Summary of Field Evaluations of Tomato Germplasm in Sanarate Guatemala, March 2004
Evaluation team: Luis Mejía and Rudi Teni, Universidad de San Carlos, Favi Vidavski, The Hebrew University of Jerusalem, and Douglas Maxwell and Mike Havey, University of Wisconsin-Madison
Goals: To
evaluate the segregating populations from the diverse crosses of
begomovirus-resistant lines by other germplasm with desirable characteristics of
shape, size, firmness, disease resistance, etc.
To evaluate four hybrids with resistance to begomoviruses.
To select plants for a genetic analysis associated with tagging the resistance genes.
Past History: Dr. Luis Mejia started a breeding program in 1998 for resistance to begomoviruses at a site in Eastern Guatemala near Sanarate. This site was selected, as it had an extremely high whitefly population year around and inoculum for the tomato begomoviruses was always present. Germplasm was collected from various breeding programs, which were focused on resistance to Tomato yellow leaf curl virus (TYLCV) in the Mediterranean region or Tomato leaf curl virus in Asia or on resistance to Tomato mottle virus and TYLCV in Florida. In all cases, begomovirus resistance had been introgressed from wild tomato species. From H. Laterrot, INRA, in France, three populations were obtained, and at least one of these populations had been field tested in Jordan. The population with introgressions from L. pimpinellifolium and L. peruvianum (designed Pimpertylc J-13) was the most useful of these. Other sources were i) hybrids (FAVI 9, FAVI 12, FAVI 13) with introgressions from L. hirsutum (Phytopathology 88:910-914) and line TY52 homozygous for the Ty1 gene from L. chilense (Theor. Appl. Genet. 88:141-146) from H. Czosnek and F. Vidavski, the Hebrew University of Jerusalem, ii) two lines, TY198 and TY197, with introgressions from L. peruvianum from Moshe Lapidot and colleagues, Volcani Center (Plant Dis. 81:1425-1428; J. Amer. Soc. Hort. Sci. 123:1004-1006), iii) line H24 from P. Hanson, AVRDC, with introgressions from L. hirsutum (J. Amer. Soc. Hort. Sci. 125:15-20), and iv) several lines from J. Scott, University of Florida, with introgressions from L. chilense (J. Amer. Soc. Hort. Sci. 126:462-467). In all cases, these lines or hybrids had moderate to high levels of viral resistance begomoviruses. Dr. Mark Nakhla, University of Wisconsin-Madison, has characterized six begomoviruses present on tomatoes from this site.
From the initial field trials, the following points were established:
Historical perspective of the begomovirus infection in Guatemala
See two images from the valley near Sanarate: one in 1994 and the other in 2004.
Personnel visiting plots at Sanarate in March:
Team - San Carlos, University of Wisconsin, Hebrew University, AVRDC (Matt Metz, USAID, not show as he took the picture.)
Conclusions from March 2004 field evaluation:
100 populations (ca. 6,000 plants) were evaluated at 85 days after transplanting by Vidavski, Mejia and Maxwell. Almost all had plants had mature fruit. The field test was severe and the commercial cultivar, Marina, Elios, Sheriff and Silverado had DSIs of 3 - 3.5 (scale: 0 no symptoms; 4 severe leaf symptoms and plants stunted).
Shape, size, and firmness were major criteria for selection of the plants for future testing. A firm fruit with a saladette shape (roma shape) of about 120 g is the most desirable fruit type for Guatemala. Silverado, Marina, Toro, and Elios are popular tomato cultivars for the major markets in Guatemala. Round tomatoes are available in the up scale grocery stores and the Sheriff-type is sold to San Salvador.
Naming lines: Breeding lines will start with letter "G" for Guatemala followed by a number (number for F1) and lower case letter indicating source of resistance, such as "h" for hirsutum, "c" for chilense, "per" for peruvianum, and "p" for pimpinellifolium. For example, G13h and G9c are two breeding lines. Other selections will have a number followed by the lower case letter and then a series of numbers indicating the generation, such as 24h-1-1-1 (F5 seeds, collected from this plant).
Example of F1 (XA-S2) from two elite parents: Approach was to create an F1 with high resistance by crossing elite breeding lines, one (G13h) with L. hirsutum resistance and the other (G171c) with L. chilense resistance. This cross was made to test the original observations that the F1 from a cross of two breeding lines, each with a different source of begomovirus resistance, would give a highly resistant F1 population. It did!!!!
Background on FAVI # Hybrids: The FAVI
hybrids result form crosses of the resistant line 902 (Phytopathology
88:910-914) with resistance genes from
L. hirsutum with susceptible breeding
lines. Line 902 was evaluated against the severe strain of
TYLCV at Hebrew University of Jerusalem. FAVI 9 was the first hybrid
tested in Guatemala, and as reported before, FAVI 9 segregated for resistance in
Guatemala. This trial had the line 902 planted for the first time
and it segregated for green shoulder and resistance.
Diversity of germplasm: View of the diversity of germplasm, showing two wild species, and a variety of fruit shapes.
Saladette types -- Elite Core Breeding lines:
Saladettes (Roma type) (L. hirsutum resistance):
Saladettes (Roma type) (L. chilense resistance):
Saladettes (Roma type) (resistance from more than one wild species):
Cucumber shape
Round shape (> 110 g fruit wt)
Gh13-m (fruit, 110 g)
117h-1-a (fruit, 150 g)
21h-3-2-1 (fruit, 160 g)
Gc9
Mandarina cross: Three F1 plants were selected. Mandarina is local open-pollinated "land race" from Guatemala.
Observations from the Salama Valley:
The Salama Valley is about 4 hours by car from Guatemala City (NE of the City) and it is a major tomato growing area. They have had serious problems with begomoviruses and more recently with a problem called chocolate spot (unknown causal agent), which is more common in the rainy season. This March, begomovirus incidence was 100% in some fields.
20 March 2004
[Breeding tomatoes for resistance-GT project] [Projects for Breeding Tomatoes for Begomovirus Resistance]