JOPRNAL OP AgttCELTCRAL RESEARCH 
Vol. XXV Washington, D. C., August ii, 1923 No. 6 
CORRELATION OF FOLIAGE DEGENERATION DISEASES 
OF THE IRISH POTATO WITH VARIATIONS OF THE 
TUBER AND SPROUT 1 
By Alfred H. Gilbert 
Associate Pathologist, Vermont Agricultural Experiment Station 
INTRODUCTION 
It has been previously shown through the observations and experi¬ 
ments of a number of investigators that mosaic and leafroll of the Irish 
potato (Solarium tuberosum} are transmitted from season to season by 
means of the tubers. Among those who have contributed chiefly to this 
conclusion are, Orton (9 ), 2 Appel (j), Wortley (75), Stewart (jj), Murphy 
(8), Melhus (7), Schultz et al. (10), and Schultz and Folsom (12). Since 
these diseases although carried in the tissues of the tubers do not 
cause any observable changes in their outward appearance, there would 
seem to be no means of distinguishing between healthy and diseased 
specimens when unsprouted tubers are held under favorable storage con¬ 
ditions. The observations and experiments reported in this paper were 
undertaken, therefore, with the purpose of discovering whether there 
were not some distinguishing characteristics associated either with the 
earlier or later stages of germination of tubers which might be utilized in 
determining the presence of mosaic or leafroll therein during the latter 
part of the storage period. It is evident that such correlations, if existent, 
would add to the knowledge of the diseases concerned by furnishing addi¬ 
tional means of diagnosis and might also be a basis for the elimination of 
undesirable seed from stocks to be used for planting. The essential 
results of these investigations were reported in abstract at the Toronto 
meeting of the American Association for the Advancement of Science in 
December, 1921, and published in a subsequent number of Phyto¬ 
pathology (6). 
Studies made at the Vermont Agricultural Experiment Station seem 
to indicate that certain definite correlations exist between both dormant 
and sprouted tubers and foliage condition in the plants grown from such 
tubers, and these studies were supplemented by observations both in the 
greenhouse and in the field as to variations in the seriousness of mosaic 
and leafroll symptoms in successive generations of plants and other 
related points. 
In April, 1921, the noteworthy paper by Schultz and Folsom entitled 
“Teafroll, Net-Necrosis and Spindling-Sprout of the Irish Potato” (12) 
appeared, and though much wider in scope than the present paper and 
developed along different lines, yet certain of the most significant conclu- 
1 Accepted for publication May 2, 1923. 
2 Reference is made by number (italic) to “Literature cited,” p. 265-266. 
Journal of Agricultural Research, 
Washington, D. C. 
afw 
Vol. XXV, No. 6 
Aug. ix, 1923 
Key No. Vt-2 
54484—23 - 1 
. (25s) 
