Led by A. Susana Goggi, seed physiology studies at the SSC deepen our understanding of the complex interactions between environment, genome, phenotype, seed treatment, and seed storage on seed characteristics and quality. They inform how biological control could be used for emergence enhancement or for control of seed-borne diseases in seeds.
Dr. Goggi and her research team examine four major issues: (1) the effect of seed production environment on seed quality and seed storability; (2) seed treatments, integrated pest management alternatives, seed harvest, and seed storage of corn and soybean; (3) selection in biofuel crops and seed quality of biomass-based biofuel crops of Miscanthus, sorghum, and Jerusalem artichoke; and (4) the effect of cropping system on seed quality, composition, and the proportion of constituent fatty acids in the seed oil of soybean and corn. The following are examples of studies under each research stream.
►The effect of production and storage environment on seed quality and storability
Seed quality refers to the germination, vigor, and composition characteristics that allow seeds to emerge and establish a healthy plant stand in the field. Studies done in collaboration with public and private sector scientists worldwide generated results relevant to the seed scientific community, seed industry and farmers who are always in search of better-quality seeds.
Sustainable intensification of crop production using perennial groundcover to regenerate and enhance ecosystem services. As farmers contemplate implementing perennial cover crop systems to protect and enhance soil, reduce nutrient export into water, and enhance the potential for carbon sequestration, they need to know whether adopting such a conservation practice will bring economic returns. Efforts along this line have elucidated the effects of seed characteristics on yield at the whole-plot and single-plant level in corn grown with perennial ground cover. Findings also demonstrated that current seed sizes sold in the market are adequate. Further narrowing the seed size and shape distribution in a seed lot would require additional seed conditioning operations which are costly and cause unnecessary seed damage. Ongoing projects explore the effect of corn plant proximity to a perennial ground cover on single-plant corn development and yield, investigate plant shade avoidance mechanisms in corn, and identify the seed characteristics and seed treatment that make for a successful perennial cover crop establishment.
TZ testing image library of seed corn physiological damages occurring in seed production (completed 2022). Seed drying is a process that involves blowing heated air through the seed mass to reduce seed moisture content to safe levels for storage. Excessive heat or low air current inside a seed drier, however, may irrevocably degrade seed quality. This study determined the extent of seed dryer damage in corn seed using the tetrazolium test and other seed quality tests.
Use of chemical defoliation in seed corn production (completed 2021). Chemical defoliation accelerates seed maturation, allowing earlier harvest, reduces seed size, and possibly, improves seed vigor. It also facilitates harvest schedules and the management of seed dryer space. However, early defoliation may increase the number of low-density seed in a seed lot. Scientists worry that seed companies may jeopardize seed quality and storability by practicing early chemical defoliation. This study demonstrated that chemical defoliation can accelerate seed corn desiccation safely. An important physiological change during the acquisition of desiccation tolerance is the migration and alignment of oil bodies along the cell membrane in corn embryo cells. These oil bodies are accumulated in the cytoplasm of the embryo cell during seed development and, as seeds dehydrate, they migrate to the cell membrane to protect cells from dehydration. This migration of oil bodies and alignment alongside of the cell membrane is essential to seed quality. By analyzing physiology and desiccation data in seed corn produced under early plant defoliation treatments, Center and private sector researchers uncovered that oil bodies within embryo cells followed normal migration patterns according to seed moisture content. Seed quality remained high regardless of defoliation treatment.
►Biological seed treatments and seed quality and seed storability
Farmers, the seed industry, and policymakers are always in search of alternatives to chemical pesticides. Microbial seed treatments, derived from naturally occurring organisms, are applied directly to the seed to enhance seed germination and seedling growth. What treatments can best stimulate seedling growth and plant establishment? Studies in this area also address novel methods for the biological control of bacteria using bacteriophages as an alternative to antibiotics or to promote germination. The findings of the following studies assisted seed growers as they decide on what sustainable and ecologically-friendly seed treatments to use.
Biostimulant seed treatment effects on seedling germination of hybrid tomato in greenhouse testing. This study investigated the use of biostimulants to enhance tomato seed germination in the greenhouse. Findings showed that the biostimulant seed treatments Cytozyme Seed+ and BioST VPH 100 did not enhance the development of tomato seedlings regardless of hybrid or seed vigor. These biostimulants were ineffective even when seed lots of similar seed vigor levels were compared.
