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The genus aronia is considered to have 3 species . The most common and widely used is Aronia melanocarpa (black chokeberry) which emerged from Eastern North America. The lesser known Aronia arbutifolia (red chokeberry) and the hybrid form of the abovementioned species called Aronia prunifolia (purple chokeberry) were first cultivated in Central and Eastern North America. In the eighteen century the first shrubs of the best-known species Aronia melanocarpa reached Europe where they were first cultivated in Scandinavia and Russia . Currently the black chokeberry has emerged as a popular shrup in Central Europe where it is mainly used for food production and cosmetic industries. Especially the growing scientific basis for its wide range of health promoting properties have caused an increased interest and demand in aronia products.

Nutrition

Nutrient	Mass in fruit [g/100g]	Mass in pomace [g/100g]
Total sugars	6.21-42.1	-
Fructose	2.2-15.8	-
Total fibre	-	57.8-71.6
Insoluble fibre	-	43.8-61.7
Lignin	-	22.68
Cellulose	-	34.56
Pectin	-	7.52
Protein	0.7	-
Fat	0.14 %	-
Vitamins	[mg/100g]	[mg/100g]
Vitamin C	7.25-98.75	-
Vitamin A	0.77	-
Vitamin B5	2.845	-
Vitamin B6	1.132	-
Minerals	[mg/100g]	[mg/100g]
Na	0.427-1.18	-
K	135-679	-
Ca	11.9-116.7	-
Mg	8.3-66.9	-
P	23.9-95.6	-
Organic compounds	[mg/100g]	[mg/100g]
Anthocyanins	284-631	-
Proanthocyanidin	522-1000	6200-9720
Flavonols	3.9-61.7	22.7-43-7

Health benefits

Chokeberries have a long tradition in folk medicine especially in North America and Europe .

The large polyphenol content of chockberries has gained scientific interest and was intensively studied in the last few decades. A majority of studies with in vitro and in vivo experiments found both therapeutic and preventive effects on non-communicable diseases:  

• Cancer prevention and treatment: During cancer treatment patients show increased levels of superoxide anion radicals that case oxidative stress in platelets undermining their biological function. Black chokeberry extract has proven to decrease superoxide anion radicals in patients with cancer and is therefore effective in dampening oxidative stress that arises through cancer and its treatment . Furthermore, different studies have demonstrated anti-carcinogenic mechanisms of aronia polyphenol such as reduced cancer cell growth, migration, adhesion and the inhibition of cancer stem cells .

• Diabetes: The consumption of aronia juice concentrate increases the concentration of adiponectin in the plasma and therefore lowers the risk of diabetes type 2 . Furthermore, an open lab study reports improvement of glycemic control due to lower glycated hemoglobin and fasting blood cellulose. Therefore, chokeberry juice can be a natural medicine to treat diabetes .
• Cardiovascular disease: Oxidative stress, increased blood pressure, obesity and elevated inflammation all increase the risk of cardiovascular disease. It was demonstrated that the consumption of aronia powder, juice or extract increases the nitric oxide synthase activity dampening hypertension and inflammation .Furthermore chockberry consumption reduces weight gain and regulates cholesterol levels and blood pressure . As Cardiovascular disease is a severe cause of death especially in the US aronia extract, juice or powder can be a promising natural treatment .
• Gut microbiota: Microbiota has proven to modulate the immune system and contributes to the progression of chronic diseases and affects insulin, lipid and energy metabolism . Fiber, sorbitol and polyphenols from aronia positively change the gut microbiota composition and have a direct anti-microbial activity against some pathogens.The bacteriostatic effect shows higher resistance to Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus while the antiviral effect significantly improves resistance towards the Influenza A virus.
• Other positive effects: A positive effect on the eye functioning as well as protection against UV radiation have also been detected health benefits after the consumption of chokeberry .

Overall aronia fruits, extract and powder are very rich in bioactive compounds and antioxidants with a wide range of health benefits for non-communicable diseases. These health promoting properties and the rich nutrition composition of the fruit and its pomace make chockberry interesting for the food industry.

