NematosporaNematospora seed rot and lint stain: seed rot and lint stain: Distribution, Importance and Distribution, Importance and Association with HemipteraAssociation with Hemiptera

Alois Bell, Juan Lopez, Jr., Enrique Medrano, Alois Bell, Juan Lopez, Jr., Enrique Medrano, Jack Bacheler, Jeremy Green, Phillip Roberts, Jack Bacheler, Jeremy Green, Phillip Roberts,

Robert Kemerait, Jr., James Marois, David Robert Kemerait, Jr., James Marois, David Wright, and Robert NicholsWright, and Robert Nichols

USDA-ARS, College Station, TXUniversity of North Carolina, Raleigh, NC

Clemson University, Clemson, SCUniversity of Georgia, Tifton, GAUniversity of Florida, Quincey, FL

Cotton Incorporated, Cary, NC

Determine the possible importance and

etiology of infectious yeast in seed rot,

internal boll rot, and tight lock of cotton.

ObjectiveObjective

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.

Introduction to PlantIntroduction to PlantPathogenic YeastPathogenic Yeast

NematosporaNematospora corylicoryli on TSA medium on TSA medium

NematosporaNematospora corylicoryli on PDA medium on PDA medium

Close-up of Nematospora coryli colonies

Colonies showing Colonies showing hyphae hyphae

Close-up of Nematospora coryli colonies

NematosporaNematospora coryli:coryli:A – vegetative budding cells, B – hyphae with ascus,A – vegetative budding cells, B – hyphae with ascus,

C – asci, D – ascosporesC – asci, D – ascospores

Bud cells, hyphae, and ascospores of Bud cells, hyphae, and ascospores of NematosporaNematospora corylicoryli

SymptomsSymptoms

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 Florida lock infected with Nematospora coryliNematospora coryli

Lock cross-section

Infected lock showing staining Infected lock showing staining and restricted openingand restricted opening

Comparison of locks infected with Comparison of locks infected with bacteria or yeastbacteria or yeast

Secondary Secondary AlternariaAlternaria and and CladosporiumCladosporium infections of locks affected by infections of locks affected by N. coryliN. coryli

Seed rot and shriveling Seed rot and shriveling caused by caused by N. coryliN. coryli

Infected Control

Occurence of Occurence of NematosporaNematospora in in Field and Greenhouse Bolls* Field and Greenhouse Bolls*

Punctured by Stink Bugs in 2005Punctured by Stink Bugs in 2005

Source of Bolls

No. Bolls Observed

No. With Punctures

No. With Nematospora

No. With

>10 6 Bacteria

Field BollsField Bolls 36 34 30 12

Greenhouse Bolls*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*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 Frequency of Caged Feral Insects Transmitting Transmitting NematosporaNematospora and and

Bacterial Pathogens to Bolls in 2006Bacterial Pathogens to Bolls in 2006No. of Bolls No. With Pathogen

Insect* Source† Total Punctured NematosporaNematospora BacteriaBacteria BothBoth

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

Total 160 147 9494 2727 1111

* 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 Effect of Insecticides on Insect Punctures and Boll Infections by Insect Punctures and Boll Infections by

NematosporaNematospora and Bacteria in 2006 and Bacteria in 2006

% Bolls*

Punctured

% Punctured Bolls With

State TreatmentNematospora Bacteria Both

NC None 60 (6.0) 38 25 17

InsecticideInsecticide 6 (1.0) 0 6 0

SC None 26 (2.0) 18 27 0

InsecticideInsecticide 4 (1.0) 50 0 0

GA None 94 (25.1) 40 62 33

InsecticideInsecticide 26 (10.5) 42 83 42

FL None 62 (21.9) 62 23 8

InsecticideInsecticide 60 (10.6) 55 24 6* Based on 50 bolls; ( ) indicates mean number of punctures.

Effects of Effects of Nematospora coryliNematospora coryli(Seed and Fiber Development in Lock)(Seed and Fiber Development in Lock)

0

100

200

300

400

500

600

700

800

900

mg

/lo

ck

Seed CottonWeight

Cotton SeedWeight

Fiber Weight

Measurement/Lock

ControlInoculated

Effects of Effects of Nematospora coryliNematospora coryli on Seed on Seed

0

20

40

60

80

100

120

Re

lati

ve

Am

ou

nt

No. Seed/Lock Seed Weight(mg)

% Fiber

Measurement

ControlInoculated

Effects of Effects of Nematospora coryliNematospora coryli(Array of Cotton Seed Weights - (Array of Cotton Seed Weights - ST 474ST 474))

0

2

4

6

8

10

12

14

16

* M

ea

n S

ee

d W

eig

ht

(mg

)

1 2 3 4 5 6 7

Seed Number

ControlInoculated

* Mean of >400 bolls from 98 cultivars.

Effects of Effects of Nematospora coryliNematospora coryli(Array of Cotton Seed Weights - (Array of Cotton Seed Weights - DP 393DP 393))

0

2

4

6

8

10

12

14

16

* M

ea

n S

ee

d W

eig

ht

(mg

)

1 2 3 4 5 6 7 8

Seed Number

ControlInoculated

* Mean of >400 bolls from 98 cultivars.

Effect of Boll Age on Damage Effect of Boll Age on Damage Caused by Caused by NematosporaNematospora

Boll Age at Inoculation*

(Days)

% Decrease in Weight

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

* Fifty bolls from four cultivars.

Effect of Boll Age on Damage Effect of Boll Age on Damage Caused by Caused by Nematospora Nematospora (...continued)(...continued)

Boll Age at Inoculation*

(Days)

% Decrease in Weight

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 Effect of Boll Age on Infection and Colonization of Nematospora coryliNematospora coryli Transmitted by Feeding of Transmitted by Feeding of

Southern Green Stink BugsSouthern Green Stink Bugs

Infested Boll

Age (Days)

Number of Bolls*

Total InfectedInfected >10,000 cfu/gm>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 4545 2727* Bolls examined 12 days after single feral insects from pearl millet were caged over bolls of specified ages.

Cultivar Reaction toCultivar Reaction to Nematospora coryliNematospora coryli

0

5

10

15

20

25

Fre

qu

en

cy o

f C

ult

ivars

% Reduction in Seed Cotton Weight

Cultivar Reaction to Cultivar Reaction to NematosporaNematospora % 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)

ConclusionsConclusions

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.