CHARACTERIZATION OF THE GENETIC AND MOLECULAR BASIS OF DISEASE RESISTANCE IN SPINACH AND SCREENING FOR DISEASE RESISTANCE

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 0190750
• Project Start Date: Oct 1, 2007
• Project End Date: Sep 30, 2012
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIVERSITY OF ARKANSAS
(N/A)
FAYETTEVILLE,AR 72703

Performing Department
Plant Pathology

Non Technical Summary
Spinach is one of the fastest growing vegetables in terms of per capita comsumption in the U.S. As a result of increased consumption and production, disease pressure has increased. In particular, downy mildew disease remains as one of the most important diseases with 10 different races of the pathogen attacking different varieties. The overall goal is to develop a set of near isogenic spinach lines (NILs) that have individual downy mildew resistance loci isolated in a susceptible, and otherwise common, genetic background. Such a set of NILs would facilitate the identification of races of the downy mildew pathogen, provide means to better understand the genetics of resistance, and provide mapping populations that could be used to identify molecular markers linked to major genes for resistance. The purpose of the proposed work is to develop open pollinated near-isogenic spinach lines (NIL) that each have a single resistance locus isolated in an otherwise susceptible genetic background for use as differentials for race identification of the spinach downy mildew pathogen, as material to better elucidate the genetic basis of resistance, and for the development of molecular markers linked to disease resistance loci.

Animal Health Component

(N/A)

Research Effort Categories

Basic

(N/A)

Applied

(N/A)

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
212	1430	1040	10%
212	1430	1080	50%
212	1430	1160	40%

Knowledge Area
212 - Pathogens and Nematodes Affecting Plants;

Subject Of Investigation
1430 - Greens and leafy vegetables;

Field Of Science
1040 - Molecular biology; 1160 - Pathology; 1080 - Genetics;

Keywords

marker assisted selection, spinach genetics, genetics of disease

resistance

Goals / Objectives
1. Develop a set of near-isogenic lines (NILs) of spinach that have various resistance loci to the downy mildew pathogen isolated in an otherwise susceptible and common genetic background. Six hypothesized disease resistance loci (Pfs-1, Pfs-2, Pfs-3, Pfs-4, Pfs-5, Pfs-6) will each be introgressed into the susceptible parent Viroflay followed by selection for resistance to a particular race of the downy mildew pathogen for four generations. An NIL for each resistance locus will be developed as a homozygous open pollinated line. 2. Screen each generation of NILs to the known races of the downy mildew pathogen. There currently are 10 known races of the downy mildew pathogen (Peronospora farinose f. sp. spinaciae) and there is a need to develop a set of open pollinated NILs that can be used to characterize isolates of the downy mildew pathogen. 3. Develop molecular markers linked to major genes for resistance to the downy mildew pathogen. Using an AFLP/SCAR marker approach, the NILs being developed will be used to search for molecular markers that co-segregate with resistant progeny in crosses between the NILs and the susceptible Viroflay recurrent parent. 4. Develop a BAC library from one NIL (NIL-Pfs1) to aid in the identification of the resistance gene cluster hypothesized to be located at the Pfs-1 locus controlling resistance to the downy mildew pathogen. 5. Develop a mapping population to determine the genetic control and quantitative trait loci that govern resistance to white rust disease (Albugo occidentalis). Crosses will be performed between white rust resistant and white rust susceptible lines and progeny will be evaluated for disease reactions under field conditions in Uvalde, Texas and DNA will be isolated from individual plants for analysis of QTLs that control resistance. 6. Screen and select Arkansas breeding material from diseased field nurseries for disease resistance and desirable horticultural characteristics. This will be done in nurseries established at Kibler, Arkansas and Uvalde, Texas, as well as commercial spinach fields in Arkasnas, Oklahoma, Texas, and California. Breeding material with elevated resistance to white rust, Fusarium wilt, several foliar diseases (primarily anthracnose), and virus diseases (CMV, BWYV, and BCTV) will be selected from the various locations. Horticultural characteristics selected for include yield potential, upright growth habit, leaf shape, texture, color, and long standing (i.e. slowness to bolt or flower) and nutritional value. 7. Screen commercial and USDA core spinach germplasm to new races of the downy mildew pathogen and Verticillium wilt, a relative new disease with the potential to affect the spinach and spinach seed production

