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 Main subject - sept/oct 2008
continuation: Hybrid maize seed production
Field production - Why female and male plants?
To breed maize it is necessary for the pollen produced in each tassel (male inflorescence) to fertilize the cobs (female inflorescence) of other plants. To achieve this, rows of female plants must be established in the field, separated from those that will grow to perform as male plants.
Maize is an open-pollinated or cross-pollinating species, which then requires that care is taken as not to allow that plants chosen to be females be able to self-pollinate. To make this possible, these plants are detasseled before they can shed any pollen. The different photographs in the text show various people executing this procedure, and in average it takes two people to detassel one hectare of maize per day. In other words, one operator is able to detassel 0.5ha in an 8-hour shift, during a work day. Since this operation is repeated more than once ("rounds", within the same area), the job demands the equivalent of 4-5 shifts per hectare.
These figures may change since they are related to the operators' expertise, certain features relating to the female plant and, basically, if the equipment known as "man carrier" is available, which helps to the manual work. Automatic detasseling machines can also be available.
If this task is carried out properly, then only the tassels from the male plants will be releasing the pollen that will penetrate the silks of the female plants. If the female plants were allowed to self-pollinate, the seeds produced will originate low-vigor plants, which is what is technically known as "recovery of the original parents". Another feature of hybrid seed production is the need for several rows of female plants to be pollinated by male plants sown into a lower number of rows.
The ratio of female plant rows (or F/M row rate) for a specific hybrid is strongly related to the pollinating capacity of the male plant line. This capacity is determined by various factors, among them, the height ratio between the male and female plant lines and the amount of pollen produced by the male plants. Obviously, the aim is to maximize seed production, to which purpose the focus is to establish the maximum number of female plants (the ones that will produce seeds). The rows of male plants may be completely destroyed after pollination is completed, with the exception of some double-cross hybrids.
Manual detasseling
Benefits of irrigation of seed crop fields
In general, hybrid seed crop fields are always under irrigation, since one of the most limiting factors to off-season seed production is the lack of appropriate rainfall, in volume and distribution. The values at stake demand an adequate supply of water throughout the crop cycle and the only way to grant it is by means of irrigation. Furthermore, this resource enables planting female and male rows at different times, which may be necessary due to the different genetics involved which in turn may imply different cycle lengths. The late-flowering parent line must be sown first, so that flowering coincides with the early-flowering parent line and fertilization can occur without restriction. Other issues refer to field operations such as fertilization, weed control, pest control and disease management practices.
High quality seeds: How to achieve high germination
The way seeds are handled upon reception and during processing at the seed processor unit (SPU) are essential to quality of the end product. During their stay at the former, the best care is aimed at maintaining the levels of germination and vigor present at the time of reception at the SPU, since there is no possible way to enhance these traits beyond their original levels.
The avoidance of mechanical injury to the seed through their passage along the different processing machines will reduce their loss of germination and vigor. Several operations along the SPU may cause physical damage to the seed, and shock- absorber materials such as canvas, rubber parts or any other type that help to absorb the banging will reduce the damage levels.
Sequence of hybrid maize milestones
Mechanical dehulling of cobs is a process that, besides causing losses, can also cause seed damage. Drying is another process contributing to seed physiological quality, and high temperatures should not be employed at the beginning of the drying process, when the seeds still contain high moisture levels and the damage could be irreversible.
The ISO 9001 System and the continuous improvement
The ISO 9001 certification scheme has the big advantage of standardizing and monitoring different procedures, besides the continuous improvement. Periodic assessments are carried out to check for the efficacy of the different processes which involve human and technical aspects related to the need for training and speciation.
After the comments on bottlenecks, investments, seed production and processing, the continuous improvement through modern strategies that are applied in the agriculture and industrial areas cannot be ignored.
Such is the case for the "Six Sigma" and "Lean" methodologies, already successful in the automobile industry and in recent times being adopted by the seed industry. Both methodologies focus on the reduction of processing defects as well as on their variation, while increasing their flux and reducing the waste products. All of these can help curb production costs and enhance seed quality.
Are biotechnology and genetic engineering a reality to hybrid maize?
There's confidence that this type of technology will continue to provide agriculture with better products; likewise, researchers are optimistic too, and according to the EU Research Commissioner Philippe Busquin, research results coupled with the increase on practical expertise have set the pace for regulatory and risk management polices, which together with the excellent safety record from genetically modified organisms, keeps public confidence high on this technology and its products. (Source: http://europa.eu.int/comm/research/quality-of-life/gmo/index.html)
Final comments
If is expected that throughout this article the relevance of hybrid maize to the Brazilian and world agriculture remains clear. Also, hybrid seed production can't be summarized to few words, such as plant, harvest and packaging. Hybrid seed production involves hundreds, maybe thousands of people and precisely controlled processes in different areas, i.e. research, production, laboratories, product development, marketing and distribution and retail logistics.
Seed production planning, confronts constant challenges, which make the seed industry, progressively, closer to market trends and its main customer, the farmer. The production of maize hybrid seeds with high physiological and genetic quality is granted through different control mechanisms, such as the ISO 9001 standards.
Anyway, all these quality standards start to be defined at the time of choosing the field area where the rows of male and female plants will be sown; later on they will be dependent on the success of factors such as detasselling, irrigation and other field routines necessary to the normal development of the crop. Harvest at proper seed moisture contents, drying at correct temperature so that seed vigor is preserved, and avoidance of mechanical injury, are all interconnected to determine the final level of seed quality. Hybrid seed production can also rely on the latest technology available to the sector, such as the use of satellite guidance systems for precision agriculture, use of molecular markers to assist selection, transgenic hybrids with different specifications and all the ongoing research concerning new technologies to help optimize field and seed processor unit routines.
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