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:ULTURE, EGYPT.

Technical and Scientific Service.

Bulletin No. 18. (Botanical Section.)

THE SMUTS OF MILLET,

By H. R. BRITON-JONES,

MYCOLOOIST, BOTANICAL SECTION.

(>'n /' .liUrd /or printing on February 24, 1931.)

Government Press, Cairo, 1922.

i'i, in-, obtained, either <!i.vctly or through any Bookseller, from

t!ie ilovERNMENT PUBLICATIONS OFFICE, Ministry of Finamv,

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Price P.T. 3.

MINISTRY OF AGRICULTURE, EGYPT.

Technical and Scientific Service.

Bulletin No. 18. (Botanical Section.)

THE SMUTS OF MILLET,

By H. R. BRITON-JONES,

VtvcOLOGIST, Km \\HAI SFITICIV

1921.)

Government Press, Cairo, 1922.

TO in

nnxs Ornri:. Mm imiirr,

uin I'.M.. i

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P.T. 3.

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MAIN

MINISTRY OF AfJllIOULTUKE, EGYPT.

Bulletin No. IS.

1 1 {i > r.vxicAi, SECTION.)

THE SMUTS OF MILLET (Arwbvpogon Sorghum Jtmt.) ,

The Long Smut (Tolyposporiiem fil//cni»i

The Long Smut is the most common smut of millet in Egypt
and its occurrence c;in lie compared with that of loose smut of wheat.
It occurs in almost every cn>|> of millet throughout 1 he count rv.
but not in sutiicicnt quantity to cause an appreciable decrease in the
yield. This is part! v due to t lie fact t hat the number of heads at tacked
liardlv ever reaches as much as t \vo per cent, and partly because only
I he individual grains are attacked by the fungus. The number of
grains attacked in a single head may be anything from live to si
but. on an average about fifteen.

When a grain is attacked it is replaced by a spore-sac which
measures ir>to:{| millimetres long by 4 to 5 millimetres broad. The di&
is conspicuous and easily recogni/able ( I'late 1, Fig. 1). The spore
splits longitudinally, starting at the tip usually, exposing eight to
ten dark brown filaments surrounded by a powder of the same colour.
The filaments are the isolated fibro- vascular bundles of the enlarged
ovary (I'late 1, Fig. 2). If a little of the powder is placed in wa let-
on a slide and examined microscopically it will be found to consist
of several spore balls which are composed of a number of closely
adhering spores (Plate I. Fig. 3). The individual spores are coverd
with warts on the free surfaces and smooth on the sides by which they
were attached to the other spores of the spore balls (Plate I. Fig. 4).
The spores are brown, round, but somewhat flattened on the smooth
sides and measure 10 to 1 ."> 11. in diameter. They germinate readily in
a one per cent solution of cane sugar and normally produce a tlr
celled thread (promycelium). Each of the cells of the promyceliutn
t hen gi\ • i its tip. or laterally near the septa, to small unicellular

structures called sporidia (I'late I, Fig. 5). The spores on germination
also produce septate germ tubes which then give rise to sporidia.
Sporidia which have become detached from the cells of the promyceliutu
give rise to secondary sporidia.

0340

__ o

The life history of the fungus is not yet known. It has been
observed that in the case of a single plant bearing three heads, only
seven grains in the youngest head were affected, whilst all tlie grains
in the other two heads were healthy. This supports a statement
made by Butler to the effect that possibly it may be due to a localized
infection of a single flower.

It is a custom of the felaheen of the provinces of Minya and Asyut
to eat the fungus when young, and it is said to have a peculiar sweet
taste. The eating of the fungus, although a perfectly sound method
of controlling the disease, cannot be recommended or condemned
here .because the effect of large quantities of this fungus on the health
of the consumer is not known. The only recommendations that can
be given for treatment of the disease are :—

(1) Obtain seed from a healthy crop.

(2) Remove and burn the spore-sacs when young.

(3) Where possible, do not grow millet for a few years on soil
where the disease has occurred.

The Head Smut (Ustilago reiliana Kuekn.).

The disease caused by the Head Smut is of rare occurrence in
Egypt and the loss caused by it is negligible It is also known in
India, Southern Europe, U.S.A., and Asia.

