Temperature during soybean seed storage and the amount of electrolytes of soaked seeds solution

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Improved germination of soybean seed treated with thiamethoxam under drought conditions

The effect of thiamethoxam on germination of soybean (Glycine max L.) seeds cv. Pintado under water deficit was studied. When used as insecticide at the recommended level (100/100 kg seeds) in the treatment of soybean seeds. thiamethoxam accelerated germination. Soybean germination was delayed under lower water availability: however pretreatment of seeds with thiamethoxam reduced the negative effects of water deficit on such process.

Effects of some phenolic compounds on soybean seed germination and on seed-borne fungi

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Determination of pore size distribution in soybean seed coats by mercury porosimetry

In this work we applied mercury porosimetry for the investigation of soybean seed coats. By using this method it was possible to determine the pore size distribution and also the pore size dispersion that is present in seed coats. The results showed that for the studied soybean genotype the seed coats had a characteristic pore diameter, but deviation of this size was not negligible. Finally, the results were confirmed by electron microscopy.

Determination of soybean seed respiration rate by the titulation method

This trial was carried out under laboratory conditions, with three lots of Iguacu soybean seeds, to determine the respiration rate by the titulation method. A randomized complete block design was used, with four repetitions, each one of them with 50 seeds and a control without seeds for each lot. The seeds were placed in gerbox with 40 mi of KOH 0.1N, on distilled water wet blotting paper for fixing the CO2 produced by seeds respiration. The material was placed in germinator at constant 25 degrees C for 16, 24 and 48 hours. After these periods, the titulation of the fixative solution was performed with HCl 0.1N to check the respiration rate. The most deteriorated seeds were those that presented the highest respiration rates, which were measured in mg of CO2/g of dry matter, when compared with the most vigorous lots. The titulation method was suitable for the evaluation of soybean seed respiration rate because the final results separated the lots in three different quality levels that were compatible with the results obtained from the accelerated aging and emergence.

Differences and similarities in the pore size distribution of soybean seed coats

In this work we apply the mercury porosimetry technique to determine the pore size distribution in soybean seed coats of different varieties. The analyses show that the porosity of soybean seed coats is different when seeds of different genotypes are compared. This result points the possibility of using pore size distribution to varietal discrimination.

EFFECT OF DROUGHT AND DEFOLIATION STRESS IN THE FIELD ON SOYBEAN SEED-GERMINATION AND VIGOR

Although drought and defoliation stress have been shown to reduce soybean [Glycine max (L.). Merr.] yield, little information has been published regarding their effects on soybean seed quality. Field experiments were conducted in 1986, 1987, and 1989 to evaluate the effect of drought and defoliation (1989 only) stress during soybean seed development on seed germination and vigor. Essex (MG [maturity group] V) and Union (MG III) were grown in 1986 and 1987, and Harper (MG III) and McCall (MG 00) in 1989. Moisture treatments were either well watered or drought stressed during seed development (R5 to R7). In 1989, a total defoliation treatment was also imposed at R6 as an additional stress factor. There were significant reductions in yield and yield components following drought stress in all 3 yr and following defoliation in 1989. Leaf conductance and transpiration also decreased in the drought stress treatments. There was no effect of drought stress on seed germination or seed vigor as measured by accelerated aging germination and the cold test across the four cultivars (determinate and indeterminate) and 3 yr. In 1989 slight changes in 3-d germination and conductivity occurred for some drought stress treatments. Most of this response, however, was related to increased occurrence of hard seed, which does not represent an indication of a change in vigor. Seed germination and vigor were significantly reduced for small, flat, shriveled, and underdeveloped seeds that only occurred following defoliation. These seeds represented a small portion of the seed lot that would normally be removed during conditioning. The data suggest that drought stress would have no effect on seed germination or vigor, unless the stress was severe enough to produce shriveled, flat, underdeveloped seeds.

Electrical conductivity of soybean seed and correlation with seed coat lignin content

The effects of soybean genotype and seed coat lignin content on bulk electrical conductivity were investigated. Seeds of nine soybean cultivars were hand harvested at R8 maturation stage in Londrina, PR., Brazil in 1995/96. Seeds were electrical conductivity tested using four replicates of 50 seeds per cultivar soaked in 75 mi of deionized water at 25 degrees C for 24 hours. Seed coat lignin content was determined using the potassium permanganate method. There was a significant relationship (R-2 = 0.84**) between electrical conductivity and seed coat lignin content, the latter being a characteristic that varies among soybean genotypes; the higher the amount of lignin in the seed coat, the lower the levels of seed exudates to the soaking solution and consequently the lower the electrical conductivity. It was concluded that seed soaking electrical conductivity is influenced by the seed coat lignin content, which is a characteristic that varies among soybean genotypes. Additionally, the EC test can be used as a valuable tool in the screening process for this characteristic, which is desirable for genetically improving soybean seed quality.

