Resistance to plant-parasitic nematodes has been developed in cotton and peanut through breeding efforts. For peanut, high levels of resistance were identified in wild relatives and introgressed into cultivated varieties through interspecific hybridization, resulting in the successful releases of NemaTAM and COAN. For cotton, sources of resistance to root-knot and reniform nematodes were identified and used in breeding programs, though developing dual resistance has proved challenging due to the complex inheritance patterns.

1. Resistance in Cotton and Peanut: One
success story and one story not yet finished
Jim Starr
Dept Plant Pathology & Microbiology
Texas A&M University

2. Resistance In Peanut
 Prior to 1989, no high levels of resistance to
Meloidogyne arenaria available or known in
cultivated peanut
 High levels of nematode resistance were
identified in diploid wild Arachis species (S. C.
Nelson et al., 1989)
A. cardenasii, A. diogoi, and A. batizocoi
are highly resistant to M. arenaria
 Diploid species are not cross-compatible with
cultivated peanut
 TxAG-6, a synthetic interspecific hybrid of
nematode resistant diploid species, and
cross-compatible with A. hypogaea
(Simpson, 1991)

3. Introgression Pathway Developed by C. E. Simpson
A. cardenasii (AA) x A. diogoi (AA)
A. batizocoi (BB) x F1 (AA)
colchicine
F1 (AB)
A. hypogaea cv. Florunner x TxAG-6 (AABB)
(AABB)
A. hypogaea cv. Florunner x F1
(AABB)
TxAG-7 (AABB)
cv COAN released after 5 BC generations
cv NemaTAM released after 7 BC
generations

4. Effect of Resistance on Nematode
Population Densities

5. Comparison of Pod Yields
NemaTAM
COAN
Tamrun 96
Florunner

6. cDNA clone R2430E Linked to the
resistance locus
R
S
Burow et al, 1996; Choi et al., 1999; Church, 2002

7. Current efforts - Peanuts
• Introgression of nematode resistance into genotypes that
also have resistance to TSWV, Sclerotinia Blight, and
the high O/L trait
– Three backcross generations of NemaTAM or sister lines into
parents with these traits have been completed and yield testing
has been initiated
– Hope to release multiple disease resistant peanut in 2010

8. Known Sources of Resistance to Root-knot
in Gossypium hirsutum
• Jackson Limbless (Orton, 1905)
• Clevewilt-6 (Jones et al., 1958)
– Has been used as a source of resistance in breeding programs
• Wild Mexico Jack Jones (Minton, 1962)
– Crossed with Clevewilt-6 to develop highly resistant Auburn and
M-series sources of resistance
• 18 Primitive race stocks (Shepherd, 1983)
• 5 accessions of G. hirsutum from the Yucatan region of
Mexico (Robinson & Percival, 1997)
• Acala C-225 ( = Acala NemX) (Oakley, 1995)

9. Inheritance of Resistance to Root-
knot nematodes
• Clevewilt – 6
– one recessive gene (Bezawada,2003)
– one dominant gene (Shen et al., 2007)
• Auburn and M-series
– Auburn 623: More than 2 genes, incomplete
dominance, transgressive segregation (Shepherd,
1974)
– M240: 2 dominant genes (Zhou, 1999)
– M315: 1 dominant + 1 additive gene (McPherson et
al., 2004)
– M78: 1 dominant gene (McPherson et al., 2004
• NemX
– 1 recessive gene, transgressive segregation (Wang et
al., 2006)

10. Half-Diallele test to determine heritance and allelic relationships
among several sources of resistance to root-knot nematodes
CW WMJJ TX1174 TX1440 TX2076 TX2079 TX2107
DP90 X X X X X X X
CW X X X X X X
WMJJ X X X X X
TX1174 X X X X
TX1440 X X X
TX2076 X X
TX2079 X
TX 1174,TX1440, TX2076, TX2079, and TX2107 identified as resistant accessions
by Robinson and Percival, 1997.

