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Discovery of the I-3 Gene Conferring
Resistance to Fusarium Wilt Race 3
• Over 900 accessions screened for resistance
• Saved seed from 5 plants/accession when>50%
healthy plants
• Inoculated over 1500 progeny lines for resistance
• Because of “tolerant” lines did field inoculations
for several seasons
• Finally settled on resistance from S. pennellii
accession LA716
Discovery of the I-3 Gene Conferring
Resistance to Fusarium Wilt Race 3
• Originally LA716 had 17 resistant and 3 susceptible plants
• Developed 3 families, only 1 of 3 had data that fit a single dominant gene model
• Ph.D. student discovered I-3 on chromosome 7 linked to isozyme marker got-2
• Fla. 7307 hybrid could have been released in 1990-5 years of breeding
• Fla. 7547 breeding line released in 1995
• Numerous commercial hybrids available today
Solanum pennellii natural habitatLA0716 Atico Arequipa-Peru
A Heterotic S. lycopersicum X S. pennellii F1 hybrid
FUSARIUM WILT RACE 3 RESISTANCE “LINKAGE”
Open, less vigorous vines, dark green foliage
Blossom-end rot susceptibility
Higher soluble solids??
Another one I’m forgetting;
it’s not easy to get old!
Single Dominant Genes In Multiple Disease
Resistant Tomato Varieties: FUNGAL
Disease Genes Organism
Soil-borne
Fusarium Wilt I, I-2, I-3 Fusarium oxysporum f.sp. lycopersici
Verticillium Wilt Ve Verticillium albo-atrum or V.dalihae
Alternaria Stem Canker Asc Alternaria alternata f.sp. lycopersici
Fusarium Crown Rot Frl F. oxysporum f.sp. radicus-lycopersici
Foliar
Gray Leaf Spot Sm Stemphyllium solani
Cladosporium Leaf Mold Cf-2,Cf-
5
Cladosporium fulvum
Late Blight Ph,Ph-2
Ph-3
Phytophthora infestans
Single Dominant Genes In Multiple Disease
Resistant Tomato Varieties: VIRAL
Disease Genes
Tomato Mosaic Virus (Tm-1) Tm-2, Tm-22
Tomato Spotted Wilt
Virus
(Sw-1, Sw-2, Sw-3, Sw-4) Sw-5
Tomato Yellow Leaf
Curl Virus
Ty-1, Ty-2
Single Dominant Genes In Multiple Disease Resistant
Tomato Varieties: BACTERIAL
Disease Genes Organism
Bacterial
Bacterial Speck Pto Pseudomonas tomato
Root-knot Nematodes Mi Meloidygyne spp.
Worms
Repulsion Linkage Problems
TYLCV (Ty-1/3 gene) and Nematode (Mi
gene)
Bacterial wilt and Nematode (Mi )
TYLCV (Ty-2 gene) and Fusarium wilt race 2
(I-2 gene)
Disease Resistances
Bacterial SpeckPseudomonas syringae pv. tomato
Cultigen Species Gene Reference
Ontario 7710 L. esculentum Pto Pitblado & Kerr (1980)
PI 125430 L. pimpinellifollum Pto-2 Pilowasky & Zutra (1986)
PI 112215 L. pimpinellifollum Pto Lawson & Summers (1984)
PI 129157 L. hirsutum
f. glabratum
Pto Lawson & Summers (1983)
PI 134418 L. hirsutum
f. glabratum
? Pitblado & MacNeill (1983)
Tanksley et al. (1996)
PI 251305 L. hirsutum
f. glabratum
? Pitblado & MacNeill (1983)
Tanksley et al. (1996)
PI 370093 L. pimpinellifollum ? Pitblado & MacNeill (1983)
Tanksley et al. (1996)
PI 126928 L. pimpinellifollum ? Fallik et al. (1983)
Rehovot 13 L. esculentum ? Fallik et al. (1983)
PI 134417 L. hirsutum
f. glabratum
Pto-3 Stockinger & Walling (1994)
PI 134417 L. hirsutum
f. glabratum
Pto-4 Stockinger & Walling (1994)
Sources of resistance to the bacterial speck pathogen P. syringae pv. tomato.
Bacterial CankerClavibacter michiganensis subsp. michiganensis
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Report of theTomato Genetics Cooperative
Volume 60 December 2010
Tomato Breeding for
Bacterial Wilt Resistance - Issues
Ubiquitous Pathogen – many races, strains etc
Profound Environmental Effects – temperature,
moisture, soil types, interactions
No Reliable, Repeatable Seedling Test
Limited Genetic Information
Association of Resistance With Small Fruit
Flavor??