Project Methods
The objectives of this project are designed to develop commercial spinach cultivars with high levels of resistance to biotic and abiotic stresses and to combine these traits with desirable horticultural characteristics. These objectives will be addressed by developing a set of NILs that have individual downy mildew resistance loci isolated in an otherwise susceptible genetic background (Bentley, 2006; Irish 2004). Viroflay will be used as used as the recurrent backcrossing parent. The procedures for doing this have previously been outlined (Bentley, 2006; Irish2004). The NILs that are developed will be used to identify molecular markers that are linked to major downy mildew disease resistance loci using an AFLP/SCAR marker methodology (Irish, 2004). At least one BAC library will be constructed from genomic DNA recovered from a line that is known to be homozygous resistant at the Pfs-1 locus (Pfs-1Pfs-1) (Bentley, 2006; Irish, 2004). A disease screening protocol will be developed to screen USDA germplasm to Verticillium wilt following a procedure that has previously been used to screen for resistance to Fusarium wilt disease of spinach (Laguna, 2000; Fiely et al, 1995). Breeding for resistance to the various diseases will emphasize the phenotype breeding technique, but traditional methods will be utilized when appropriate. The main thrust will be to utilize breeding families and lines already developed because these contain high quality gene pools and multiple disease resistance. Horticultural characters will be selected in conjunction with disease screening. Major emphasis will be placed on long standing, i.e., slowness to flower, savoy, semi savoy, flat-leaf types, and nutritional value. Other horticultural factors such as plant color, leaf shape, leaf angle, length of the petiole and yield potential will be carefully considered during the selection process. Individual plants will be removed from the field and transported to isolation cages in the spinach greenhouse at the Experiment Station in Fayetteville. Seed will be produced for the next field selection cycle. Since spinach is a wind pollinated crop these isolation techniques limit the number of selections that can be handled.

Progress 10/01/07 to 09/30/12

Outputs
OUTPUTS: This project was designed to characterize the genetic and molecular basis of disease resistance in spinach as well as screening for disease resistance. The focus of the effort was on downy mildew, one of the most important spinach diseases anywhere spinach is grown. The overall objectives were to develop a set of near-isogenic lines (NILs) of spinach that have various resistance loci to the downy mildew pathogen isolated in an otherwise susceptible and common genetic background. Six hypothesized disease resistance loci (RPF1, RPF2, RPF3, RPF4, RPF5, and RPF6) have been successfully transferred into a Viroflay susceptible background and NIL lines have been developed by four backcrosses followed by 4 selfings of the particular lines. These lines are currently being used to identify molecular markers linked to these major genes for resistance. A total of 14 races of the downy mildew pathogen (Peronospora farinose f. sp. spinaciae) have been identified with race 14 being described in 2012. A number of novel deviating strains also have been identified in 2012. Currently a wide range of germplasm has been evaluated to all of the contemporary races of the downy mildew pathogen. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Six resistance loci were originally hypothesized in commercial germplasm to control downy mildew of spinach. This project subsequently has demonstrated that these loci are major genes and segregate as single dominant loci in the NILs that have been tested. In addition, molecular markers have been developed that are closely linked to at least two of the major resistance genes RPF1 and RPF2. In addition, a BAC library has been constructed of NIL1 and is being utilized to search for genes and sequences of interest.

Publications

• Villarroel-Zeballos, M. I., Feng, C., Iglesia, A., duToit, L. J., and Correll, J. C. 2012. Screening for resistance to Verticillium wilt in spinach and isolation of Verticillium dahliae from seed of spinach accessions. HortScience 47:1297. Correll, J. C., Feng, C., Kammeijer, K. E., and Koike, S. 2012. Downy mildew of spinach: An overview of resistance. Phytopathology 102. Feng, C., Correll, J. C., du Toit, L. J., and Bluhm, B. H. 2012. Development of a multiplex real-time PCR assay for multiple seedborne spinach pathogens. Phytopathology 102.

Progress 01/01/11 to 12/31/11

Outputs
OUTPUTS: Significant progress continues to be made in developing a better understanding of the genetic and molecular basis of resistance in spinach to the downy mildew pathogen. Near isogenic lines are being developed whereby individual resistance loci are being isolated in an otherwise susceptible genetic background. Two NILs have been developed and progress has been made with four addtional lines. The four additional liines should be completed by 2014. Surveys continue to examine the population structure of the downy mildew pathogen in the United States. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: TARGET AUDIENCES: The spinach research community and vegetable production stakeholders. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Work continues to elucidate the race diversity of the spinach downy mildew pathogen. Work conducted by teh laboratory established the presence of a new race, race 13 and several deviating strains. Efforts to phenotypically characterize the spinach downy mildew pathogen on a wide range of spinach germplasm continue.

