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 Enquiries SEED News - july/aug 2008
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This section is coordinated by the professors from the Federal University of Pelotas-Brazil, with the objective of answering the inquiries sent by the readers.
Send your question to e-mail: silmar@seednews.inf.br
"I enjoyed the subject of the last edition of SEED News, which approached the positive aspects of film coating in seeds. Based on this, I would like you to explain how the process of improvement of the distribution of treatment on the surface of the seed was determined."
It can be seen that film coating provides a better distribution of an insecticide and/or a fungicide on the surface of the seed, from its weight. Firstly, 100 soybean seeds were weighed individually, classified by width and without coating. Afterwards, the distribution of weight was determined. The same was done for coated seeds only with fungicide, and with coated seed with fungicide and film coating. The results showed that many of the seeds coated only with fungicide presented a sub or super dosage, while the seeds with fungicide and film coating presented a uniform distribution of the covering.
"It can be observed that in a batch of seeds there are big and small ones. So, how can the situation, in which the treatment of seeds should be coated with the same dosage, be seen?"
Indeed, in a batch of seeds there is a great difference in relation to size; in some species more than in others. In corn and soybean, the difference is quite accentuated, making it possible to normally classify and commercialize by size. The quality of the treatment process in classified seeds can be considered good. Nevertheless, when the difference in size is big, the quality of the process is compromised, because with the products for seed treatment are indicated by weight, where 100 kg of seeds are treated, the small ones will receive less of the product than the big ones, as they possess a smaller surface for coating. In this way, the classification of seeds for the treatment process is essential.
"I have frequently heard that hybrid material produces much more than the conventional varieties. Is this a great truth, or does it depend on many factors?"
Hybrids in general produce much more than conventional varieties. However, this will depend on the degree of heterosis of the hybrid and of the species. For corn, for example, the increase can be more than 100%, when one compares a simple hybrid with a variety. However, it will be less than 100% in comparison to double corn hybrid with a variety. On the other hand, in rice, a hybrid can produce 30% more than a variety, being still attractive enough to the farmer. But for wheat, the productivity gains with hybrids are in the zone of 5 to 10%, which stops being attractive.
"I would like you to explain what should be done, so that a variety or a hybrid can be commercialized?"
To avoid low performance materials from being put on the market, resulting in serious damage to the farmer, there are procedures that should be adopted before a material is commercialized. The material must be registered and, for this, the obtainer presents the research results relative to the values of the variety and use (VCU), which can vary from species to species. For the large crops, it is one kind of VCU, and for vegetables, another. Apart from the registration of a variety, it is essential for the commerce that the obtainer can also protect the variety and like this, avoid that the seeds of his/her variety become public property.
"Would it be possible to provide me with a good example of an essentially derived variety (EDV), because I am having difficulty in understanding the subject."
An EDV is the one that derives from another one, as the definition explains. But, in practice, to characterize a situation is a little more difficult, because, by the way, the International Seed Federation, directly interested in the subject, has been discussing details for 20 years. Now, an example can be given: in the case of Brazil, where several soybean varieties of high agronomic performance receive the gene that gives tolerance to the Glyphosate herbicide, so these new varieties are considered EDV.
"I frequently attend lectures in which the rate of seed usage (RSU) is mentioned for a determined region. After all, I thought that all farmers used seeds for their cultures. Can you explain what RSU is?"
Of course the farmer uses some kind of material to establish his crop; however, one only considers it a seed when s/he uses material coming from a seed producer. So, RUS is the percentage of seed usage in relation to the total cultivated area.
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