Entry
Locationz
MeanJPN AVR TSS PLP NEP IND AUS MAR REU GDL FLA BRA
H7996 100 85 100 97 100 87 100 96 100 97 100 100 97
BF-Okitsu 100 68 100 100 97 100 100 54 100 97 100 97 93
H7997S 64 80 100 93 98 100 90 86 100 94 100 100 93
TML46 80 83 100 90 100 90 95 88 93 84 96 100 92
H7998S 32 63 100 97 100 100 95 100 100 95 100 100 92
TML114 35 77 100 100 100 98 100 88 100 95 83 100 91
R3034 90 72 97 87 95 94 80 77 100 99 100 100 91
Neptune 0 0 44 60 67 3 50 2 32 42 96 73 43
L390(Susc.) 0 0 0 7 0 0 0 2 6 37 56 23 13
Mean 34 40 87 81 87 73 73 52 83 68 84 77 71
WD LSD 23 19 15 26 20 20 26 33 56 26 27 23 12
Percent survival for entries in International Set of
Resistant Sources to Bacterial Wilt in Tomato evaluated in
12 field trials in 1995
zJPN – Japan, AVR – Taiwan (AVRDC), TSS – Taiwan, PLP – Philippines, NEP – Nepal, IND – India, AUS – Australia,
MAR – Mauritius, REU – Reunion, GDL – Guadeloupe, FLA – Florida, USA, BRA – Brazil
Strains = race 1, biovar 3 except FLA & BRA = race 1, biovar 1 and GDL = race 1 & both biovars
Effect of fruit size on bacterial wilt resistance
From the 1995 World Testing of 35
Bacterial Wilt Bred Genotypes
Genotype Number Survival (%)
Large Fruited 12 59.3
Small Fruited 23 79.9*
*significant at p<0.0001
QTL’s Associated With Bacterial Wilt Resistance
Hawaii 7996(Thoquet et al., 1996. Mol. Pl.-Mic. Int. 9:826-836, 837-842.)
Chromosome 3
Chromosome 4 – two locations
Chromosome 6 – two locations (30 cM apart)
Chromosome 8
Chromosome 10 – (weak)
Chromosome 11 – (?)
Chromosome 12- confirmed along with a chromosome 6 locus
by Mejia et al., 2009
L 285(Danesh et al., 1994. Mol. Pl.-Mic. Int 7:464-471.)
Chromosome 6 – possibly same as above
Chromosome 10 – different region than above
Chromosome 7 – (shoot inoc. only)
Background of Large-Fruited, Bacterial Wilt Resistance Project
8626, 8599, 8493C, etc.
20 recurrent parents
8109F6
7834
F5
I
Hawaii 7997
7236
Neptune
F2 F3 F4 F5 F7(R2=0.67*)
Recurrent Parent Summer 2003 Spring 2004 Spring 2006z Fall 2006 Fall 2007 Spring 2008
7771 15 cdy 79 a 89 ab 86 a 41 cd 71 b
8059 15 cd 71 a 100 a 93 a 75 a-c 91 ab
7776 35 a-d 71 a 90 ab 93 a 64 a-d 93 ab
8111 (8626) 45 a-c Nix 80 b 93 a 86 a 92 ab
8027 (8599) 35 a-d 79 a 100 a 100 a 81 ab 90 ab
7777 40 a-c 71 a 100 a 71 a 75 a-c 76 ab
8110 20 b-d 100 a 100 a 79 a 55 b-d 85 ab
7987 65 a 93 a 100 a 71 a 36 d 78 ab
Controls
Neptune 20 b-d 100 a 100 a 90 a 45 cd 96 ab
Fla. 8109 55 ab 100 a 100 a 97 a -- 100 a
Hawaii 7997 70 a 90 a 100 a 100 a 95 a 100 a
Fla. MH-1 0 d 40 b 63 c 10 b 0 e 31 c
z Artificial inoculation failed but there was a natural infestation of bacterial wilt in the fieldY Mean separation in columns by Duncan’s Multiple Range Test at P≤ 0.05.
Percentage of healthy plants after bacterial wilt inoculation for controls and after crossing with Fla. 8109.