Cultivation

Soil and climate requirements

The aronia is a characteristic shrub of the northern hemisphere. Its climatic requirements are temperate and cool temperatures. The shrubs are extremely winter hardy and can survive temperatures down to -30 C° without damage if they are in winter dormancy. After flowers formation in late April/ early May, the plants become sensitive to frost. Chokeberries are usually planted in early spring after thaw but autumn is also possible if the plantation is mulched or a snow covered during frost.

The chokeberry has a shallow and compact root system and thrives in humus and nutrient rich soils that are frost free, unflooded and with a rather low groundwater level. While the plant is moisture-loving, it also tolerates dry periods. Depending on the timing and intensity, these dry periods are yield limiting. While the crop needs more than 500mm of precipitation, good yields can be obtained at 700-800mm. Furthermore, chokeberries are sun loving and usually thrive better under direct sunlight rather than in shade.

Seedbed requirements and sowing

Chokeberries grows on medium-heavy soils, which can be neutral to slightly acidic. Before planting, it is advisable to promote soil structure and humus formation, which can be enhanced by green manuring using organic fertilizers and deep tillage of the soil. Planting aronia in an existing grass sward is not recommended, due to the strong competition of weeds in the understock area. Commonly, 2-3 year old bare root plants are set between October and November. Machine planting places about 3000 seedlings/ha each 20-25cm deep into the soil. Plant distance is 60cm and row distance is given by the harvest machine.

Crop sequence requirements

If aronia is planted directly after a previous cultivation of other Rosaceae, an intercrop such as cereals is recommended, as well as staggered row planting, since chockberries might suffer from a replant disease (also: soil fatigue).

Cultivation management

For the first two years, much attention should be given to keeping the understock area clear during maintenance. The understock maintenance can be done by machine hacking or by using a string trimmer with protection. Covering the plant strip with mulch also helps to minimize weeds. When maintaining the alley, it is important to cut it every 3-4 weeks. For the last cut before winter a low cutting height may be chosen to not encourage mouse populations.

The young plants are sensitive to drought stress, so proper watering should be guaranteed. At the beginning the plant needs to put its energy into vegetative growth, therefore it helps to remove flower buds. In order to achieve a balanced fruit quality in the long term, the plant, which grows as a shrub, should be trimmed regularly. Furthermore, uniform plant stands are easier to manage and harvest by machine. As a rule, chokeberry branches achieve the highest yields in the 5-6 year period, so cutting is not done again until the 7th year.

The aim of both the mechanical and the manual cutting system, is to let the shrubs grow into a closed hedge. While in the mechanical cutting the whole plant is cut back to a few centimeters above the ground every 6th year during the winter dormancy. The manual cutting removes the oldest shoots, the weak annual shoots and those shoots that are inside the cane slightly above the base of the cane in the winter dormancy. In the case of manual cutting, the ages of 1-6 year old shoots should be present in equal proportions after cutting, thus the chokeberry forms robust shoots and allows uniform harvests from year to year.

Fertilization requirements

For optimal fertilization, collecting soil samples before the planting of the seedlings is required. The soil analysis enables planning of effective fertilizer applications. In the first two years, after planting the seedlings, there must be enough nutrients in the soil so that the seedlings can grow optimally. Some of those important nutrients are phosphate (P), potassium (K) and magnesium (Mg) and, therefore, they should be present at the beginning of vegetation period. When potassium levels in the soil are low, the nutrients can be supplied via cattle manure and cattle slurry. If the potassium content in the soil is high, it is better to use compost, since a too high potassium concentration inhibits the uptake of magnesium, calcium and ammonium. However, there is no need to be too sensitive about potassium levels in the first few years, since a high amount is basically needed. It is clear that nitrogen fertilization is necessary. Often, one half is applied at the beginning of vegetation period and the other half at flowering. Since the plant already has a greater growth potential in the second year, the amounts of fertilizer can be increased a little. From the third year on, the chokeberry has the full nutrient requirement. Depending on the vigor, wood maturity and yield, the fertilizer quantities can be slightly adjusted upwards or downwards. Through the targeted strip fertilization, the amount of fertilizer can be reduced by 1/3, which may be of economic interest to the cultivator.

