Source Article: Liu, X., Xiao, Y., Zi, J. et al. Differential effects of low and high temperature stress on pollen germination and tube length of mango (Mangifera indica L.) genotypes. Sci Rep 13, 611 (2023). https://doi.org/10.1038/s41598-023-27917-5
Featured Image Caption: Mango is the fifth most produced fruit crop in the world.Image Source: Ancelin Bonnet, CC0, via Wikimedia Commons
Mango is one of the most popular fruits in the world. People love its sweet and tart flavor and have been cultivating it for thousands of years. Unfortunately, mango flowering is sensitive to temperature, and climate change is increasing global average temperatures and temperature variability. If mango flowering is prevented by temperature stress, mango trees cannot produce fruits. How can we protect mangos from the risks of climate change?
Fortunately, there are many diverse types of mangos with different traits. If we figure out which mango varieties are most resilient to warm and variable temperatures, we can then grow more of these varieties, preparing for climate change and protecting mangoes. But first, scientists needed to find out which varieties grew well at which temperatures.
Mango Pollen Put To The Test
Luckily there are some aspects of flowering that are simple to measure and that reflect temperature stress for many types of plants. As a result, researchers could test which temperatures different mango varieties were least stressed at, and the range of temperatures in which they could produce fruit. They did this by collecting pollen from flowering mango trees of four varieties that are common in China, and exposing samples of pollen to either 1, 3, or 5 hours of various temperatures ranging from 14 to 36 degrees Celsius (57 to 97 degrees Fahrenheit). Then, they germinated, or sprouted, the pollen samples in the lab. Pollen germination, the process of a pollen grain sprouting a tube to fertilize the egg, is an important step in the formation of a fruit.
They measured pollen germination rate, that is, the fraction of the pollen that sprouted. They also measured pollen tube length. The higher the fraction of pollen that sprouted and the longer the pollen tube, the less stressed the plant was and the more fruits it would likely produce at the experimental temperature. By comparing the pollen germination rate and tube length for each of the four varieties at each temperature, the scientists were able to determine the ideal temperature and range of acceptable temperatures for each mango variety to produce fruit.
Different Temperatures For Different Varieties
The researchers found that the four varieties had significantly different temperature tolerances based on pollen germination rate, but all sprouted very successfully at 24 to 30 C (75-86 F). The variety with the coolest temperature preferences, apple mango, could sprout at temperatures between 20 and 30 C (69-87 F), with its maximum germination rate at 27 C (80 F). The apple mango also had the narrowest range of temperatures tolerable for germination. The variety with the warmest temperature preferences, Jinhuang, could sprout at temperatures between 23 and 34 C (73-94 F), with its maximum germination rate at 30 C (87 F). The Renong No. 1 variety had the largest range of tolerable temperatures, from 22 to 34 C (72-93 F).
The researchers also found that the four varieties had very different temperature tolerances based on pollen tube length. Pollen tube length revealed that the same two varieties had the coolest and warmest temperature preferences as in the germination rate experiments. Based on pollen tube length, however, the Deshehari variety had the narrowest range of tolerable temperatures and the shortest pollen tube, even at its most preferred temperature. This finding likely explains the low fruit yield of this variety. Closely aligning with the results of the germination rate experiments, the Renong No. 1 variety had the largest range of tolerable temperatures, from 20.5 to 34 C (69-93 F).
Because of its tolerance for warm temperatures and its large range of tolerable temperatures, the Renong No. 1 variety is likely to fare well in the future given climate change. It can survive both warmer temperatures and more temperature variation. This variety was recommended for planting in warm, subtropical areas, like Southern China, while other varieties might be better suited for slightly cooler climates.
Protecting Food From Climate Change
With climate change currently affecting temperature and precipitation all over the world, similar approaches are being used for many different crops, including chickpeas, potatoes, tomatoes, rice, wheat, and cotton. By testing the range of tolerable temperatures for different varieties of crops, scientists can recommend varieties that are expected to tolerate climate change the best in specific regions.
Scientists can also artificially breed new varieties of crop plants to tolerate climate change. The mango researchers emphasize that new mango varieties should be created that can tolerate higher temperatures and a larger range of temperatures in order to protect mangoes from climate change. In fact, the mango variety that performed the best in the most conditions, Renong No. 1, was intentionally bred by the Chinese Academy of Tropical Agricultural Sciences.
Some scientists even argue that genetically modified (GM) crops have a role to play in adapting to and mitigating climate change. GM crops can greatly increase the amount of food produced on the same amount of farmland, preventing the need to convert new land into farmland. By sparing land from farming, we can prevent a large amount of carbon emissions to the atmosphere, which would otherwise contribute to intensifying climate change. These crops can also be intentionally modified to tolerate climate change, reducing the risk of crop failure and famine.
Overall, as climate change threatens the food production of major crops around the world, scientists have a variety of creative solutions that may help protect food!