Volume 20, No. 2, 1998

Download Cover and Contents

(pp. 121-124)
Improving Our Understanding of Vegetable and Flower Seed Quality (free download)

(pp. 125-130)
Seed Quality Problems Commonly Encountered During Vegetable and Flower Seed  Production
James T. Watkins
ABSTRACT:
A seed company’s ability to produce high quality vegetable and flower seed depends greatly on how it manipulates common and unusual environmental and cultural situations arising in the production field. Many of these situations can be planned for, limited and controlled; however, problems always occur that are unexpected.

Crop location, planting time, pollination, pest control, irrigation, nutrition and harvesting methods for each seed crop must all be considered, reviewed and/or controlled to ensure successful seed production. This review discusses the common cultural and environmental problems vegetable and flower seed companies have in producing high quality seed.
Download entire article

(pp. 131-135)
Flower Seed Testing and Reporting Needs of the Professional Grower
Paul T. Karlovich
ABSTRACT:
Flower seed quality has improved markedly in the past 20 years. Standardized germination testing has not developed to more accurately reflect this improved seed quality. Eleven ideas are presented to improve seed testing and the reporting of seed testing results. Imaging technology is the most important of these. A failure to adopt and interpret the results of computer images following a germination test will ultimately lead to the obsolescence of AOSA in flower seed testing because this important work will be fulfilled by commercial companies.
Download entire article

(pp. 136-161)
Seed Quality Problems Commonly Encountered in the Laboratory for Vegetable and Flower Seeds
Deborah J. Lionakis Meyer
ABSTRACT:
Purity and germination testing provide a baseline value of vegetable and flower seed quality. The history of standardization of seed testing protocols for vegetable and flower seeds utilized by the Association of Official Seed Analysts over the past 100 years is reviewed. The ability to assess and convey levels of seed quality for vegetable and flower seeds is hampered by the lack of appropriate or standardized laboratory testing methods, or both. This discussion provides examples of problems ranging from kind and seed unit identification, classification of contaminants, germination test methods and seedling evaluation. Emphasis is placed on the need to develop and refine laboratory testing procedures and improve seed analyst training with the focus on standardization within and among laboratories.
Download entire article

(pp. 162-175)
A Walk on the Wild Side: Quality Assurance Problems Unique to the Wildflower Seed Trade
Jane T. Hall
ABSTRACT:
The successful result of a quality wildflower planting is the establishment of a natural environment of beauty for people to enjoy. Although the term “wildflower” appears simple, it is one of contention in the current wildflower market place. Wildflowers are desired for their less formal presentation and adaptation to a variety of environmental conditions. These same traits create problems with quality assurance of wildflower seed; problems that arise from the basic nature of wildflowers due to their wildness. The wildness of wildflower seed is expressed in a variety of ways that affect stand establishment, seed production, conditioning, laboratory testing and marketing.
Download entire article

(pp. 176-186)
Unique Seed Quality Problems of sh2 Sweet Corn
Dale O.Wilson, Jr.* and S. Krishna Mohan
ABSTRACT:
The high sucrose content of shrunken-2 (sh2) or supersweet sweet corn inhibits drying of the seed crop in the field, and necessitates a long (70 day +) period of maturation after pollination before harvest and artificial drying of the seed crop. During this time, the ear is highly susceptible to invasion by insects and rotting by fungi. Stringent insect control is crucial for production of disease-free seed.

Certain of the ear-rotting fungi, most notably  Penicillium oxalicum, are seed-transmitted, causing disease and mortality in sweet corn seedlings. This necessitates treatment of the seeds with a strong mixture of fungicides, including a broad-spectrum systemic fungicide where possible. During maturation of the seed crop in the field, physiological changes gradually occur in the seed, rendering it capable of high seed vigor after commercial harvest and drying. Seed parents differ dramatically in inherent seed vigor, resistance to stress and pests, and in the length of the maturation period needed to produce seed of the highest possible vigor. Commercial seed lots sometimes exhibit poor seed vigor, in spite of high germination. Vigor tests, such as the accelerated aging test, are useful for predicting the field emergence potential of sh2 seed lots.
Download entire article

(pp. 187-197)
Seed-borne Pathogens of Vegetable and Flower Seeds: Their Devastation, Identification and Control
J.W. Sheppard
ABSTRACT:
Recognition of the importance of seed-borne diseases in vegetable and flower seeds is often overlooked, particularly in the case of flower seeds. Plant diseases may be found in, on or with seed and seed lots. Seed-borne diseases may be grouped according to their causal agents, fungi, bacteria, viruses nematodes etc..

