Climate change impacts
In the peach-producing area of the Hida region of Gifu Prefecture, blight has been increasingly attacking juvenile peach trees, starting in the trunk and eventually causing trees to wither and die. A variety of factors may contribute to this blight, however, a significant cause may be freeze damage, as the blight commonly affects 3-to 4-year-old juvenile trees, with the damage occurring most frequently in the south-west facing part of the trunk, 10 to 30 cm above the ground. Straw wrapping and whitewash have previously been applied to the tree trunks to remedy this. However, results were nominal, indicating the need for new countermeasures. The incidence of freeze damage is increasing in peach-growing regions throughout Japan, which has been attributed to warmer winters due to global warming in recent years.
Adaptation activity
As the freezing resistance of apples and grapes is known to vary greatly according to the type of rootstock, comparative testing of the freezing resistance of peaches was carried out using different varieties. The results showed that there was a significant difference in the occurrence of freeze damage depending on the rootstocks used, indicating the possibility of alleviating the problem by using more freeze-resistant varieties.
In order to cultivate rootstocks that would be more effective in preventing freeze damage, in 1996, the Gifu Prefectural Research Institute for Agricultural Technology in Hilly and Mountainous Areas selected promising lines from natural hybrid seedlings of the ornamental Hana peach native to Kokufu-cho, Takayama City, Gifu Prefecture. In March 2006, Takao Miyashiro and Gifu Prefecture jointly applied for registration of the variety, which was granted in March 2008 and registered as Hida kokufu beni shidare. The seedling height and trunk diameter of Hida kokufu beni shidare are relatively uniform, they also have robust root mass and root depth, and have a high degree of grafting compatibility with main varieties when used as a rootstock. When used as a rootstock grown from seeds (see Note), it was found that the occurrence of dead wood due to freeze damage to trunks of juvenile trees was greatly reduced compared to common rootstocks (conventional rootstocks) such as Ohatsu momo and Nagano wild peach trees varieties (Fig. 1).
On the other hand, the seeds of the Hida kokufu beni shidare have a deep dormancy, and the germination rate was extremely low in conventional low-temperature storage, thus hindering the efficient production of saplings. For this reason, effective storage methods for breaking down the dormancy of seeds were investigated. It was found that splitting the nucleus with a hammer or vise, removing the seeds, moistening them thoroughly in a flat-bottomed container lined with absorbent paper, and incubating them at a temperature of 30-35°C for 2-3 days while keeping them moist, increased the germination rate (Fig. 2).
Outputs / Expected benefits
The Hida kokufu beni shidare is now being planted not only in Gifu Prefecture but also in other peach-growing areas in Japan. It is expected that old orchards will increasingly be updated with new varieties, enabling the stable production of high-quality fruit, leading to higher incomes for peach producers and greater regional economic stability and development. .
Footnote
(NOTE) Rootstock produced by seed germination
