It has been a matter of interest whether the increased levels of seed requests the past few years will be sustained. During calendar 1987, 2270 seed samples were supplied in response to 184 requests (letters or phone calls). The corresponding figures for 1988 were 3349 samples and 215 requests. In 1989 about 3000 samples were supplied in response to 222 requests. It appears that the transition to a higher level of requests has a strong probability of being continued.

The summer, 1989 season was the best of the past four years, though some irrigation was necessary to counteract periods of drouth. The improved field conditions were reflected in a larger than usual harvest.

The following categories of stocks were important components of the field and greenhouse plantings of the past year:

(1) There was a special increase of B-A translocations because of the continuing substantial level of requests.

(2) Stocks of defective kernel (dek) mutants submitted by Dr. Neuffer and Dr. Sheridan were propagated for the first time.

(3) Increases were obtained of many dominant or recessive new symbolized, mostly located genes submitted by Dr. Neuffer.

(4) There were increases of additional miscellaneous located, symbolized genes newly received from various sources.

(5) There were increases of stocks in low supply, all chromosomes. Extensive plantings were made of selected stocks of chromosomes 5, 6, 7, 8, 9 and 10.

(6) There were plantings of new accessions of unidentified, untested genes. There were substantial selfing blocks of mutants expressed as seedling traits.

(7) Numerous field plantings were made to test or confirm genetic constitutions with regard to mature plant traits.

(8) Greenhouse sandbench plantings were made to determine or verify genotypes relative to seedling traits.

During the fall of 1989 source samples of several dozen new accessions of wx-marked reciprocal translocations were received that were developed by Dr. D. S. Robertson. When combined as a supplement to our previous stocks, this enlarged collection will provide substantially improved coverage of the chromosome complement as a technique for locating genes to chromosome. From this overall collection, a smaller, selected listing will probably be recommended as a basis for generalized, routine initial screening to determine chromosome locations of gene loci by those who wish to use the wx-marked translocation technique.

In general, the sequential listing of chromosome stocks in the annual catalog has followed the pattern of beginning with markers at the left, or short arm, end of each linkage map and proceeding to the right. The rationale for this ordering has been to simplify the search for tester combinations marking particular chromosome regions. Once storage drawer space becomes limiting, however, there is reduced flexibility in intercalating stocks of new marker genes that may be mapped to approximate positions. Some of the additions to this year's catalog consist of single-trait stocks. Most of these newly-available mutant alleles which have been assigned to chromosome have been grouped together in the catalog at the end of the listing for each chromosome, partly as a matter of storage convenience.

Details of listings of catalog stock items change from year to year. Requests should be based on the most recent listing. Occasionally, it is necessary to discontinue distribution of certain items because of inadequate supplies or because of errors detected in pedigrees. When these items are requested before catalog corrections can be made, an effort is made to substitute with similar marker combinations and to explain the reason for the substitution.

We are making a concerted effort to work through the stocks of untested, unidentified mutant genes to rejuvenate seed supplies when appropriate and to assemble stocks into common categories. In the process, results of any allelism testing and mapping studies will be summarized to determine the extent of current information. When this sorting has been completed, it should be much easier to organize plantings of particular categories of mutant genes for the purpose of efficient and comprehensive allelism testing both on this project and by cooperators.

There is a continuing need to submit basic stocks of the collection to the National Seed Storage Laboratory in order to provide an alternative site to guard against loss. Under current staffing, there has been no opportunity to fulfill this important objective, but it remains an item of unmet high priority.

Additional personnel were added to the Stock Center program in the spring of 1989. Dr. Susan Gabay-Laughnan, who has extensive experience in a broad range of maize genetics, is now assisting part-time with all aspects of the Stock Center program. In addition, Janet Day is serving part-time as a laboratory specialist, assisting in both laboratory and field nursery operations.

                                                                                                                                E. B. Patterson
                                                                                                                                S-118 Turner Hall
                                                                                                                                Agronomy Department
                                                                                                                                University of Illinois
                                                                                                                                1102 S. Goodwin Avenue
                                                                                                                                Urbana, IL 61801

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