Abstract
Several chemicals applied to dry seeds by means of organic solvents were successful in preserving seed quality as determined by germinating capability of seeds or ATP content. The fungicide (pentachloronitrobenzene)-treated, injured or healthy pea (Pisum sativum L. cv. Alaska) seeds were highly resistant to infection by Aspergillus ruber (Konig, Spiekerman and Bremer) Thom and Church (NRRL 52), a storage fungus. The insecticide, Chlorpyrifos 3 caused the lima bean (Phaseolus lunatus L. cv. Fordhook 242) seeds to produce seedlings with reduced levels of damage from the seed-corn maggot, Hylemya platura (Meigen). The antibiotics, chloramphenicol and puromycin, slowed down the rate of deterioration of lettuce (Lactuca sativa L. cv. Grand Rapids) seeds stored under accelerated aging conditions [43°C & 85% Relative Humidity (RH)].
The effects of fruit age on the seed quality and germination percentage of ‘Duncan’ and ‘Flame’ grapefruit and ‘Hamlin’ sweet orange were investigated. Our results suggested that seed germination varied from 98% to 100% for the two grapefruit cultivars and 85% to 100% for ‘Hamlin’ regardless of time of harvest. Within the first 5 months of the harvest season, chilling of ‘Duncan’ and ‘Hamlin’ seeds at 4 °C for 7 days after fruit sampling resulted in a lower germination percentage only with the ‘Hamlin’ seeds. Seed moisture content of all three cultivars varied slightly through the season and remained steady at 60% and 70% for batches of fresh seeds stored at room temperature or at 4 °C. Our results suggest that high seed viability and germination percentage can allow the use of these seeds for experimentation regardless of the time the fruit were picked during the harvest season.
Significant industry interest exists for evaluating the lower Sacramento Valley as a production region for specialty dry beans. This interest is being driven by erratic or inconsistent production in the existing commercial production regions, mostly in the Pacific Northwest and the Mid-West regions. The environmental conditions in the Sacramento Valley are favorable for producing consistent yields of high-quality dry beans. Specialty beans are generally typified by limited markets and relatively high producer returns, and offers an attractive rotation crop for local growers.
Variety evaluations including many of the most popular or likely candidates for a local specialty bean industry were conducted in 1991 and 1993. Parameters evaluated included plant architecture, flowering dates, pod set and retention, maturity dates and seed yield. Additional qualitative evaluations to determine varietal quality were also conducted. Many varieties were identified that had both acceptable yield and seed quality potential.
Standardized seed vigor tests must be developed for greenhouse-grown flower species. Current vigor tests used to evaluate large-seeded agronomic crops are generally not useful for evaluating smaller-seeded flower species. One alternative is to use radicle length in seedlings grown under controlled environments as an indicator of seed vigor. For that purpose, a seed vigor test was developed that uses digital images taken using a flat bed scanner to measure radicle length in small-seeded flower species. A novel, cellulose substrate was used for germinating seeds. It provided similar moisture-holding properties to standard germination blotters used by commercial seed analysts, but is clear. This has allowed for quick image acquisition without removing seedlings from the petri dish. Correlations were made between seedling growth (radicle length, total seedling length, and total seedling area) with other vigor tests (saturated salts accelerated aging) and greenhouse plug flat emergence. For several seed lots of impatiens that varied in initial seed quality, radicle length after 4 days showed good correlations (>R 2 = 0.79) with other measures of seed vigor for describing seed quality. This system is an improvement over other attempts to use computer-aided assessment of digital images because it provides digital images that do not vary due to external lighting; it uses software that can evaluate radicle length in a petri dish assay that does not require a slant-board for straight radicle growth; it relies on standard germination technics used by every seed lab; it uses a clear substrate to replace the opaque blotter to allow digital images to be taken within the petri dish; and accurate measurements of seedling parts is performed in under 2 min per petri dish.
