James Munro

The importance of potato virus X

SummarySevere mosaics caused by potato virus X alone are commonly found in potato crops where new seed replacement is infrequent, and the varieties grown are wholly infected with the virus. These severe mosaics often arise in single stems of otherwise symptomless plants and spread rapidly through leaves of each stem until all foliage is showing severe symptoms. The rapid movement of a strain, newly arisen either by mutation or host selection, through parts of a plant already infected with that virus nullifies the principle of cross-protection.

Comparative rates of movement of potato virus X into tubers and eyes of three potato varieties

SummaryWhen Keswick, Canso, and Katahdin plants were inoculated with potato virus X 35 days or less before harvest, the virus moved into more tubers of Keswick than of Canso or Katahdin. The least number of infected tubers was found in Katahdin. The number of tubers not wholly infected increased in the three varieties as the time from inoculation to harvest decreased. In partially infected tubers of Keswick, virus X was found in eyes from the eye end more frequently than in eyes from the stem end or sides, but in Canso and Katahdin the location of an eye had no apparent effect on whether or not an eye become infected. Infected and non-infected tubers were found under some plants in each of the three varieties. Little, if any, movement of virus had taken place within tubers during storage.

Report of committee on PVX testing

The methods in use for PVX testing are Gomphrena globosa, chloroplast agglutination, pricipitin, latex agglutination and single radial diffusion. In Canada, testing programs exist in British Columbia, Alberta, Manitoba, Quebec, New Brunswick, and Prince Edward Island. In the United States PVX testing services are utilized in Idaho, Maine, Minnesota , Montana , Nebraska , New York, Nor th Dakota , Oregon, Wisconsin, and Wyoming. In both countries tests are applied to samples f rom selected growers a n d f rom official seed farms. In mos t areas where a testing service is in operat ion PVX control is considered feasible and practicable. Improved yields and grades have been repor ted . The use of tuber line or family increase sys tem is c o m m o n and has facili tated PVX testing. Tubers f rom selected plants are classif ied as Pre-Elite, Nuclear I or Index stock. Stem cuttings are utilized at this level in several areas. In successive years of increase the tuber progenies are classified as Elite I or Nuclear II, Elite II or Premium, Elite I I I , Foundation, and Certified. All plants at the initial level are usually tes ted with smaller percentages being tested each year as the stocks p roceed through a four to six year product ion program. At the Elite III , Foundat ion and Cert if ied levels tests usually involve 100 to 1000 leaflets taken at random f rom a seed lot or field. One area has a tolerance limit for PVX in all seed classes. In at least six others the incidence of PVX does not influence classification but the ex-

Report of the potato virus investigations committee

Dr. D. S. MacLachlan, Chairman of this Committee, has resigned from his position in potato virus research, and simultaneously his activities within the Potato Association have ceased. Consequently this report, prepared at short notice, is not comprehensive. No attempt has been made to cover recent developments in potato virus investigations other than that supplied by members of this committee. The following has been brought to the attention of the committee:

Honorary Life Membership

binding on the current executive in the year in which the resolutions are passed. Instead of the Policy Committee being an ad-hoc committee, appointed iu response to specific needs as was recommended in July 1967, I suggest that it be a standing committee, because specific needs are always present. I further suggest that the committee consist of members who are either, or are both, experienced in Association affairs and Past Presidents. I further suggest that the retiring president automatically replace a member on this committee each year after the annual meeting. This concludes my report. You will find that the committee reports to follow, are nmch concerned with what I have said.

Use of molecular gel column to prepare potato virus X inocula for antisera

SummaryA simple technique has been developed to obtain purified potato virus X in physiological saline solution by passage through a gel column. The virus solution is the concentrated by dialysis with polyethylene glycol for use in intravenous injections for the production of potato virus X-immune rabbit antiserum.ResumenSe ha desarrollado una técnica sencilla para obtener el virus X de patata purificado en una solución salina fisiólógica por pasarse por una columna de gelatina. Luego, se concentra la solución del virus por diálisis con el glicol polietileno para usarse en intervenciones in travenosas para la producción del antisuero de conejo inmune del virus X de patata.

The reactions of some potato varieties and seedlings to potato virus F

SummaryReactions caused by infections with virus F alone and jointly with each of the viruses A, X and Y were studied in 30 potato varieties and seedlings. Infections resulting from mechanical inoculations with virus F alone to virus-free plants did not cause symptoms, but severe necroses developed when the plants were graft inoculated. When plants were inoculated jointly with virus F and potato virus A. X or Y. brown necrotic lesions and blotches developed on most of the leaves. Similar symptoms developed when plants already infected with any one of these 3 viruses were mechanically inoculated with virus F.One strain of the virus caused tuber necroses in all of the potato plants inoculated; tuber necroses were found only in four varieties when infected with the other strain.A routine method was developed to expedite seedling tests for hypersensitivity to viruses A or X by the added use of virus F.

Dr. Donald John MacLeod honored

It is my privilege tonight to present Dr. D. J. MacLeod as a candidate for Honorary Life Membership in the Potato Association of America. When I was asked to perform this very pleasant task I thought that I would look into the history of the MacLeod Clan. I found that whenever an award of merit had been made to a MacLeod it was invariably accompanied by the music, sound, wail, or whine of the bagpipes. You have heard that delightful nmsic tonight3 Yet when someone, not connected with the organizing committee, suggested that pipe nmsic be played, it was before any of us had knowledge that Dr. MacLeod was to be honored. The piper even wore one of the MacLeod tartans. Apparently the little people or leprechauns of the Western Isles of Scotland still look after their own no 1hatter where they wander. A c a d e m i c C a r e e r Donald John MacLeod was born on a farm in 1894 some 60 miles east of Ottawa at Dunvegan, Ontario, where he spoke in Gaelic and in French before he knew that there was an English language. He graduated from Queens University, Kingston, Ontario, with a B.A. in lnedical bacteriology in 1921 and obtained his M.A. in 1923. Between 1921 and 1923 he was awarded three National Research Council Fellowships. In 1937 D. J. MacLeod felt a need for more advanced knowledge in the narrow specialized field of potato viruses. He went to Cambridge, England, and studied under Dr. Redcliffe N. Salaman and Dr. Kenneth M. Smith at that tilne both outstanding in their respective fields of work, potato breeding and potato viruses. He obtained the Ph.D. from