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Blackberry

Fruit of Rubus species

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  • 5 chapters
Blackberries in a range of ripeness, in West Hartford, Connecticut
Ragesoss · CC BY-SA 3.0

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Through Species, Apomixis and Invasive species

Blackberry fruit production is abundant with annual volumes of 20,000 pounds (9,100 kg) per 1 acre (0.40 ha) possible, making this plant commercially attractive.

Rubus armeniacus (Himalayan or Armenian blackberry) is considered a noxious weed and invasive species in many regions of the Pacific Northwest of Canada and the United States, where it grows out of control in urban and suburban parks and woodlands.

Description

The blackberry looks similar to its raspberry relatives. What distinguishes the blackberry is the connection between the berry and the torus (receptacle or stem). When a raspberry is picked, the torus remains on the vine. This is why there is a hollow core in the raspberry fruit. When a blackberry is picked, the torus stays with the fruit.

The term bramble, a word referring to any impenetrable thicket, has in some circles traditionally been applied specifically to the blackberry or its products, though in the United States it applies to all members of the genus Rubus. In the western US, the term caneberry is used to refer to blackberries and raspberries as a group rather than the term bramble. Briar or brier may be used to refer to the dense vines of the plant, though this name is used for other thorny thickets (such as Smilax) as well.

The usually black fruit is not a berry in the botanical sense, as it is termed botanically as an aggregate fruit, composed of small drupelets. It is a widespread and well-known group of over 375 species, many of which are closely related apomictic microspecies native throughout Europe, northwestern Africa, temperate western and central Asia and North and South America.

Plants

Blackberries are perennial plants bearing biennial stems (called canes) from their roots.

In its first year, a new stem, the primocane, reaches a full length of about 3–6 metres (10–20 feet) trailing on the ground and bearing large palmate compound leaves with 5–7 new leaves; it does not produce any flowers. In its second year, the cane is a floricane with a non-growing stem. The lateral buds open to produce flowering laterals. First- and second-year shoots produce short-curved, sharp thorns. Thornless cultivars have been developed during the early 21st century.

Unmanaged plants tend to aggregate in a dense tangle of stems and branches, which can be controlled in gardens or farms using trellises. Blackberry shrubs can tolerate poor soils, spreading readily in wasteland, ditches, and roadsides.

The flowers bloom in late spring and early summer on the tips of branches. Each flower is about 2–3 centimetres (3⁄4–1+1⁄4 inches) in diameter, with five white-pink petals. Each drupelet develops around an ovule fertilized by a male gamete from a pollen grain. The most likely cause of undeveloped ovules is inadequate pollinator visits. Infection with raspberry bushy dwarf virus sometimes causes no visible symptoms and sometimes causes incomplete drupelet development and crumbly fruit.

Genetics

The loci controlling the primocane fruiting was mapped in the F Locus, on LG7, whereas thorns/thornlessness was mapped on LG4. Better understanding of the genetics is useful for genetic screening of cross-breds, and for genetic engineering to control for desirable traits.

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