A BACTERIAL LEAFSPOT OF MARTYNIA 1 
By Charlotte Elliott 
Pathologist, Laboratory of Plant Pathology and Office of Cereal Investigations, 
Bureau of Plant Industry, United States Department of Agriculture 
INTRODUCTION 
Martynia louisiana is a coarse 
spreading annual with large pubescent 
leaves. The fruit is a capsule with a 
fleshy, hairy covering and long curved 
beak, which gives it the common name 
devil's claw or unicorn plant. It grows 
as a weed in the warmer parts of central 
United States and is also cultivated, 
the young fruits being used for pickles. 
In July, 1922, diseased leaves of 
Martynia louisiana (M. proboscidea ) 
were sent in by J. G. Lill, of the Office 
of Sugar Plant Investigations, from 
Garden City, Kans., (PI. 1, A) where 
the plants were growing as weeds in 
and along the borders of sugar-beet 
fields. Bacteria were isolated from 
the leaf spots but pure culture inocula¬ 
tions have shown that the organism 
isolated was not infectious to beets and 
was in no way connected with the 
spotting of the beet leaves. Finding 
no description in literature of a bac¬ 
terial leaf spot of Martynia, the follow¬ 
ing study of the disease as it occurred 
on the host plant and of the morphol¬ 
ogy, physiology, and cultural characters 
of the causal organism was made. 
• DESCRIPTION OF LESIONS 
The leaves were heavily spotted 
with lesions mostly round but angular 
when bounded by veins. The infected 
tissue is water-soaked, sunken (PI. 1, 
A) and translucent. The youngest 
spots are 1 to 2 mm. in diameter. The 
translucent centers are not more than 
2 mm. in diameter; but narrow, swollen, 
brown margins, slightly raised above the 
surrounding tissue, develop as the spots 
become older. When several spots 
coalesce they form irregular patches of 
dry, light-brown tissue a few millimeters 
to a centimeter or more wide with trans¬ 
lucent dots scattered over them. From 
sections (Pi. 2, A, B, and C) of these 
lesions bacteria stream in abundance. 
ISOLATIONS AND INOCULATIONS 
Isolations were made in two ways. 
Lesions were washed through 12 sterile 
water blanks, crushed in sterile broth 
and plates were poured. Other lesions 
were dipped in 95 per cent alcohol, 
then into HgCh 1-1,000 for two 
minutes, washed through three sterile 
water blanks, crushed in sterile broth 
and plates poured. 
Both methods gave practically pure 
cultures of a white organism which 
when sprayed on Martynia plants 
produced typical lesions of the disease 
(PI. 1, B). Reisolations from these 
lesions again gave the same white 
colonies which again produced the leaf- 
spot when sprayed on Martynia. 
Inoculations were made by spraying 
plants both in the field* and greenhouse 
with water suspensions of the causal 
organism. Check plants were sprayed 
with sterile water. Inoculated green¬ 
house plants and checks were held in 
damp chambers three to four days. 
Four to six days after inoculation, 
lesions began to appear as water-soaked 
dots on the under surfaces of the 
leaves. Two or three days later the 
lesions may be a millimeter in diameter 
and visible on the upper as well as the 
under surface. The checks remained 
healthy. 
In two greenhouse experiments infec¬ 
tion appeared to progress through the 
veins, many of which, leading from 
marginal or other lesions, were water- 
soaked and darkened or more trans¬ 
parent than normal. Petioles collapsed 
at the point of junction with the blade 
and later entire leaves and petioles 
died and dried. From the petioles 
the infection passed into the stem 
until entire plants collapsed and dried 
up. In field experiments infection 
seemed to pass from growing tips 
through the stem into the more or less 
fully developed fruits, causing at first a 
water-soaked appearance. Later, this 
tissue turned brown, shriveled, and died 
1 Received for publication June 14, 1924—issued February, 1925. 
Journal of Agricultural Research, 
Washington, D. C. 
( 483 ) 
Vol. XXIX No. 10 
Nov. 15,1924 
Key No. G-436 
