This section is coordinated by professors from the Federal University of Pelotas/Brazil, with the objective of answering inquires sent by the readers. Send your questions to firstname.lastname@example.org
“Several equipments are used in soybean seeds processing in order to remove undesirable materials and to classify the seeds, as one can see in SEED News last issue. However, I ask you for an explanation: why is the gravity board/table put after classifying seeds according their sizes?”
The machines used for seeds processing operate based on some basics, usually only one but more than one can be used, as it is for the gravity board/table. Such machine separates materials based on the specific weight difference among them, but when seeds size is not uniform it also tends to separate according to seed size, thus reducing the efficacy of the process. So, in order to separate according to specific weight, with high efficiency, it is important that seeds should be as more uniform as possible, putting the size classifier before the gravity board/table.
“I would like to know the place of the origin center of maize as well as what is being done to avoid losing genetic variability and, thus, make it able to be used in breeding programs.”
Maize has its origin place in Central America. To avoid losing the valuable genetic diversity that maize features, as any other species, scientific expeditions are performed for collecting materials in field, thus preventing man from destroying any material thoughtlessly. As for maize, over 30,000 accesses (samples with up to 2,500 seeds) have been collected, which are stored at the international center for maize and wheat breeding (CIMMYT), under low moisture and temperature conditions.
“I often hear that it is advisable to use high vigor seeds since they, besides surpassing adverse conditions easily, also tend to produce more. This way, I would like to know what
can be considered as a high vigor lot as to maize.”
The maize seed companies do use high technology, harvesting the seed on the cob close to the physiological maturity point, among other procedures. Thus, selling seed with high physiological quality and separating those seed lots that usually do not have germination
above 90% and 85 at the cold test. This allows us to say that a high vigor seed lot for maize is one that presents more than 85 % on the cold test.
“I liked dr. Delouche's essay about statistics and approximations, a lot. So, I would like you to comment the relation between such parameters and seeds quality.”
The evaluation of a seed lot quality is performed in a small fraction which represents the whole lot. For germination, 400 seeds are used, which represent more than 60 million seeds in a 10 tons lot. So results can vary, which, up to a given point, is accepted. Such variation is higher for seed lots that show low physiological quality because they have more dead seeds or seeds that will raise abnormal seedlings. This is one more reason for using high physiological quality seeds.
“Seeds quality is affected by several factors, among them temperature, and I have noticed that in soybean harvest during January and February, the temperature of the grain mass is superior to 30°C. Could you inform how long can seed keep such temperature before losing its quality?”
Seed producers already know that hot soybeans do not resist too long and so they cool the seed mass as soon as possible – usually within one week. It is known that reducing temperature in 5°C the seeds storage potential is doubled.
“I am a soybeans seed producer and some days ago a farmer who bought seeds from us put a prosecution against our company asking for indemnity because his crop had been
decimated by a disease called Asian rust. What can I do?”
The responsibility of a seed producer is up to crop establishment because up to that moment the process has much to do with seeds quality. After that stage, risks are up to the farmer, mainly if the disease is not transmitted by the seed and the cultivar is not characterized as resistant to the disease (for Asian rust there are no resistant varieties at market level).