Compendium of Potato Diseases - (PDF, 101 mb) - USAID

3) Avoid contamination of clean fields by inoculum transfer Verticillium Wilt
through infested soil or diseased tubers and plant refuse.
The disease apparently occurs wherever potatoes are grown,
Selected References although it may be confused with other diseases that cause early
maturity.
GOSS, R.W. 1923. Relation of environment and other Iactors to potato
wilt caused by I..oarint oxi.vorinn. Neb. Agric. Exp. in. Res. Symptoms
Bull. 23. 84 pp.
Verticillium wilt causes early senescence of plants. Leaves,
GOSS, R. W. 1924. Potato wilt and stem-end rot caused by I usariumn which become pale green or yellow and die prematurely, are
eumartii Neb. Agric. Exp. Sin. Res. Bull. 27. 83 pp.
described as "early dying" or having "early maturity."
GOSS, R. W. 1940. A dry rot of potato steins caused by Ihusariwn l)uring the ,,rowing season, plants may lose their turgor and
solani. Phytopathology 30:160-165.
wilt, especially on hot, sunny days (Plate 50). Single stems or
Mcl.EAN. J. G., and .1.C. WAI.KER. 1941. A comparison of Fusarito, leaves on one ide ofthe stem may wilt first. Vascular tissue of
avenaceawn. ' oxirsporui,and 1. ,olani var. e'u artiiinrelation to
s
potato wilt in Wisconsin. I. Agric. Res. 63:495-525.
stems becomes a light brown, best observed if the stem issevered
RADTKE. W., and A. ESCANI)E. 1975. Verglcichendc Unter- at about ground level with a long slanting cut. Externally visible
suchungen Uiber verschiedene Methoden tur Inokulation von Kar- necrotic stem streaking occurs in certain cultivars when soil
toffelsiimlingen mit I.uvariun solani (Mart.) Sace. f. sp. cnm' ariii moisture and fertility are high.
(Carp.) Snyder et Hansen. Potato Res. 18:243-255.
Tubers from infected plants, but not necessarily all tubers,
SNYDER, W. C., and I|. N. HANSEN. 1941). 1941, 1945. The species usually develop a light brown discoloration in the vascular ring
concept in Flsarium.Am .J. Bot. 27:64-67; 28:738-742; 32:657-666. (Plate 5I, Fig. 68A); severe vascular discoloration may extend
UPSIONE, caused by M. IPusariumo.i-sporuni. E. 1970. A corky rot plant of ,Jersey Pathol. Royal 19:165-167.ovrhlwytouhheue.Caiesmydeopnie
potato tubers ay through the tuber. Cavities may develop inside
severely affected tubers. Pinkish or tan discoloration (see pink
(Prepared by J. E. Huguelet and W. J. Hooker)
bA
eye) may develop around the eyes oras irregular blotches on the
surface of affected tubers. This may be confused with mild late
blight infection.
Causal Organisms
V'erlicillium alho-airum Reinke & Berth. develops septate,
resting dark mycelium on stems in the field and also in culture,
in contrast to 1'. dahliae Kleb., which forms dark mycelial
strands with black, thick-walled pseudosclerotia (Fig. 69), also
called microsclerotia, 30-60(lm in diameter. Vegetative hyphac
of both are similar (2-4 pm in dia meter and colorless). Conidiophores
are septate with side branches (Fig. 6813), swollen at the
base, and arranged in a whorl. First-formed conidia of I'.alhoairtim
;,re (T-12 X 2.5-3 p in. Those of 1'. dlalijot are 3-5.5 X
1.5-2 pin. Conidia produced later, particularly those in culture,
may be considerably smaller, 3--6 x 2-3 pm. Conidia arc usually
single celled but may he one-septate (Fig. 68C and )).
Both types may be present within a single potato plant.
Disease Cycle
Infection is through root hairs, wounds (including those at
points of emergence of adventitious roots), and through sprout
and leaf surfaces. Hyphae progress intracellularly and
intercellularly to the xylem (Fig. 68D). Transport of conidia
within vessels of potato is probable. Conidia are short-lived and
Fig. 68. A, Verticillium vascular discoloration in tuber. B,
Verticillium albo-atrumin culture: a, "ater droplets surrounding Fig. 69. Verticillium isolates from potato. A,Dark mycelial type in
conidia on tips of conidiophores; b, a single conidium (bar one-month culture, at X100 and X375 approximately. B, Pseudorepresents
50 mm). C, Conidia from culture; D, fungus mycelium sclerotial isolate in cne-month culture, x175 and x200. (Courtesy
in discolored xylem of tuber tissue (bar represents 10 pm). D. B. Robinson et a. 1957)
62