Development of Fusarium in Cotton Bolls:

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Development of Fusarium in Cotton Bolls
Greenhouse and Field Results Breno Leite,
David Wright, Jim Marois Daniel Mailhot
University of Florida, Quincy, FL
Beltwide Cotton Conferences, 2007
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Beltwide Cotton Conferences, 2007
Open Cotton Bolls
Healthy Hardlocked
Locks fail to allow fiber outward expansion
Do not fluff out
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Beltwide Cotton Conferences, 2007
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Beltwide Cotton Conferences, 2007
Hardlock causes yield losses ranging from 20 -
70
Harvested Rows
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Beltwide Cotton Conferences, 2007
Hardlock

• Associated with infection by Fusarium
  verticillioides
• through the flowers
• Most severe along Gulf Coast and is a
• major limiting factor of Florida cotton
  yield
• Flower thrips and bumblebees are likely to be
  contributing
• factors for infection and Fusarium dispersal
  
• (will be discussed in another presentation)

330 PM 01/11/07 Relationship Between Flower
Visitors and Cotton Hardlock, B. Leite, J.
Marois, D. Wright, E. Osekre and D. J. Mailhot
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Beltwide Cotton Conferences, 2007
Development of the bud from match head square to
flower
Mature cotton flower. The cotton flower contains
both male and female parts.
Illustrations Source Cooperative Extension
Service, University of Georgia
College of Agricultural and Environmental Sciences
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Beltwide Cotton Conferences, 2007
Fusarium conidia
Illustrations Source Cooperative Extension
Service, University of Georgia
College of Agricultural and Environmental Sciences
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Beltwide Cotton Conferences, 2007
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Beltwide Cotton Conferences, 2007
Hardlock of cotton seriously affects yield in
many areas of the southeastern United States, and
can be devastating in the panhandle of
Florida. In 2002 it caused over 20,000,000
in lost yield, reducing Floridas average yield
from 650 lb/acre to less than 400 lb/acre.
Hardlock is more severe when there is High
nitrogen High plant density Insect damage Seed
rot High temperature and humidity (?) Cool nights
(Dan Mailhot)
PhD thesis University of Florida
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Beltwide Cotton Conferences, 2007
Our Objective
General Characterize the causal agent of the
disease and to develop effective control measures
against the disease. Specific Find the
principles of disease establishment. Follow
step by step the pathway of Fusarium conidia
germination. Find out why some control
measures fail or failed in past years.
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Beltwide Cotton Conferences
Traditional boll rots. Boll rots usually are the
product of insect damage or pathogen activity
after the bolls have opened or early in the
season when the carpel turns brown or black and
never opens. Boll rots occur during wet weather
when the cotton boll or fiber is colonized by a
number of pathogens, although only a few fungi
are responsible for the majority of infections.
These include Alternaria gossypina (Thuem.)
Hopkins, Curvularia spp., Diplodia gossypina
Cke., Helmithosporium gossypii Tucker, Fusarium
spp., and Phomopsis .
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Beltwide Cotton Conferences, 2007
Thus far we have shown that the majority of
hardlock is caused by the fungal pathogen
Fusarium verticillioides, also known as F.
moniliforme. This is the same organism that
causes corn ear rot. We have shown that the main
mode of infection is through the cotton flowers,
and that fungicides applied to the flowers will
control the disease. This is an entirely new
approach to the etiology and control of the
disease and in 2003 field plots are replicated
throughout the southeastern states in an attempt
to reproduce the results developed at the NFREC
at Quincy. This has become a regional project
with university faculty from Louisiana,
Mississippi, Alabama, Georgia, South Carolina and
Florida (NFREC and WFREC) working together, with
major funding provided by Cotton Incorporated.
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Beltwide Cotton Conferences, 2007
Image analysis (Software Image J NIH) to
estimate fiber density in a determined area.
Device designed to facilitate fiber count per
area (A). Typical healthy fiber density (B).
Typical hardlock fiber density - type 4. Close
view suggests that there is debris deposited in
between the fibers (C). A healthy cottonseed (H)
with a diseased cottonseed, hardlock type 4
(D).
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Beltwide Cotton Conferences, 2007
Relationship between density ( fiber per area)
and cottonseed weight. Healthier locks
consistently exhibit higher seed weight and less
fiber density (ideal for picking). In contrast,
seeds from bolls with hardlock (type 3 and 4)
have lower weight and high fiber density (not
harvestable).
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Beltwide Cotton Conferences, 2007
Detection of Fusarium-like structures (hyphae and
macroconidia) associated with hardlock of cotton.
Structures, hyphae (A, C, D) and macroconidia (E,
F) were observed in between the lines demarked
above (B). Notice the yellow-brown coloration.
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Beltwide Cotton Conferences, 2007
Average temperature from 0000 to 0600 and
hardlock severity
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Beltwide Cotton Conferences, 2007
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Beltwide Cotton Conferences, 2007
Conclusions
Mean temperature from 0000 to 0600 negatively
associated with hardlock severity Relationship
strongest between 21 and 25ºC Predictions
typically within 20 of observed hardlock for day
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Beltwide Cotton Conferences, 2007
Average daily temperature (TEMP) and average
relative humidity (RH) at Jay, FL. The
information for these graphs was obtained from
the Florida Automated Weather Network (FAWN
http//fawn.ifas.ufl.edu). Preliminary work
revealed that differences between Quincy and Jay,
FL, were found mainly during June and July of
2006. In the beginning of June RH in Jay was
approximately 10 units lower than Quincy (A).
These differences decreased during the next 60
days. RH was still low when bloom started in
July. In contrast, temperature was slightly
higher throughout the same period (B).