Seed Production in New Zealand Seed Testing

New Zealand Journal of Agriculture, Volume 97, Issue 5, 15 November 1958, Page 473

Seed Production in New Zealand Seed Testing

By

A. V. LITHGOW,

Officer in Charge, Department of Agriculture Seed-testing Station, Palmerston Norti

The value of seed cannot be estimated from a cursory examination. I Careful analysis is required to determine its purity, the types of impurity present, and the germinating capacity of the pure seed. The Department of Agriculture Seed-testing Station at Palmerston North undertakes this inspection and provides the information on which the value of the seed can be based.

IN 1869 the first seed-testing station was established in Saxony by Professor Nobbe. The value of the station was quickly realised, and by the turn of the century most European states had such stations and seed was also being tested in the United States of America. Now all progressive countries have seed-testing stations, both private and official. The keen

buyer demands evidence that the seed he buys is good and has been tested by stations whose efficient service is his guarantee. New Zealand Service The New Zealand Department of Agriculture was not slow to follow the example set overseas. Under the

guidance of Mr A. H. Cockayne and later of Mr E. B. Levy the work in New Zealand developed until by 1918 a sound foundation of seed testing had been laid. In the following years the demand for tested seed expanded steadily. Without this service seed traders had to attempt to value seed by its appearance, and though they could form an approximate idea of its purity, undesirable weed seeds often passed unnoticed and the germinating power of the seed was unknown. Merchants found that seeds supported by an

independently issued certificate were bought more readily by discriminating buyers and were in greater demand overseas. In addition, they found that they themselves could buy more confidently if they knew the purity and germination of a line. Since 1925 the New Zealand Station has been a member of the International Seed Testing Association, which has aimed at bringing about a more uniform technique in testing. Before this association was formed a variety of methods used in different countries made interpretation and comparison of certificates no easy task. The methods recommended by the international association have been adopted in New Zealand, with the result that in overseas countries complete reliance can be placed on New Zealand certificates. This has greatly assisted the export trade of the Dominion. In 1910, when the Station was situated in Wellington, the work was regarded as a part-time occupation for one man, and some 180

samples were tested for purity and germination. During the First World War it was transferred temporarily to Weraroa, and by 1918 the number of samples handled annually had risen to nearly 4,000. In 1928 the Station was transferred to Palmerston North; the staff had then increased to 10 and in that year more than 10,000 samples were examined. Today a staff of 70 analysts handles up to 35,000 samples for purity, up to 50,000 samples for germination, 14,000 samples for strains tests, some 3,000 samples for the blind seed service, and investigates seasonal and other problems in seed testing. Further, a research staff of five is available for assisting with any analysis problems.

In 1910 the work of the Station was limited to purity and germination analyses. Though most samples are still subjected to these tests, strains testing of perennial ryegrass by ultraviolet light and of white clover by the picric acid test is also undertaken now. Other services include moisture testing, the pre-harvest examination of ryegrass for blind seed disease, and herbage dissection. In addition to the routine activities of the Station, considerable investigation work is also done. Research is undertaken into problems associated

with seed quality and the technique of seed testing, and no effort is spared to ensure that the New Zealand Station is -conversant with overseas findings in this field. Examples of research undertaken by the Station which have been of direct benefit to the farming community include investigations into the application of the ultra-violet light test to perennial ryegrass seed, the picric acid test to white clover seed, and blind seed disease of the ryegrass species. The Station also provides information for the Purchasing Officer for Seeds, who buys seeds for all Government Departments. With the test results of every worth-while line of seed at its disposal, no organisation is better placed to advise on the purchase of seed at its true worth. When land development is undertaken the department concerned knows that its seed purchases have been made to the best advantage and that the quality will contribute to the success of the venture. In some years over £300,000 worth of seed has been bought for land development through the Purchasing Officer for Seeds. Standards of Quality The quality of seed is defined by three factors, its purity, its germination, and its strain.

