Seed Varieties and Cultivator Genetics: Know Your Origins!
When it comes to selecting and testing the genetics of seeds, it’s important to do your homework. Though perhaps a daunting task for some growers, Dr. Lynette Morgan has you covered with these tips.
An indoor garden represents considerable investments in time, effort, skill, knowledge, and often money, as well as the potential for great rewards and enjoyment. Such an important investment deserves to be backed up with the right genetics for the job at hand, whether it’s to produce homegrown fruit and vegetables or to create a beautiful environment to relax in.
While many crops can be a little challenging for inexperienced growers, some of these difficulties can be removed by carefully selecting varieties, cultivars, and genetics that favor the system of production and growing conditions.
Plant breeding and selection has been an ongoing process for thousands of years, and modern techniques have led to huge increases in crop productivity, disease resistance, and a whole host of other factors that hydroponic growers can take advantage of.
For many growers, seed is the most commonly used method of propagation as it allows not only ease of transport and storage, but also high numbers of young plants to be produced relatively quickly with reliable results.
While this may seem to be a straightforward process, the genetics within the seed are one of the most important factors that determine the outcome of the crop and these may not always be predictable. Seeds contain the all the genetics of a plant, including the programming for every process from germination through to flowering, fruiting, and regeneration.
What are the Different Seed Types?
When considering which cultivars to select for an indoor garden, the choice can be overwhelming, particularly with popular crops such as tomatoes, capsicum, cucumber, and lettuce.
Seed companies will often list their cultivars with the abbreviation OP for open-pollinated types and F1 for hybrid seed, with most commercial greenhouse types being F1 hybrids.
Hybrid and open-pollinated cultivars differ in their genetic stability and characteristics. Hybrid seeds are not genetically modified and were first produced in corn crops over 100 years ago. Hybrid seeds are produced by plant breeders carefully selecting for superior and consistent traits and producing inbred lines through a process of repeated self-pollination.
The inbred lines are then cross-pollinated with each other to produce first generation (F1) hybrid seeds. This results in heterosis or hybrid vigour, which is the tendency of crossbred offspring to have biological qualities superior to those of both their parents. F1 hybrids are also heterozygous in many genes.
Hybrid seeds are purchased each time a crop is grown as any successive seeds collected from these plants will not have the same characteristics as the parental hybrids. The commercial hydroponic industry worldwide is largely based on the use of F1 hybrid seed for the major crops such as tomatoes, capsicum, cucumber, and many others.
These hybrids produce significantly greater yields, have earlier harvests, greater shelf life, and improved uniformity than many of the older, open-pollinated varieties of the same crops, and many have impressive disease resistance bred into them.
Hybrid seeds are widely available to indoor gardeners for a huge range of plants and although the cost is greater than open-pollinated seed, the improvement in genetics is often well worth the expense.
Open-pollinated (OP) or standard cultivars will produce plants that are not as stable in their genetics as hybrid seeds. Most open-pollinated varieties will have characteristics that are roughly identical to their parents, which is known as “breeding true,” but are prone to a degree of genetic diversity.
Open-pollinated varieties may be either self-pollinated or cross-pollinated by insects or wind during seed production in the field and are less labour intensive to produce than hybrid seed, making them considerably less expensive.
Hydroponic growers can produce and collect their own open-pollinated seed from many crops. However, with this process, it is important to only select the most productive, healthiest plants as you want these good genes to be passed on to successive generations.
Both hybrid and open-pollinated seeds can be produced organically, and organic seeds are becoming more widely available from major seed companies. Since hybrid seeds are not genetically engineered, they can be grown using organic methods.
That is, provided no chemicals were used in the cross-pollination process. (Typically, hand pollination or hand emasculation of the parent plants is used during the hybridization process for organic seed production.)
Organically produced seeds must meet certain strict criteria for production and handling, including being grown on certified land with only organically allowable inputs for fertilizers, pest, and disease control compounds.
Heirloom and Genetically Modified Seeds
Heirloom and genetically modified (GM) seeds are at the two extremes of the seed spectrum. Heirloom seeds are typically open-pollinated and have been passed down from generation to generation. There is some debate about how long a variety must be in known cultivation before it can be classified as heirloom.
Some say 100 years, others 50, and many claim that pre-1945 is a good definition. Heirloom seeds can be somewhat variable in their characteristics as cross-pollination in gardens and fields can introduce genetics from other cultivars, thus diluting genes and introducing different traits.
However, the main advantage is that seeds can be collected from heirloom plants and saved for the next crop for many generations.
Genetically modified fruit and vegetable seed is not available for sale to home gardeners and is used exclusively by commercial growers, often under license and with strict production guidelines to prevent cross-contamination of other crops.
Genetic modification uses laboratory techniques referred to as recombinant DNA technology to transfer certain desirable genes between organisms. This results in a more precise and rapid method of obtaining the correct genes required for certain traits such as pest and disease tolerance, herbicide resistance, and other characteristics.
While GM seed production was first introduced in the 1990s, it is still mostly used on large-scale field crops such as corn, cotton, soybeans, alfalfa, beet, and canola.
