Last July we were visiting the Steyr tractor factory in St. Valentin (Austria), as we have already told you in this article. On the second day, we were lucky to go to the field where we were able to test several Steyr tractors. A Vermande machine arrived to a plot nearby the event to cut the tassel of maize plants, so we took the opportunity to see it since it is an unusual job for us.
The corn plant has a male part (tassel) and a female part (ear). The male inflorescence (tassel) normally becomes visible among the last leaves of the plant, 7 to 10 days before the styles of the female inflorescence appear. Usually, 2 to 3 days before the pollen release takes place, theearsreach their maximum size and this is completely unfolded, so the plant reaches its final height. The tassel is composed of a central stem, which corresponds to an extension of the stem of the plant. In this stem is developed a spike, under which several fine branches of feathery aspect are originated that correspond to lateral spikes. When the time comes, the pollination process begins, with the pollen falling from the top of the plant (tassel) to the middle part of the plant where the female part (ear) is located. This would be a natural or open pollination process. In the fields of hybrid seed generation, this process is altered in the following way that we will show you in the next paragraphs.
The fields we saw in Austria are used to produce hybrid seeds. In this field, two varieties of maize were sown. The sowing system is by means of a 6 furrow sowing machine; having one seed variety in the 4 central furrows and the other seed variety in the two outer furrows. In this way, the field is planted with 4 furrows of one variety and two furrows of another variety. To the variety that is used in the 4 central furrows, the tassel is removed to have a much more controlled pollination. The plants in these furrows, from which the tassel has been removed, are pollinated by the plants in the furrows that have the tassel (of a different variety), so that hybrid seeds are obtained by being pollinated with different varieties.
The most common corn sowing frames for hybrid seed generation are 6:2, 6:1, 4:2, or 4:1. For example, for frame 4:2, it would be 4 female furrows, which are the rows from which the tassel is removed (male part of the plant) and 2 male furrows (rows that are used to pollinate plants that have run out of tassel).
Hybrid maize produces much higher yields than maize produced by open pollination, as well as other important features such as resistance to disease, drought, climate, etc. In the case of modern maize seed, the varieties to be hybridized are carefully selected so that the new variety shows specifictraits found in both mother plants.
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