Late Blight-resistant Tomato Varieties Evaluation

Monica Ozores-Hampton and Pamela Roberts

Late Blight (Phytophthora infestans)• Responsible for entire crop losses in the Solanaceae family

such as tomato, potato, and eggplant in less than 5 days

• Yield losses caused by Late Blight worldwide exceed 6.7 billion dollars

• Considered to be a major threat to food security worldwide

• Damages primarily to Florida’s winter production

– Low temperatures (below 54°F)

– High relative humidity (91 to 100%)

– Foggy and rainy conditions plus wind

• Leaves present lesions with

growth and spores of the

pathogen

• Extensive defoliation and

reduced photosynthetic leaf area

• Stems lesions with sporulation

of the pathogen

• Developing fruit wilts and rots

• Final secondary inoculum and

death of the plant

http://www.longislandhort.cornell.edu/vegpath/photos/lateblight_tomato.htm

Late Blight Symptoms

Late Blight Control– Commercially available pesticides and biological controls have

proven effectiveness in delaying the onset of the diseases

– However, the rapid spread of the pathogen (oomycete) and the inability to apply a curative agent prior to total economic loss can be difficult

– Biological control - bacterial antagonists are the most successful in the control of P. infestans

– Recommendations: Integrated pest management (IPM) with pesticides, cultural controls, and Late Blight (LB) forecasting

Disease-resistant Tomato Varieties – Development of disease-resistant tomato varieties offers the most

effective solution and we have some available in the market

– Researchers have identified three specific genes lending to resistance against the pathogen:

• (1951) Ph-1 gene offers complete specific resistant to P. infestans Race 0

• Ph-2 gene shows partial resistance (environmental conditions may have effects on the expression of the resistant phenotype)

• Ph-3 gene is originally from tomato’s wild relative S. pimpinellifolium L.

The coupling of Ph-2 and Ph-3 resistant genes in commercial cultivars will increase the long-term resistance to P. infestans because of the multiple pathways of resistance required to overcome for the pathogen. Continued identification of new resistant genes will be needed to maintain resistance in commercial varieties

Variety Tomato type Growth habit Seed company

Mountain Magic Campari I Bejo Seeds

Fantasio Campari I Suttons Seeds

JTO-545 Roma - Experimental

Plum Regal Roma I Johnny Seeds

Juliet Roma I Johnny Seeds

Defiant Round D Johnny Seeds

Iron Lady Round D High Mowing Seeds

Old Brooks Round I Totally Tomato

Legend OP Round D Territorial Seed

Mountain Merit Round D Bejo Seeds

Ferline Small Round I Thompson & Morgan Seeds

New Yorker Round D Seed Library

Brandywine Round I Johnny Seeds

Mountain Fresh Round D Johnny Seeds

Golden Sweet Grape D Johnny Seeds

Lizzano Cherry Semi-D Park Seed

Matt’s Wild Cherry Cherry I Johnny Seeds

Jasper Cherry I Johnny Seeds

Objective

The objective of this study was to evaluate P. infestans resistant tomato varieties on

disease resistance, yield, and fruit quality in southwest Florida

Materials and Methods

Variety Resistance Company Growth habit

Round

Defiant PhR Heterozygous; Ph2 and Ph3 Johnny’s Selected Seeds Determinate

Mountain Merit Heterozygous; Ph2 and Ph3 Bejo Seeds Determinate

Iron Lady Homozygous; Ph2 and Ph3 High Mowing Organic Seeds Determinate

FL 47 Susceptible Seminis Determinate

Roma

Plum Regal Homozygous; Ph3 Bejo Seeds Determinate

Mini-Roma

Juliet Susceptible Johnny’s Selected Seeds Indeterminate

Campary

Mountain Magic Heterozygous; Ph2 and Ph3 Bejo Seeds Indeterminate

Cherry

Jasper Undetermined resistance; likely

Ph2 and/or Ph3

Johnny’s Selected Seeds Indeterminate

5.8 g22.7 g61.1-31.1 g

Experimental Design

• Study conducted in UF/SWFREC Immokalee, FL

• Complete randomized block design with 4 replications

• Spring: 3 Jan. 2014

• Plot size: 24 ft (16 plants)

• Harvest unit: 10 plants (round, roma-type, and campari) and 6 plants (mini-

roma and cherry)

• Plant spacing: 6 ft center - 18 inches

• Plant population: 4,840 plants/acre

Data Collection• Symptoms of Late blight were first identified on plants in the field on 18 Feb.

