Seed production in the family Cucurbitaceae is more complicated than in dry-seeded grain crops because seeds mature within a moist fruit and are often held at high moisture content for several weeks before seed harvest. Muskmelon (Cucumis melo L.), a member of this family, was used as a model system to contrast seed development with crops that are dry at maturity. A detailed time course for `Top Mark' fruit and seed development is presented based on previous studies. In muskmelon fruit, precocious germination is inhibited osmotically by the low water potential of the surrounding fruit tissue. Muskmelon seeds exhibit primary dormancy that affects viability very early in development but has a greater effect on seed vigor and is removed by afterripening during dry storage. Osmotically distended or fish-mouth seeds are dead seeds that occur in cucurbit seed lots after aging kills the embryo without disrupting the semipermeable endosperm that completely surrounds and protects the embryo. Cucurbit seed crops should be harvested before the onset of fruit senescence to prevent aging of the seeds inside. Open-pollinated cucurbit seed crops are frequently once-over mechanically harvested. Mechanical harvesting combines seeds from many stages of development into a single seed lot, which may adversely affect quality and increase seed to seed variability. Hand harvesting cucurbit fruit at the optimal stage of development could improve seed quality in some instances but is more costly and time consuming and would increase production costs.
Gregory E. Welbaum
Seeds of `Kumamotonokagayaki'(Kk), `Goldenball' (Gb), and `Purple Gem' (PG) (Zinnia violacea Cav.) were harvested at various stages of maturity and subsequent seed and plant performance were evaluated. The largest increase in ovule or embryo length and width occurred from 0 to 10 days after pollination (DAP). The seed weight was unchanged after 23, 25, and 30 DAP for Kk, Gb, and PG, respectively. The pericarp color was completely green from seeds harvested 20 DAP, while the seeds harvested from 30 to 35 DAP contained a mixture of green and brown seeds. Pericarp color change from green to brown was not a reliable index to harvest seeds. The percentage germination increased from seeds harvested from 10 to 19 DAP for all cultivars. From 20 to 40 DAP, germination was unaffected and >90%, while the rate of germination as measured by days to visible germination decreased slightly. Seeds harvested 20 to 40 DAP produced plants with similar growth and quality characteristics. Considering a 20- to 30-day difference between the first and last floret to open in a capitulum, capitula should be harvested 50 days after anthesis for good seed quality and to prevent shattering.
Xiaolei Hu, Miller McDonald, and David Tay
During the past 2 decades, automated plug production in the flower seed industry has created important requirements by growers for high-quality flower seeds. Using computerized imaging technology, a new seed vigor testing system, Seed Vigor Imaging System (SVIS), was developed at The Ohio State University. By analyzing the digital images of seedlings, it can detect and measure the length of hypocotyls and radicles separately, and then generate a value for the growth and uniformity each. This system provides a fast, labor-saving and objective approach to measuring seed quality. In this study, its capacity and correlation with field performance was studied and compared with other traditional tests, i.e. standard germination test, germinate rate, and accelerated aging test. Five species (dianthus, cleome, rudbeckia, salvia, and lettuce) were selected and their quality was tracked continuously by SVIS and other mentioned tests. It was found that stressed test (ageing test) was able to detect the quality deterioration earlier than others under ideal conditions, but SVIS could generate much more information, such as the growth, uniformity, and vigor level of the seed lot. Therefore, SVIS following 3-day ageing was developed and shown to be the most sensitive and comprehensive vigor test for those ornamental species mentioned above. Being fast and objective, this system will also benefit the global seed trade by providing a unique quality standard. In addition, it can also be of great usage to seed companies and germplasm centers worldwide for the routine quality track during shipment/storage and inventory management.
Kent J. Bradford
In 1981, R.H. Ellis and E.H. Roberts published a classic paper on the quantification of aging and survival in seeds (Seed Sci. & Technol. 9:373). This paper and subsequent refinements described a model of seed aging in storage that was based on the fact that to a good approximation, deaths over time in a seed population are normally distributed. The model provides a quantitative description of seed longevity across a wide range of storage temperatures and moisture contents. Despite its theoretical importance and practical success, the Ellis–Roberts approach has not been widely adopted by the seed industry to assess seed quality and predict longevity in storage. This may be due, in part, to the rather unfamiliar statistics (probit analysis) used in the model and the apparent complexity of the equations. It will be the argument of this presentation, however, that the precise quantification of seed longevity that this model affords is less significant than the insight that it provides into the nature of seed populations and how to think about them. The objective of this presentation will be to demystify the Ellis–Roberts model and illustrate with concrete examples how the application of population-based thinking is advantageous in many aspects of seed storage and quality assessment.
