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International Society for Infectious Diseases

Date: Thu 5 Jul 2018
Source: My SunshineCoast [edited]

Scientists at Sugar Research Australia (SRA) have named the organism
responsible for chlorotic streak disease (CSD) in sugarcane, as part
of a breakthrough that had been a scientific mystery for almost 90
years. The researchers identified the single-celled organism as a type
of Cercozoa. The Cerozoon responsible for CSD is new to science and
was given the name _Phytocercomonas venanatans_. The name means "swims
in the veins" and refers to its method of movement and its specific
home in sugarcane xylem vessels. It is about 10 micrometres in length,
about 0.01 millimetres. The search for the culprit behind CSD dates
back to 1929 when the disease was 1st identified, almost
simultaneously in Australia, Indonesia, and Hawaii.

"Now that techniques are available to visualise, isolate and quantify
the CSD organism experimentally, we can begin to address questions
such as how the organism infects naturally through the roots, how it
lives within the plant and causes disease, how cells are released back
into the soil, and how the organism survives for extended periods
outside the plant," SRA's Dr Chuong Ngo said.

Dr Kathy Braithwaite, SRA, is developing a variety resistance
screening method for CSD to incorporate into the SRA plant breeding
program and provide data on CSD susceptibility [for] new varieties.
The project is also working on a diagnostic test. The CSD test already
exists as a research tool and is hoped to be used to assist in
delivering clean plant source material. Previous research in Australia
has shown yield losses from CSD as high as 40 per cent of sugar yield
in susceptible varieties, with an estimated cost of AUD 8-10 million
annually, making it one of the most costly diseases facing the
Communicated by:

[Chlorotic streak disease (CSD) of sugar cane is widespread in many
areas worldwide and was 1st recognised in 1929. Symptoms include white
to yellow, often fragmented leaf streaks with uneven margins, followed
by leaf necrosis, reddish necrosis of vascular tissue in stalk nodes
and stunting of plants. Germination of seedcanes may be reduced. Yield
losses of up to 25 per cent have been reported, depending on the cane
cultivar. Symptoms may be transient since expression is dependent on
environmental factors such as temperature and high soil moisture, and
this may make diagnosis difficult.

CSD is favoured by high rainfall and/or poor drainage and incidence is
affected by weather conditions during the previous year. Transmission
occurs via planting material, contaminated soil and water. The disease
agent does not appear to survive in subterranean aquifers such as
bores. Some disease control is achieved by placing seedcane sources in
water heated to 50 deg C for up to 3 hours, but rapid reinfection of
seedcanes in the field may occur. Meristem tissue culture was
successfully used to eliminate CSD from seedcane lines. In Australia,
up to 50 000 ha may be affected annually and highly productive
varieties used widely are highly susceptible and may collapse under
heavy disease pressure.

_Phytocercomonas venanatans_ (Pv), reported above as a new member of
phylum Cercozoa, is a novel pathogen. Cercozoa are a highly diverse
group of microscopic eucaryots, closely related based on molecular
data but highly divergent in morphology and ecology. They include
species from soils, fresh and marine waters, or the phyllosphere of
plants. Many of their families are still poorly described and the vast
majority of species are still unknown. Much research is still needed
on this phylum and, therefore, the identification of this new species
from sugar cane is an important contribution.

Another plant disease caused by a member of the Cercozoa (although
from a different taxonomic order within it) is clubroot of
_Brassicaceae_. It is a destructive soil-borne disease caused by
_Plasmodiophora brassicae_ and affects nearly all cultivated members
of brassicas, including oilseed rape and cabbages (for more
information see ProMED-mail post

In Australia, the cause of another sugar cane disease of unknown
aetiology, Yellow canopy syndrome (YCS), is still being investigated.
YCS has only been reported from Queensland and does not resemble any
known diseases of the crop observed anywhere else in the world (see,
for example, ProMED-mail post
Australia (with states):

CSD symptoms:
<> and
Pv, microscopy:

Additional news story:
CSD information:
Identification and characterisation of Pv:
<> and
Pv taxonomy:
Information and classification of phylum Cercozoa:
<> and
Taxonomy of Cercozoa: 
<> and
Sugar Research Australia:
. - Mod.DHA

HealthMap/ProMED map available at:
Australia: <>]

[See Also:
Chlorotic streak, sugarcane - Australia: (QLD)]
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