The effect of microbial seed treatments on stand establishment and uniformity. This study examined the effects of QuickRootsTM seed treatment (Bacillus amyloliquefaciens and Trichoderma virens) on stand establishment and uniformity of two Pioneer corn hybrids selected based on their divergent stress emergence scores. Seed companies include these stress emergence scores on the seed-sale label to facilitate the selection of hybrid seed by farmers. The researchers found that the product had a negative effect on stand establishment regardless of the hybrid’s stress emergence score. This information is useful to farmers seeking to maximize stand establishment and uniformity for better grain yields.
Use of biological seed treatments to enhance seedling emergence and establishment in organic corn hybrid seed. This research showed that the biological seed treatment Seed Start 200 enhanced seedling emergence and establishment better than any other treatment investigated.. It suggests that organic farmers may use this biological seed treatment as a viable alternative to improve seed vigor and seedling emergence in the field.
Use of bacteriophages to control seed-borne diseases. Bacteriophages are naturally occurring viruses that can be used to combat bacterial diseases in seed. They are used as environmentally safe alternatives to antibiotics intended to reduce bacterial resistance. There are but a few antibacterial products in the market that are used to treat seeds. This research demonstrated that a bacteriophage-polymer mixture can be used as a seed treatment against bacterial diseases in maize seeds. These bacteriophages can remain active on the seed throughout storage and lyse the bacteria around seeds germinated in culture media. They remain active for up to six months on treated seed.
Seed priming with plasma-activated water. This study found that plasma-activated water hastened seed germination and increased seedling dry weight in the laboratory, a phenomenon not observed in soil and cold germination conditions. The findings have a bearing on farmers’ management practices and can assist in the design planting equipment that will allow plasma-activated water applications at planting.
►Breeding corn and soybean seed with improved characteristics while maintaining seed quality
Integrating plant breeding, genetics, and seed science, this research stream sought to stymie the unintended detrimental effects of plant breeding and selection on seed quality characteristics and seed germination. These studies advance the development and release of new cultivars, parental lines, and hybrids.
Disease pressure in seed fields and its effect on seed quality. As part of the effort to understand the interactions between plant genetics, disease resistance, and seed quality, this work evaluated seed composition and germination of soybean seed produced under disease pressure in SDS- and SCN-tolerant soybean varieties. The findings fueled public-private partnership in predicting seed quality of tolerant soybean under disease pressure.
Genome fluidity in soybean seeds. Genome fluidity refers to the genomes’ capacity to reorganize; it has been observed in many plants. Knowing more about it enables a better understanding of the phenotypic and genotypic changes in plants as they adapt to stress and climatic changes. Many of these genome changes, known as “allele-switching” or de novo variation, are stable and heritable. Resulting from biotic or abiotic environmental stress, these can modify metabolic pathways leading to changes in seed composition, a trait closely associated with seed quality and seed vigor.
Reducing phytate content in corn while preserving good seed germination. Phytic acid, the only source of phosphorus in seeds, is essential for seed germination. Monogastric animals, however, cannot digest phytic acid; it also blocks animal’s absorption of essential nutrients in feed. This research collaboration identified, for the first time, low-phytate corn inbreds with good seed quality. It demonstrated that inbreds can retain good germination and seed quality after recurrent selection for their low phytate trait.
Biomass-based ethanol production crops in Iowa. Many crops, including Miscanthus, Jerusalem artichoke, and sorghum, are good sources of biomass. Two develop new cultivars, breeders must successfully produce new crosses with exotic materials selected for improved plant characteristics. Some of these exotic materials have germination problems, produce few seeds, or require large field plantings to determine cold tolerance at seedling stage. Knowledge generated through these studies helped Iowa seed companies make business decisions based on science.
►Effect of cropping system on seed quality, composition, and the proportion of constituent fatty acids in the seed oil of soybean and corn
This string of studies investigates the detrimental effects of abiotic and biotic stress during vegetative and reproductive stages of plant development on seed quality and composition.
Effect of phosphorus (P) and potassium (K) fertilization on seed quality and storability. Seed production fields are often over-fertilized to maximize yield. This project provided evidence that excessive P and K fertilization changes the viability, composition, and fatty acid profiles of soybean seed. The finding gave plant breeders key information on the influence of soil fertility when selecting and developing new varieties because fatty acid composition changes with soil fertility (i.e., low oleic and linolenic acids in soybean).
Effect of seed treatment and storage environment on soybean seed quality. Most corn seed and some soybean seed sold in the U.S. and other developed countries are treated with chemical fungicides and insecticides to prevent pathogen infections and insect damage during the early stages of germination. Soybean seeds exposed to inadequate storage conditions in dealers’ warehouses and farmers’ storage sheds can lose seed viability and vigor. This study investigated the effect of seed composition, seed treatment and maturity group on storability of soybean seed. Seed growers unable to sell/plant their seed during the current planting season find use for its results.