Sung Eun Lee*, Sang Gyu Lee, and Chiwon W. Lee
The influence of plant density on yield of three confectionery seed pumpkin accessions was investigated under non-irrigated field conditions. Seeds of Golden Delicious (GD), open-pollinated Chinese snow-white seed (CS), and a selection from Austrian hull-less (HL) pumpkin were planted 30, 60, and 90 cm apart in rows that were 127 cm apart with seedlings thinned to one plant per hill. Plants were grown from 23 May to 18 Sept. One fruit per plant was harvested from five plants for each of the three replications. The number of seeds (and dry weight of seed) per fruit were 242 (59 g), 304 (87 g), and 334 (106 g), respectively, at 30, 60, and 90 cm spacing for GD. The number of seeds (and dry weight of seed) per fruit were 219 (108 g), 266 (108 g), and 258 (106 g), respectively, at 30, 60, and 90 cm spacing for CS. The number of seeds (and dry weight of seed) per fruit were 376 (76 g), 404 (94 g), and 304 (82 g), respectively, at 30, 60, and 90 cm spacing for HL. Highest seed yield was at 60 cm plant spacing for CS and HL, whereas GD produced highest seed yield at 90 cm plant spacing. The differences in total seed yield, seed size, and confectionery seed quality, as influenced by plant density and seed source, were also characterized.
Warley M. Nascimento
The growing of transplants in plug cell trays is the primary method of producing brassica transplants in many countries. Seed quality is an important aspect to achieve success in transplant production. Seed size may affect seed performance, seedling growth and development of brassica transplants. Seeds of cauliflower (`Vitoria de vero') and cabbage (`Unio') from Embrapa Vegetables were used in this study. During seed conditioning, seeds were classified using round screens generating three (>1.5, 1.5-2.0, and 2.0-2.5 mm) and four (>1.5, 1.5-2.0, 2.0-2.5, and < 2.5 mm) seed size categories, for cauliflower and cabbage, respectively. The original seed lot was used as control. Seed weight increased with seed size. Seed germination (laboratory) and seedling emergence (greenhouse) were not affected by seed size. In both species, root and shoot weight, and leaf area, measured 30 days after seeding, in greenhouse conditions, increased with seed size. Also, transplants from larger seed size resulted in a significantly higher root weight, shoot weight, and leaf area relative to the original (control) seeds. The results indicate that, overall, an adequate seed conditioning improve brassica transplant quality.
D. P. Coyne, J. R. Steadman, D. T. Lindgren, D.S. Nuland, J. S. Beaver, F. Saladin, and E. Arnaud Santana
Disease of beans, particularly common bacterial blight (CBB) (DR, NE), rust (DR, NE), web blight (WB) (DR) and bean golden mosaic virus (BGMV) (DR) are major constraints to bean yields and seed quality. The objectives were to identify resistant (R) germplasm, to conduct genetic studies, to develop R cultivars (DR, NE), to improve research facilities and capabilities (DR), to train personnel and educate graduate students (DR, NE). The expected impact is (1) the improvement of breeding programs, yields and income to farmers and (2) returning specialists will permit improved research in the DR. The most significant advances in research were as follows: (i) BAC-6 dry bean breeding line was found to be R to CBB seed infection, (ii) The reaction to CBB was inherited quantitatively with low NSH estimates, (iii) Rust race nonspecific R was correlated with abaxial leaf pubescence; the latter trait was inherited qualitatively, (iv) R to BGMV and WB were identified and (v) Improved cultivars and breeding lines were developed (DR, NE).
Andrés R. Schwember and Kent J. Bradford
Seed priming (controlled hydration followed by drying) is used to alleviate high temperature inhibition of germination and improve seedling emergence of lettuce (Lactuca sativa L.) and other species. However, seed priming can also reduce the longevity of seeds during dry storage. Alternative drying methods [i.e., slow drying or moisture content reduction (MCR) before drying] can extend seed longevity compared to conventional rapid drying procedures after priming. Three postpriming drying treatments were tested on `Conquistador' and `Genecorp Green' lettuce seeds: rapid drying, slow drying and MCR (10% fresh weight loss, then held at 100% relative humidity (RH) for 6 hours, followed by rapid drying). The effects of the postpriming treatments on seed quality and longevity were compared based upon standard germination tests, germination rates, thermogradient table tests, controlled deterioration (CD) tests, and headspace volatiles analysis. The latter may be correlated with seed longevity as release of volatiles (e.g., acetaldehyde, ethanol) is associated with lipid peroxidation. While neither slow drying nor MCR before drying restored lettuce seed longevity to that of the control (not primed) seeds, the MCR method generally gave better results in both cultivars compared to rapid drying. Among the CD test conditions used, 50 °C and 75% RH gave the most consistent results for estimating potential longevity. Headspace volatile emissions from both control and primed lettuce seeds were very low and were not well correlated with seed longevity. Alternative postpriming drying regimes can extend seed longevity while retaining the beneficial effects of priming.
Daniel J. Cantliffe
Science and Technology is one that gives a good overview of the whole area of seed development, dormancy and germination, including hormonal regulation of seed germination as well as seed quality aspects such as testing, seed vigor, seed-borne pathogens
Matthew D. Kleinhenz
programs and international working groups.” “Mark explained relationships among seed quality, stand establishment, and system productivity and helped steer improvements in all through independent and collaborative efforts. Mark bridged research, real