Historically based on tradition and experience, the decision-making process in agriculture has been transformed in recent years by technological innovations that increase production and provide solutions to the challenges posed by pests, natural limitations of farmland and the effects of climate change.
Brazilian researchers have developed a technique that helps select seeds of soybeans and other legumes by stages of maturity, ensuring physiological quality without destroying samples.
Scientists used light and artificial intelligence (AI) to show that chlorophyll fluorescence is an effective and reliable indicator of soybean seed maturity. They validated the results using machine learning algorithms. The new technique can be used to classify commercial seeds.
The greener and less mature the seeds are, the less vigor and germination capacity they have, so their quality is lower. As a result, soybean seed lots with more than 8% green seeds will have their market value reduced and cannot be exported. Green seeds also produce less oil, with higher acidity and higher refining costs.
Manual analysis of seed quality is required by law in Brazil. It must be performed by a technician accredited by the Department of Agriculture and includes visual separation by color. Green seeds are discarded and destroyed, forming waste.
“I consider this study a milestone. To date, no studies in the literature have addressed the possibility of separating seed stages based on chlorophyll fluorescence. In addition to soybeans, the method can also be used for other legumes. It’s a great advance in scientific knowledge,” he said Thiago Barbosa Batista First author of an article about the study released in the diary frontiers in plant science.
The research was part of Batista’s doctoral thesis that was co-developed FAPESP’s support. His thesis supervisor was Edvaldo Aparecido Amaral da Silva Professor at the School of Agricultural Sciences at São Paulo State University (FCA-UNESP) in Botucatu and last author of the article.
“The phenotyping of different seed types was the main reason for establishing our topic group. We focused on chlorophyll retention and its low-quality association, which in turn led to the need to analyze the stages of seed development. The results of this study improve the reliability of characterizing maturity when seeds show similar shades of green, especially at nearby stages,” said Amaral da Silva, leader of a Project on the “green seed problem”.
The study was conducted in collaboration with Clíssia Barboza da Silva, researcher at the Radiation Biology and Environment Laboratory of the Center for Nuclear Energy in Agriculture (CENA-USP) of the University of São Paulo. Barboza da Silva is also supported by FAPESP through three projects (17/15220-7, 18/03802-4 and 18/01774-3).
“This technique avoids the destruction of seeds, which are automatically classified by the AI algorithm. We are currently analyzing samples, but this could be done seed by seed in the future,” she said.
For several years, Barboza da Silva has been analyzing seeds using light-based technologies such as autofluorescence spectral imaging. In September 2021, a study she led showed that autofluorescence-based images could be used to detect changes in the optical properties of soybean seed tissue and consistently distinguish between high and low vigor seeds. An article about the study was published in Scientific Reports.
maturity in pictures
Researchers sowed soybean seeds in pots and maintained relative humidity at 65% and average air temperature at 24.2°C. The pods were collected manually during the ripening period, and the seeds were classified by reproductive stage as R7.1 (beginning of ripening), R7.2 (mass ripening), R7.3 (seeds separated from mother plant), R8 (harvest point) or R9 (final maturity).
Physical parameters, germination, vigor and pigment dynamics were analyzed for seeds collected at different stages of maturation.
High-resolution autofluorescence spectral images (2192 x 2192 pixels) were acquired using a VideometerLab4 system with light-emitting diodes (LEDs) at different excitation wavelengths in combination with optical long-pass filters.
Autofluorescence signals were extracted from images acquired at different excitation/emission combinations, but the researchers concluded that the 660/700 nanometer (nm) and 405/600 nm combinations were the fastest and most accurate in identifying the different stages of the seed ripening were.
Chlorophyll is highly fluorescent. It emits light when exposed to radiation of certain wavelengths because it does not use all of the energy in the light and “loses” some of it through fluorescence. This “excess” is captured by the equipment, which converts it into an electrical signal and creates an image with varying shades of grey, white and black. The lighter the area, the higher the chlorophyll content, indicating that the seed is less mature.
Mature seeds normally retain chlorophyll as a source of energy while storing the nutrients (lipids, proteins and carbohydrates) necessary for the young plant to develop. After fulfilling this function, the chlorophyll degrades, and the less chlorophyll left, the more advanced the seed’s maturation process, with more nutrients and better quality.
The “green seed problem” refers to chlorophyll retention in mature seeds and is associated with lower oil and seed quality. It can be caused by frost but is made worse by the high temperatures and water shortages brought on by climate change in recent years.
About the Sao Paulo Research Foundation (FAPESP)
The São Paulo Research Foundation (FAPESP) is a public body with a mission to support scientific research in all fields of knowledge by awarding grants, fellowships and grants to researchers affiliated with universities and research institutions in the state of São Paulo, Brazil . FAPESP recognizes that the very best research can only be achieved by collaborating with the best researchers at the international level. Therefore, it has established partnerships with funding agencies, universities, private companies and research institutes in other countries known for the quality of their research and has encouraged scientists funded by its fellowships to further develop their international collaborations. Learn more about FAPESP at www.FAPESP.br/en and visit the news agency FAPESP at www.agencia.FAPESP.br/en to keep abreast of the latest scientific breakthroughs, FAPESP helps achieve this through its many programs, awards, and research centers. You can also subscribe to the FAPESP news agency at http://agencia.FAPESP.br/subscribe
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