What is a seedless fruit

How are seedless grapes grown?

Fruit enjoyment without hard troublemakers - seedless table grapes enjoy great popularity. But somehow these fruits appear unnatural: How can corresponding grape varieties be cultivated - without seed formation, crossing is not possible? Are these any high-tech products? Frank B. asked us about that - thank you very much.

"In principle, seedless grapes were not the first to produce modern breeding methods - corresponding grape varieties have existed for a very long time," says Ernst-Heinrich Rühl, head of the Institute for Vine Breeding at Geisenheim University. "The raisins and sultanas, for example, are dried grapes from very old grape varieties that do not develop any seeds," says Rühl. Early on, people specifically propagated vines in which hardly any hard stones developed in the berries. These plants are the result of natural mutations in the genetic make-up, which is responsible for the development of the seeds in the fruits. "The corresponding gene is now also known," says Rühl.

As the viticulture expert explains, the propagation of vine plants was and is also possible without seeds - using vegetative techniques. This means what is commonly referred to as cuttings or offshoots: By rooting cut parts of the plant, any number of genetically identical clones of an original plant can be created. In viticulture, this is the standard method: the vines that grow on the slopes of the world's wine-growing regions are usually vegetatively propagated copies of certain grape varieties.

Modern breeding in the "incubator"

"However, you can actually only breed new varieties from seeds that are the result of crossing two different plants," emphasizes Rühl. As he explains, this has recently become possible with the so-called seedless grape varieties. This is because, strictly speaking, they are not seedless at all: "There are nuclear systems in the grapes - they are, however, tiny so that you do not notice them when you eat the fruit," says Rühl. In the normal way, no seedlings will sprout from these stunted tiny creatures. But laboratory techniques can make this possible today: The core systems are taken from the grapes and cultivated on a nutrient medium. “They are like premature babies that are cared for in an incubator,” says Rühl. Plants then develop from them that have combinations of the characteristics of their parents.

"When breeding such new seedless varieties, the focus is primarily on aspects that have to do with consumer preferences and with production or trade," says Rühl. In concrete terms, this means that people in the supermarket have access to thick grapes - accordingly, large berries are an important breeding goal. However, this characteristic is linked to other breeding challenges: "Seedless table grapes are largely grown in California, Chile or South Africa and then shipped," says Rühl. Despite their size, they must therefore sit firmly on the panicles and be less susceptible to mold formation so that they can withstand storage and sometimes long transport. “When breeding modern varieties of seedless table grapes, the goal is to achieve the best possible combinations of large fruitiness and resilience,” says the viticulture expert.

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18th November 2018

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