Neptune Fla.8626F6
Inbred Disease
severity
Comment
7777 F3 6.0 az Susceptible
8436 B 5.2 ab T3
7907 B12 F3 5.2 ab
8401 5.0 ab
8594 4.8 ab
8495 B 4.3 a-c
8610 4.0 bc
8494 H 3.8 bc
8561 B 3.8 bc T3
8608 3.7 bc
8599 3.5 bc Bacterial wilt resistant
8611 3.0 c
z Horsfall-Barratt, Mean separation by DMRT, P ≤ 0.05.
Bacterial spot race T4 disease severity, Fletcher, NC 2007.
Spring 2010 Fall 2010
Genotype (Healthy %) (Healthy %)
H7997 90 55.0 az
Fla. 8109 90 45.0 ab
157-II4 (8599 x 8059) F5 92 43.0 a-c
174-2 (8208 x 8626) F5 65 29.0 b-d
157-II1 (8599 x 8059) F5 92 28.5 b-d
211-6 (8599 x 8626) F4 67 28.5 b-d
186-II1 [7776 x 8493C] F4 83 28.5 b-d
211-II3 (8599 x 8626) F4 67 21.5 c-e
186-II3 [7776 x 8493C] F4 83 21.5 c-e
157-3 (8599 x 8059) F5 92 21.5 c-e
186-II4 [7776 x 8493C] F4 83 21.5 c-e
162-II2 (7781 x 8626) F5 58 21.5 c-e
168-II5 (7997 x 8626) F5 67 14.5 de
157 3 selections + 3 others 14.0 de
12 selections 7.0 de
MH-1 + Neptune + 31 selections Nep +75, MH-1=0 0.0 e
z Mean separation in columns by Duncan’s Multiple Range Test at P ≤ 0.05.
Fall 2010 Bacterial wilt disease incidence.
Fla. 8109
• Hypothesis: Fla. 8109 has a crossover
uncoupling the linkage of a resistance
gene from a gene causing small fruit.
• However, Fla. 8109 is not quite as
resistant as Hawaii7997
• Recovery of the resistance of Fla. 8109 is
not frequent indicating the involvement of
several genes
Future Researh
• Test Fla. 8109 around world to discern if
resistance is broad-based like Hawaiian lines
• Genetic marker study with Fla. 8109, Neptune,
Hawaii 7997, Fla. 8626, and susceptible lines to
locate all genes and find the putative crossover
• With markers find the genes that confer the
bacterial spot tolerance from the bacterial wilt
resistant lines
• Explore nature of huge fruit size derived from
Fla. 8109 crosses
Bacterial Spot
• Causal agent:
– Xanthomonas euvesicatoria (Race T1)
– Xanthomonas vesicatoria (Race T2)
– Xanthomonas perforans (Races T3, T4, T5)
T4 Partial Resistance
PI 126932
(S. pimpinellifolium)
(Low R)
PI 128216
(S. pimpinellifolium)
(Mod R)
PI 114490
(S. lycopersicum)
(Good R)
Fla 8326
(Mod R)
Fla 8233
(Mod-Good R)
Fla 8517
(Mod-Good R)
Fla 7776 moderately susceptible
Fla 7946 highly susceptible
H7998 H7998H7998
T3 HR+ T3 HR+ T3 HR+
Molecular Markers
• Resistant breeding lines screened with polymorphic markers to identify regions of possible introgression
• Selective Genotyping:
– R and S selections made from the F2 generation of each:
• 8326 x 7946
• 8233 x 7776
• 8517 x 7776
– Within each family:
• Each polymorphic marker analyzed for Transmission Disequillibrium(George, et al., 1999; Zhu and Elston, 2001)
Chr 12
Chr 2 Chr 3 Chr 4 Chr 5 Chr 6
Chr 7 Chr 9Chr 8 Chr 10
Chr 1
Chr 11
8326 n.s.
8326
8326
8233 n.s.
8233 n.s.8517
8517
8517
82338517
8233 n.s.
Marker Summary
• Partial resistance in Florida breeding lines 8233, 8326, 8517
• 4 significant loci:
– chr 3* PI 114490
– chr 9* PI 128216
– chr 11* H7998 / PI 128216
– chr 12* non-OH9242
• 3 plausible QTL:
– chr 1 PI 126932
– chr 5 PI 128216
– chr 10 PI 128216
Hutton, et al. 2010. Identification of QTL associated with resistance
to bacterial spot race T4 in tomato. Theor. Appl. Genet. 121 (7):1275-1287.