Publications

• Feng, C., and Correll, J. C. 2011. Details on the spinach BAC library as a resource. International Spinach Conference, Amsterdam, Netherlands.
• Feng, C., Yang, W., Hirsch, R. L., Bluhm, B. H., and Correll, J. C. 2011. Approaches for fine mapping the RPF1 resistance locus to the downy mildew pathogen. International Spinach Conference, Amsterdam, Netherlands.
• Correll, J. C., and Feng, C. 2011. Downy mildew of spinach: are we making progress. International Spinach Conference, Amsterdam, Netherlands.
• du Toit, L. J., Derie, M. L., Holmes, B. J., and Correll, J. C. 2011. Effect of seed treatments and soil fumigation on seed transmission and soil infestation by Verticillium in a baby leaf spinach head lettuce rotation. International Spinach Conference, Amsterdam, Netherlands.
• Iglesias-Garcia, A., Feng, C., duToit, L. J., and Correll, J. C. 2011. Pathogenicity, virulence, and molecular characterization of Verticillium Species from spinach and other hosts. International Spinach Conference, Amsterdam, Netherlands.
• Correll, J. C., Bluhm, B. H., Feng, C., Lamour, K., duToit, L. J., and Koike, S.T. 2011. Spinach: Better Management of Downy Mildew and White Rust through Genomics. European Journal of Plant Pathology, Special Invited Issue 129:193.
• Feng, C., Correll, J.C., Kammeijer, K. E., and Koike, S. T. 2011. Characterization of new races (races 11 and 12) and several novel strains of spinach downy mildew pathogen Peronospora farinosa f. sp. spinaciae. Phytopathology 101: S52.
• Dijkstra, J., Correll, J. C., Smilde, D., and de Visser, J. 2011International Working Group on Peronospora farinosa International Spinach Conference, Amsterdam, Netherlands.

Progress 01/01/10 to 12/31/10

Outputs
OUTPUTS: Significant progress has been made in developing a better understanding of the genetic and molecular basis of resistance in spinach to the downy mildew pathogen. Near isogenic lines are being developed whereby individual resistance loci are being isolated in an otherwise susceptible genetic background. Surveys continue to examine the population structure of the downy mildew pathogen in the United States. A second NIL, NIL2 has been completed in 2010. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: TARGET AUDIENCES: The spinach research community and vegetable production stakeholders. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Several near isogenic lines where 6 different downy mildew resistance loci are being isolated in an otherwise susceptible genetic background of spinach are in various stages of completion. Two NILs, NIL1 and NIL2 have been completed and seed made available to the community. In addtion, a second candidate molecular marker, linked to the RPF2 locus, has been identified and is being evaluated.

Publications

• Feng, C., Correll, J. C., and Bluhm, B. H. 2010. A spinach BAC library for marker development, gene discovery, and functional genomics. Phytopathology 100:S35.
• Wang, W., Iglesia-Garcia, A., duToit, L., Bluhm, B. H., and Correll, J. C. 2010. Effect of limestone on development of Verticillium wilt of spinach. Phytopathology 100:S142.
• Iglesias-Garcia, A., Feng, C., du Toit, L., Subbarao, K., and Correll, J. C. 2010. Virulence and molecular characterization of Verticillium species from spinach. Phytopathology 100:S53.

Progress 01/01/09 to 12/31/09

Outputs
OUTPUTS: Efforts continue to develop a genetic and molecular understanding of resistance in spinach to the downy mildew pathogen. Near isogenic lines are being developed whereby individual resistance loci are being isolated in an otherwise susceptible genetic background. Surveys continue to examine the population structure of the downy mildew pathogen in the United States. PARTICIPANTS: Several near isogenic lines where 6 different downy mildew resistance loci are being isolated in an otherwise susceptible genetic background of spinahc. Two NILs are close to completion and the other four are in advanced stages. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Several near isogenic lines where 6 different downy mildew resistance loci are being isolated in an otherwise susceptible genetic background of spinahc. Two NILs are close to completion and the other four are in advanced stages.