Purity

Good seed is of high purity; that is, it does not contain large quantities of unwanted or possibly harmful weed seeds which, if sown, might ruin the resultant crop. Practically all samples contain some weed seeds, and the buyer must decide whether those in the line offered are likely to be a menace in the conditions under which the seed will be sown. Other crop seeds are usually viewed with tolerance, but one exception is perennial ryegrass seed as an impurity in cocksfoot seed intended to be sown for further seed production; if appreciable proportions are present, the ryegrass tends to dominate the cocksfoot in a seeding stand. Inert matter, though harmless, is valueless, and unduly large amounts of broken seed, dirt, and chaffy material can affect adversely the true value of the seed.

A purity analysis is made by inspection. When a sample from a line of seed is submitted for examination a small working sample is taken in such a way as to be representative of the seed submitted. From this sample are separated all other crop seeds, weed seeds, and inert matter, and their description is recorded. All these separations are weighed carefully on a precision balance, and the pure seed content is calculated as a percentage of the sum of all the separations. Thus, a purity of 98 per cent, means that in every 100 lb. of the line 98 lb. is pure seed.

The certificate issued by the Seedtesting Station records the percentages of each separation present in the sample, and also lists, in approximate order of the amount present, the botanical names of the weed seed and other crop seed impurities observed during the analysis. Botanical rather than common plant names are used on certificates to avoid the confusion which exists in common plant names. Many examples could be quoted of the same common name being applied to widely different species and, conversely, of the one plant being known in different districts by different common names. The botanical name is also essential in sales overseas, where the divergence in application of common names is even greater.

Germination

Pure seed has no value unless it will grow and produce healthy, mature plants. In testing for germination it is not possible to grow the seed to maturity under field conditions and estimate the percentage of plants produced. Under laboratory testing some 400 pure seeds are placed on damp, absorbent paper in a germinator cabinet at the most suitable temperature for rapid germination. After a

number of days, fixed for each variety under test, the tests are examined and seedlings which to the trained eye of the analyst appear capable of continued growth are counted and removed. Later the seeds are again inspected and any further healthy seedlings removed.

The length of time between counts varies with the species. At least two counts are always made and sometimes as many as four are necessary. However, only two are reported— early or interim count and a final count at the conclusion of the test. The interim report gives the speed of germination and is an indication of the seed’s vitality; the final count defines the total percentage of viable seed.

When the results of a germination test are reported certain additional information is given. Hard seeds are found in varying quantities in legumes. These seeds are normal in that they are alive, but they have a very tough seed coat, and germination is delayed until water can penetrate it. Unless

they are present in very large numbers, they are usually regarded as normally germinating seeds, as after a comparatively short period in the soil most of them will grow.

In the laboratory a seedling is regarded as normal if it produces those parts essential for its continued growth and the development of a mature plant. Sometimes the seedling, will produce a root which shows distinct fractures or a sprout without any seed leaves. Such damage is usually caused by mechanical injury to the embryo within the seed. These seedlings would never reach a healthy maturity and are classified as abnormal growths.

Generally samples show comparatively few of these abnormal growths, but under certain conditions there may be a very large increase in the proportion of them. Legumes are the worst offenders in this respect and on occasions lupin seed has been so damaged as to produce far more abnormal than normal seedlings. Red clover usually shows far more abnormal growths under germination test than does white clover. If the proportion of broken or damaged seed in a sample is high, it can be assumed that abnormals will also be found among the germinating seedlings.

By considering the results of both the purity and the germination analyses together the buyer can estimate what percentage of the seed he buys is pure living seed and thus arrive at an estimate of its true worth. If the analysis shows a purity of 98 per cent, 98 lb. in every 100 lb. is pure seed. If this pure seed has a germination of 90 per cent, 90 per cent of the 98 lb. or 88.2 lb. in, every 100 lb. of the seed (88.2 per cent) is pure living seed.

The value of seed cannot be estimated from either purity or germination alone. Two lines may have the same purity—say, 98 per centbut the germination of the first may be 90 per cent and of the second 60 per cent. A comparison of value is then 90 per cent of 98 to 60 per cent of 98, or 88.2 to 58.8.

