Interspecific Hybridization in Horticulture

Boysenberry bush in summer day
Boysenberry bush stokaji / Getty Images

Hybridization is the process of interbreeding between individuals of different species (interspecific hybridization) or genetically divergent individuals from the same species (intraspecific hybridization). Offspring produced by hybridization may be fertile, partially fertile, or sterile.

Plants hybridize much more frequently and successfully than animals do. Pollen from flowering plants disperses widely and may land on flowers of other species. Plant forms are less stringently controlled than animal forms, and so the intermediate form of a plant hybrid is more likely to be physiologically successful.

One of the first persons to study plant hybridization was Josef Kölrueter, who published the results of his experiments on tobacco in 1760. Kölrueter concluded that interspecific hybridization in nature is rare unless humans disturb the habitat. Since that time, many instances of hybridization among various plant species have been documented.

Often interspecific hybrids are sterile or for some other reason cannot interbreed with the parental species. Occasionally sterile interspecific hybrids can undergo a doubling of their chromosome set and become fertile tetraploids (four sets of chromosomes). For example, the bread wheat that humans use today is a result of two hybridizations each followed by chromosome doubling to produce fertile hexaploids (six sets of chromosomes). In such instances, the hybrids can become new species with characteristics different from either of the parents.

Interspecific Hybrid Plants

An interspecific hybrid is a cross between plants in two different species. Many times they will be from the same genus, but not always. In animals, hybridization often results in sterility or low fertility, but this is less often the case with plants.

A good indication that a plant is a hybrid is when its name has an "x" in it. For example, Annona squamosa × A. cherimola is a cross between the sugar apple and the cherimoya called the atemoya.

Reasons for Creating Interspecific Hybrids

These are the primary reasons for creating interspecific hybrid plants:

Improved Yield

Crop yields increase dramatically when hybridization is used to exceed one or more of the parents in size and reproductive potential. For example, boysenberries (Rubus ursinus x idaeus) were developed at Knott's Berry Farm in California. They are a result of a set of crosses between blackberries (Rubus fruticosus), European raspberries (Rubus idaeus) and loganberries (Rubus × loganobaccus). Hybrids can yield up to 100 percent more crops thanks to their resistance to disease and increased vigor.

Longer Growing Season

Many hybrid plant varieties are bred to extend the growing season and mature faster than non-hybrid varieties. Hybrids may also be developed to turn annual plants into perennials; for farmers, this can increase profitability reduce some of the environmental impacts of agriculture.

Higher Quality

Interspecific hybrids may surpass traditional varieties in taste, shelf-life, size, texture, nutrition, etc. Stone fruit, in particular, has a seemingly unending number of interspecific hybrid varieties developed for their flavor and novel appearance: pluots, plumcots, and apriums are all common examples of this phenomenon at work, but there are also nectaplums, peacharines, and pluerries now being grown in fruit orchards.