Does Seed Selection Matter in Hydroponics?
Growers may choose a certain cultivar for many different reason. Those who have experienced specific types of disease and want to avoid the use of sprays may chose hybrids with inbred resistance. For example, many hybrid tomato cultivars have resistance to powdery mildew, many different types of viruses, fusarium root rot, phytophtora blight, and many others.
Higher yields, uniform fruit production, and longer shelf life are also some of the main reasons growers select hybrid cultivars. For those not as concerned with yields and disease resistance, open-pollinated/heirloom types may appeal more for factors such as unique appearance, unusual colors, flavor, and aroma, as well as conserving these genetics for future generations.
Open-pollinated and heirloom seeds are typically less expensive and can be saved for future crops by the grower, although some care needs to be taken with this process to avoid unwanted genetic contamination between different cultivars.
Whatever type of seed is selected, there is a range of seed treatments that can assist with handling, sowing, germination percentage, and early disease control. While many seed treatments are designed to assist germination under unfavorable field conditions, many have benefits for hydroponic production as well.
Small, irregularly shaped, and difficult to handle seeds—such as those for lettuce, onion, carrot, and a wide range of ornamental and flowering crops—are available in pelleted form, which is ideal for smaller growers who are hand-sowing or using automated seeders.
Pelleting results in a thick layer of inert material coating the seed, increasing its size and facilitation handling. The pelleting material may also contain various compounds such as fertilizers, fungicides, and microbial inoculants to assist germination and early seedling growth.
Seed coating is another technology that can offer an advantage to hydroponic growers. A basic seed coating may contain a fungicide to give initial protection against certain diseases or germination failures.
Seeds of some higher-value crops such as capsicum may also be treated with a thin polymer film, which encloses the fungicides or other compounds initially applied directly to the seed. Polymer seed coatings are often highly colored, which allows greater visibility when sowing seed.
Primed seeds are another option that can be beneficial for hydroponic growers. Priming is a treatment that initially soaks the seed in a salt solution under controlled temperature conditions. This allows water to be imbibed and germination to be briefly initiated, though not to the stage where the radicle (embryo root) expands out through the seed coat.
The seed is then re-dried and stored before sowing. This treatment increases the rate of seed germination, and it is often used in crops such as lettuce, celery, and capsicum.
How do I Save Seeds for Next Season?
Seeds can be collected and saved from open-pollinated/standard cultivars, including heirlooms. Selecting seed from only the most productive, disease-free, vigorous plants can help with issues of genetic variability and disease carry-over.
Most seeds need to be dried down to between four and 12 per cent moisture to store optimally after collection. This can be carried out by sun drying, use of cool temperature home dehydrators, or by room drying (providing humidity levels are low enough.)
Once fully dry, most seeds store well under refrigeration in an air tight container. Adding some small desiccant packages is also advisable to prevent moisture, which rapidly deteriorates seeds.
Many of the failures with self-collected seeds come from not drying down and storing the seeds correctly post-harvest. Also, failures come from not harvesting at the correct stage of maturity (seed must be fully ripe before harvest). Harvesting earlier means the embryo inside may not be fully developed enough to germinate.
When saving seeds, it is also important to remember that seeds not can carry more than the genetics for the next crop; they can also harbor diseases both within the seed coat and on their outer surface. Treating seeds with a diluted bleach solution once dry or before sowing can assist with control of seed coat borne disease pathogens.
Once saved, seeds can benefit from being viability tested, particularly if it has been stored for a long time or is resulting in unexplained low germination percentages. On a small scale, this can be done with the paper surface germination method, in which a small sample of seeds are germinated on or between sheets of moist paper (such as paper towels) under ideal temperature conditions for the species.
After a certain number of days (typically between three to seven, depending on species), count how many of the germinated seeds produced normal seedlings. The overall percentage of germinated seeds can then be used to determine the viability of the seed lot for use.
On the other hand, the presence of abnormal seedlings with deformities, stunted growth, roots trapped in the seed coat, rots and decay, thickened shoots, or other problems indicates an issue with the seed lot and it should be discarded.
While germination testing is useful for most commonly grown hydroponic plants, it doesn’t help growers differentiate between seeds that are non-viable and those that are alive but dormant and unable to germinate. In the latter case, the seed dormancy must be treated before germination can occur.
Seed/cultivar selection, collection, treatment, and storage are all a vital part of hydroponic gardening for most growers. Trialing different cultivars has long been an important process for many growers both large and small, and vital information can often be gained from growing different varieties side by side in the same environment.
Understanding the genetics of different varieties, and their characteristics and potential, is a valuable investment in any crop long before the first seed is sown.
Written by Lynette Morgan | Author, Partner at SUNTEC International Hydroponic Consultants
Dr. Lynette Morgan holds a B. Hort. Tech. degree and a PhD in hydroponic greenhouse production from Massey University, New Zealand. A partner with SUNTEC International Hydroponic Consultants, Lynette is involved in remote and on-site consultancy services for new and existing commercial greenhouse growers worldwide as well as research trials and product development for manufacturers of hydroponic products. Lynette has authored five hydroponic technical books and is working on her sixth.