11. Sources of Resistance to Meloidogyne
incognita in Gossypium hirsutum
Accession Collected Origin
Clevewilt-6 N/A N/A
Wild Mexico Jack 1951 Interior of Mexico
Jones
Tx1174* 1972 Veracruz, Mexico
Tx1440* 1979 Yucatan, Mexico
Tx2076* 1985 Tabasco, Mexico
Tx2079* 1985 Campeche, Mexico
Tx2107* 1985 Quintana Roos, Mexico
* Robinson and Percival, 1997

12. Half – Diallele Study
• 28 populations created
• Resistance measured as eggs/g roots from tests
conducted in a greenhouse
• Resistance was defined as a level of
reproduction that was significantly (p > 0.05)
lower than that of the susceptible control
• For each population, the two parents, the F1 and
the F2 generation was tested, along with a
susceptible control
– DP-90 was used as the susceptible control for populations for
which both parents were putatively resistant

13. Reproduction of Meloidogyne incognita on Parental Lines
used in Half-Diallele Study
DP 90
Clevewilt-6
Wild Mexico Jack Jones
Tx2107
Tx1440
Tx2079
Tx2076
Tx1174
2,000 4,000 6,000 8,0000 10,000 12,000
Mean eggs/g roots from seven tests

14. DP 90 x Clevewilt-6
30000
25000
20000 High level of reproduction on
F1 indicates recessive inheritance
Eggs/g root
15000
10000
5000
A B A
0
DP90 Clevewilt F1
50000
40000
Eggs/g root
30000
Two recessive genes (9:7 ratio)
20000
model gives best fit to observed
2 genes 1 gene segregation in F2
10000
0
F2 individuals

15. DP-90 x Wild Mexico Jack Jones
16000
14000
12000
10000
Eggs/g roots
8000
High level of reproduction on
6000
F1 indicates recessive inheritance
4000
B B A
2000
0
DP90 WMJJ F1
12000
10000
Two recessive genes model
8000
gives best fit to observed
Eggs/g roots
6000
segregation in F2
4000 2 genes 1 gene
2000
0
0 10 20 30 40 50 60 70 80
F2 individuals

16. Clevewilt-6 x Wild Mexico Jack Jones
6000
5000
Resistance of F1 is similar to that of
4000
parents as expected for two resistant
parents with at least some of same
Eggs/g root
3000 resistance genes in each parent.
2000
A A A
1000
0
CW WMJJ F1
25000
That some of the F2 are highly
20000 susceptible indicates that some of the
genes for resistance in Clevewilt are
different from those in Wild Mexico
Eggs/g root
15000
Jack Jones.
10000
5000
0
0 20 40 60
F2 individuals

17. 30000
Clevewilt x Tx 2076
25000
20000 Resistance in F1 supports previous
Eggs/g root
15000
conclusion that resistance is inherited
as a dominant trait.
10000
5000
A B BC C
0
DP 90 Clevewilt TX2076 F1
14000
That some of the F2 are highly
12000 Clevewilt x TX2076
susceptible indicates that Clevewilt
10000
and TX2076 have different resistance
Eggs/g roots
8000 genes
6000
4000
2000
0
0 10 20 30 40 50 60 70
F2 individuals

18. Reproduction of Meloidogyne incognita in F1 individuals as
percentage of the susceptible parent DP90
300
250
Percentage of DP90
200
150
100
50
0
These data suggest that resistance in Texas accessions is inherited as a
dominant trait

19. Tx2107 x Tx1440
14000
12000
10000
Eggs/g roots
8000
6000
In this cross of two moderately
4000
resistant parents, the resistance in the
2000 F1 generation is similar to that of the
0 parental lines. The resistance in the F2
DP90 Tx2107 Tx1440 F1 generation shows a large variation but
14000
all individuals show at least moderate
resistance. These data suggest that
12000
the genes for resistance in Tx2107 and
10000
Tx1440 may be identical and have
Eggs/g roots
8000 additive effects.
6000
4000
2000
0
0 10 20 30 40 50 60 70
F2 individuals

