Transcript Nematospora

Nematospora seed rot and lint stain:
Distribution, Importance and
Association with Hemiptera
Alois Bell, Juan Lopez, Jr., Enrique Medrano,
Jack Bacheler, Jeremy Green, Phillip Roberts,
Robert Kemerait, Jr., James Marois, David
Wright, and Robert Nichols
USDA-ARS, College Station, TX
University of North Carolina, Raleigh, NC
Clemson University, Clemson, SC
University of Georgia, Tifton, GA
University of Florida, Quincey, FL
Cotton Incorporated, Cary, NC
Objective
Determine the possible importance and
etiology of infectious yeast in seed rot,
internal boll rot, and tight lock of cotton.
Introduction to Plant
Pathogenic Yeast
1. Belong to four closely related genera and readily
produce 2-celled, needle-shaped ascospores.
2. Ashbya and Eremothecium are filamentous,
whereas Holleya and Nematospora are dimorphic.
Recent studies place all in Eremothecium.
3. Specifically associated with heteropterous insects,
and are restricted to warmer climates.
4. Cause diseases of many families of angiosperms,
usually attacking fruits or seeds pierced by bugs
during feeding. Important crop hosts include cotton,
okra, soybean, green bean, cowpea, citrus,
pistachio, tomato, and mustard.
Nematospora coryli on TSA medium
Nematospora coryli on PDA medium
Close-up of Nematospora coryli colonies
Close-up of Nematospora coryli colonies
Colonies showing
hyphae
Nematospora coryli:
A – vegetative budding cells, B – hyphae with ascus,
C – asci, D – ascospores
Bud cells, hyphae, and ascospores of
Nematospora coryli
Symptoms
1. Prior to boll opening: lint is first stained yellow and
later reddish-brown and may become dry. Seed
coats are discolored and embryos are killed or their
development is severly inhibited.
2. At boll opening: sutures may not split completely,
locks do not fluff normally and infections by
secondary fungi are common, sometimes
blackening the lock.
3. After opening: cotton locks are stained tan to
reddish brown. Seed is shriveled with discoloration
of fuzz and absence of black pigment in seed coat.
Florida lock infected with
Nematospora coryli
Lock cross-section
Infected lock showing staining
and restricted opening
Comparison of locks infected with
bacteria or yeast
Secondary Alternaria and Cladosporium
infections of locks affected by N. coryli
Seed rot and shriveling
caused by N. coryli
Infected
Control
Occurence of Nematospora in
Field and Greenhouse Bolls*
Punctured by Stink Bugs in 2005
Source of
Bolls
No. Bolls
Observed
No. With
Punctures
Field Bolls
36
34
No. With
No. With
Nematospora >10 6 Bacteria
30
12
Greenhouse Bolls* (SGSB collected from millet on 9/15 & 10/6)
Females
49
14
8
6
Males
41
14
9
5
Nymphs
12
2
2
0
Greenhouse Bolls* (SGSB collected from light trap on 10/5)
Females
10
3
1
3
Males
6
3
0
3
* Single insects caged over bolls for 8 days. Microbial content measured 12 days after
insects removed.
Frequency of Caged Feral Insects
Transmitting Nematospora and
Bacterial Pathogens to Bolls in 2006
No. of Bolls
No. With Pathogen
Insect* Source† Total Punctured Nematospora Bacteria Both
SGSB
Millet
99
92
66
13
3
BSB
Millet
11
10
7
4
2
BSB
P Trap
41
37
14
7
3
LFPB
Millet
9
8
7
4
3
160
147
94
27
11
Total
* SGSB = Southern green stink bug; BSB = Brown stink bug; LFPB = Leaf-footed plant bug.
† Collected from pearl millet by hand or from pheromone traps.
Effect of Insecticides on
Insect Punctures and Boll Infections by
Nematospora and Bacteria in 2006
State
NC
SC
GA
FL
% Punctured Bolls With
% Bolls*
Punctured
Nematospora
Bacteria
Both
None
60 (6.0)
38
25
17
Insecticide
6 (1.0)
0
6
0
None
26 (2.0)
18
27
0
Insecticide
4 (1.0)
50
0
0
None
94 (25.1)
40
62
33
Insecticide
26 (10.5)
42
83
42
None
62 (21.9)
62
23
8
Insecticide
60 (10.6)
55
24
6
Treatment
* Based on 50 bolls; ( ) indicates mean number of punctures.
