INVESTIGATORS:
*Dr. H. Czosnek, and F. Vidavski, Department of Field Crops, Vegetable Crops, and Genetics, Faculty of Agriculture, The Hebrew University of Jerusalem
Dr. L. Mejia, Professor, Faculty of Agronomy, San Carlos University, Guatemala City
Dr. M. Lapidot, Agricultural Research Organization, The Volcani Center
Dr. Douglas P. Maxwell, Dept. of Plant Pathology, Univ. of Wisconsin, Madison
Dr. Michael J. Havey, USDA-ARS, Dept. of Horticulture, University of Wisconsin-Madison,
* Lead Investigator
Overall aim:
Introduce molecular marker-assisted breeding technology into Guatemala using the development of locally adapted tomato cultivars resistant to whitefly-transmitted geminiviruses and other economically important pathogens as a model system.
Specific research objectives:
1. Introduce the principles of molecular marker-assisted breeding technology into a research program and into the M. Sc. Degree Program at Universidad de San Carlos, Guatemala City.
2. 2. Determine whether the markers used to map genes for resistance to TYLCV and ToLCV (Eastern Hemisphere geminiviruses) identify identical loci in the tomato breeding lines selected for resistance to the Guatemalan geminiviruses.
3. 3. Identify molecular markers linked to genes for resistance to whitefly-transmitted geminiviruses from Guatemala that are different than those in objective 2.
4. 4. Determine if the field-selected resistant tomato germplasm is resistant to all three tomato-infecting whitefly-transmitted geminiviruses in Guatemala.
5. 5. Combine the independent sources of resistance to whitefly-transmitted geminiviruses and evaluate this material in the field in Guatemala and Israel.
6. 6. Use molecular markers to combine genes for resistance to whitefly-transmitted geminiviruses and other pathogens into improved resistant genotypes of tomatoes suited for the Guatemalan market.
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Brief summary of major achievements:
1. Introduction of molecular marker-assisted breeding technology into research program and the M. Sc. Degree program
One M.Sc. student at San Carlos University did her degree on the application of the REX marker for the root knot nematode resistant gene, Mi-1, and this has resulted in a major research project as the current markers for the Mi-1 gene give false positives with the main source of geminivirus virus resistance being used in Guatemala and the MERC Tomato Project, ie, the line Ih902 from Hebrew University of Jerusalem. This project will be continued by a Ph. D. student from Morocco on the the MERC Tomato Project.
Two workshops were held on Marker-Assisted Breeding: January 2003 and March 2004. These were well attended by students, some growers for special sessions, and industry representatives.
For training, 2-4 four scientists come to UW-Madison each summer for three summers for 6 weeks to work on marker-assisted breeding. One of these scientists will start a M.Sc. program in plant pathology on bacterial wilt, and another has been offered a Research Assistantship for a Ph. D. program starting in January 2005. The two individuals are currently faculty members at San Carlos University.
A PCR-based method was used to determine, if the introgressions from L. hirsutum in line Ih902 are in either the location of chromosome 6 for the Ty-1 gene or chromosome 11 for the Ty-2 gene. RFLP probes were sequenced and these sequences used to search data bases for matches with genomic DNA of Arabidopsis and then PCR primers designed from exons, which would amplify introns. This approach worked very well and the introgression for Ty-2 gene was verified with the primers from TG105 for chromosome 11. There was a large indel associated with the L. hirsutum for the Ty-2 gene in the breeding line H24 from Peter Hanson at AVRDC. No introgression was associated with this region for Ty-2 gene in the lines derived from 902. Also, no introgression was consistently associated with the Ty-1 gene region in chromosome 6 for the lines derived from 902; but a useful marker was developed for the Ty-1 introgression TG436), which is from L. chilense. In all, over 10 RFLP probes were converted to PCR primers and sequences determined for each of these regions for about 10 lines.
3. Identify markers that are linked to resistance genes derived from line Ih902
An RFLP approach was also used to “scan” all 12 chromosomes for polymorphism in Gh1 line (derived from line 902) and no polymorphisms were detected with over 120 combinations of restriction enzymes and probes. In the current grant, it is proposed that this effort continue with an AFLP approach.
4. Evaluate germplasm for resistance to begomoviruses in Guatemala
At least 7 different begomoviruses have now been identified in the area, Sanarate, were the field trials are conducted (M. K. Nakhla, UW-Madison). After 6 years of selection from hybrids obtained from Hebrew University of Jerusalem, over 30 breeding lines (L. hirsutum-derived resistance) with excellent resistance and various fruit characteristics are now available. Also, at least 10 lines selected from lines (L. chilense-derived resistance) provided by Jay Scott, University of Florida, are now available. Both round fruit and saladette lines have been selected. Also, one line with L. peruvianum-derived resistance was selected.
