K. H. Fernow

Spindle tuber virus in seeds and pollen of infected potato plants

The presence of potato spindle tuber virus (PSTV) in seed and pollen of diseased plants was demonstrated. Transmission through the seed from open-pollinated female parents to the seedlings occurred frequently (average 31%) but varied in individual collections from zero to 100%. The amount of transmission did not appear to be correlated with variety or with age of the seed. All PSTV infections encountered appeared to be caused by mild strains. It is suggested that only healthy parents should be used for breeding purposes.ResumenLa presencia del virus que causa tubérculos ahusados (PSTV) ha sido demonstrada en semillas y polen de plantas infectadas. Transmisión del virus por semilla obtenida de padres femininos libremente polinizados a las plantulas sucedió con frecuencia (promedio 31%) pero varió en colecciones individuales desde zero a 100%. La magnitud de la infección parece no correlacionarse con la variedad o con la edad de la semilla. Todas las infecciones con PSTV encontradas parecen haber sido causadas por cepas no muy virulentas. Se sugiere que solamente padres sanos sean usados para propagación.

The Tomato test for eliminating spindle tuber from Potato planting stock.

ArstractA lot of 792 tubers, of which about 20% were infected with the potato spindle tuber virus (PSTV), were subjected to greenhouse index tests, using tomato as a test plant. Tomato seedlings in the cotyledon stage were rubbed with the test material, either foliage or the surfaces of seed pieces cut from test tubers with a mellon-baller. Fourteen days later the test plants were inoculated with a severe strain of PSTV to detect the presence of mild strains. Tubers giving negative results were planted for propogation and those giving positive or doubtful results were planted in an observation plot. All potato plants were inspected visually and those in the observation plot were given an additional tomato test. The results indicate the validity and value of the tomato test for the elimination of PSTV from seed stocks before planting. The tuber test conducted in the winter was less efficient than the foliage test conducted in the spring. A modification of the test procedure is advocated in which two test plants are rubbed from each source, one to be challenged and one not. This increases the accuracy of the test, particularly during periods when symptoms of PSTV are poorly expressed.ResumenUn lote de 792 tubérculos, de los cuales más o menos 20% estaban infectados con el virus de papa ahusada (PSTV) fué sujeto de un ensayo de índice en invernadero, usando plantas de tomate como plantas de ensayo. Plantas germinadas de tomate con cotiledones fueron restregadas con el material de ensayo consistente ya sea de follaje, ya sea de las superficies de pedazos de papas cortadas de los tubérculos de ensayo con un cortador de melones. Catorce días más tarde las plantas de ensayo fueron inoculadas con una forma virulenta de PSTV para descubrir la presencia de formas blandas. Tubérculos que dieron resultados negativos fueron plantados para ser progados y aquellos que dieron resultados positivos o ambíguos fueron plantados en un lote de observación. Todas las plantas de papa fueron inspeccionadas visualmente y aquellas en el lote de observación recibieron un ensayo adicional con plantas de tomate. Los resultados indicaron la validez y la ventaja del ensayo por medio de plantas de tomate para la eliminación de PSTV de las papas antes de sembrar. El ensayo por medio de tubérculos conducido en invierno fue menos eficaz que el ensayo por medio del follaje hecho en primavera. Se recomienda una modificación del procedimiento de ensayo en la cual dos plantas de cada origen se restriegan y de las cuales una se examina y la otra no. Esto aumenta le exactitud del ensayo, especialmente durante los períodos cuando los síntomas de PSTV están pobremente expresados.

Leafroll control by use of insecticides

SummaryIn 1951 and 1952, tests were conducted near Ithaca, New York, on the effect of insecticidal applications on the amount and pattern of spread of potato leafroll virus from known sources of inoculum. Systox was very effective in reducing disease incidence, parathion reduced virus spread almost as well, and DDT appeared most helpful where the amount of virus spread was relatively light but actually detrimental where spread was heavy.Most of the spread occurred on rows immediately adjoining rows on which the inoculum sources was prevalent. This steep gradient of infection indicated that wingless aphids apparently were responsible for most of the spread. In rows farther from the inoculum the percentage of disease was much lower and it was less easy to demonstrate control.Since Systox has not been authorized for use on food plants it can not be recommended at the present time. It is recommended that potato seed growers in New York use parathion at frequent intervals throughout the season and continue until the vines are killed.