Structural changes in soybean seed coat due to harvest time and storage

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Discrimination of soybean seed lots by multivariate exploratory techniques

Physiological potential characterization of seed lots is usually performed by germination and vigor tests; however, the choice of a single test does not reflect such potential, once each test assesses seeds of differentiated mode. Multivariate techniques allow understanding structural dependence contained in each variable, as well as characterize groups of seed lots according to specific standards. The study aimed at evaluating variability among soybean seed lots and discriminate these lots by multivariate exploratory techniques as function of seed vigor. Experiment was performed with 20 soybean seed lots (10 lots cv. BRS Valiosa RR and 10 lots cv. M-SOY 7908 RR). Seed physiological potential was assessed by testing for: germination (standard, and under different water availability); vigor (accelerated aging and electrical conductivity); and field seedling emergence. Cluster analysis of seed lots, as well as Principal Component Analysis was performed using data obtained on all tests. Multivariate techniques allowed stratifying seed lots into two distinct groups. Principal Component Analysis showed that values obtained for variables: field seedling emergence, accelerated aging, and germination under different water availability were linked to BRS Valiosa RR; while to variables germination and electrical conductivity, were linked to M-SOY 7908 RR.

A Comparison of Soybean Seed Treatments

Seed treatment options are available to manage various fungi, insects, and nematodes that can damage soybeans before, during, and after emergence. These treatments are potentially beneficial for stand establishment and for protection against soybean cyst nematode (SCN). However, these seed treatments represent an additional cost to the producer.

Electrical conductivity of the seed soaking solution and soybean seedling emergence

Vigor of soybean [Glycine max (L.) Merrill] seeds can be evaluated by measuring the electrical conductivity (EC) of the seed soaking solution, which has shown a satisfactory relationship with field seedling emergence, but has not had aproper definition of range yet. This work studies the relationship between EC and soybean seedling emergence both in the field and laboratory conditions, using twenty two seed lots. Seed water content, standard germination and vigor (EC, accelerated aging and cold tests) were evaluated under laboratory conditions using -0.03; -0.20; -0.40 and -0.60 MPa matric potentials, and field seedling emergence was also observed. There was direct relationship between EC and field seedling emergence (FE). Under laboratory conditions, a decreasing relationship was found between EC and FE as water content in the substrate decreased, Relationships between these two parameters were also found when -0.03; -0.20 and -0.40 MPa matric potentials were used. EC tests can be used successfully to evaluate soybean seed vigor and identify lots with higher or lower field emergence potential.

Seed-borne pathogens and electrical conductivity of soybean seeds

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Acid-stable amperometric soybean peroxidase biosensor based on a self-gelatinizable grafting copolymer of polyvinyl alcohol and 4-vinylpyridine

A peroxidase was extracted from Chinese soybean seed coat, and its thermostability and acid-stability were characterized. This peroxidase was immobilized into a self-gelatinizable grafting copolymer of polyvinyl alcohol with 4-vinylpyridine(PVA-g-PVP) to construct an acid-stable hydrogen peroxide biosensor. The effect of pH was studied for optimum analytical performances by amperometric and spectro-photometric methods, also the K-m(app) and the stability of the soybean peroxidase-based biosensor are discussed. At pH 3.0, the soybean peroxidase maintained its bioactivity and the enzyme electrode had a linear range from 0.01 to 6.2 mM with a detection limit of 1.0 x 10(-7) M. In addition, the main characteristics of different hydrogen peroxide sensors were compared.

Effects of row spacing on productivity and nodulation of two soybean varieties under hot sub-moist tropical conditions in south-western Ethiopia

The objective of this study was to determine the optimum row spacing to improve the productivity of two soybean (Glycine max L.) varieties under the tropical hot sub-moist agroecological conditions of Ethiopia. A two-year split-plot design experiment was conducted to determine the effect of variety (Awasa-95 [early-maturing], Afgat [medium-maturing]) and row spacing (RS: 20, 25, 30, 35, 40, 45, 50, 55, 60 cm) on the productivity, nodulation and weed infestation of soybean. Seed and total dry matter (TDM) yield per ha and per plant, and weed dry biomass per m^2 were significantly affected by RS. Soybean variety had a significant effect on plant density at harvest and some yield components (plant height, number of seeds/pod, and 1000 seed weight). Generally, seed and TDM yield per ha and per plant were high at 40 cm RS, and weed dry biomass per m^2 was higher for RS >= 40 cm than for narrower RS. However, the results did not demonstrate a consistent pattern along the RS gradient. The medium-maturing variety Afgat experienced higher mortality and ended up with lower final plant density at harvest, but higher plant height, number of seeds per pod and 1000 seed weight than the early-maturing variety Awasa-95. The results indicate that 40 cm RS with 5 cm plant spacing within a row can be used for high productivity and low weed infestation of both soybean varieties in the hot sub-moist tropical environment of south-western Ethiopia.