20. Tx1197 xTx2076
7000
6000
5000
Eggs/g roots
4000
3000
In this cross of two highly resistant
individuals, the F1 generation is also
2000
highly resistant. That no susceptible
1000
individuals were detected in the F2
0 population suggests that the Tx1174
DP90 Tx1174 Tx2076 F1
and Tx2076 have the same
4000
resistance gene(s) .
3000
Eggs/g roots
2000
1000
0
0 10 20 30 40 50 60 70
F2 individuals

21. Preliminary Conclusions
• Resistance in Clevewilt and Wild Mexico Jack
Jones is inherited as a recessive trait
• Resistance in the Texas accessions is inherited
as a dominant trait
• These resistant accessions appear to have at
least some unique genes for resistance
• Because cotton is an allotetraploid, inheritance
of resistance in these genotypes does not
conform to models based on a diploid system

22. Preliminary Conclusions, Cont’d
• The cotton germplasm pool has numerous
genes for resistance to M. incognita
• These sources of resistance should be
useful to the cotton breeding community
for developing cotton cultivars with a broad
base of resistance

23. Resistance to R. reniformis
• Resistance to R. reniformis in cotton not well characterized
– Only moderate resistance known in G. hirsutum
– G. hirsutum an allotetraploid with an AD1 genome
• Some accessions of G. barbadense resistant
– G. barbadense an allotetraploid with an AD2 genome
• G. longicalyx immune, but a diploid species

24. Development of cotton with resistance
to M. incognita and R. reniformis
• G. hirsutum M315 (Shepherd et al, 199?)
as source of resistance to M. incognita
• G. barbadense Tx110 (Yik & Birchfield,
1984) as source of resistance to R.
reniformis
• Used a pedigree breeding strategy
– selected for day neutrality in F2 generation
– selected for resistance to R. reniformis in F3
and F4 generations

25. Resistance in F1 generation to Root-knot
and Reniform nematodes
100
M. incognita R. reniformis
4
80
3
60
2 40
20
1
0
0
Crosses made by E. Zhou

26. Development of resistance to reniform nematodes– means
of each F4:5 family not different from mean of Tx110
G. hirsutum M315
F4:5 families
G. barbadense Tx110
K. Ripple, MS Thesis 2003

27. Resistance to Reniform And Root-knot in F7 generation
100000
80000
R. reniformis/500 cm soil
3
60000
40000
20000
3.5
0
M315 RNR11 RNR10 RNR14 RNR1 RNR9 RNR13 RNR12 RNR2 3.0
F7 line
2.5
Gall index (0-5)
2.0
1.5
1.0
0.5
0.0
M315 F6 DP90

28. Effect of aldicarb treatments on populations of reniform
nematodes on resistant and susceptible cotton
genotypes
Reniform nematodes/100 cm3 soil

29. Effect of aldicarb on seed cotton yield of cotton genotypes
resistant and susceptible to the reniform nematode in a
nematode infested field
Seed cotton (g)/3 m row lenght

30. Conclusions
• Pedigree breeding program to introgress
resistance to Reniform nematode yields
moderate success
– Resulting germplasm has moderate
resistance and poor yield
– Likely to be difficult to use in a breeding
program
• Also trying a backcross breeding progam

31. Colleagues – Graduate Students -
C. E. Simpson Peanut - Cotton -
T. A. Lee, Jr. T. Wheeler E. Zhou
A. Paterson S. Nelson K. Ripple
C, W. Smith S. Abdel-Molmen T. Faske
M.Y. Shim
Post-doctoral Scientists - K. Choi
M. Burow G. Church
I. Bendezue
E. Moresco
Support staff – Funding –
S. McBride Cotton Incorporated
E. Tomaszewski National Peanut Board
E. Morgan Texas Peanut Producers
L. Torrez USDA- NRI
A. Grim Texas Higher Education Coordinating Board