Publications

• Correll, J. C., Feng, C. Kudrna, D. A., Ammiraju, J., Raju, Wing, R. A. 2009. Construction of a spinach (Spinacae oleracae) BAC library. Plant and Animal Genomes XVII. Pg 604.
• Correll, J. C., Koike, S. T., and Smilde, D. 2009. Naming of Spinach downy mildew races, a case study. Phytopathology 99:S156.
• Correll, J. C., Feng, C. and Koike, S. T. 2009. Downy mildew on spinach: the genetics and deployment of disease resistance. The T. E. Morelock International Spinach Conference. Pg 22.
• Iglesias, A., Correll, J. C., Feng, C., and du Toit, L. J. 2009. Molecular and virulence characterization of Verticillium species from spinach. The T. E. Morelock International Spinach Conference. Pg 25. Feng, C., Iglesias, A., Welch, K., Rafiei, F., Correll, J. C., and du Toit, L. J. 2009. Molecular seed assay for detection of multiple spinach pathogens. The T. E. Morelock International Spinach Conference. Pg 28.
• Feng, C., Iglesias, A., Welch, K., Rafiei, F., Correll, J. C., and du Toit, L. J. 2009. Molecular seed assay for detection of multiple spinach pathogens. The T. E. Morelock International Spinach Conference. Pg 28.

Progress 01/01/08 to 12/31/08

Outputs
OUTPUTS: The spinach breeding and pathology efforts continues to make good progress selecting for disease resistance to white rust disease and developing open pollinated lines as differentials for downy mildew race characterization. Spinach breeding nurseries were conducted in Arkansas and Texas and advanced lines for white rust have been selected. Seed of a downy mildew differential NIL1 was produced and distributed to various seed companies and organizations doing work on downy mildew. Screening of downy mildew isolates indicated that a novel strain, designated UA2708PL, was widespread and the strain have been nominated as race 11. Addtional molecular markers are being developed and evaluated for the potential to use these as markers linnked to major genes for resistance. PARTICIPANTS: A new race of the spinach downy mildew pathogen was characterized. TARGET AUDIENCES: Spinach research personnel, vegetable extension personnel, and spinach growers and processors. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Enough seed of the first downy mildew near isogenic line (NIL1) was produced for limited distribution and testing. A larger scale commercial seed increase will be done in 2009. A new race, race 11 has been characterized.

Publications

• Correll, J. C. Koike, S. Feng, C., and Morelock, T.E. 2008. Update on spinach downy mildew in Arkansas and California. International Spinach Meeting. San Antonio, TX. Dec 1.
• Irish, B. M., Correll, J. C., Feng, C., Bentley, T., and de los Reyes, B. G. 2008. Characterization of a resistance locus (Pfs-1) to the spinach downy mildew pathogen (Peronospora farinose f. sp. spinaciae) and the development of a molecular marker linked to Pfs-1. Phytopathology 98:98:894-900.
• Morelock, T. E., and Correll, J. C. 2008. Spinach Breeding. Pp. 183-212. In:J Prohens and F. Nuez (eds.), Vegetables I, Springer, New York.
• Villarroel-Zeballos, M. I., du Toit, L. J., and Correll, J. C. 2008. Screening for disease resistance to Verticillium dahliae in spinach. Phytopathology 98 :S163.
• Correll, J. C., du Toit, L. J., and Villarroel-Zeballos, M. 2008. Verticlillium wilt and seed transmission. International Spinach Conference. San Antonio, TX. Dec. 1.
• Correll, J.. C. and Koike, S. 2008. Update on a new strain of downy mildew in the United States. Monterey County, CA - Plant Disease Seminar. Nov. 11

Progress 01/01/07 to 12/31/07

Outputs
OUTPUTS: The spinach breeding and pathology efforts continues to make good progress selecting for disease resistance to white rust disease and developing open pollinated lines as differentials for downy mildew race characterization. Spinach breeding nurseries were grown at the University of Arkansas Vegetable Substation at Kibler, Arkansas and the Del Monte research farm at Crystal City, Texas. Approximately 250 breeding lines were grown at Kibler and 150 at Crystal City. Excellent white rust pressure was observed at Crystal City and several promising breeding lines were identified. Arkansas variety releases are being widely used in commercial hybrids that exhibit white rust resistance. The flat leaf breeding line 97-154 was released in 2007. In addition, novel isolates of the downy mildew pathogen from U.S. production areas continue to be evaluated for their race identity. Molecular markers were identified linked to race 6 resistance of the downy mildew pathogen and additional mapping populations are being developed to assist in the identification of molecular markers linked to other downy mildew resistance loci. PARTICIPANTS: James Correll, University of Arkansas, Fayetteville Teddy Morelock, University of Arkansas, Fayetteville