Follow-up(Fall ‘08, Fall ’09)
• Fall 2008 F2 populations (~270 plants ea.):
– 8233 x 8111
– 8517 x 7946
– 8326 x 7946
• Fall 2009 F2 populations (~320 plants ea.):
– 8233 x 7946
– 8517 x 7946
• Each plant genotyped and phenotyped
• Stepwise ANOVA
T4 QTL vs. (Rx-4) T3 HRChr 11
C2 10050
SL 10737i
C2 30825
LEOH 57
C2 54470
SL 20181
cLEC-24-c3
ANOVA
T4 Resistance T3 HR
Marker F Value P F Value P
C2_At4g10050 95.43 <.0001 44.81 <.0001
LEOH 57 86.68 <.0001 49.48 <.0001
SL 10737i 88.45 <.0001 52.56 <.0001
C2_At1g30825 40.37 <.0001 157.41 <.0001
C2_At3g54470 23.35 <.0001 143.18 <.0001
cLEC-24-C3 29.83 <.0001 409.76 <.0001
Fall 2008
+ ++/ //- - -
Fall 2009
+ ++/ //- - - + / - + / -
Bacterial Spot Susceptibility and I-3
• Two approaches to the problem:
– Overcome by incorporating resistance loci
– Separate I-3 from susceptibility
Lim, et al. 2008. High resolution genetic and physical mapping of the I-3 region of tomato chromosome 7 reveals almost
continuous microsynteny with grape chromosome 12 but interspersed microsynteny with duplications on Aribidopsis
chromosomes 1, 2 and 3. Theor Appl Genet 118:57-75.
Fla. 7946
Fla. 8517
0629 06300631
I-3- I-3-I-3+
7946 x 8517 selections:
0630 Severity Rating = 2.5
0629 06300631
I-3- I-3-I-3+
Chr 3: - + +
Chr 11: + + -?
Chr 12: - + +
Fla. 8208 x Fla. 8626
Fla. 8208 x Fla. 8626 Brand X
Bacterial Spot Disease of Tomato
PNAS November 23, 1999 vol. 96: 14153–14158
• Transformed VF36 tomato variety with 35S:Bs2
• Bacterial growth curves on T2 plants show growth suppression with
BS2
• Field test in 2000 of one BS2 line shows resistance to Xcv infection
and greater fruit yield compared to untransformed VF36.
• 2B undertook additional field testing for resistance and yield
determinations between 2006 – 2009. Six tests, 2 locations, 2
seasons. 2Blades
1990 Nature 346: 385-6
2Blades
• AvrBs2 widely distributed
• Function conserved
Bs2 pipelineEnhancing durability
Bacterial spot specific resistance: Xv4
Xanthomonas race structure in tomato:
Avr occurrence in tomato strains
2Blades
AvrRxv AvrXv3 AvrXv4 AvrBs2 Comments
T1 + - - +Initially the most prevalent strain. Now it is less common.
T2 - - - +Common in Ohio and mid-west. It has probably been introduced to FL many times but prefers a cooler climate. Not found in the Carribbean, but is found in South America and southeast Asia. No resistance genes yet characterized, but there is a good QTL for recessive resistance. Mostly copper resistant.
T3 - + + +Until recently the most widespread. Came in from Thailand. Produces a toxin that inhibits growth of T1. All have picked up resistance to copper. Normally don’t go to pepper.
T4 - - + +Has become the most widespread strain in past 5 years. This race is a mutation of T3, with an insertion in avrXv3. Found in an area of low T3 incidence. Jay found in NC.
T5 - - - +Don’t know what resistance gene in pepper detects race 5 to prevent growth
VF36
2008 Field Trial, Balm, FL
VF36-Bs2
2Blades
Jay Scott, Jeff Jones,
Bob Stall, UF IFAS
Genotype Marketable
Yield
(kg/plant)
Total Yield
(kg/plant)
Fruit Weight
(g)
Disease
Severity2
VF36 0.25 b1 0.80 b 133 c 7.4 a
VF36 Bs2
homozygous
0.96 a 1.78 a 132 c 3.0 d
VF36 Bs2
hemizygous
1.01 a 1.97 a 138 c 3.0 d
FL 47 1.19 a 1.94 a 176 a 5.6 c
FL 91 1.26 a 1.71 a 180 a 5.6 c
Sebring 1.18 a 1.67 a 170 ab 6.1 b
1 Means in column width the same letter are not significantly different, P ≤ 0.05,
Duncans multiple range test.2 Disease severity based on the Horsfall-Baratt scale.
