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‘Shedding new light on a hot topic’: Researchers unravel tuberisation of potatoes

This article was written and prepared by Jorge Luis Alonso G.

Researchers Julia E. Stockem (Solynta and Wageningen University and Research), Michiel E. de Vries (Solynta), and Paul C. Struik (Wageningen University and Research) conducted three greenhouse experiments to evaluate the effects of light intensity, temperature and the proportion of far-red light in the light spectrum on tuber production.

The research project took place at Solynta facilities in Wageningen, using Solynta potato genotypes. According to the research team, their findings will help breeding for heat tolerant varieties and optimise growing conditions for tuber production in indoor farming systems.

The results of the study were first published in the journal Annals of Applied Biology in May, 2023.

The article below is a summary of the scientific paper.

Recently, researchers have made significant progress in producing new potato varieties through hybrid breeding. This approach involves continuously self-breeding potato plants until consistent and uniform lines are achieved. When two of these inbred lines are crossed, the result is a true hybrid seed (HTPS) genotype.

This method of potato breeding has several advantages. First, it’s faster because of the straightforward genetic process. Second, it is easier to transport and store these true seeds. Finally, compared to the traditional method of growing potatoes, these seeds are primarily disease-free.

When it comes to multiplying potato starter material, there are several methods available. For example, mini-tubers can be grown from in vitro plantlets under carefully controlled conditions. In addition, hybrid breeding can produce true seeds that produce small seedling tubers. These methods not only provide disease resistance but also allow for growth in controlled environments.

Plants have the flexibility to be grown in a variety of media: in greenhouses with soil, in soilless media, or even in vertical farming systems. The latter is particularly advantageous as it guarantees optimal growth conditions regardless of location, climate or specific growing seasons.

Environmental factors, of which light and temperature are the most important, play a significant role in the growth and yield of potatoes. In conditions where water is abundant, these two elements are the primary drivers of potato growth.

For more focused research, climate chambers are an excellent option. These rooms provide controlled environments that allow researchers to identify the individual effects of different environmental factors on tuber yield. This understanding is paramount when it comes to maximizing minituber yields in vertical farms or understanding the broader nuances of potato development.

Optimizing temperature and light for potato tuber production

A closer look at temperature reveals that it plays a crucial role in the development of potatoes. Elevated temperatures can stimulate sprout growth, but can also delay tuber formation. A moderate temperature, around 17°C, is generally ideal for tuber formation. However, this can vary from variety to variety and can be influenced by photoperiod.

The StSP6A signal is responsible for inducing tuberization in potatoes. Unfortunately, high temperatures can disrupt its expression and other related hormonal signals, resulting in inhibited tuber growth.

Other negative effects of high temperatures include a reduction in leaf area, a decrease in photosynthetic efficiency, and an inhibition of starch accumulation in tubers.

Light, characterized by its photoperiod, intensity and spectrum, is another essential factor. Photoperiod, for example, has a major impact on plant development. Some potato varieties require shorter days to produce tubers. Meanwhile, light intensity affects plant structure and CO2 assimilation rates. The spectrum of light also has a noticeable effect, with far-red light accelerating tuber initiation and blue light delaying the process.

Given the complex nature of plant growth and the various environmental factors at play, controlled plant production facilities are invaluable. They facilitate the fine-tuning of conditions, especially for minituber production.

Recognizing the diverse responses of potato genotypes to factors such as light and temperature, researchers have conducted studies in climate chambers. By zooming in on the influence of light intensity and spectrum on day-neutral potato varieties, these studies aim to deepen our understanding of how these factors affect potato tuber production.

Such knowledge will not only improve growing conditions in controlled environments but also lay the groundwork for innovations in vertical potato farming and even space-based agriculture.

The key role of environmental factors

The effects of high temperature, light intensity and light spectrum on diploid potato genotypes have been studied in detail in three greenhouse trials at Wageningen University and Research.

To study the effect of temperature on tuber production: The research involved three separate tests focusing on different temperature changes. It found that as temperatures increased, the tubers (a type of plant) became lighter because there were fewer and they were smaller. This observation is consistent with previous studies, especially those done on a type of plant called tetraploid varieties. For example, different plant varieties showed different responses to temperature changes. They also observed that larger differences between day and night temperatures sometimes made tubers heavier.

Shedding light on the influence of intensity on yield: The study found that increasing the brightness of the light improved the number of tubers and overall yield. The brighter light also caused the plants to absorb CO2 more quickly. Interestingly, a type of plant called diploid inbred lines produced more tubers when the light was brighter. However, it’s important to note that not all tests showed the same responses to these light changes.

Deciphering the role of far-red light in tuber production: The researchers changed the amount of far-red light and this affected how the plants grew and developed. Specifically, the balance between regular red light and far-red light affected things like when certain plants flowered. In potatoes, they found a clear link between flowering and tuber formation. Consistent with previous research, they found that more tubers were produced when there was a lot of far-red light.

Understanding the dynamic between light and temperature: Low light and high temperatures both reduced tuber weight. But interestingly, when there was a lot of light, the negative effects of high temperatures on tuber weight were reduced. This is consistent with what previous studies have found, suggesting that light levels can alter how temperature affects tuber weight.

Conclusion

In this study, researchers investigated how light intensity, the proportion of far-red light, and temperature affect various aspects of diploid potato inbred lines. Specifically, they looked at the number, weight, and overall yield of tubers.

When the light intensity or the proportion of far-red light was increased, there was a noticeable boost in the total fresh weight of the tubers. This increase was due to a rise in the number of tubers each plant produced.

On the temperature front, both the count and weight of tubers were influenced by the average temperature. Interestingly, while varying day and night temperatures had an impact on tuber weight, the average temperature played a more substantial role.

In fact, as average temperatures rose, there was a decrease in the number and weight of the tubers. However, a significant difference between day and night temperatures led to the production of heavier tubers.

The study also shed light on the different responses of these inbred lines to higher temperatures. Despite this variation, there was no direct relationship to light intensity.

This variation in temperature sensitivity has important implications. It may pave the way for breeding potatoes that can better withstand temperature-related stresses. By combining both susceptible and resistant lines, researchers can develop mapping populations. These populations are then critical for in-depth molecular research to better understand how tubers form at elevated temperatures.

It’s important to maintain the right climatic conditions when conducting such studies, especially since plants can respond differently to different temperatures under different lighting conditions. With the threat of climate change looming, the need to breed stress-tolerant crops is paramount.

Potatoes that can withstand these changes could play a key role in ensuring food security in the future. Finally, the results of this research highlight the potential benefits of manipulating factors such as light intensity, temperature, and the ratio of far-red light in the growth process of potatoes. This is particularly relevant for the indoor production of mini or micro tubers.

The primary goal in these systems is to produce a large number of tubers without compromising on weight, leading to a more efficient production process. There’s potential for future research to investigate whether increasing far-red light levels can lead to even higher tuber counts.

Source: Stockem, J. E., de Vries, M. E., & Struik, P. C. (2023). Shedding light on a hot topic: Tuberisation in potato. Annals of Applied Biology, 183(2), 170–180. https://doi.org/10.1111/aab.12844
Author: This article was written and prepared by Jorge Luis Alonso G, based on the original scientific paper.
Photo: Credit Solynta

Editor & Publisher: Lukie Pieterse


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