The percentages of seeds germinating at the interim and the final stages of counting are recorded on the certificate with the percentages of hard seeds and abnormal growths. The calculated percentage of pure living seed in the sample completes the information supplied.

All seed certified under the New Zealand Department of Agriculture’s certification scheme is sampled independently by Departmental officers and tested for purity* and germination at the Seed-testing Station. Strains Much seed is tested for strain or type by plot testing. This involves

the growing of the seed under field conditions, observing it during its

growing period, and classifying it according to the results of these inspections. The Seed-testing Station is unable to undertake such work, but it has developed laboratory tests for the identification of strain in two of New Zealand’s most important species, perennial ryegrass and white clover, and carries out routine tests of this nature in association with the certification scheme. For identifying the seed of true perennial ryegrass the ultra-violet light test is used. The seed is grown on moist filter paper and observed under a screened mercury-vapour lamp. Short-lived strains produce on the paper a substance which glows under the ultra-violet light rays; true New Zealand perennial ryegrass does not .do this.

The other laboratory test, the picric acid test for white clover, depends on the fact that the better strains of white clover contain greater quantities of certain , glucosides than do the poorer strains. These glucosides break down when the plant tissue is crushed, liberating small quantities of hydrocyanic acid gas. This gas can be detected when it comes in contact with paper which has been soaked in picric acid. Normally the paper is bright yellow, but contact with hydrocyanic acid causes it to turn brown. Thus, with pure lines of the best strains of seed the paper turns a dark, reddish brown, while with the poorest strains there is little or no change in the colour of the paper. With these methods the standard of the strain can be assessed in about 10 days instead of the manv months necessary when the plot test method is used.

Moisture Tests When seed is to be shipped or stored it is desirable that its moisture content be known. If the seed contains too much moisture, it will deteriorate very rapidly and germinate unsatisfactorily. Chewings fescue, crested dogstail, peas, wheat, and barley are the principal seeds submitted for testing of moisture content. In addition, the Station acts for the Wheat Research Institute and carries out pre-harvest moisture tests on wheat samples from North Island growers. Blind Seed Disease in Ryegrass During December and January each year a sub-station is established at the offices of the Department of Agriculture at Timaru for the pre-harvest examination of ryegrass for blind seed disease. In some seasons over 3,000 samples are submitted for examination. Samples taken from crops before they are harvested are examined and the degree of infestation by blind seed disease estimated. This service enables the grower to spare himself the labour and expense

of harvesting, crops which have been so seriously damaged by the disease that they are capable of producing only seed of low germination. Special Service for Farmers A free advisory service is provided for farmers desiring information on any particular line of seed, and is availed of mostly in respect of seed for which purity and germination certificates are not available. A sample of this nature forwarded to the Seedtesting Station is reported on by letter, as the information so supplied is regarded as of an advisory nature only and not as a basis for trading. General Service for Merchants and Farmers The major service provided is the testing of samples to provide certificates which serve as a basis for trading both within New Zealand and overseas. Demands for internal trading are usually satisfied by the ordinary purity and germination certificates, but the export trade often requires more detailed tests. Special searches may be made to ensure that the samples submitted are

free from dodder; seed for export to Australia must comply with the Australian Quarantine Act; for the Canadian buyer all lines must be covered by certificates which record the grade of seed in accordance with the regulations of that country; the United States of America lays down certain conditions with which seed must comply before it can be imported. Tests for all these purposes are carried out and certificates issued.

Each week during the year about 1,000 samples come to the Station for test, including seeds of all kindsflowers, vegetables, trees, cereals, clovers, and grasses. With a growing conception of the variation in values between different lines, pride of place must go to the better seed. These values can be determined only by accurate testing, and the certificates covering these tests must have the confidence of merchants not only in New Zealand but also overseas. The value to the seed trade of a service such as that given by the Seed-testing Station is indisputable.