RETURN TO AGGIE
HORTICULTURE


 


This article appeared in the April 2002 web issue of Horticulture Update,
edited by Douglas F. Welsh, Ph.D., and produced by Extension Horticulture,
Texas Cooperative Extension, The Texas A&M University System, College Station, Texas.


Plant Genealogy

This article appeared in "Today's Garden," March 2002,
produced by the National Garden Bureau (www.ngb.org).
Chief contributors were Ellen Leue, Mike Uchneat,
David Lemon, and Janis Kieft.

Some people think all new varieties are hybrids. This is not true. There are new flowers and vegetables introduced each year that are open-pollinated (OP) varieties. To understand the difference between a hybrid and an open-pollinated variety, think of plant genealogy. An open-pollinated plant has one parent; a hybrid has two parents.

In simplest terms, hybrid seed can be defined as the seed that results from the cross-pollination of two inbred parent plants. Open-pollinated varieties, by contrast, have only one parent line. Many seeds being offered for sale in packets, by mail order, and at nurseries are F1 hybrids, but there are a number of classes where this method of hybridization does not work.

click on image for larger view New varieties are created by a plant breeder. When a breeder has uniform, genetically-stable inbred plants, he or she can consider creating new hybrids. To produce hybrid seed, pollen is moved -- often by hand but possibly by insects or the wind -- from the anthers of one inbred plant (male) and placed on the stigmas of the second inbred plant (female). The seed that grows as a result of this pollination is 'hybrid seed'. Hybrids are often the preferred type of a variety for a number of reasons. The hybrid parents are chosen to complement each other and/or compensate for each other's flaws, creating a new variety that is better than the best qualities of each of the parents. Hybrids tend to be very uniform, have better seed quality, and they can be more vigorous plants. Many show other aspects of improved performance, such as earlier or more sustained flowering, larger flowers, or, in vegetables, earlier or larger fruits.

Most large-scale production of F1 hybrid seed is produced in greenhouses or enclosed shade houses. The female flower plants are grown on greenhouse benches, and workers place the selected pollen on the receptive female. This control of the cross-pollination is critical for hybrid seed production. The production structures are enclosed or sealed so that no bees or other pollen-carrying insects enter the structure.

In certain cases the creation of hybrid seed is not feasible for several reasons. First, the biology of the plant or the flower configuration are designed for self-pollination, resulting in open-pollinated plants.

In other cases, the cost of creating a hybrid plant is prohibitive, and the hybrids may not be notably superior. For example, Salvia splendens hybrids were created, offered by several companies, and are no longer sold because the hybrids were not noticeably improved over open-pollinated plants.

Open-pollinated flowers or vegetables are often easier and faster to breed and produce. Breeders create new varieties by selecting 'parent' plants by repeatedly self-pollinating a particular plant and its resulting progency over several generations. For instance, a plant breeder may find a plant with an interesting or unique characteristic, either growing in the green house or perhaps even growing in the wild. The breeder would pollinate this plant, and grow out large numbers of the second generation, as this is where the most variations occur, and good combinations of characteristics from the parents are sometimes found. Normally, a number of selections are made in the greenhouse and outdoors. To make sure that the variety is true to type, the best individual plants are chosen; these are self-pollinated, and the whole process is repeated from as few as three to possibly eight or more times.

click on image for larger view Production of OP varieties often takes place in acres of fields where thousands of plants are grown. Bees may be provided to enhance pollination, and seed may be harvested by hand or with specialized equipment. The only obstacle is that each variety or color must be produced at a location distant from other varieties or colors, so that cross-pollination contamination does not occur.

Once the variety has been developed, named, and introduced, the work has not ended. Some classes of OP flowers or vegetables need to be very closely watched, as they can become quite variable for plant or flower type. Continuous stock-seed maintenance is very important, to maintain good quality.

When a promising line has been developed, it is then tested under various climatic conditions. Outstanding varieties may be considered for entry in the All-America Selections or Fleuroselect (European) trials.

What are Organic Seeds?

We have received inquiries about organic seed. We offer this explanation.

They are seeds harvested from plants that have been grown without the use of synthetic chemical fertilizers or pesticides. Also, organic seeds are not treated with any fungicide or other synthetic chemical (after harvesting) prior to sale. Organic seed is sold through retail outlets and mail-order catalogs. Some organic seeds are sold as 'Certified Organic Seeds'. 'Certified' seed is seed that has been certified by an independent organization that says the seed meets specific organic standards established by the organization. There are many different certifying organizations in the U. S. and internationally, including Oregon Tilth (www.tilth.org) and California Certified Organic Farmers (www.ccof.org).

A list of NGB member seed companies that sell organic seed to home gardeners is available by e-mailing Ngbinfo@aol.com or by faxing (630) 963-8864 with your request.

The following are examples of well-known garden flowers and vegetables that are F1 hybrids or open-pollinated.

FLOWERS
F1 Hybrid Open Pollinated
Begonia Alyssum
Impatiens Calendula
Lisianthus Celosia
Marigold, American Cosmos
Nicotiana Dahlia
Petunia Lobelia
Seed Geranium Marigold, French
Snapdragon Nasturtium
Poppy Rudbeckia
Salvia Vinca
 
VEGETABLES
F1 Hybrid Open-Pollinated
Broccoli Bean, green
Cabbage Herbs
Pepper Lettuce
Tomato Peas
Squash, summer Radish


 


RETURN TO HORTICULTURE UPDATE