SEE: www.plantpath.wisc.edu/GeminivirusResistantTomatoes/CDR/GT.htm
5. Combine different genes for resistance and evaluate hybrids in Guatemala and Israel
Hybrids created from crosses of lines with hirsutum resistance (Gh13) and chilense resistance (Gc19) have been highly resistant in Guatemala and now are being tested in Mali as part of the IPM CRSP. The parent lines with hirsutum resistance have been tested in Israel and found to be highly resistant to TYLCV (Volcani). Also, hybrids from crosses of two parental lines with hirsutum resistance are highly resistant, and this F1 was sent to Egypt for use in their Tomato-TYLCV MERC project. Last year 4 hybrids were tested in grower’s fields and two selected. One grower has requested plants from one hybrid to start a new business of fresh-packaged tomatoes. This year over 60 hybrids (XA) will be evaluated in October. Yields of hybrids from this program were generally 2-3 times the production from current commercial hybrids. Major horticultural trait for firmness and shape are now being addressed in a recurrent selection program.
6. Develop hybrids for the Guatemala market
Because of the success of this breeding program, San Carlos University has licensed the breeding lines to a new locally owned company, Gentropic Seeds, which was started in 2004, specifically to introduce geminivirus-resistant hybrids into the market for Guatemala and Central America.
References:
Mejia, L., F. Vidavski, H. Czosnek, M. Lapidot, M. Friedmann, M. Pilowsky, and D. P. Maxwell. 2001. Evaluation of tomato germplasm for resistance to geminiviruses in Guatemala. Caribbean Division of the APS, Cuba, June 2001.
Luis Mejía, Facultad de Agronomía, Universidad de San Carlos, Guatemala; Hanokh Czosnek and Favi Vidavski, The Hebrew University of Jerusalem, Israel; Moshe Lapidot, Michael Friedmann and Meir Pilowsky, The Volcani Center, Israel; Douglas Maxwell, University of Wisconsin, Madison. 2002. Evaluation of tomato germplasm resistant to TYLCV for resistance to bipartite whitefly transmitted geminiviruses in Guatemala. Amer. Phytopathology Meeting, Milwaukee, WI, July 2002.
Mejía, L., R. E. Teni, and A. Sánchez, Universidad de San Carlos, Guatemala; A. Pallides, F. Vidavski and H. Czosnek, the Hebrew University of Jerusalem, Rehovot, Israel; M. Lapidot, Volcani Center, Bet Dagan, Israel; J. Scott, University of Florida-Bradenton; M. J. Havey, USDA and University of Wisconsin-Madison, and M. K. Nakhla and D. P. Maxwell, University of Wisconsin-Madison. 2004. EVALUATION OF TOMATO GERMPLASM AND SELECTION OF BREEDING LINES FOR RESISTANCE TO BEGOMOVIRUSES IN GUATEMALA. First International Tomato Disease Symposium, June Orlando, FL. Presented by L. Mejía. A similar talk was presented by H. Czosnek at the 4th International Symposium on Geminiviruses in South Africa in Feburary 2004. A manuscript is being prepared as a conference proceedings.
Nakhla, M.K. and A. Sorenson, University of Wisconsin-Madison; L. Mejía, Universidad de San Carlos, Guatemala; P. Ramírez, and J.P. Karkashian, Universidad de Costa Rica, San Jose; and D.P. Maxwell, University of Wisconsin-Madison. 2004. Molecular Characterization of Tomato-Infecting Begomoviruses in Central America and Development of DNA-Based Detection Methods. First International Tomato Disease Symposium, June Orlando, FL.
Zea, C., A. Sánchez, and L. Mejía, Universidad de San Carlos, Guatemala; M. A. Arévalo, Diagnóstico y Asesoria en Protección Vegetal, Guatemala; F. Vidavski, the Hebrew University of Jerusalem, Rehovot, Israel; M. Salus, C. Martin, and D. P. Maxwell, University of Wisconsin-Madison. 2004. PROBLEMS ASSOCIATED WITH THE USE OF MOLECULAR MARKERS FOR TAGGING THE Mi GENE IN TOMATO BREEDING LINES. First International Tomato Disease Symposium, June Orlando, FL.