Development of disease in a crop as a result of seed-borne inoculum is a result of the interactions between the pathogen, its host and the environment. Epidemiology is the study of these interactions. Effective disease management programs and the development of reliable and accurate methods for seed health testing is dependent upon an understanding of plant disease epidemiology.
Download entire article

(pp. 198-208)
The Use of Biologicals to Enhance Vegetable Seed Quality
Mark A. Bennett
ABSTRACT:
Beneficial bacteria and fungi provide promising alternatives or supplements to chemicals as seed treatments against soilborne pathogens. This review provides an assessment of biological control agents (BCA’s) currently used with vegetable crop species, and key limitations to expanded use of BCA’s as seed treatments. Research areas for improved biological efficacy and reliability in field and greenhouse settings are also discussed.

The ability of BCA’s to effectively colonize and grow with the seedling root system may be particularly useful when crops experience environmental stress. Improved application methods to optimize the density and uniformity of biologicals on seeds are increasing the reliability of BCA technology. Early results also suggest variable levels of BCA compatibility with chemical seed treatments and other microbial applications. Progress in storability, ease of application and economy of BCA production will be needed to move biologicals beyond their niche position in the seed treatment market.
Download entire article

(pp. 209-235)
The Evolution and Effects of Priming Vegetable Seeds
Gregory E.Welbaum*, Zhengxing Shen, Melkizedek O. Oluoch, and Lewis W. Jett
ABSTRACT:
Priming is a treatment that partially hydrates seeds so that germination processes begin, but radicle emergence does not occur. Experimentally, priming treatments are limited only to conditions that do not result in premature radicle extension and may include: equilibration under conditions of high humidity, soaking in water or osmotic solution, equilibration with a matricpotential control surface, intermixture with a porous matrix material, and moisture addition to a seed water content less than required for germination.

Commercial priming technology has evolved from osmotic priming to solid matrix priming and finally drum priming which is gaining acceptance for large-scale use. The degree of enhancement from priming depends upon the initial quality of the seed, the species being treated, treatment conditions such as temperature, water potential (Ψ), duration, and other conditions specific to the priming medium. There is no simple recipe for determining the best priming treatment for a particular species. Priming treatments must be determined empirically. In several species, the optimal Ψ for priming ranges from the least negative Ψ that prevents radicle emergence to approximately -2.5MPa. Some reported effects of priming include increased germination rate, greater germination uniformity, increased germination percentage, advancement of maturity, wider temperature range for germination, repair of cellular damage, weakening of barriers to embryo growth, reduced seed storage life, increased protein synthesis, and removal of dormancy. However, it is increasingly apparent that the effects of priming differ widely among species. The evolution of priming technology is reviewed as well as our current knowledge of how priming enhances germination performance.
Download entire article

(pp. 236-250)
Seed Dormancy in Commercial Vegetable and Flower Species
Robert L. Geneve
ABSTRACT:
Seed dormancy in small-seeded vegetable and flower crops impacts both seed production and germination. Seed dormancy can also complicate assessment of seed quality by the seed analyst who requires prompt germination to evaluate a seed lot. These crops also display diverse mechanisms for seed dormancy. This review surveys and categorizes the different seed dormancy conditions found in this important group of plants.

Vegetable and flower genera are listed according to dormancy type. Categories of dormancy include primary and secondary dormancy.Within primary dormancy, examples of vegetable and flower genera can be found that display exogenous, endogenous and combinational dormancy. Secondary dormancy can be an important problem in selected vegetable and flower seeds. Specific examples are given for each type of dormancy along with methods to alleviate dormancy. Tables are included that group vegetable and flower genera according to dormancy type.
Download entire article