Effects of Nematospora coryli
(Seed and Fiber Development in Lock)
900
800
700
mg/lock
600
Control
Inoculated
500
400
300
200
100
0
Seed Cotton
Weight
Cotton Seed
Weight
Measurement/Lock
Fiber Weight
Effects of Nematospora coryli on Seed
120
Relative Amount
100
80
Control
Inoculated
60
40
20
0
No. Seed/Lock
Seed Weight
(mg)
Measurement
% Fiber
Effects of Nematospora coryli
(Array of Cotton Seed Weights - ST 474)
* Mean Seed Weight (mg)
16
14
12
10
Control
Inoculated
8
6
* Mean of
4
>400 bolls
from 98
cultivars.
2
0
1
2
3
4
Seed Number
5
6
7
Effects of Nematospora coryli
(Array of Cotton Seed Weights - DP 393)
* Mean Seed Weight (mg)
16
14
12
10
Control
Inoculated
8
6
* Mean of
4
>400 bolls
from 98
cultivars.
2
0
1
2
3
4
5
Seed Number
6
7
8
Effect of Boll Age on Damage
Caused by Nematospora
Boll Age at
Inoculation*
(Days)
Lock
Fiber
Seed
4
18
18
19
6
36
39
34
8
38
41
36
10
17
15
18
12
26
25
28
14
28
30
28
% Decrease in Weight
* Fifty bolls from four cultivars.
Effect of Boll Age on Damage
Caused by Nematospora (...continued)
% Decrease in Weight
Boll Age at
Inoculation*
(Days)
Lock
Fiber
Seed
14-15
45
50
45
16-17
38
42
37
18-19
36
39
34
20-21
16
19
15
* Fifty bolls from four cultivars.
Effect of Boll Age on Infection and Colonization of
Nematospora coryli Transmitted by Feeding of
Southern Green Stink Bugs
Number of Bolls*
Infested Boll
Age (Days)
Total
Infected
>10,000 cfu/gm
15-17
9
9
2
18-20
18
14
10
21-23
6
5
2
24-26
4
2
0
27-29
6
5
3
30-34
15
10
10
Total
57
45
27
* Bolls examined 12 days after single feral insects from pearl millet were caged over
bolls of specified ages.
25
20
15
10
5
0
1-1
0
11
-20
21
-30
31
-40
41
-50
51
-60
61
-70
71
-80
81
-90
91
-10
0
Frequency of Cultivars
Cultivar Reaction to
Nematospora coryli
% Reduction in Seed Cotton Weight
Cultivar Reaction to Nematospora
% Reduction in Fiber Weight
Susceptible Cultivars
Resistant Cultivars
ST 5242 BR (80.1)
Phyt 710 R Acala (13.7)
ST 5599 BR (69.3)
DP 110 RF (14.5)
NG 3273 B2RF (63.8)
BW 6896 B2F (15.9)
BW 2038 B2F (63.6)
FM 966 LL (16.9)
BW 3255 B2F (61.6)
DP 444 BG/RR (17.6)
NG 3550 RF (60.3)
AFD 5065 B2F (18.9)
FM 960 RR (59.8)
CPCSD Acala Fiesta (20.6)
DP 164 B2RF (59.0)
ST 6622 RF (21.4)
Phyt 370 WR (58.2)
BW 8245 B2F (24.8)
DP 167 RF (58.1)
AFD 5062 LL (24.9)
ST 4357 B2RF (54.8)
FM 958 LL (25.9)
ST 4700 B2RF (54.8)
CG 3020 B2RF (26.6)
Conclusions
1. Nematospora occurs in many bolls punctured by
bugs during feeding.
2. A high percentage of feral insects carry
Nematospora which may persist and be transmitted
repeatedly.
3. Most cultivars are highly susceptible to
Nematospora and suffer loses of 40-60% of the
fiber, as well as reducing seed quality.
4. Insect control is the best way to prevent infection,
although improved cultivar resistance may be
possible.