Seed-borne pathogens and electrical conductivity of soybean seeds

Adequate procedures to evaluate seed vigor are important. Regarding the electrical conductivity test (EC), the interference in the test results caused by seed-borne pathogens has not been clarified. This research was carried out to study the influence of Phomopsis sojae (Leh.) and Colletotrichum dematium (Pers. ex Fr.) Grove var. truncata (Schw.) Arx. fungi on EC results. Soybean seeds (Glycine max L.) were inoculated with those fungi using potato, agar and dextrose (PDA) medium with manitol (-1.0 MPa) and incubated for 20 h at 25 °C. The colony diameter, index of mycelial growth, seed water content, occurrence of seed-borne pathogens, physiological potential of the seeds, measured by germination and vigor tests (seed germination index, cold test, accelerated aging and electrical conductivity), and seedling field emergence were determined. The contents of K+, Ca2+, and Mg2+ in the seed and in the soaking solution were also determined. A complete 2 × 4 factorial design with two seed sizes (5.5 and 6.5 mm) and four treatments (control, seeds incubated without fungi, seeds incubated with Phomopsis and seeds incubated with Colletotrichum) were used with eight (5.5 mm large seeds) and six (6.5 mm large seeds) replications. All seeds submitted to PDA medium had their germination reduced in comparison to the control seeds. This reduction was also observed when seed vigor and leached ions were considered. The presence of Phomopsis sojae fungus in soybean seed samples submitted to the EC test may be the cause of misleading results

Physiological ripening of Anadenanthera colubrina (Vellozo) Brenan seeds

Abstract: The seed physiological maturity knowledgment is critical determine its maximum production and physiological quality. The objective of this study was to determine the ideal time to harvest by evaluating seeds physiological maturity. Seventeen weekly harvests of fruits and seeds from matrices located in the Brazilian city of Botucatu, SP, were performed from May to September 2001. Fruits size and weight, seed water content and dry matter, and germination and emission of primary root were evaluated. Seeds showed maximum dimension in the thirteenth week of collection, while the highest fruit weight was obtained in the twelfth week of collection. Water content decreased over time. Seeds dry matter showed its highest value in the sixteenth week harvest, while germination percentage showed its highest value between the fourteenth and fifteenth week harvest. The percentage of primary root emission was observed with maximum value in the tenth week harvest. Based on the results, it is concluded that the best Anadenanthera colubrina harvest season occurs between the fourteenth and fifteenth weeks

Accelerated aging as vigor test for sunn hemp seeds

ABSTRACT: This study aimed to determine the most appropriate method to assess the sunn hemp ( Crotalaria juncea L.) seed vigor in the accelerated aging test. Five seed lots from harvest 2007/2008 were evaluated for germination, vigor and seedling emergence in the field. Accelerated aging test was performed at 41°C during 48, 72 and 96 hours, with and without sodium chloride saturated solution. Then, the promising procedure was also performed for 2008/2009 and 2009/2010 harvests. In the traditional accelerated aging test, the no-uniform water acquisition by the seeds adversely affected results. Accelerated aging test with sodium chloride saturated solution is the most appropriate method to evaluate the physiological potential of sunn hemp seeds, and the combination of 41°C and 96 hours is efficient for separating of seed lots in different vigor levels