2014 by natural infestation (46 days after planting).– Disease severity as a percentage (0-100%) of foliage exhibiting symptoms

and taken at four-day intervals until disease severity was higher than 80% on susceptible plants

• Tomato fruit were manually harvested at maturity stages 2 to 6 (breaker to red)and count and weighed – Round tomatoes: graded into marketable yield size categories for extra-large

(5x6), large (6x6), medium (6x7), and small fruit (7x7) (USDA, 1997)– Roma-type tomatoes: graded into extra-large, large, medium, and small fruit

(USDA, 1997)– Campari tomatoes: graded into large, medium, and small size categories– Chery and mini-roma tomatoes: graded into marketable and unmarketable– Unmarketable tomatoes

• Off-shape, scratch• Blossom end scar

Harvest Dates (weekly)

25 Mar. 2 Apr. 10 Apr. 16 Apr. 24 Apr. 30 Apr. 8 May

Jasper Jasper Jasper Jasper Jasper Jasper Jasper

Juliet Defiant PhR Juliet Juliet Juliet Juliet

Iron Lady Defiant PhR Defiant PhR Defiant PhR Iron Lady

Mountain Merit

Iron Lady Iron Lady Iron Lady Mountain

Merit

Mountain Magic

Mountain

Merit

Mountain

Merit

Mountain

Merit

Plum Regal

Plum Regal Plum Regal Plum Regal Mountain

Magic

Mountain

Magic

Mountain

Magic

Mountain

Magic

Postharvest Analysis

TSS (⁰Brix ) pH (0 to 14) Skin color (Rating 1-6)

Statistical Analysis

• Analysis of Variance (ANOVA)

• Mean separation

– Duncan’s multiple range test

– 95% confidence level (P-value)

Results

Disease Severity of Late blight Tomato Variety Evaluation

TreatmentDisease Severity (%)

Feb-27-2014 Mar-3-2014 Mar-7-2014 Mar-11-2014

Defiant PhR 0.0c 0.0d 1.3e 1.4eIron Lady 0.0c 0.0d 0.3e 0.5eMountain Merit 0.5c 0.3d 2.5e 4.5dePlum Regal (Ph3) 7.1c 10.3c 21.3c 13.1cMountain Magic 0.0c 0.0d 1.5e 2.4eJasper 0.5c 2.3d 12.3d 7.9dJuliet 36.3b 76.3b 81.3b 86.9bFL 47 48.1a 82.5a 89.4a 95.0aLSD (P=.05) 11.57 3.63 7.14 5.22Standard Deviation 7.87 2.47 4.85 3.55P. Value 0.0001 0.0001 0.0001 0.0001

Apr. 30, 2014

VarietyX-large Large Medium Small Unmarketable Total

marketable

Round (25 lb-box/acre)

Defiant PhR 145by 155b 240b 563a 370a 1,102a

Iron Lady 168b 280a 381a 541a 484a 1,369a

Mountain Merit 491a 361a 253b 198b 485a 1,303a

FL 47 0b 0c 0c 0c 0b 0b

P-value 0.001 0.0001 0.0001 0.0001 0.002 0.0001

Significance *** *** *** *** ** ***

Roma (25 lb-box/acre)

Plum Regal 259 605 313 315 209 1,492

Round and Roma-type Tomato Total Harvest

Cherry and Mini-roma Tomato Total Harvest

Variety Marketable Unmarketable Fruit Size

Yield (tons/acre) (g)

Jasper 134.4 2.9 5.8

Juliet 2.7 1.1 22.7

Variety

Yield (tons/acre) Fruit size (g)

Large Medium Small Unmarketable Total

marketable

Large Medium Small

Mountain

Magic

0.7 6.8 5.2 0.5 12.7 61.1 45.5 31.1

Campary Tomato Total Harvest

Postharvest Evaluation

VarietyTSS

(⁰Brix )

pH

(0-14)

Color

(Rating 1-6)

Round

Defiant PhR 4.10a 4.65a 5.63a

Iron Lady 3.13b 4.36b 5.13b

Mountain Merit 4.23a 4.79a 5.48ab

P-value 0.0001 0.001 0.01

Significance *** *** **

Roma

Plum Regal 3.25 4.74 5.69

Mini-roma

Juliet 6.18 4.68 5.88

Campary

Mountain Magic 6.23 4.76 5.81

Cherry

Jasper 7.28 4.45 5.81

Late Blight Field Day at UF/SWFREC on April 30

Conclusions

• Tomato varieties containing both Ph2 and Ph3 had less than 10% Late Blight symptomatic foliage and produced higher marketable yields than susceptible varieties.

• Several of these varieties might be suitable for homeowner and potentially organic growers to avoid losses due to Late Blight in Florida.

• Further studies will be performed to repeat these results.

Acknowledgements

• Specialty Crop Block Grant Program

• Redi-Plants, Corp.

• Jessy, Joel and Gilma from Pathology and

vegetable program