“Kaorino,” ultra-early season strawberry resistant to anthracnose

Strawberry is the Mie Prefecture’s important farm produce that is the second largest in gross production . The Mie Prefectural Agricultural Research Institute has worked on the development of a strawberry variety resistant to anthracnose causing great damage across the country since around 1990. Anthracnose affects strawberry seedlings from early summer to autumn. It is highly infectious dangerous disease. We interviewed Hatsuyoshi Kitamura, Principal Researcher and Manager of the Vegetable Horticulture Section, the Production Technology Lab of the Mie Prefectural Agricultural Research Institute, and Hiroya Izuoka, Manager of the Research Strategy Section, the Fundamental Technology Lab. They have been engaged in the development of an anthracnose-resistant variety “Kaorino.”

Damage by anthracnose spread the country and seedlings died.

Please tell me the outline of the Mie Prefectural Agricultural Research Institute and how you have come to develop the anthracnose-resistant variety “Kaorino.”

Izuoka:The Mie Prefectural Agricultural Research Institute was set up in Tsu City in 1877 as the agricultural experiment station. After relocation and merger, the institute was finally moved to the current location in Matsusaka City in 1970. The Mie Prefectural Agricultural Research Institute has 44 researchers and 42 technical and administrative staff members, or 86 employees in total. There are five laboratories in the prefecture. The Fundamental Technology Lab and the Production Technology Lab are located here in Matsusaka City. Labs in other locations are the Iga Agricultural Lab for the research of rice and grapes, the Kinan Fruit Lab for Citrus unshiu and the Tea, Flower and Garden Tree Lab for Ise tea, flowers and trees. The institute in Matsusaka City is in the same building as the Central Agricultural Development and Extension Center and thus we are in the environment in which research and promotion of practical use are carried out in collaboration.

Kitamura:Strawberry cultivation in Mie Prefecture began in around 1960. As rice paddies were converted, strawberry fields increased in area and strawberries were developed into one of the main produce. The variety grown those days was vulnerable to anthracnose and there were no resistant varieties available. They were seriously damaged by the disease just as in other production regions. For the development of strawberry production, the prefecture launched the development of a resistant variety.

What research did you carry out to develop a variety resistant to anthracnose?

Kitamura:To begin with, we bred “Early Hoko” long believed to be resistant to anthracnose with “Nyoho,” “Toyonoka” and other varieties not resistant to the disease but high in quality and early-ripening trait to create more resistant hybrids. Now, there are varieties resistant to anthracnose, early ripening, high in quality and high yielding like “Kaorino” and varieties developed by the National Agriculture and Food Research Organization. Those days, as the main purposes of strawberry hybrids were to improve the taste, appearances and yields, there was no commercial variety resistant to anthracnose. We had no other choice but to create hybrid parents with desirable traits for ourselves. We injected Colletorichum acutatum, anthracnose fungus, into hybrid strains we created and picked out those that survived. We repeated this process. About 10 years later, we developed a variety resistant to anthracnose “Sanchigo.” “Sanchigo” was not put into commercial application as it ripened late and the cultivation method was not suitable for the producers.

Being resistant to anthracnose was not enough to encourage farmers to grow the new variety.

Kitamura:Strawberries fetch the highest price in the Christmas season. If strawberries are not harvested in time for the season, the producers will miss the chance to sell their strawberries at a high price. We should have developed a variety not only resistant to anthracnose but also meeting producers’ needs such as harvest time and yield. To meet the needs, we repeated complicated breeding (Figure 2) and developed “Kaorino” at last. This variety of strawberry is characterized by a fresh and elegant aroma as the name suggests and gentle sweetness with little sourness.

Strawberries are one of a few agricultural products sold with their variety names. I am not sure how much consumers are conscious but we expect they will remember the name if they have it and like it.

“Kaorino” adaptable to climate change impacts

What did you do to encourage the farmers to grow “Kaorino”?

Kitamura:We have promoted the new variety, working closely with various organizations, such as the prefecture’s extension center, the producer’s group and seedling suppliers. As a different variety required a different cultivation method, farmers in some areas didn’t agree to produce “Kaorino.” In such an area, we asked a key producer to grow it and the cultivation spread to other producers later by word of mouth.
“Kaorino” is an anthracnose-resistant variety but it can be infected if it is cultivated in an improper way or under poor conditions. To avoid that, we compiled cultivation guidelines combining the activities of the extension workers and our research findings and improved them repeatedly.
In Mie Prefecture, strawberries were produced at small-scale farms and therefore a regional brand strategy was not suitable unlike a major production region. Furthermore, Mie Prefecture was not alone in suffering damage by anthracnose. Under the circumstances, we decided not to limit production within the prefecture and advertise to consumers in cooperation with producers including those in other prefectures.
As a result, more and more producers were choosing “Kaorino” inside and outside Mie Prefecture. “Kaorino” became one of the main varieties in Mie. The number of registered producers in other prefectures exceeded 1,000. The development has required a long time and labor but I really feel the effort has paid off.

How does climate change affect the spread of anthracnose?

Kitamura:Anthracnose spreads via raindrops. As the seedlings are usually reared outdoors from spring to autumn, the spread is considered to be subject to climate change impacts. Anthracnose is prone to occur at a high air temperature. If global warming progresses, anthracnose is expected to spread more easily.

Are there any problems due to climate change impacts in strawberry production?

Kitamura:Flowering of strawberry is induced by short day and low temperature in summer and autumn. Recently, floral induction is often delayed due to high temperature in summer and the start of harvest is delayed increasingly. For example, in comparison between “Kaorino” and “Akihime” in the start of harvest in 2010, when the average air temperature was high, the harvest of “Akihime” was delayed due to high temperatures but the harvest of “Kaorino” was started relatively early. If harvest is delayed, the strawberries will miss the season when they can fetch a high price. That is critical to producers and distributors. “Kaorino” can be said to be adaptable to climate change in that respect as well. I am not a specialist in meteorology. Still I realize recent extreme weather, a rise in summer temperature and changes in rainfall. Our institute will need to consider countermeasures.

Aiming for a popular variety in any era

While considering climate change impacts, what studies are you considering taking up in the future? Please tell me future outlooks.

Kitamura:“Kaorino” is now being produced in not only warm areas but also areas on the Sea of Japan side and the Tohoku region. One of the reasons, I hear, is that “Kaorino” is relatively resistant to low temperatures in winter. It is important to communicate the cultivation method suitable for those areas and added values effectively.

There are trends in strawberry taste and color. Some varieties are created to meet the needs. We are hoping to create varieties with traits constantly in demand in any era. One of such traits will be resistance to diseases. These efforts often lead directly to an increase in incomes of producers and I feel my job very rewarding. Having people I can cooperate with, such as researchers and producers inside and outside the prefecture, is really encouraging.

Strawberry producers are aging and suffering a shortage of successors. We are considering developing a seed-propagated cultivar that saves labor in rearing seedlings, in addition to those resistant to diseases, high in quality and high yielding.

Izuoka:Unlike strawberries grown in a greenhouse, rice and orchard trees are grown by open field cultivation and therefore they can be affected more seriously by climate change. We will seriously consider measures for those crops besides strawberries.

References

• Handbook “Mie Prefectural Agricultural Research Institute”
• Features of “Kaorino” bred by Mie Prefecture and essentials of the cultivation. October 2013. Mie Prefecture
• 2018 Mie Prefecture Climate Change Impact Report – Now Begins a Challenge of Adaptation. March 2019. Mie Prefecture
• Breeding and Extension of the New Strawberry Cultivar ‘Kaorino’ with Extremely Early Flowering and Resistance to Anthracnose. 2015