Impacts
Spinach germplasm that is resistant to white rust is being used commercially and as parents in otehr breeding programs

Publications

• Irish, B, Correll, J. C., Koike, S. T., Morelock, T. E. 2007. Identification and cultivar reactions to races 8, 9, and 10 of the spinach downy mildew pathogen (Peronospora farinosa. f. sp. spinaciae) in the United States and Europe. Plant Disease 91:1392-1396.
• Tomlinson, A. N., Correll, J. C., Koike, S. T., Kammeijer, K. 2007. First report of race 8 of downy mildew, caused by Peronospora farinosa f. sp. spinaciae, of spinach in the United States. Plant Disease 91:1205.
• Irish, B. M., Correll, J. C., Feng, C., Bentley, T., and de los Reyes, B. G. 2008. Characterization of a resistance locus (Pfs-1) to the spinach downy mildew pathogen (Peronospora farinose f. sp. spinaciae) and the development of a molecular marker linked to Pfs-1. Phytopathology 98: (in press).

Progress 01/01/06 to 12/31/06

Outputs
The spinach breeding program continues to make good progress selecting for disease resistance to white rust disease and developing open pollinated lines as differentials for downy mildew race characterization. Spinach breeding nurseries were grown at the University of Arkansas Vegetable Substation at Kibler, Arkansas and the Del Monte research farm at Crystal City, Texas. Approximately 250 breeding lines were grown at Kibler and 150 at Crystal City. Excellent white rust pressure was observed at Crystal City and several promising breeding lines were identified. Arkansas variety releases are being widely used in commercial hybrids that exhibit white rust resistance. The flat leaf breeding line 97 154 will be released in 2007. In addition, novel isolates of the downy mildew pathogen from U.S. production areas continue to be evaluated for their race identity. Molecular markers were identified linked to race 6 resistances of the downy mildew pathogen and additional mapping populations are being developed to assist in the identification of molecular markers linked to other downy mildew resistance loci.

Impacts
The development of spinach lines with improved levels of white rust resistance will be valuable for commercial production in areas where white rust disease is endemic. In addition, this germplasm can be use to introgress resistance into other commercial open pollinated and hybrid cultivars with valuable phenotypic traits. The development of a set of near-isogenic lines with different downy mildew resistance genes continues and should be useful to develop a better understanding of the genetics of resistance to this important disease as well as a basis for developing molecular markers linked to disease resistance.

Publications

• Irish, B. Correll, J. C., Koike, S. T., Morelock, T. E. 2007. Identification and cultivar reactions to races 8, 9, and 10 of the spinach downy mildew pathogen, Peronospora farinosa. f. sp. spinaciae in the United States and Europe. Plant Disease.
• Irish, B. M., Correll, J. C., Feng, C., Bentley, T., and de los Reyes, B. G. 2007. Characterization of a resistance locus, Pfs 1, to the spinach downy mildew pathogen Personospora farinose f. sp. spinaciae. Phytopathology.
• Villarroel, M. I., du Toit, L. J., and Correll, J. C. 2006. Genetic and molecular characterization of Verticillium dahliae. International Spinach Meeting. August. Mt. Vernon, WA.
• Correll, J. C., Feng, C. Bentley, T. C. Koike, S. T., Irish, B. M., and Morelock, T. E. 2006. Update on downy mildew of spinach in the U.S. and Europe. Overview of races of the downy mildew pathogen on spinach and efforts to develop molecular markers linked to disease resistance loci. International Spinach Meeting. August. Mt. Vernon, WA.
• Tomlinson, A.N., Correll, J. C. Feng, C., and Irish, B. M. 2006. Genetic mapping and identification of important traits in spinach using a genomic BAC library. International Spinach Meeting. August. Mt. Vernon, WA.
• Bentley, T. C., Irish, B. M., and Correll, J. C. 2006. Generation of an open pollinated near-isogenic spinach line with homozygous resistance to the downy mildew pathogen. Phytopathology 96: S13.
• Tomlinson, A. N. Correll, J. C. Feng, C., and Irish, B. M. 2006. Genetic mapping and identification of genes for important traits using a genomic library. Phytopathology 96: S115.
• Villarroel, M. I., du Toit, L. J., and Correll, J. C. 2006. Genetic and molecular characterization of Verticillium dahliae from spinach and screening for disease resistance. Phytopathology 96: S118.
• Morelock, T. E., and Correll, J. C. 2007. Spinach Breeding. Submitted Sept 2006.

