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 Main subject - sept/oct 2008
Hybrid maize seed production
Rubens Eric Zanovello de Godoi
eric.godoi@monsanto.com
The present production of seeds from hybrid maize is the result of approximately 70 years of scientific and technological achievements, which initiated with the release of the first commercial hybrid in Brazil in 1939. The fact that there are genetically modified maize varieties available to Brazilian growers is proof of how the level of agriculture in this country has improved. The importance of hybrid maize seeds in the area grown to this species is evident when its evolution and productivity are considered through the last four years. During this period, the area sown to hybrid maize jumped from 8.2 million hectares to 10.3 million hectares and yield increased beyond 17%.
In spite of the interference of various factors, it can be inferred that this increase in productivity is also correlated to the increase in hybrid seed usage. This trend has been observed in other parts of the world, whenever the technology provided a breakthrough. In the U.S.A., up to the 1930s decade the vast majority of the seed used belonged to that of common varieties (also known as cross-pollinated); from the next decades until today hybrid varieties, initially with double-cross hybrids, later shifting to single-cross hybrids and today involving single-cross hybrids that have been genetically modified (known as "Biotech hybrids")
Hybrid maize
Conceptually, hybrid maize exploits one of the best known and valuable contributions from genetic breeding to humans and agriculture, hybrid vigor or heterosis. This was discovered 100 years ago by George H. Shull, and since then several milestone events followed to come up to present times, when it is possible to grow hybrid maize varieties that have been genetically modified.
For the summer growing season of 2008/09, Brazil will have this technology available, which besides controlling the sugarcane borer and suppressing the fall armyworm, will bring about a reduction in the amount of insecticides used during the crop cycle. The benefits to the environment are not only limited to insecticide use reduction, but also what comes with it: the amount of diesel oil used as fuel, the water as dilutant, etc.
The seeds of the new hybrid maize varieties will also carry improvements in the nutritional quality of the kernel and in the near future disease resistance, enhanced N-use efficiency and tolerance to water stress.
What is hybrid vigor?
Hybrid vigor results from pre-programmed breeding between different inbred lines (genetically different), which are considered the fundamental units to the development of seed production schemes for hybrid maize. In general, inbred lines are of low yield potential since they need to be manually pollinated to create them, a process that reduces the efficiency of seed formation. The reduction in potential seed yield of inbred lines can be of four times that of hybrid maize varieties or even higher, which is why this phase is known as the Achilles' heel of hybrid maize seed production.
The first hybrid to be produced was the single-cross hybrid, where the progressive loss on vigor and productivity through successive inbred generations is depicted.
There are several types of hybrids and all of them originate from inbred lines. Some of them were created on the basis that they would permit a cost-efficient seed production system, which was the case for the double-cross maize hybrid created by Donald Jones in 1918. This researcher tried to overcome the low seed production from female lines of the first single-cross maize hybrids, which were inbred lines with low seed yield potential. Jones decided to use as female plants, the hybrid created from two inbred lines, resulting in enhanced seed yields. Within this type of hybrids a small part of the vigor is lost, however, at the time they were created these hybrids made possible seed production at a reasonable cost.
Graf. 1 - Area dedicated to hybrid maize cropping through the last four growing seasons
The current trend on hybrid seed production focuses more the use of hybrids created from a reduced number of inbred lines, such as the three-way hybrids (the female is a single-cross hybrid, while the male is an inbred line), modified single-cross hybrids (female is a single-cross hybrid between related inbred lines, while the male plant is an inbred line), and the single-cross hybrid (the result of crossing two unrelated inbred parents).
This is why seed companies have provided guidelines to their research breeders as to select inbred lines that can produce good hybrids, without losing focus on the issue of profitable seed production. It is at this stage that the available technology regarding genetic engineering, through the use of molecular markers or double haploid use, can help breeders reduce the number of selection cycles, thus increasing the effectiveness of the breeding program. The flip side of this reality is that these resources are not available to everyone in the plant breeding activity, since they demand continuous and considerable financial resources worth millions of dollars, being that some of the leading world companies in this sector are reported to invest approximately USD 2 million daily, for agricultural research purposes.
Programming production, a constant challenge
One of the hardest parts of hybrid variety breeding is to mount a precise-as- possible scheme for hybrid seed production, since the latter must be timed and adapted to market requirements, timing and trends. As in any industrial process, it is absolutely necessary to work within an environment of fluent communication between those at market analysis department and those at sales & production depatment, which when it comes to the seed business can be extremely challenging. In part, this is due to the need to always identify the growers' need and those of the market in due time, within an environment in which several events may determine a radical change on what was planned even at the level of having to modify breeding research scope, as when new diseases break out.
Another factor stressing the importance of planning is that for certain hybrids a yield estimate for, at least, three harvest seasons is necessary, such as for modified single-cross hybrids, three-way hybrids and double-cross hybrids. Considering the latter as an example, since it is the most complex of all hybrids, the quantity of seeds from lines "A", "B", "C" and "D" must be increased within one harvest season. The next season will be dedicated to crossing "A" with "B", which will be assuming the role of male single-cross hybrid (AB), and also crossing inbred lines "C" with "D", to breed what will be the female single-cross hybrid (CD). Finally, during the third growing season the double-cross hybrid will be bred by crossing both single-cross hybrids, AB x CD.
Graf. 2 - Average maize yields on the U.S.A since the times of the civil war to present
When production is being planned, the process described in the previous paragraph happens the other way around: the first step is to come up with an estimate for what could be the sales (volume) for the double-cross hybrid. Then, and based on the records on seed yield potential from both male and female inbred lines, the estimate on the volume of seeds from the single-cross parents and the individual inbred lines is calculated.
There is yet another factor contributing for seed production being a constant challenge, and that is the weather. The first section of the seed "factory" is outdoors, i.e. the crop field where the seeds are produced, which implies that they are subjected to weather conditions such as rainfall, drought or even frosts that can, at times, cause considerable loss during harvest.
For countries like the U.S.A. there's the need to even plan on the basis of the occurrence of severe winter conditions, which is not the case for Brazil, since in some states the crop is grown in two distinct seasons, summer and winter. In this way, much as it happens in this country, Argentina and Chile can produce seeds during the Northern Hemisphere winter season and then export these seeds, a scheme which constitutes a very interesting business opportunity.
Hybrid seeds are exported to the U.S.A. but also to other Latin American countries that encounter difficulties to meet their own seed production. There's another way though, which is inverse and calls for the import of seeds under certain circumstances, i.e. the possibility of using the genetic resources from different international branches of a company at its headquarters' genetic engineering laboratories, where studies can be undertaken or genes introduced into parental lines. Few of the seeds produced under these conditions will return to the country of origin, to initiate the increase in hybrid seed production.
Bottlenecks to the production of high quality seeds
The last years have witnessed an important change in the world scenario of commodities and particularly, in the case of maize, the stocks are very low, thus forcing a rise in the price of foods.
The seed industry has been under great pressure by an enhanced demand, which could lead to a bottleneck in the production of high quality seeds if some key points are not anticipated. The seed companies have foreseen this moment and are investing millions of dollars to expand their facilities in different states, so that their capacity can be enhanced.
To be able to increase volume and quality simultaneously, the acquisition of state of-the-art machinery to equip seed processor units will have to include damage seed separator machines that operate through high definition imagery and color filters, known as "color sorters". This type of equipment is capable of sorting seeds infected by fungus and, in some cases, by insects and discards them, leaving the seeds with high germination capacity ready to be bagged and marketed.
page 2 ->> Hybrid maize seed production
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