Upstream of maize cultivation, seed production

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With the arrival of April, the start of corn planting was given everywhere in France. From July, the fields of landscapes of the Hexagon will be colored green, as the foliage system of the plant occupies the space. The seeds sown by the farmers in their fields were produced the previous year by specialized companies, seed companies, and a few farmers, the multiplier farmers.

Maize seed production is organized around two types of key players: seed companies and seed multipliers . The companies contract with specialized farmers so that they, from a small amount of seeds, harvest a larger number. The farmers-multipliers harvest is then cleaned, sorted, controlled, processed and packaged in the factories of the production company. A few months after the harvest, it will then be marketed to farmers, who can sow in their fields corn plants with varied markets. 

In France, 1,000 varieties are listed in the Catalog official list of species and varieties. The Catalog describes all the varieties marketed, so that the farmer has all the necessary information before selecting one variety over another. Each variety has its own characteristics, and will be better adapted to animal or human food, green chemistry (plastics …) or other industrial processing (use of starch for multiple outlets).

The reproduction mode sets the rules

As soon as spring arrives, the seed production activityat his best. It is organized around the mode of reproduction of each plant. Corn is a monoecious plant. Dioecious plants require a male foot and a female foot to reproduce (this is the case of asparagus or kiwi); Monoecious plants, on the other hand, have flowers of each sex on the same footing. The male sex flower in corn is the “panicle” at the high end of the plant, its female sex flower is the future “spike” (miniature form of the spike inserted in the axil of a leaf, which will develop after fertilization). Mystery of nature: corn has a strong tendency to allogamy … Having both sexes on the same foot, it could self-fertilize. However, its panicle generally fertilizes the female ears of the other feet.

How is the production of corn seeds organized? Philippe Vernat, from the Centersem seed production cooperative (in Touraine), explains: “The farmers-multipliers arealternating rows with a variety that will play the role of male and a variety that will play the role of female. Males and females are ” pure lines “. It is the crossing of these lines that gives birth to a ” hybrid “. The hybrid will have a strong genetic heritage of the qualities of mother and father. “.

An expertly organized fertilization

From one variety to another, the pollen contained in the male panicle has a variable capacity, carried by the wind, to travel a distance. “In this context, different sowing devices are possible,” notes Philippe Vernat. We speak mainly of 2/2 device (2 female rows framed by 2 male rows) or 4/3 device (4 female rows framed by 3 male rows). The latter is the most commonly used. “.

To ensure that the maize of the female row will not self pollinate, we will castrate their panicle before pollen emission. Thus, the latter can only welcome the pollen of a corn of the male rank. This operation is very technical … In fact, it is necessary for the multiplier-farmer to sow the male and female rows in such a way that the panicles of male rows are ready to release their pollen at the moment when the ears of the female rows are ready to receive it. “The period of castrations is intense and stressful, analyzes Philippe Vernat.It should not be done too early, because the plant must be allowed to grow. Neither should the castration be performed too late, because then it is certain that self-fertilization will take place. On the cob it would give floors that do not belong to the variety of plant that one seeks to obtain. However, varietal purity is essential for the farmer who will buy the seeds … “.

It is the silks of the ear that will guide the pollen in the heart of the ear and allow fertilization. After this stage, the ears of corn will grow and turn yellow, until seeds are ready to be harvested. After treatment and conditioning in the factory, they can be marketed to farmers. At each key stage, quality controls will be ensured, as required by French and European regulations.

The French organization of quality controls

Quality control of seeds and seedlings marketed to farmers and gardeners is a regulatory obligation and must be “certified”. It is essentially a question of ensuring that these seeds are of the desired good variety, able to germinate and healthy. From one species to another, the controls put in place can take very different forms. The main reason is that the modes of reproduction of plants induce different organizations. How does corn seed certification work?

At each stage of production, controls are carried out either by the FNPSMS (National Federation of Maize and Sorghum Seed Production) or by SOC (Official Control and Certification Service). FNPSMS organizes quality controls in the fields. Its authorized technicians will check that the requirements stipulated by the official technical regulations are respected. In concrete terms, they confirm that the rules of isolation and castrations are well followed. He also notes that there are no maize plants that do not have the right variety in the field. This is indicated by the color of the leaves, bristles, etc. As for the Soc inspectors, they carry out a 2nd level control: they make sure that the FNPSMS approved technicians strictly follow the regulatory requirements.

Further controls will be carried out by the experts of the Soc… First, after the harvest (in the autumn and during the winter), quality controls on the seed germination capacity will be carried out in the factories; this is where the seeds are packaged in bags for marketing. Secondly, in the fields, one year after the harvest. In fact, samples of certified batches are made during the conditioning of the seeds to be reseeded in the spring. Goal ? Establish the varietal purity of the past harvest, ie the absence of maize plants belonging to other varieties. We talk about “posteriori checks”. Unlike a plant such as wheat, for example, it is only possible to fix exactly one year after the varietal purity of a lot. Simply because corn is a hybrid

Dr. Kimberly Seltzer

Postdoctoral Scholar, UC Berkeley Research Assistant, MIT

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