Progress 01/01/05 to 12/31/05

Outputs
The spinach breeding program continues to make good progress selecting for disease ressitance to white rust disease and developing open pollinated lines as differentials for downy mildew race characterization. Breeding nurseries were grown at Kibler, Arkansas and Crystal City, Texas. Arkansas genetics continue to be the standard for white rust resistance and Arkansas material is the basis for the white rust resistance in seed company hybrids. Arkansas 88-212 a high quality semi-savoy with a high level of white rust resistance is also in the process of being released. The nutritional analysis of U of A spinach breeding lines is progressing well with Arkansas lines having many of the highest readings for lutein and beta carotene. Analysis of spinach lines for ORAC (oxygen radical absorptance capacity) total phenolics, cinnamic acids and flavonoids is very exciting since U of A material have the highest levels for all these traits. In addition, novel isolates of the downy mildew pathogen continue to be evaluated for their race identity. Molecular markers were identified linked to race 6 resistance of the downy mildew pathogen.

Impacts
The continued development of spinach lines with improved levels of white rust resistance will be valuable for commercial production in areas where white rust disease is endemic. In addition, this germplasm can be use to introgress resistance into other commercial open pollinated and hybrid cultivars with valuable phenotypic traits. The development of a set of near-isogenic lines with different downy mildew resistance genes is underway and could be used to develop a better understanding of the genetics of ressitance to this important disease as well as a basis for developing molecular markers linked to disease resistance.

Publications

• Bentley, T. C., Irish, B. M., Correll, J. C., and Morelock, T. E. 2005. The use of molecular markers for downy mildew resistance and the development of open pollinated spinach differentials for race characterization. National Spinach Conference. (November 16-17) Fayetteville, AR.
• Irish, B. M., Correll, J. C., Morelock, T. E., and de los Reyes, B. 2006. Molecular characterization of spinach germplasm using the AFLP technique. Theoretical and Applied Genetics: (submitted).
• Irish, B, Correll, J. C., Koike, S. T., Morelock, T. E. 2006. Identification and cultivar reactions to races 8, 9, and 10 of the spinach downy mildew pathogen (Peronospora farinosa. f. sp. spinaciae) in the United States and Europe. Plant Disease (submitted).
• Correll, J. C., Koike, S. T, Bentley, T. C., and Morelock, T. E. 2005. Update on downy mildew of spinach in the United States and Europe. National Spinach Conference. (November 16-17) Fayetteville, AR.
• Villarroel-Zeballos, M. I., Tomlinson, A. N., Correll, J. C., and du Toit, L. J. 2005. Genetic characterization of Verticillium from spinach. National Spinach Conference. (November 16-17) Fayetteville, AR.
• Tomlinson, A. N., Correll, J. C., Feng, C., and Morelock, T. E. 2005. Initiation of BAC library construction and genetic mapping of the spinach genome. National Spinach Conference. (November 16-17) Fayetteville, AR.

Progress 01/01/04 to 12/30/04

Outputs
The spinach breeding program made good progress during the past year. Breeding nurseries were grown at Kibler, Arkansas and Crystal City, Texas. Arkansas genetics continue to be the standard for white rust resistance and Arkansas material is the basis for the white rust resistance in seed company hybrids. Breeding line 91-415 is in the process of being released.. This breeding line should be replace F380. It has a more upright growth habit and better color than F380 with about the same level of white rust resistance. Arkansas 88-212 a high quality semi-savoy with a high level of white rust resistance is also in the process of being released. The nutritional analysis of U of A spinach breeding lines is progressing well with Arkansas lines having many of the highest readings for lutein and beta carotene. Analysis of spinach lines for ORAC (oxygen radical absorptance capacity) total phenolics, cinnamic acids and flavonoids is very exciting since U of A material have the highest levels for all these traits. In addition, novel isolates of the downy mildew pathogen continue to be evaluated for their race identity. Three new races of the downy mildew pathogen were described. Molecular markers were identified linked to race 6 resistance of the downy mildew pathogen.

Impacts
New races of the downy mildew pathogen are evaluated to facilitate breeding for disease resistance. Molecular markers were identified linked to race 6 resistance of the downy mildew pathogen.

