Two Actions by Hyogo to Protect Paddy Rice from High Temperatures
Recent abnormally high temperatures have caused quality degradation of brown rice across Japan. The response to this degradation has been efforts throughout the country to improve cultivation techniques and develop and expand varieties resistant to high temperatures. According to the 2016 Global Warming Impact Survey Report from the Ministry of Agriculture, Forestry and Fisheries, the cultivated area of varieties resistant to high temperatures reached a record high of 91,400 hectares in 2016, approximately 2.4 times greater than six years before.
Hyogo prefecture is the largest producer of rice for sake in Japan and one of the largest rice producers in the Kinki region. All rice varieties are not yet heat resistant. The degradation in the quality of rice is a serious problem in Hyogo prefecture. Yamadanishiki, known as the king of sake rice, is the local brand of sake rice and is resistant to high temperatures. We interviewed two people from the Hyogo Prefectural Technology Center for Agriculture, Forestry and Fisheries about the challenging task of developing a new brand of rice.
Proposing the Optimal Cultivation Period Based on Science for Yamadanishiki
weather sensitivity survey to monitor the impact of climate change on cultivation conditions other than weather, which could be the amount of water or fertilizer used. What became apparent after 1998 was when the ears of Yamadanishiki rice emerge, the heading date, started to move forward. We saw an increase in the number of stems and ears, which leads to quality degradation. Poorer grades started occurring during 1998 and after according to the Ministry of Agriculture, Forestry and Fisheries (MAFF) agricultural product inspection. Sake brewers began to notice frequent indications of poor solubility.*
*Solubility refers to the ability of rice to dissolve or to be digested. Yamadanishiki rice is highly soluble and conducive to the growth of aspergillus oryzae, which is colloquially known as koji. After washing and steaming, the sake rice is mixed with koji and yeast and fermented.
The rise of atmospheric temperatures was apparent. Comparing averages from heading to harvest, which is roughly from summer to fall, in the decades before 1997 and after 1998, the temperature rose by 2˚C in the grain-filling period from heading date to harvest. The easiest way to avoid high temperatures in the grain-filling period is delaying the heading date. If, however, we asked farmers to delay rice planting, they would not listen. We needed science to educate them about climate change.
For that reason, the Center with three other entities -- the Faculty of Agriculture at the University of Miyazaki; the Western Region Agricultural Research Center of the National Agriculture and Food Research Organization; and JA Minori, an agricultural cooperative -- established a joint research institute to prevent high-temperature damage to sake rice. The primary purpose of the institute was to understand the relationship between climate and Yamadanishiki’s quality and adaptability in sake brewing. With the support of MAFF’s Practical Technological Development Project for the Promotion of New Agricultural, Forestry, and Fisheries Policies (2010 to 2012), the joint research facility developed the Yamadanishiki Optimal Cultivation Period Determination Support System in 2013. This system shows the transplanting day (rice planting day) broken down by the location of rice fields in a combination of Excel spreadsheets and an online map service.
Our research into the data from the weather sensitivity survey of the recent 10 years showed that the optimal grain-filling for Yamadanishiki rice is an average temperature of below 23˚C in the 11 to 20 days after heading. We have established approximately 40 fixed points to monitor temperature and rice growth for five years. This monitoring data was arranged on 50 m grid cells and incorporated into the basic information system with the atmospheric temperature information to show the optimal transplanting day at each location when you input the positional information of a rice field.
The system has been distributed to local agricultural cooperatives and Agricultural Improvement and Extension Centers in Yamadanishiki producing areas since 2013 to provide appropriate farming guidance. We subsequently developed a transplanting day map that lists all transplanting days available to producers. These resources are available online. The optimal transplanting day is about a week later than producers used in the past for locations where it may be difficult to transplant on that date because of regulations from conventional water use practices. We believe that proposing a schedule to avoid high temperatures is a significant achievement.
Rice production depends on weather. Good weather equals better and more rice with minimal effort. When rice planting is delayed and when the temperature is lower than normal, both yield and quality decline. My hope is that farmers will make wise use of our information, with reference to the Japan Meteorological Agency three-month forecast issued at the end of April.
Yamadanishiki, which was first produced at the Hyogo Prefecture Agricultural Experimental Station, the predecessor of the current center, recently celebrated its 80th anniversary. Yamadanishiki producers are proud of their rice. We are determined to provide guidance to them and to further enhance the precision of the system to help preserve the quality of Yamadanishiki rice.
Marketing a Cultivar to Replace Kinuhikari
When the average atmospheric temperature in the 20 days after heading exceeds 27˚C, the number of white unripe grains increases. “White unripe grain” is the generic term for unripe grains of brown rice that look somewhat milky because the appropriate amount of starch has not yet accumulated.
The heading date of Kinuhikari, a major cultivar in Hyogo prefecture, is around August 6. The average temperature in the 20 days after August 6 is more than 26.5˚C in the southern part of the prefecture. A slight temperature increase can in an instant cause the temperature to cross into the danger line, which means poor quality and poor yield. The summer of 2010 was exceedingly hot, and the rice grade showed a remarkable decline on a national level. That 2010 summer gave us a strong sense of urgency.
This sense of urgency made us decide to develop a new cultivar, original to our prefecture, to replace Kinuhikari. We started last year to work with a total of 18 JA Group organizations in the prefecture. While achieving breed improvement generally takes 14 or so years, we aim to achieve improvement in nine years, which includes the time to set up the facilities and equipment for developing the new cultivar.
New Cultivar Management Project for Stable Food Rice
Although many years are required to investigate whether a cultivar is resistant to high temperatures if conventionally cultivated, we can reduce the research period if we focus on genes. For example, if you breed Cultivar A, which is resistant to high temperatures, with Cultivar B, which is susceptible to high temperatures, and continue to create grandchildren and great grandchildren, you will have both resistant and weak individuals. You can then decipher the genes that the strong individuals have and the weak individuals lack, learning the genes that are specific to the strong individuals. We mark these genes, and, when we see that marker, we know that particular genes produce rice resistant to high temperatures.
To develop this genetic marker, the Center built a high-temperature resistance greenhouse last July. The test temperature is set to 28 to 29˚C on average, considering the future impact of climate change. We are investigating how to manage temperatures in the greenhouse. We cannot conduct tests if the right temperature range is not established. When the greenhouse is closed, the temperature easily exceeds 40 to 50˚C. Rice blooms at around 10:00 am to 1:00 pm after ear emergence. If the temperature is greater than 35˚C at that time, the pollen dies, eventually causing the phenomenon of high temperature-induced spikelet sterility. To prevent pollen death, we carefully control the greenhouse by, for example, frequently opening windows and adjusting the air conditioning.
Each rice plant in the greenhouse has its own unique genetic makeup. We manually check the white unripe grain percentage for all plants. This is an exhausting task because the work is intense, the amount of work is huge, and the heat in the greenhouse is extreme, a combination that can make you lightheaded. We roll up our sleeves so that we can, as soon as possible, do what we need to do to market tasty rice that is resistant to high temperatures.
Ten years are needed to complete a single round of cultivation work to breed new piece. I am determined to maintain the perspective of a decade into the future as I tackle this work.
Reference website
(Published on December 22, 2017)
