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726. What is the Good Relationship Between Fruits, People and the Earth? ~Tropics and Subtropics are Treasure Troves of Fruits~

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726. What is the Good Relationship Between Fruits, People and the Earth? ~ Tropics and Subtropics are Treasure Troves of Fruits ~

Today's Pick up is a translation of an article in Japanese published in JIRCAS Koho magazine and introduces research on building good relationships between fruits, people, and the earth from the viewpoint of a young researcher of JIRCAS.

Fruits are part of the diet in Southeast Asia

How often do you eat fruits? Japanese supermarkets are gorgeous with seasonal fruits and beautifully cut fruits. Japanese people may have a strong image of fruit as something to be eaten occasionally as an after-dinner dessert or as a luxury item to be given as a gift. However, people in Thailand, Laos, and other Southeast Asian countries have a much different image of fruits. A wide variety of fruits are available at markets throughout the year at reasonable prices, and fruit has become part of the daily diet for good health. A wide variety of fruits are grown in different parts of the country, and fresh fruits are readily available at any time of the year.

Fruits are rich in antioxidants

Now, let's talk about the nutritional benefits of fruits. Fruits contain not only sugar as a source of energy, but also minerals and vitamins that are essential for human life, as well as various functional components that maintain good health. The following is a brief introduction to tropical fruits and what kind of nutrition they contain. You will find many fruits that are unfamiliar to Japanese and other people living in temperate regions. Let's start with fruits rich in antioxidants. You have probably heard of polyphenols (anthocyanins, tannins, etc.) and carotenoids, which are well-known antioxidants. Mangoes and passion fruit are rich in vitamins and carotenoids. Also, although Japanese people are not familiar with it, you can take anthocyanins by eating jabuticaba, a "tropical grape" with a beautiful purple color. Sapodilla, which looks like a potato and tastes like a dried persimmon, contains high levels of tannins, just like persimmons.

Seeds play a leading role in some fruits

Next, we turn our attention to the seeds. Fruits are not only eaten for their pulp. The famous jackfruit, one of the world's largest fruits, is delicious both in its pulp and seeds, and is rich in protein. Nuts such as cashews and macadamias, and avocados are high in unsaturated fatty acids. Although they may seem a bit far from the image of fruits, chocolate, which we Japanese usually eat, and pepper, a spice used in cooking, are processed from the fruits of tropical fruit trees called cacao and black pepper, respectively. In addition, there are seeds used as medicine. Medicinal ingredients with anti-cancer properties have been found in the seeds of fruit trees of the Annonaceae family, including cherimoya, sugar apple, and atemoya. In addition, the dried pulp of the longan, a relative species of lychee, has long been used as a herbal medicine.

Let's get healthy with fruits!

As you can see, tropical and subtropical fruit trees are used in a surprisingly wide range of ways. By incorporating them into your daily diet in various forms, you can enjoy the nutritional benefits in a delicious and enjoyable way, and help maintain good health.

Even if you are not a fan of fruits, you may find something you like among the many tropical and subtropical fruits that are available in a wide variety of ways. You may be able to find something you like among the many tropical and subtropical fruits. A decade ago, "tropical fruits" were still a rarity in Japan and other temperate regions, but nowadays you can buy a wide variety of tropical fruits, from subtropical fruits such as avocado and passion fruit to mango and pineapple, and sometimes even tropical fruits such as durian and mangosteen.

The year 2021 was the International Year of Fruits and Vegetables (IYFV2021) as designated by the United Nations. The idea of "healthy eating with fruits" is spreading around the world.

Why is it hard for mango tree to bear fruit?

We buy and eat the beautiful fruits in the produce aisle, but when we actually grow fruit trees, it is easy for the fruit to vary in size, color, shape, and taste, making it difficult to produce fruit of consistent quality. Often, flowers do not bloom and do not bear fruits. Mangoes, for example, are notoriously difficult to produce. A "panicle" inflorescence of several thousand to more than 10,000 small flowers is formed at the tip of a branch, but only a few of these flowers become fruit at most. This is thought to be due in part to the fact that there are too many flowers blooming and competing for nutrients. It has been found that removing some of the flower buds in the panicle to reduce the number of flowers (Matsuda & Ogata, 2021) has resulted in more stable fruit set. We are conducting research to make this technology usable in the growers’ orchards.

Stress is the enemy of fruit tree growth!

Fruit orchards are subject to environmental stresses such as high or low temperatures, drought or excessive humidity, high light or lack of sunlight, and so on. In order to produce fruit consistently, fruit trees must be protected from these strong environmental stresses.

In particular, high temperatures are becoming a problem due to climate change. This is complicated by the fact that different types of fruit trees need to be protected from the damaging effects of high temperatures in different ways. For example, let us discuss passion fruit and cherimoya, which are native to the tropical highlands. The climate in the tropical highlands is cool throughout the year, so when temperatures exceed 30°C (86°F), both species are less likely to produce fruit, even if they flower. However, the stamens of the cherimoya are more sensitive to high temperatures than the pistil, so it is important to keep the pollen as cool as possible during pollination. On the other hand, the opposite is true for passionfruit: the stamens are more resistant to high temperatures than the pistil, and pollen germinates rather well at temperatures above 30°C (Matsuda & Ogata, 2020). Thus, even for pollination alone, physiological responses to the environment differ among tree species, and even within the same tree species, there are differences among cultivars.

Passing on the genetic resources of tropical fruit trees to the future

We have introduced the flowering of mango and the temperature of passionfruit and cherimoya as examples, but it will be useful for the cultivation of fruit trees if we can unravel the mechanisms of each fruit and accumulate information. The global environment is constantly changing. In order to cope with the changing environment, it is necessary to study a wide variety of genetic resources that show various physiological responses and utilize the useful ones. The Tropical Agriculture Research Front on Ishigaki Island has hundreds of genetic resources of more than 40 species of tropical fruit trees. It is our important job as researchers to carefully maintain these genetic resources so that they can be used by future researchers to solve problems while working on research to solve current and near-term problems.


Note: This is a translation (with some modifications) of an article in Japanese published in JIRCAS Koho (Public Relations) magazine.


Matsuda, H. and T. Ogata 2020. Varietal Differences in Thermal Response of Passion Fruit Pollen Germination. Tropical Agriculture and Development 64: 90–96.

Matsuda, H. and T. Ogata 2021. Effects of Floral Disbudding on ‘Irwin’ Mango Flowering and Fruit Set. Tropical Agriculture and Development 65: 132–137.


Contributor: MATSUDA Hiroshi (Tropical Agriculture Research Front)