Harvest and post-harvest treatment

The continuous monitoring of fruit development helps to determine the specific time of harvest. To monitor the fruit development about 200 berries per hectare are removed, mixed and pressed into juice. From this juice the sugar content can be measured, which should be between 15-20° Brix, because only then the sugar content is high enough to overtone the tannins in taste.

The harvest of the chokeberry takes place between the end of August and the beginning of September. In this time span, there are fruits of different ripeness on the shrub. While the upper part is often already ripe, the lower part is not yet edible. A recommended harvest time is when the upper berries begin to shrivel slightly, but do not yet show any weight loss. In this way, a large part can be harvested in an optimal ripening state while the other part can still post-ripen.

Today the people do harvesting still by hand, especially for fresh sales and the production of dried berries, where the appearance of the berries is important. The majority of other harvesting is done by machine. In manual harvesting, cleanly harvested fruits are stored in bunches. Thus, about 7kg can be picked by hand and per working hour. It is important that the berries are processed the same day to keep the quality high. For mechanical harvesting, the bushes are pulled in sideways by the harvesting machine and the berries are knocked off with sticks. Machine harvesting requires 3 people and the machine can harvest one hectare in one day. In the case of mechanical harvesting, many berries are injured after harvesting and in any case should be processed the same day.

Yield

After growing chokeberries from seeds it takes between 3 and 5 years until the plants begin to yield fruits. However, from a parent plant up to 20 rooted plants can be derived which already start yielding after 2 to 3 years. After the plants are fully matured a well growing plantation can yield between 3 to 12 tones of chokeberry fruits per hectare.

Pests and diseases

Chokeberries have a low susceptibility to plant diseases and only little problems with pests . Their resistance makes chokeberries a well suited crop for organic agriculture. The high content of flavonoids in the fruits and their acidic taste are likely to protect the chokeberry against pathogens and pests.

Here is a list of some possible pests and diseases of aronia:

Pests

• Aphids e.g.apple aphid (Aphis pomi), woolly aphid (Eriosoma lanigerum)
• Mites e.g leaf blister mite (Eriophyes piri)
• Drosophila suzukii – some studies found that Drosophila suzukii mainly infests damaged or destemmed fruits, while intact fruits are more resistant
• Tooth-nose snout weevils (Rhynchitidae)
• Wasps
• Cockchafer grub
• Codling moth

Also, birds, mice and deer might feed on different parts of the chokeberry and thereby dammage the plant.

Fungal diseases

• Dead arm disease (Phomopsis viticola)
• Rusts (Pucciniales)
• Powdry mildew (Erysiphales)

Bacterial diseases

• Pseudomonas syringae
• An infection with fire blight is theortically possible, as chokberries belong to the family of Rosaceae, but has so far not been observed.

The treatment methods for the different pests and diseases differ depending on the chosen agricultural practice (e.g. organic vs. conventional agriculture). Often mechanical measures can be taken such as ensuring sufficient sunlight and aeration between the plants or spanning nets as a protection against picking birds.

Breeding aims and genetic preconditions for breeding

One part of the breeding efforts focuse on improving red chokeberries for their use as ornamental plants. Breeding goals include the reduction of the plants stature, reduction of its tendency towards legginess, incresing the fruit size and improving leave retention for a longer lasting fall foliage. Breeding of the red chokeberry is difficult, because the available accessions are tetraploid plants and thus, are likely to produce apomictic seeds. Furthermore, the breeding of polyploids makes mutation breeding more challenging because the additional sets of chromosome can mask incomplete mutations. If breeders had access to a wild diploid A. arbutifolia breeding would arguably become more successful.

The breeding success of the black chokeberry for food production in Europe and Russia has been restricted because the genetic pool of the domesticated Russian plants is very homogenous. Breeding efforts aim to increase the content of flavonoids, antioxidants and anti-cancer compounds while maintaining or increasing the fruit size. Further breeding targets are improvement of the flavor of the berry, which currentley quite sour .