Thinning is the most important step in achieving large, unique-sized fruit and preventing
alternative bearing of Fuji apple trees.
Nagano Fruit Tree Experiment Station
492 Ogawara Suzaka, Nagano 382, Japan
IMPORTAND CONSUMPTION OF FRUIT IN JAPAN
About 1.5 million tons of fresh fruit were imported into Japan in 1997.The main imported fruits
are bananas (822,294 t), citrus (512,077 t), kiwifruits (38,301 t) and cherries (12,457 t).Apple
importation was only 131 tons in 1997 (Table 1).The consumption of fruit is not so high in
Japan because fruit are mainly eaten fresh as a dessert.The annual consumption of apples is
approximately 5 kg per person and furthermore it has tended to decrease gradually, recently
being replaced by soft drinks and snacks (Fig. 1).Japanese housewives peel and cut apples into
several pieces so as to share them with their family at the dinner table.
51,200 ha (126,500 acres) with a production of 1,000,000 metric tons in 1996 (Fig. 2).Apples
are grown mainly in Aomori, Nagano, Iwate, Yamagata, Akita, Fukushima, Hokkaido, Miyagi,
Gunma and some other prefectures.These main apple growing areas are located from latitudes
36º to 44º north.Two main prefectures, Aomori (50%) and Nagano (23%), produce about 73%
of Japan’s apples.Fuji (48%), Tsugaru (14%) and Orin (9%) are the main varieties (Fig. 3).The
mean annual temperature varies from 9ºC (48ºF) in Aomori to 12ºC (54ºF) in Nagano.Fuji
apples grown in Nagano mature a little earlier than those in Aomori (Table 2).Therefore, fully
matured Fuji apples with enough watercore are mainly harvested in late October to November in
Nagano and are quickly shipped to market.
Table 3.There is a large difference in precipitation in the growing season and in temperatures
from August to November.
APPLE MANAGEMENT PRACTICES
There were about 85,000 apple growers and 53,900 ha of apple orchards in 1990 and the growers
are decreasing gradually now.Growers who have less than 0.5 ha orchards occupy 63% of the
total growers and they do farming as a side job.The average yield of apples per ha is about
25 tons in Nagano and the recent price of apples determined by auction at the central wholesale
markets is 200 to 300 yen per kg (at 125 yen/$US; .72 to 1.09 $US/lb.).
It was essential to use artificial pollination for improving fruit set in Japan.It is necessary to
collect 10,000 to 15,000 flowers at the balloon stage for the pollination of a 1-hectare orchard.
Pollination is made by touching only the king flowers in blossom clusters on terminal buds by
using the pollen and a pollination brush.This practice is expensive and it takes about 180 hours
of labor per hectare.Recently, usage of insect pollinators such as Osmia bees is increasing in
order to reduce labor.
Thinning is the most important step in achieving large, unique-sized fruit and preventing
alternative bearing of Fuji apple trees.Blossom and fruitlet hand thinning has been done mainly
to grow large fruits (300-350 g) which are the most important with high consumer demand in the
Japanese market.This expensive practice makes up about 24% of total labor hours for apple
growing in Nagano.Today, lime sulfur and carbaryl are being used as blossom and fruitlet
thinners.However, hand thinning is used to thin off lateral fruits which remain in the clusters
and fruitlets from axillary buds (1-year wood).Hand thinning to determine optimum crop load
is necessary whether spray thinning is undertaken or not.
Paper bagging has been developed mainly for the purpose of improving fruit color in Japan.
Double bags are used for major varieties such as Fuji and Tsugaru.About 30% of Fuji apples are
bagged in Nagano now, but it is decreasing because of lower prices in the market.Bags must be
put on the fruit by early July.Outer bags should be removed about 35 days before harvest and
inner bags should be left on until about a week before harvest to prevent sunburn of the fruit
skin.The inside of the outer bag is painted black to prevent light penetration and inner bags are
coated with fungicides including paraffin to reduce russet on the fruit,alternaria leaf spot and
sooty blotch(Gloeodes pomigena). An average worker can bag only 3,000 fruit per day.It is
thought that bagging for Fuji will decrease gradually as new red strains are introduced.
Fruit which has a green leaf pattern and half color due to shade cannot be sold with a good return
in the Japanese market.Leaf removal near the fruit, therefore, done 20 to 30 days before harvest
is one of the most important practices to improve fruit color.Growers also turn the fruit (1/4 to
1/2 turn) to expose the shady side to the sunlight in order to grow unicolor fruit.About 18% of
the labor time is used for this practice.It is also thought that this practice will continue in
importance in the future in order to satisfy the Japanese market or consumers’ demand, even with
the introduction of new sorting systems equipped with an infrared analyzer.