Yellow dwarf in New York state

This disease has been known in New York since 1917 but i t is doubtfu l whe the r the po ta to inspectors were all capable of correct diagnosis before 1920. At tha t t ime the disease was prevalent in table stock fields in the neighborhood of the Adirondacks and the Hudson River Valley. Occasional cases occurred in other pa r t s of the state. Since 1920 the amoun t of yel low d w a r f in these areas has decreased and it is now not very impor t an t in the dis tr icts where it fo rmer ly prevai led.

Chemical elimination of volunteer potatoes

SummaryVolunteer potato plants, which occur frequently in New York State, constitute a menace to seed production. Their elimination by cultural means is not always practicable. Amitrol was found capable of destroying both plants and new tubers.

John S. Niederhauser honored

his experience with the Central Andean potatoes, and he has spent study leaves at Cambridge, England and at the Max Planck Institute in Germany. Dr. Cardenas is the first Latin American scientist to be honored by election to Life Membership in the Potato Association of America. It is not only a well-deserved honor at the culmination of his brilliant career as a scientist and a teacher, but is perhaps symbolic of the gradual and important strengthening of ties amongst those interested in the culture of potatoes throughout the Americas. -John S. Niederhauser

Report of the Seed Potato Certification Committee

races, and a continuing source of virus-free tubers of the same. I t was suggested that committee members might exchange tester stocks and after a year or so ago agree on one set. The use of true-breeding S. demissum lines was also suggested, some of which have been developed by Dr. Schick of Germany. 3. A thorough discussion of the problem of testing seedlings and clones for field resistance. This should include a consideration of uniform standards for measuring field resistance, and the possibility of exchanging clones of known resistance for comparison.

Potato meeting: Seed potato certification conference

ada wilt be held at Freehold, New Jersey, under the auspices of the Po ta to Associa t ion of America . A similar conference held at Freehold last )Tear proved to be very much wor th while in that it cleared up some points concerning the var ious degenera t ion diseases as well as other mat te r s pe r ta in ing to the inspect ion service. This year it is expected that a n u m b e r of the inspectors will at tend. I t is i m p o r t a n t tha t as many men in actual charge of the field inspections be presen t as possible since it is on them tha t the responsibi l i ty falls of accept ing or re jec t ing a field.

Accuracy in potato inspection

La te b l igh t occurs every year in Ju ly and A u g u s t and sp ray ing is a lmost universal . T h e Uni ted Sta tes and I re land were the first two countr ies to take up this pract ice about 1890, and at the present t ime there is no place in the wor ld where the crop is sp rayed more widely and successful ly than in I re land. Th i s may be seen by the number of sp ray ing m a c h i n e s sold t h rough agency of the Depa r t men t of Agr icu l tu re alone, which still averages more than 1.,400 a year over a period of ten years. The n umber in use some years ago exceeded 70,000. I t is calculated that the value of the crop saved in this w a y exceeds 10 mill ion dollars per year , and in years like 1924 the whole crop may be said to have been saved. A new developmefl t which is be ing pushed mos t v igorous ly in the Free Sta te is the g rowing of seed pota toes for the Engl ish trade. Th i s is at present a pract ical monopo ly of Scot land s , bu t the health and v igour of Ir ish po ta toes is second to none, in fact, like the Pr ince E d w a r d Is land product , they s tand in a class by themselves . T h e only d rawback has been mixed s tocks and unpopular variet ies, but this is be ing rapidly overcome by a pota to certification scheme, which is in charge of W. D. Davidson . The sys tem adopted is based on Amer i can practice, and in 1925 abou t 2,300 acres were certified. T r a d e wi th England is be ing fostered by the d is t r ibut ion of 10 bushel samples which are provided free by g rowers of certified seed, and are then dis t r ibuted b y the Dep a r t m e n t to represen ta t ive f a rmers in England. T h e service also propaga tes special mosaic-free s tocks according to Du tch methods .

Growing potatoes for seed purposes

F rom the s tandpoint of the producer the price is justified by the extra expense of inspection and certification, the ext ra labor of seed selection, roguing and sorting, the increase in the percentage of the culls and insurance against failure of the crop to qualify af ter the expenses have been incurred. If these factors are all given proper consideration it is probable that certified seed product ion does not give an excessive re turn to the grower. On the other hand it is probable that the growing of certified seed has st imulated many growers to take be t te r care of their own seed and use bet ter cultural methods thus increasing their efficiency in potato production.