9), United States (10.5), and Canada (9.2). For rice crops, Australia has the highest yield with 11.5 tons per hectare. Other countries top in the list includes Egypt (6.8), Mexico (6.1), United States (6.0), and Russia (5.4).
Agronomy expert Tanja Folnovic, who was not involved in the study, opined that the climate of croplands greatly affects farming. While these conditions can’t be changed, farmers can adjust it using farming techniques, such as conservation agriculture, intercropping, mulching, agroforestry, integrated crop-livestock management, improved water management, and improved grazing. She also encouraged the use of innovative practices, such as better flood- and drought-tolerant crops, weather forecasts, and livestock and crop insurance.
Closing yield gaps
The yield gap is the difference between what farm yields in crops to what it could yield. Folnovic added that to meet the global demand for food, it is important to make croplands more productive. However, many croplands fall short of their full yield potential for their climate. To help close yield gaps, she advised increasing water use efficiency and changing crop use and diet. About 35% of crop production is for animal feed, 62% is for food, and 3% is for fuel and other industrial uses. Changing more crop production toward food use can potentially add about 50% more calories to the worldwide food supply, she went on.
Folnovic advises and the findings of Cornell University researchers are important as the most recent UN data estimates that the world population is increasing rapidly and is expected to reach 8 billion by 2024. Such an exponential increase in population is a serious threat to sustainable global food production, considering that there is no associated increase in arable land. Not to mention that the rapid global environmental changes also present a threat to crop production. Engineering crops have the potential to achieve greater yields and can help ensure food availability for the world population.