Usually the millet ear is converted into a large spore-sac (sorus)
which measures 7'5 to 10 centimetres long by 3'75 to 5-5 centimetres
broad (Plate II, Fig. 1). The grey membrane of the sorus usually
ruptures before emerging from the sheathing leaves, exposing a
network of dark brown almost black fibrous filaments, surrounded
and intermingled by a powder of the same colour. The fibrous
filaments are the fibro- vascular bundles of the millet and the powder
is composed of the spores of the fungus (Plate II, Fig. 2). "ki-
termingled with groups of sterile, hyaline cells. The hyaline cells
measure 7 to 15 \i in diameter. The spores are dark brown, round,
covered with small spines and measure usually 13 u in diameter.
The size of the spores is very uniform. They germinate readily in a
one per cent solution of cane sugar and produce a .short, thick,
four-celled promycelium, bearing sporidia at the apex and near the
septa (Plate II. Fig. 3). The sporidia bud off other sporidia readily
and remain joined end to end to form chains. The spores retain
their power of germination for as long a period as eight years.

Infection of the flowers does not take place in the case of this
disease. The method of infection is usually from spores which arg>
present in the soil. These attack the young millet seedling so that
the whole plant becomes infected, resulting in (lie production of a

— 3 —

smutted oar. Sometimes only the lower portion of the ear 1
infected and the upper portion may grow out to form leafy shoots.
This fungus also causes the Head Smut of maixc.

Special treatment is unnecessary ! his disease at pro,-

but it is advisable to out and burn diseased cars, at the same time
preventing the sporefl being shed on the ground. Ill the event of a se1.
local attack taking place millet should not be grown on that soil
for five years. By that time probably most, of the spores will have
germinated and perished.

The Grain Smut (Sphaceolotheca sorgki, Lk., Clinton).

The (irain Smut occurs more often than the Head Smut and less
often than the Long Smut. The loss caused by the disease is negli-
gible at present. It is known in most parts of the world where millet
is grown, and is said to cause great losses sometimes in dilTerent
parts of India.

As in Long Smut the individual grains are attacked. The number
of diseased grains exceeds that in Long Si i o-isos whc:

grain in a head is infeoted yre not infrequent. It has also been
served that some grains may be attacked by Long or Head Smut and
some with drain Smut. The attacked grain is replaced by a grey,
oval, spore-sac (sorus). measuring 4 to 1:2 millimetres long by -2 to
3 millimetres broad. The glumes remain unaltered and can be seen
surrounding the bases of the sori (Plate 111. Figs. I and -2). The wall
of the sorus becomes ruptured fairly easily. The sac is filled with
a dark brown mass of spores and a central, rigid, slender, column
of tissue (Plate III, Fig. 3). The latter is composed of the tissue of
the millet and is traversed by libro-vascular bundles. The sp
when seen in mass are dark brown, but when placed in water tln>\ soon
separate into individual spores, and on examining under a microscope
they will be seen to be light brown in colour, slightly oval or round,
smooth, and measure 5 to 7 11, in diameter (Plate 111, Fig. 1).

Spores from specimens of the disease collected this year germi-
nated readily in water. They can, however, retain their germinating
powers for as long a, period as six years or more. Spores pheed in
water vary considerably in their method of germination. Some
produce a four-celled promycelium the cells of which give rise to
spindle-shaped sporidia (Plate III, Fig. o). The latter rarely bud on"
secondary sporidia. Other spores, instead of forming sporidia, give
rise to germ tubes laterally and apically from the cells of the promy-
cehnni. Again some spores do not produce a definite promycelium,
but instead septate branching germ tubes are formed.

Infection takes place in the same manner as in the closed Smut
of barley. Spores adhere to the seed coats, and when sown together

— 4 —

germination of the seed ;md spores takes place. The young seedling
then becomes infected between the time of germination of the seed
and appearance of the seedling above the ground. As with barley
there is no method by which a diseased plant can be distinguished
from a healthy one in the field, until the ears are formed when the
diseased produce smutted grains. It is not likely that infection
takes place from spores in the soil, particularly in Egypt, where the
soil is irrigated. This method of watering at intervals, coupled with
a variation in the temperature of the soil between one season and
another, probably ensures the germination of most of the spores in the
soil and their death in the absence of millet seedlings.

TREATMENT.

The treatment of this disease must aim at killing the spores
adhering to the seed coats by some means which will not. appreciably
interfere with the gernrina lion of the seed. There.' ral methods

of disinfecting the seed, but only two will be considered here because
they are as effective as the others and at the same time simpler.
They also serve a double purpose as stated below.

