X Marker-Assisted Breeding
Recent Improvements in Japanese Wheat Varieties
Abstract In Japan, the breeding of new wheat varieties for use in bread, Chinese noodles, as well as other noodles, is an urgently required objective if domestic wheat production and food self-sufficiency ratio have to increase. Many molecular markers are now available; those used in wheat breeding programs in Japan are generally to assess the amylose content, dough strength, grain hardness, wheat yellow mosaic virus, preharvest sprouting, and Fusarium head blight. Hard and extrastrong wheat varieties have been released using marker-assisted selection.
Background: Domestic Wheat in Japan
Figure 35.1 shows the trends in wheat production area and yield in Japan after World War II. The disorder in the immediate aftermath of the war resulted in a sharp decrease in the production area, which recovered to a maximum level in 1949. However, from 1949 until about 1975, the production area decreased to less than 100,000 ha, in particular with a sharp decrease from 1963. After 1975, the production area began to gradually increase, peaking by around 1988, before decreasing until 1994. Recently, the production area has stabilized at approximately 200,000 ha. Rice production is the main influence on these trends in wheat production area.
Rice is the staple food in Japan. Therefore, following World War II, the Japanese Government boosted rice production. As a result, the area covered by wheat production decreased. However, in about 1970, farmers produced too much rice, and the Government consequently introduced a rice production adjustment in 1970. This adjustment contained two policies: the first was non-cropping, and the second was to changing some rice production area to cultivation of other crops. The second policy led to many farmers beginning to cultivate wheat instead of rice, which led to increase in wheat production.
Fig. 35.1 Production area and yield of Japanese wheat
Despite the gradual increase in production after the end of World War II (Fig. 35.1), we can see occasional sharp drops in yield (circles in Fig. 35.1); the drop in 1963 was one of the triggers for a sharp decrease in production area. Yield is unstable, primarily because of degradation in crop quality because of humid and wet weather conditions during the harvest season, specifically causing preharvest sprouting and Fusarium head blight damage.
Various products are made from wheat flour in Japan. Chinese noodles are more yellow and elastic than Japanese noodles because the dough is kneaded with kansui, a sodium-carbonate-infused alkaline mineral water, rather than plain water. Instant noodles are also produced. These are dried or precooked and often sold with packets of flavoring, including seasoning oil. Wheat flour is also used in domestic cooking. Each product has a different self-sufficiency ratio (Fig. 35.2). Domestic wheat is mainly used for Japanese noodles, the self-sufficiency ratio of which is already 70.5 %. In contrast, the self-sufficiency ratio of bread, and Chinese and other noodles, is very low.
Wheat Breeding in Japan
Wheat breeding stations are classified into three types in Japan. The first is the National Agriculture and Food Research Organization (NARO) (Fig. 35.3), which manages five wheat breeding stations. NARO was originally a national institute, prior to the privatization of national agricultural institutes in 2001. The second comprises Prefectural Research Institutes, and the third is the Institute of Agricultural
Fig. 35.2 Self-sufficiency ratio for Japanese wheat
Fig. 35.3 Wheat breeding stations in Japan
Cooperative Associations. No private seed companies in Japan are operating a wheat breeding program; most of the wheat breeding stations are public institutes. Therefore, breeding objectives are always influenced by Government policy.
Every 5 years, the Ministry of Agriculture, Forestry and Fisheries sets the provisions contained in the Basic Law on Food, Agriculture and Rural Areas. These provisions determine the policy basis for food and agriculture. The most recent version, which was approved on May 30, 2010, for the first time set a target for the food self-sufficiency ratio; the target is to achieve a ratio of 50 % in 2020 (40 % in 2008). In order to achieve this, the Government drew up a new policy plan in which domestic wheat production is set to increase from 880,000 t in 2008 to 1,800,000 t in 2020. Current wheat breeding objectives have been established to enable this target food self-sufficiency ratio to be achieved.
To increase domestic wheat production from 880,000 to 1,800,000 t, there needs to be an increased use of domestically grown wheat in wheat products with a currently low self-sufficiency ratio. The target products are bread, Chinese noodles, and other noodles, which are made from hard wheat flour (Fig. 35.2); therefore, breeding of hard wheat is an urgent objective. Hard wheat was not a breeding objective prior to 1999 because domestic wheat was mainly used in the production of Japanese noodles, which are made from soft wheat flour. Hard wheat breeding is however now a higher priority than soft wheat. The required quality standard is equivalent to the Hard Red Winter (HRW) class. However, soft wheat cultivars are still in demand for making Japanese noodles (Udon). The required quality is equivalent to the Australian Standard White (ASW) class; currently, domestic wheat flour yield and color is inferior to ASW.
The wheat harvest coincides with the start of the rainy season, other than in Hokkaido (Fig. 35.4). This means there is always a risk that domestic wheat will be
Fig. 35.4 Wheat harvest and rainy seasons in Japan
exposed to conditions of high humidity and wet weather during the harvest season in Japan. Resistance to preharvest sprouting and Fusarium head blight resistance are required for both hard and soft wheat.