Publications

• Irish, B.M., Correll, J. C., Reid, R. N., and Morelock, T. E. 2004. First report of Peronospora farinosa f. sp. spinaciae race 5 on spinach in Florida. Plant Disease 88:84.
• Irish, B. M., Correll, J. C. and Morelock, T. E. 2004. Molecular marker identification for downy mildew resistance in spinach. Texas A&M National Spinach Conference (December15-18). San Antonio, TX.
• Correll, J. C., Irish, B. M., Koike, S. T., Bentley, T. C., and Morelock, T. E. 2004. Update on downy mildew of spinach in the United States and Europe. Texas A&M National Spinach Conference (December15-18). San Antonio, TX .
• Tomlinson, A., Correll, J. C., and du Toit, L. J. 2004. Genetic and molecular characterization of Verticillium from spinach. Texas A&M National Spinach Conference (December15-18). San Antonio, TX.
• Irish, B. M., Correll, J. C., de los Reyes, B. and Feng, C 2004. Molecular of characterization of spinach germplasm and a marker linked to downy mildew resistance using AFLPs. Phytopathology 94: S44.

Progress 01/01/03 to 12/31/03

Outputs
Breeding and disease screening efforts continue with spinach being evaluated at nursuries at the vegetable substationc in Kibler, AR, the Del Monte Research farm in Crystal City, TX, and the Texas A&M Research and Extension Center at Uvalde, TX. Wintergreen spinach cultivar (88-310) was released in 2003. It is a high quality, slow growing, semi-savoy with a high level of white rust resistance that shows excellent potential for root-cut, whole leaf and baby leaf spinach in the Arkansas, Oklahoma, and Texas production area. It is currently being grown on a limited acreage in the Texas Winter Garden. Downy mildew disease screening continues with a wide range of germplasm. In addtion, novel isolates of the downy mildew pathogen continue to be evaluated for their race identity. Three new races of the downy mildew pathogen were described.

Impacts
New races of the downy mildew pathogen are evaluated to facilitate breeding for disease resistance.

Publications

• Irish, B, Correll, J. C., Koike, S. T., Morelock, T. E. 2003. Identification and cultivar reactions to three new races of the spinach downy mildew pathogen (Peronospora farinosa. f. sp. spinaciae) in the United States and Europe. Plant Disease 87: 567-572.
• Irish, B, Correll, J. C., Raid, R. N., and Morelock, T. E. 2004. First report of Peronospora farinosa f. sp. spinaciae race 5 on spinach in Florida. Plant Disease 88:84.
• Correll, J.C., Irish, B. M. and Morelock, T. E. 2003. Update on downy mildew and white rust in the United States. Eucarpia Leafy Vegetable Conference, Eucarpia: 49-53.

Progress 01/01/02 to 12/31/02

Outputs
Spinach and disease screening nurseries were grown at the Vegetable Substation at Kibler, AR, the Del Monte Research farm at Crystal City, TX, and at the Texas A&M Research and Extension Center at Uvalde, TX. Significant disease pressure from Albugo occidentalis (white rust), Colletotrichum dematium (anthracnose), Fusarium oxysporum f. sp. spinaciae (Fusarium wilt), and damping off pathogens such as Pythium sp. Rhizoctonia solani, and Phytophthora sp. were present at most of the locations. Genetic material from the Arkansas breeding program remains some of the most white rust resistant material in these screening nurseries. A large seed increase of the flat leaf breeding line 91-415 was made in Washington state and commercial trials have been planted in Arkansas, Texas, and Oklahoma. This breeding line should replace F380 and it will be released in 2003. Efforts also have continued on screening for disease resistance to race 6 of the downy mildew pathogen (Peronospora farinosa f. sp. spinaciae). Also, race identification of isolates collected from many spinach growing areas has been conducted and races 5 and 6 predominate in the areas sampled.

Impacts
The spinach breeding and disease control efforts have helped improve the production of commercial spinach cultivars used in fresh and processing markets.

Publications

• Irish, B. M., Correll, J. C., and Morelock, T. E. 2002.The effect of surfactants on white rust of spinach. Plant Disease 86: 791-796.
• Irish, B, Correll, J. C., Koike, S. T., Morelock, T. E. 2003. Identification and cultivar reactions of three new races of the spinach downy mildew pathogen (Peronospora farinosa. f. sp. spinaciae) in the United States and Europe. Plant Disease 87: (in press).