SEASON 1 and 2 - Fall 2007 and Spring 2008 Balm, Florida
Next Generation BS2 Tomato
Commercial GermplasmGoal: Deliver resistance in commercially relevant germplasm
• Evaluate public germplasm sources (NC and FL) for applicability to FL market
• Select FL8000 based upon in-vitro (UCD) and field performance (UF)
Jay Scott breeding program data Balm, FL, Spring 2008
Marketable yield Fruit size Culls
Hybrid1 (25 lb. box/A) (oz) (% by wt.)
Fla. 8314 (BST)2 2039 a 6.0 bc 23 b-d
Fla. 8612 (TSWV) 1632 ab 7.2 ab 38 a-c
Florida 47 1203 b-d 7.0 a-c 41 ab
Crista (TSWV) 784 cd 7.7 a 46 a
Sebring (FCR, F3) 656 d 6.7 a-c 43 ab
1 Resistance: BST = bacterial spot; TSWV = tomato spotted wilt; FCR&F3 = Fusarium; crown rot & wilt race 32 Parents of this cross are FL8000 and FL8111bData from Jay Scott, UF IFAS 2Blades
Hybrid Total x-large Fruit wt. (oz) Marketable
(%)
Fla.8314 1729 a2 1072 ab 5.7 c-e 86.4 ab
Phoenix 1528 ab 1201a 6.6 a 87.6 ab
Solar Fire 1492 a-c 828 a-e 5.5 c-g 83.9 a-c
Quincy 1398 a-d 1142 a 6.7 a 88.9
Talladega 1380 a-e 937 a-c 5.9 b-d 84.7 a-c
Florida 91 1224 a-f 924 a-d 6.1 bc 86.6 ab
Sebring 1130 b-f 695 b-g 5.7 c-e 88.8 a
Florida 47 1103 b-f 566 c-h 5.9 b-d 82.3 a-c
Fla.8153 967 c-f 392 f-h 5.0 f-h 80.5 a-c
Fla.7964 962 c-f 548 c-h 5.4 d-g 76.7 bc
Crista 830 ef 524 d-h 5.9 b-d 81.0 a-c
Amelia 777 f 591 c-g 5.9 b-d 73.7 c
Tomato Yield Trial at Quincy, Florida- Fall 2005Marketable yield (25 lb. box/A)
Marketable yield Fruit size Culls
Hybrid (25 lb box/A) (g) (% by wt.)
Fla. 8314 1806 az 144 e 29 d
Fla. 8455 1538 ab 183 ab 32 cd
Tasti-Lee 1529 ab 154 de 33 b-d
Sanibel 1478 ab 175 bc 43 ab
Fla. 8787 1301 ab 187 ab 41 a-c
Florida 47 1267 ab 195 a 41 a-c
Tribeca 1242 b 162 cd 48 a
z Mean separation in columns by DMRT at P ≤ 0.05.
Marketable yield, fruit size, and culls for tomato hybrids grown at
Pine Island Farms, Dade County, Florida. Winter 2010.
Data from Breeding program of Jay Scott, UF IFAS
Next Generation BS2 TomatoMinimum regulatory and consumer issues
Goal: All plant (tomato) DNA vector
Two Blades Vector Ver 3.0
RB Tomato Promoter 3’ UTR termBS2 Tom DNALB
• Find and test public domain promoters with optimal expression, only pepper
and tomato DNA
• UCB – build and test candidates in transient assay
• UCD - test candidate promoter constructs in MicroTom
J. W. ScottUniv. Florida - Gulf Coast REC
14625 CR 672
Wimauma, Florida 33598
USA
BACTERIAL DISEASES;
OPPORTUNITIES FOR THE TOMATO
BREEDER
Reaction to:**
Line Bred from Breeder Pseudomonas Fusarium 2 Coryne-bacterium
Carette CRA 66 (=OTB 2?) Kaan (Guadeloupe, France) R RRR RR
53.RC CRA 66 (=OTB 2?) Kaan (Guadeloupe, France) RR RRR RR
Venus L. esculentum var. cerasiforme
Henderson (North Carolina, USA) R RR R
Saturn (PI 129.080, Columbia) and
Henderson (North Carolina, USA) R RR R
72 TR 4.4. L. Esculentum var. pyriforme
Henderson (North Carolina, USA) RR RRR RR
74 TR 10 (Beltsville 3814, Puerto Rico)
Henderson (North Carolina, USA) R RR R
I.R.A.T. L3 Complex hybrid including L. pimpinellifolium
Daly (I.R.A.T., Martinque, France) RR RRR RRR
Farako-Ba (University of Puerto Rico)
D’Arondel des Hayes (Upper Volta) RR RR R
Kewalo* L. pimpinellifoliumPI 127805A (Peru)
Gilbert (Hawaii, USA) R R S
Hawaii* 7996 ? Gilbert (Hawaii, USA) RRR RR RR
MR 4 Same as 72 TR 4.4. Forster, Echandi (North Carolina, USA)