(1) Copper Sulphate. — The seed is immersed in a two per cent
solution of copper sulphate for ten minutes, spread out on sack-
ing or a clean floor and allowed to dry. The seed is then ready for
sowing. In some countries the seed is sprinkled with the solution
instead of immersing, but the latter is recommended here because:

(1) any spore-sacs which may be amongst the healthy seed will
float on the surface of the liquid and can easily be skimmed off ;

(2) many of the seeds are attacked by weevil and these also float on
the surface of the liquid and can be removed ; (3) the bad seed float
on the surface. To do this thoroughly the seed should be stirred for
two or three minutes. Even in the absence of Smut it is advisable
for the above reasons to immerse the seed in water and after stirring
to remove those remaining on the surface. This will save much
time, labour, and the cost of resowing. A wooden and not a metal
vessel must be used when making the solution. The solution can be
used over and over again as long as it is not allowed to evaporate. If
the seed is to be put back in the same basket (maqtaf or ghalaq) or
sack after treatment, it should be first immersed in the solution so as
to prevent the seed becoming contaminated with the spores of the
fungus which may be left in the basket or sack. There is no objection
to immersing the basket containing the seed in the solution provided
the seed is stirred and those that float are removed.

(2) Formalin.— The seed is immersed in a half per cent solution
of commercial formalin (i.e. ing 37 to 40 per cent formaldeh\ cle)

for two hours, thei I out on the ground and allowed to dry

rapidly in the sun. The remarks made above with r to the

removal of floating seed and spore-sacs apply in this case also. The
seed should then be sown as soon as possible.

COST OF TREATMENT.

Formalin. -Four or five qadali* of millet seed are usually sown
per fedddti in Egypt. Four qad«/ts .ire equal to eight lit that

ten litres of the solution will be ample for treating sufficient seed for
one fcdddn. A half per cent of ten litres is 50 c.c. and this is the amount
of formalin required. Commercial formalin (i.e. containing 37 to 40
per cent formaldehyde) when bought wholesale costs P.T. 55 per
litre. Thus the cost of treating the seed with formalin is P.T. 2-75 per
fedddn. If the solution is used for a second lot of seed tin's will of cpi
reduce the cost of treatment to M ms. 1 1 per fed. [sot >n.

Cop/ier Sulphate.- Copper sulj. .ughtat P.T. 15 per

kilo-. ::00 gr;:;. the amount n< for

of -2 i I'.T. 3. Three

cultivators HSH, sullicic fur
one /'. !»y shari; !'.T. I each.

The methods of seed disinfection described above were demon-
ted this ve.irin twelve diffe vl!'- Kaei> h.t of .
divided into tliia ^wn untreated,
with two per cent copper sulphate, and the

third sown after ti. /, ith half i formalin. The result

showed that the chemical had no ill efi niination of the

seed. In all the treated and i: present

showing that disinfection of seed is inelTective against .! nut.

•1 Smut did n<,< occur in any of i led or untreated pi

In eleven out of twelve experhi iain Smut was also absent, but

in the twelfth it appeared in the untreated only. Th- no

Grain Smut in the treated plois of this experiment. This sla

treatment of seed with copper sulphate or formalin is effective
insl < irain Smir

BIBLIOGRAPHY. — "Fungi and 1 n 1'h'nts." BUTLER.

EXPLANATION OF THE PLATES.

PLATE I. — LONG SMUT (Tolyposporium filifenim Busse) :— -

Fig. 1. — Portion of Millet Head showing long spore-sacs (natural
size).

Fig. 2. — Spore-sac opened to show filaments (natural size).

Fig. 3.— Spore ball.

Fig. 4. — Spores.

Fig. 5. — Spores germinating.

PLATE II. — HEAD SMUT ( Ustilayo reiliana Kuehri) :—
Fig. 1. — Smutted ear (natural size).
Fig. 2.— Spores (x 650).
Fig. 3. — Spores germinating ( x 650).

PLATE III. — GRAIN SMUT (Sphaceolotheca sorghi, Lk., CLINTON) :—
Fig. 1. — Smutted ear (natural size).
Fig. 2. — Smutted grain.

Fig. 3. — Centra] portion remaining after^shedcling of spores.
Fig. 4.— Spores ( X 650).
Fig. 5. — Spores germinating ( x 650).

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