The Intergeneric Hybrid in Horticulture

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Updated on 08/12/19

Leyland cypress — Stephen Shepherd / Getty Images

A hybrid is the offspring of genetically dissimilar parents or stock, especially the offspring produced by breeding plants or animals of different varieties, species, or races. A hybrid can also come from something of mixed origin or composition, such as a word whose elements are derived from different languages. A hybrid is something having two kinds of components that produce the same or similar results. The offspring of two plants of different breeds, varieties, or species, especially as produced through human manipulation for specific genetic characteristics, is a hybrid.

Charles Darwin promoted the concept of cross-breeding, but Gregor Mendel is credited with starting the hybrid plant revolution with his genetic studies of peas in the early 1900s. Hybridization took off from there as horticulturists realized they could cross-breed plants within the same species, but from different varieties, to attain specific desired physical results inherent in the parent plants. Today’s gardeners have thousands of hybridized plants to choose from which feature traits such as disease resistance, larger fruits, and prolific growth habits.

Examples of hybrid plants include :

Sweet corn: The vast majority of U.S. sweet corn grown are hybrid varieties. The characteristics of these varieties have made it easier for home gardeners to grow and they are sweeter than past crops.
Meyer lemons: Meyer lemons, originating in China, are a cross between a true lemon tree and mandarin orange tree. The fruit is much sweeter than traditional lemons, which makes this variety a favorite of gardeners and chefs alike.
Better Boy tomatoes: Better Boys have been bred to be resistant to verticillium wilt, fusarium wilt, and nematodes, which are all common tomato plant problems. Gardeners and tomato lovers favor the large, bright red fruit, which can weigh up to one pound and mature within 75 days of seedlings being transplanted into the ground.

Intergeneric Hybrid

An intergeneric hybrid is a cross between plants in two different genera in the same family. They are closely related enough that pollination will produce a hybrid, though the seeds of this hybrid are usually sterile.

The more distant the relationship between the two genera, the greater the difficulty of intergeneric hybridization. Genera that generate intergeneric hybrid are always genetically related members of the same taxonomic tribe. Intergeneric hybridization represents an opportunity to combine genomes from distinctly different plants and to introgress traits not found in the main genus of interest. Many intergeneric hybrids are infertile.

This type of hybridization is more for scientific interest than for any other use.

Cypress

For example, the Leyland cypress (× Cupressocyparis leylandii) is a result of crossing a Monterey cypress (Cupressus macrocarpa) with a Nootka cypress (Chamaecyparis nootkatensis). Propagation of the Leyland cypress is usually carried out through cuttings, though it is possible for this tree to produce seeds that will germinate. Asexual propagation, however, is preferable since it will ensure that the new plant has the same characteristics.