RR RRR RR
Plovdiv 8/12 L. pimpinellifolium Elenkov (Maritaz Institute, Bulgaria) S S RR
Monalbo susceptible check Laterott (I.N.R.A., Avignon, France) S S S
* sp. lines; ** RRR = outstanding resistance; RR = good resistance; R = fair resistance, S = susceptibility
Lines OriginSource of resistance to
P. solanacearum
Reaction to pathotype 2
Verticillium BrasilianV3-190 strain
IRAT-L3 Martinique 199 UPR 39-15 r
CRA 66 Guadeloupe NC. 1953-64-Nor West Indies ecotype
S
CARAIBO Guadeloupe CRA 66 S
FARAKO-BA Burkina-Faso UPR 199 39-15 r
H7997 Hawaii PI 127805 A S
H7998 Hawaii PI 127805 A S
RODADE South Africa North Carolina BW2 S
SCORPIO Australia UPCA 1169 S
UPCA 1169 Philippines “Complexe” S
72.T.R.4.4 North Carolina PI 129080 and Beltsville 3814 S
r = high level of resistanceS = susceptibility
BACTERIAL SPOT RESISTANCE IS NOT ASSOCIATED WITH BACTERIAL WILT RESISTANCE IN TOMATO
J.W. Scott, G.C. Somodi, and J.B. JonesUniv. of Florida/IFAS, Gulf Coast Research & Education Center
Proc. Fla. State Hort. Soc. 101:390-392. 1988.
Table 3. Segregation of F2 Plants derived from Hawaii 7998 x ‘Walter’ for bacterial spot and bacterial wilt resistance for two field experiments.
BACTERIAL SPOT RESISTANCE IS NOT ASSOCIATED WITH BACTERIAL WILT RESISTANCE IN TOMATO
J.W. Scott, G.C. Somodi, and J.B. JonesUniv. of Florida/IFAS, Gulf Coast Research & Education Center
Proc. Fla. State Hort. Soc. 101:390-392. 1988.
Experiment Correlation coefficient Probability
Summer-Fall 1986 0.03 0.65
Fall 1987 – Spring 1998 -0.03 0.81
Table 4. Correlation coefficients between bacterial spot and bacterial wilt infection for F2 plants derived from ‘Walter’ x Hawaii 7998 in two experiments.
Combining bacterial spot resistance from
races T1 and T3 provides T2 resistance
zAll data from Wooster, Ohio in cooperation with Sally Miller and David Francis.
Scott, J.W. et al. 2005. Acta Hort 695:161-172.
GenotypeRace T2 Disease Severity
z
Resistance
(Race)1995 1996 1999 2000
Fla. 7600 - 5.3 a - - T1
PI126932 5.3 a - - - T3
Solar Set 6.0 a 5.8 a 5.5 a 5.3 a (susc.)
PI114490 2.0 b 2.0 b 2.0 c 2.0 c T2
Fla. 7835 - - 3.3 b 3.3 b T1, T3
Disease severity of marker classes
Race PI 114490 FL 7600z Ohio 9242 P LSD0.05 Effect
T1 4.63 4.20 5.34 <0.0001 0.17 PI = FL > OH
T2 4.50 4.86 6.18 <0.0001 0.94 PI = FL > OH
T3 5.18 4.81 6.66 <0.0001 0.59 PI = FL > OH
T4 6.14 5.93 7.20 <0.0001 0.49 PI = FL > OH
Z Resistance from Hawaii 7998
Chromosome 11 marker TOM144 associates with resistance to tomato bacterial spot races T1 through T4.
Summary of the impediments to varietal development
Incomplete resistances combined with variable pathogen strains and unreliable disease screens
Linkage drag and clustering of R genes in repulsion are also concerns
Loss of public tomato breeding positions and a lack of funding
Not enough coordination of the research efforts
Future Prospects
Improved molecular marker technology, if properly applied, will provide some hopeSynthesize lines with combinations of bacterial resistance genes and test for pathogens/races of interestTest disease resistant lines for “pleiotropic” resistance to other diseasesPrivate companies should work together by funding this research so we can all develop varieties to keep our farmers in business and our species well fed and healthy