Among the factors affecting germinability of a seed lot are the environmental conditions under which the seeds are produced. The objective of this study was to determine the effects of temperature during seed development on seed quality of two Asteraceae species. Seeds of lettuce cv. Tango and Helianthus debilis cv. Vanilla Ice and sp. cucumerifolius were produced in a greenhouse under one of two treatments: i) hot (27, 40, and 20 °C temperatures average, max, and min, respectively), and ii) cool (23, 33, and 18 °C temperatures average, max, and min, respectively). In both species, heavier seeds were produced under the cool conditions and no differences were observed in standard germination. In lettuce, germination percentage and rate were both affected by increased levels of exogenous ABA concentrations and reduced water potential (PEG solutions), and, in both cases, seeds from cool treatments were more affected. Germination at 30 °C and constant light was higher for seeds from the hot treatment. Lettuce seed showed a strong light requirement for germination. However, seeds from the hot treatment gave better dark germination at 13 and 19 °C. Seeds of H. debilis did not required light for germination, and the germination percentage and rates were evaluated at 13, 21, and 29 °C. For both lines, seeds from each treatment behave similarly; however, the germination of H. debilis cv. Vanilla Ice at 29 °C was higher when seeds were produced in the hot conditions. The results showed that temperature during seed development affected aspects of seed quality that are not detectable by the standard germination, but by germination at suboptimal conditions. Within the Asteraceae family, differences varied among and within species.
Color sorting was performed to upgrade seed quality by removal of fluorescent coated seeds. The fluorescent coating was attributed to sinapine leakage from nonviable seeds. Nine seedlots, three seedlots each of cabbage (Brassica oleracea L. Capitata group), broccoli, and cauliflower (B. oleracea L. Botrytis group) were custom coated. Seed samples were pretreated before coating with or without 1.0% NaOCl for 10 minutes to enhance leakage. All samples revealed a percentage of seeds with fluorescence. The light emission from selected fluorescent and nonfluorescent coated seeds was quantified by fiber-optic spectrophotometry. Fluorescence was expressed from 400 to 560 nm, with peak emission being from 430 to 450 nm. These data confirmed our visual interpretation of blue-green fluorescence. The ratio of light emission from fluorescent compared to nonfluorescent coated seeds ranged from 4.5 to 7.0 for all samples and averaged 5.7. An ultraviolet (UV) color sorter was employed to separate fluorescent (reject) from nonfluorescent (accept) coated seeds. The percentage of nonfluorescent coated seeds (averaged over seedlot and NaOCl pretreatment) before and after sorting was 89.5% and 95.9%, respectively. Therefore, color sorting was able to remove a high percentage of fluorescent coated seeds with an average loss (rejection of nonfluorescent coated seeds) of 6%. An increase in the percent germination was recorded in eight of the nine seedlots following color sorting, and the greatest improvement was obtained with seedlots of medium quality. Germination of three medium quality lots was increased by 10 to 15 percentage points. The average increase in germination with or without NaOCl pretreatment was 8.2 and 5.5 percentage points, respectively. In conclusion, the germination of Brassica seedlots could be improved by separating (removing) fluorescent from nonfluorescent coated seeds. UV color sorting technology was employed to demonstrate that seed conditioning could be conducted on a commercial basis to upgrade seed quality.