Optimum harvest date for each cultivar is usually decided by the calendar day.Ground color and
red surface color have been used as external maturity indices.Soluble solids and watercore,
firmness, titratable acids and starch decrease are used as internal maturity indices.Fruits with
watercore, especially Fuji apples, are usually sold at retail shops expensively as “honeyed
(Mitsuiri) apples.”Watercore is called “honey (Mitsu)” in Japan.Watercore is thought to be
caused by accumulation of sorbitol promoted by low temperature (below 13ºC) just before
harvest.Therefore, fruit growers in Nagano usually delay the harvest as late as possible, but it
can happen that the fruit can be damaged by a sudden freeze in the late fall.
orchard.Most fruit growers belong to cooperative associations so that the fruit is mainly graded
at the packing houses of the associations.At the packing house, fruit is graded visually.
Recently, many cooperative packing houses have a new sorting system with instruments for
analyzing the sugar content of the fruit with infrared.For selling apples in the Japanese market,
not only the appearance but also internal quality such as brix (soluble solids), crispness and
juiciness are important because Japanese consumers prefer sweet, crisp apples.Apples graded
automatically for brix by using optical instruments (color meters and infrared analyzers) have
recently sold at higher prices.Japanese fruit growers, therefore, begin to make every effort to
raise apples not only with good appearance but also with more than 15% brix (Table 4).
NEW CULTIVARS
Many new cultivars have been released in recent years from experiment stations or private farms
in Japan.Akibae (Table 5), Shinano Sweet (NA-10), Shinano Red (NA-12), Shinano Gold (NA-
15) are thought to be promising now.Shinano Sweet is a cross of Fuji x Tsugaru originating
from Nagano Fruit Tree Experiment Station.Harvesting time is the same as Delicious and fruit
are large (about 350 g) with red striped color.The flesh is slightly soft in texture, very juicy,
very sweet in flavor and never mealy (Table 6).Shinano Red is a cross of Tsugaru x Vista Bella
originating from Nagano Fruit Tree Experiment Station.Harvesting time is early, the same as
Summerred, and it has a red striped color (Table 7).Shinano Gold is a cross of Golden
Delicious x Fuji originating from Nagano Fruit Tree Experiment Station.Harvesting time is
3 weeks earlier than Fuji and the fruit is yellow.Flesh is crisp, juicy and mildly sub-acid with an
excellent flavor (Table 8).
Hozuri is a
chance seedling of Fuji from Fukushima Fruit Tree Experiment Station with large fruit, red
striped color, and acid taste.Akita-gold is a cross of Golden Delicious x Fuji originating from
Akita Fruit Tree Experiment Station with medium fruit size, yellow color and somewhat acid
taste.Gunmameigetsu is a cross of Akagi x Fuji originating from Gunma Horticultural
Experiment Station with medium fruit size, yellow color with a pink blush and sweet taste.
Kitaro is a cross of Fuji x Hatsuaki originating from Fruit Research Center of NIAFF in Morioka
with medium fruit size and yellow color.Aori-9, a cross of Akane x Orin, and Aori-13, a cross
of Sekaiichi x Akane, are quite new varieties originating from Aomori apple research station.
RED STRAINS OF FUJI
Recently, many strains have been founded in apple growing areas around the world but there is
no clone which is superior in every country.In Japan, it was shown by collaborative work that
fruit color of red sports depends on the environmental condition of each growing area.Thus, it
has been recommended that growers should choose the clone which most suits their area.
Nagano Fruit Tree Experiment Station recently collected many types of red strains from
commercial orchards.From this study, it is clear that red strains of Fuji are classified in three
types (blush, stripe and intermediate) by their coloring characteristics.
Nagafu-1 is a typical
clone of this type.Nagafu-2 and Nagafu-6 which have been planted commercially in Japan are
typical clones with stripe.Fruits of intermediate type color are deep red with unclear stripe.
Nagafu-12 is a typical intermediate type and it has been recommended recently in Nagano
(Table 10).Akifu-47, Mishima-Fuji, Rakuraku-Fuji and 2001-Fuji clones which color well not
only with direct light but also with diffuse light are beginning to be planted now.These four
clones are thought to be the same clone by recent investigation.Other new local strains
originating from Nagafu-2 or Nagafu-6 are shown in Table 11.Hirosaki-Fuji and Korin, early
maturing red strains, are attracting growers’attention now.They mature about 30 days earlier
than Fuji and also color well.
ROOTSTOCKS AND ORCHARD SYSTEMS
The apple rootstocks actually used in old Japanese orchards wereM. prunifolia Bork.var. ringo
Asami (Marubakaido in Japanese) andM. sieboldii Mill. (Mitsubakaido in Japanese).
Marubakaido has also been used as the understock with dwarfing interstems for apple trees in
Japan because it is easily propagated by hardwood cuttings.The early use of M.9 as an
interstem with Marubakaido resulted in severe growth retardation or death of trees because M.9
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