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 Enquiries SEED News - may/june 2005
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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
Green soybean seeds
I have been observing in this year that my soybean seed lots presented a certain amount of seeds of green color. I would like to know if I should worry about the quality of these seed lots.
Seeds of green coloration possess inferior physiological quality, detected mainly by the potential storage loss and vigor tests that apply stresses to the seed. In this respect, the Wageningen UR University in Holland developed an equipment to physically separate these green seeds from the others ones. Seeds lots with more than 10% of seeds of green coloration should be discarded as seeds.
Logistics
Interesting the article on the logistics of seed production that the producers should adopt to obtain the right seed at the right amount and to distribute them appropriately. Could you comment a little about personnel qualification for that process as a whole?
Nowadays the seed producer cannot be considered anymore as a farmer that also produces seed for the market. The production involves different materials that should all be produced practically at the same time in variable amounts depending at the defined market with a year of antecedence, and that involves agronomic and commercialization knowledge. Another aspect is in relation to analysis of the production data, processing, laboratory, distribution and marketing, and annotations in the tip of the pencil are not enough, requesting qualified personnel with specific training. The data should be taken, analyzed and interpreted.
Hybrid
The production of hybrid rice seeds involves the male sterility, up to that I have no difficulty in understanding, however I have no idea on how seed of a sterile male material is produced. Could you help me?
Very well, there is more than one way of producing rice seeds of a sterile male material; however the simplest way is to use the genetic induction by temperature and photoperiod to obtain that material. Therefore a material can be normal in conditions with day length of 14/10 hours and with temperatures up to 32 °C during the reproductive phase and to present sterile male in conditions of 12/12 hours day length and temperatures higher than 32 °C. Thus, seed production will be in conditions of lower temperatures and photoperiod of 14/10 hours.
Milling
I am harvesting rice with 20-21% of moisture content and after drying the material presents 62 to the 66% of whole grain, after some hours this percentage begins to decrease, for instance after 4 hours it decreases up to 2% and 12 hours after being at the silo this income falls below 58%. The men in charge of the drying process say that don't know what is happening; I tell them that it is temperture stress. I need help to solve this problem.
The rice seeds fissures easily when there is a gradient of moisture content or temperature in its interior. In your case, probably the drying speed was superior to two percentage points per hour, or the seeds did not wait for a period of two hours before moving to a silo for homogenization of the temperature and moisture content in the seed. The solution is to follow up the process registering the drying speed and have a place for homogenization after drying.
Seed health
A lot of soybean seeds presented low emergence percentage, even having the quality standards for commercialization. Being evaluated the health quality the results indicated the presence of several fungi, with larger percentages of Cladosporium sp (8, 0%), Aspergillus sp. (4, 0%), Nigrospora sp. (2, 0%) and Fusarium sp. (1, 25%). May these fungi be responsible for the low emergence?
The evaluation of the health quality supplies very useful information when making decisions as the need of seed treatment, as well as the use of a lot as seed, for sowing purposes. In the present case the low emergence was not caused by the fungi contained in the seeds, because the ones that have the highest affect on seed quality are Aspergillus sp. and Fusarium sp. As the incidence of these two fungi is very low, their effects upon the quality of the seeds will also be small. Therefore, the low emergence is due to other causes, possibly to the low vigor of the seeds, to climatic factor or even the soil. In case the problem is of low vigor, the treatment of the seeds would not have effect.
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