Historical Paper - Volume 2 2008 - International Seed Testing ...

HISTORICAL REPORT FROM THE PURITY COMMITTEE
A guide with colour photos of some 200 species of agricultural, horticultural and
weed species has been published by NIAB, United Kingdom (Jones et al., 2004), and a
descriptive and illustrated seed-book on 175 weeds was worked out by GEVES France. A
French edition was published in 1999 and an English edition in 2004 (Dragos 2004).
More than 1,400 images of seeds and fruits have been made available online by
professor, Dr. Arnold Larsen, Colorado State University, USA (www.seedimages.com).
The web site includes colour images of seeds as well as descriptions and keys to the
described species.
Dr. John H. Wiersema and his colleagues in GRIN Taxonomy, United States
Department of Agriculture/Agricultural Research Service have added over 3,800 seed/
fruit or embryo images or drawings to GRIN, with plans to add another 5,000 in the
future. They can be retrieved by family, genus, or species from the web page (http://www.
ars-grin.gov/cgi-bin/npgs/html/taxassoc.pl) and are also linked from the relevant family,
genus, or species pages in GRIN. Many of the same images are also available at the
“Family Guide for Fruits and Seeds” on Systematic Botany and Mycology website which
also provides detailed seed and fruit descriptions for most vascular plant families.
Professor Miller McDonald and his staff at Ohio State University, USA, have on the
website (www.oardc.ohio-state.edu/seedid) placed a number of images of cultivated and
weed species. The web site includes a very useful basic and advanced seed identification
quiz.
8.3 Chemical methods
Chemical methods have been utilised as an aid for purity analyses mainly for distinguishing
between species, for which visual identification at the species level is either not possible
or uncertain.
The fluorescence test for separating Lolium perenne from Lolium multiflorum has been
widely used as a supplement to the purity analysis (ISTA Rules 8.9.4). The method was
described by Gentner (1929b), and improvements of the technique have been published in
various papers, among others Nieser (1953) and Harrison (1954).
A number of papers reported that the non-fluorescent Lolium perenne did include
some seeds with fluorescent roots, and Lolium multiflorum included some non-fluorescent
seedlings. Plants that deviated in fluorescence all had the morphological characteristic
of the species, and seedling root fluorescence was not linked to species and botanical
characteristics (Dorph-Petersen 1934; Jensen and Langkilde 1965, Jensen 1980, Okora et
al., 1999). The content of seedlings, deviating in the fluorescent character, varied from 0
to 20%.
Considerable differences occurred both between samples and cultivars (Baekgaard
1955; 1962; Jensen and Olsen 1975; Jensen and Olesen 1975). Due to the variation in the
content of fluorescent seeds, a content of 5% fluorescence in seed lots of Lolium perenne
was allowed in the USA (Justice 1950). To day, the method is rarely used for separation
between Lolium species, but some countries still used it in description of new varieties.
Elekes (1975) used the differences in fluorescence and chemical colour reaction
to separate between caryopses of Poa pratensis and Poa trivialis and between Phleum
pratense, P. nodosum and P. bertolonii.
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