The Importance of Quality Seeds
The dramatic population growth is the key factor to improve farming productivity. According to the information from United Nations, the world’s population is expected to increase from 7.8 billion in 2020 to 9.7 billion in 2050 and could peak at nearly 11 billion around 2100.
As the global population continues to grow, so does the pressure on limited land resources. The global cropland area per capita decreased continuously over the period between 1961 and 2016: from about 0.45 hectare per capita in 1961 to 0.21 hectare per capita in 2016.
According to the Food and Agriculture Organization of the United Nations, producing quality seeds means quality yields. Seed is one of the least expensive but most important factors influencing yields.
Plant Breeding Technology
- Plant breeding
There are many technologies, operations, and methods of plant breeding, but they are all inseparable from the following four basic principles, which are determined according to the similarities and differences and affinity of chromosomes, so as to select the feasibility and methods of breeding. Plant breeding starts from the entire plant, and the period is in the flowering season.
- Pure Line Selection
Select pure lines with similar or identical genetic properties and good quality and passing them from generation to generation. The principle is based on the same genes they carry.
People engaged in plant breeding have a long history of using hybridization to improve crops. Pure line breeding is selected by inbreeding segregation and hybridization is the process of interbreeding between individuals of different species.
Mutation is one of the methods of breeding, but its use is not wide. The reason is that most mutations are not benign. This type of breeding is mostly used for ornamental rather than edible plants.
There are two causes of mutations: one is natural mutation, the probability of which is not high; the other is man-made mutation, chemical treatment or X-ray irradiation of seeds causes chromosome mutations, so that useful mutations can be selected and applied from many mutations. This method Has produced good results in barley breeding.
Plants unlike animals which have a characteristic of polyploid, polyploid plants are generally increasing trend in size, which is valuable in agronomic crops, so a lot of practical examples. One of them is to produce seedless watermelon using the principle of triploids sterility property.
In the breeding process of seedless watermelon, a diploid watermelon is crossed with a tetraploid to obtain a triploid seed. Because the watermelon produced by the triploid seedlings has a single set of chromosomes, it cannot match and cannot produce seeds during cell division, thus forming the current seedless watermelon.
- Pure Line Selection
Since the discovery of the structure of DNA in 1953, a series of other discoveries, including restriction enzyme, plasmids, Ti-Plasmid and T-DNA, and the regeneration of plant cells, have contributed to the development of biotechnology in the 1970s. In 1983, the first transgenic plant experiment was successful. It was the transfer of legume genes to tobacco. This was the first time that plant genes could be combined across “family” (from Leguminosae to Solanaceae). Later, animal genes were successfully transferred to plants, which is to transfer the firefly genes to tobacco to make it glow. So far, the types and number of genetically modified plants are no less than a hundred, ranging from dicots to monocots, from Solanaceae to cruciferae, from vegetables to flowers and fruits, from trees to shrubs.
Seed Treatment Technology
- Seed Coating
As the method of plug seedlings is gradually being widely used, it is necessary to use an automatic sewing machine for sowing. The prerequisite for using this type of machine is the seed must be of sufficient weight or size so that a single seed can be sucked in a vacuum. The seeds can be treated to increase weight, size, or reduce the entanglement of the seeds. The weight ratio of the seed after treatment is generally about 2-50 times, but it depends on the coating material and the size of the treatment. For example, lettuce is 30-35:1 and sugar beet is 2:11.
In addition, adding various pesticides, fertilizers and other materials in the coating process can reduce the excessive use of pesticides and indirectly reduce environmental pollution. At present, seed coating technology has been widely used and its processing methods include coating and film coating, seed pelleting, seed granules, seed tapes, seed mats, etc.
Priming is to place the seeds in a limited moisture condition to soak and absorb water, allowing the seeds to undergo the metabolic reactions before germination, but the radicle cannot break through the seed coat due to the moisture content limitation, and the seeds are then dried to the initial moisture content to restore their preservation ability. After sowing, the seeds treated with osmosis treatment can not only germinate quickly and neatly, but also improve the quality of low vigor seeds, reduce the dormancy of seeds, and promote the germination of seeds under environmental adversities.
- Fluid drilling
Fluid seeding is to allow the seeds to be pre-germinated in the laboratory with the most appropriate germination conditions. In this stage, the seeds can overcome the unfavorable germination conditions of the seedbed or field to promote rapid and neat germination in the field.
- Artificial seeds
Artificial seeds refer to the somatic embryos obtained by the way of tissue culture for asexual propagation, and the somatic embryos are wrapped by appropriate methods to replace natural seeds for propagation.
Artificial seed technology includes: somatic embryo production, artificial endosperm to provide nutrients needed for development, protective outer covering of somatic embryo, artificial seed coat and artificial seed storage, artificial seed manufacturing machinery and other technologies.
Temperature and humidity are the keys to the longevity of seeds. According to the Association of Official Seed Analysts (AOSA) guidelines, the sum of the temperature (calculated in Fahrenheit ℉) and relative humidity (RH) for storing seeds must be less than 100.
Since seed resources are limited, establishment of seed bank could conserve biodiversity through storing of seed. Currently, there are more than a thousand seed banks in the world, which play important roles in conservation, scientific research and crisis response.
The world’s largest seed bank — the Millennium Seed Bank, was established in 1996 by Kew Gardens of the Royal Botanic Garden in the United Kingdom. Until 2017, it has preserved the seeds of more than 37,600 species of wild plants, accounting for more than 13% of the world’s wild plant species.
Svalbard Global Seed Vault, located under the permafrost in the polar regions of Norway, was established in 2008. It serves as a vault for all seed banks in the world. It is also called the “Doomsday Seed Bank” or the “Noah’s Ark for seeds”. Seeds stored in the hypoxic environment below -18 degrees Celsius have a validity period of up to a thousand year.