Conventional methods to control the onion maggot or onion fly, Delia antiqua (Meigen), have relied on in-furrow applications of the toxicant pesticide, chlorpyrifos. The objective of this research was to develop an onion (Allium cepa L.) seed treatment that utilizes a new chemistry compound that is environmentally safe. Cyromazine is an insect growth regulator with a mode of action different from traditional pesticides used to control onion maggot. Cyromazine has low mammalian toxicity and is relatively nontoxic to other insects, including beneficials. High seed loading rates (50 g·kg-1 active ingredient) are required for optimal efficacy, and conventional slurry methods are inadequate to apply these high loading rates. Film coating and pelleting were performed at Cornell Univ. to apply cyromazine and a registered fungicide (a formulation of thiram and carboxin) to onion seeds. Results of field studies performed over several years revealed that stand losses due to the onion maggot ranged from ≈20% to 60%. Cyromazine applied by either film coating or pelleting decreased the loss by onion maggot from 1% to 8%, and efficacy was comparable to an in-furrow application of chlorpyrifos. Cyromazine was registered as a seed treatment and is commercially used in the northeastern and midwestern United States, where onion maggot is a serious pest. Field emergence was not negatively affected by cyromazine coated onto the seeds when onion seeds are sown in organic (muck) soils. There is other evidence, however, that cyromazine seed treatments may cause phytotoxicity to germination and seedling growth. Testing seed quality in sand or on roll towels revealed a high percentage of abnormal seedlings. Retarded root growth was observed in seeds treated with cyromazine, resulting in an increase in abnormal seedling classifications. A finely ground sphagnum peatmoss applied over the seeds in a roll towel test ameliorated the abnormal root growth symptoms, and seedlings had robust growth. Collectively, film coating and pelleting were effective delivery systems for the application of plant protectants required at time of sowing. Modification of the standard germination test was needed to accurately assess onion seed quality. Moreover, this project was successful due to a team effort of a university seed scientist and entomologists working with onion growers and industry. Future registrations on small acreage, high-value horticultural crops are envisioned to require similar multi-partner approaches. Chemical name used: N-cyclopropyl-1,3,5-triazine-2,4,6-triamine (cyromazine).
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
Abstract
Previous research showed a relationship between viability and electrolyte leakage; here, we develop an index of viability based on electrolyte leakage from sample populations of seeds soaked in deionized distilled water. Conductivity of leachates from individual seeds was determined for 10 lots of lettuce (Lactuca sativa L.), each germinating at 99%. Conductivity data for two lots of soybean (Glycine max L.) seeds germinating at 100% and 74%, respectively, were obtained from literature. Cumulative frequency distributions (CFD) with a class interval of one µA, were fitted with a natural logarithmic form of the Richards function, which requires no arbitrary starting values. The procedure provided an effective estimation of slopes [(dCF/dµA)MAX] of hypothetical lines tangent to inflection points of the respective sigmoidal CFD curves. We suggest that this maximum slope, or internal slope can be used as a seed viability index. The index is unaffected by outlier µA readings and reflects the shape of the CFD. It is also a measure of seed-to-seed variability in leachate conductivity. The se of the 10 internal slopes derived from the 10 lettuce seed lots was 3.8. The viability index is sensitive, since nearly a four-fold difference in internal slope was found for the two soybean seed lots. The greater the internal slope, the less the variation among individual seed conductivities and the higher the seed quality.
Abstract
Plants of two cultivars of processing tomato (Lycopersicon esculentum Mill, cvs. UC82B and VF145B-7879) were sprayed with ethephon solutions 10 days prior to harvest. Seeds were extracted from fruits that had been tagged at anthesis to allow separation into age classes ranging from 31 to 70 days at harvest. Seed dry weight increased rapidly until ≈40 days after anthesis, then remained relatively constant for 10 to 15 days before increasing again. During the plateau phase, the initial (5-day) germination percentages increased by 20% to 40% and final (10-day) germination increased by 6% to 10%. Germination percentages then fell slightly with increasing maturity and dry weight accumulation. Preharvest ethephon treatment caused younger fruit to ripen and shifted the development of maximum germinability toward young seed ages, without influencing dry weight accumulation. Seeds ≤53 days old at harvest increased in germination due to ethephon treatment, whereas seeds older than 53 days showed decreased germination. Since the bulk of harvested seeds will be in the older classes, overall seed quality may be affected adversely by preharvest ethephon applications. Although seed lots from ethephon-treated plants still had acceptable germination, there would appear to be no benefit from ethephon applications to tomatoes destined solely for seed production. Chemical names used: (2-chloroethyl)phosphonic acid (ethephon).