Summary of Field Evaluations of Tomato Germplasm in Sanarate Guatemala, October 2004

Evaluation team:  Luis Mejía and Rudi Teni, Universidad de San Carlos, Luis Rodriguez, Gentropic Seed Co., Antigua, Guatemala, and Douglas Maxwell and Martha Maxwell, University of Wisconsin-Madison

Personnel visiting plots at Sanarate in October 04:

Deans from University of San Carlos, Guatemala and University of Wisconsin-Madison visit field plots.


Evaluation team

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 61 hybrids with resistance to begomoviruses produced by Gentropic Seed Co.

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 has an extremely high whitefly population year around and inoculum for the tomato begomoviruses is 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 previous field trials, the following points were established:

• The TY52 (Ty1 gene resistance) and line H24 (Ty2 gene) were susceptible with very high virus pressure.
• TY197 (peruvianum), TY198 (peruvianum), FAVI 9 (hirsutum), FAVI 12 (hirsutum) and lines from Scott (all chilense source of resistance, Gc9, Gc16, Gc172, Gc173) had high levels of begomovirus resistance and breeding lines were selected from these populations.
• The Pimpertylc J-13 population was moderately resistance and selections were from made from this population, eg, Gpim10.
• Combining different sources of resistance increased the level of resistance, eg, hybrid H5.
• At least seven begomoviruses are present at the field site.
• In the last couple years, a soil-borne pathogen identified by Jay Scott as Ralstonia solanacearum has caused consider losses in some of the breeding lines.  The FAVI 9, FAVI 12 and Scott lines have been most resistant to this problem.  Breeding lines from TY197 were very susceptible and those from TY198 were more resistant.
• F1 populations from crosses of lines with L. hirsutum-resistant (Vidavski and Czosnek hybrids as source of resistance) by susceptible lines are moderately resistant.
• F1 populations from crosses of lines with L. chilense-resistant (Scott lines as source of resistance) by susceptible lines are susceptible. Only in F2 populations are moderately resistant plants observed.  Excellent breeding lines with high resistance can be obtained by selecting resistant plants from each selfed generation.

Information about trial:

After last trail, which ended in April 04, the field was fallow until early July when a susceptible tomato hybrid was transplanted in various locations througt the field. Approximately two weeks later, the one month old seedlings, which were produced at Pilones de Antigua, were transplanted. No insecticides were used in the field plots. Commerical cultivars, Marina, Silverado, Don Raul, Tequelia, Charanda, and Sheriff, were planted throughout the plot area. In all cases these commerical hybrids had DSI of 4 at 85 days after transplanting and essential no yield.

This area of Guatemala is normally very dry and has a few rains during the rainy season (May to October), but this year there were heavy rains in late September and early October. As a result, leaf spots were a severe problem and some lines were killed. Dr. Caitilyn Allen, University of Wisconsin-Madison, thought the disease was Xanthomonas leaf spot.

Begomovirus infection in Guatemala for October 2004

    During this "wet season", serious begomovirus infections were reported in the Salama Valley and also in the area near the Ipala Volcano (south and east of Guatemala City). We visited the area near Aqua Blanca and most fields had >90% incidence for plants less than 30 days after transplanting.

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 "pim" for pimpinellifolium.  For example, Gh13 and Gc9 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 Gh24-1-1-1 (F5 seeds, collected from this plant).  

Scoring plants: (see Selection Criteria)

Plants were scored for DSI, stage, fruit shape, firmness, color of fruit, yield, vigor, and overall. Other characteristics considered were green shoulder, jointless, determinate (T=1), semi-determinate (T=8), indeterminate (T=3).

Conclusions from October 2004 field evaluation:

            221 populations (breeding lines, two blocks) and 61 XA hybrids (two blocks) were evaluated at about 85 days after transplanting.  All plants had mature fruit.  During the previous 10 days, many nights it had rained hard. What was thought to be bacterial spot moved through the plot very rapidly. The begomovirus pressure was very high as susceptible cultivars had been planted about 2 weeks before the test lines. DSI for commercial cultivar, Silverado, was 4 (scale: 0 no symptoms; 4 severe leaf symptoms and plants stunted). There were over 300 susceptible control plants and each plant had a DSI > 3.5.

              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. 

• Resistant hybrids:   61 hybrids were evaluate in two locations: no virus pressure and high virus pressure. These hybrids were made from F4 parents. In some their was considerable segregation and others were nearly uniform for plant type. From the 61 hybrids, about 10 were selected for making the crosses again using F6 parents. This will be evaluated in October 2005. Two of these XA hybrids looked very promising and might have immediate potential for the growers. One of these is a determinant, roma type, which is currently being evaluated in Agua Blanca in a field that has nearly 100% of the plants infected at 40 days after transplanting.

• Progress: 

               LINES: Selection continued on all lines from March 04. About 230 plants were selected and seeds saved from these plants. An idea of the range of lines with different characteristics can be obtained by reviewing the lines for March 04.

               Each year, there seems to be one line that seems to be better than the others. This year it is the progeny from Gc178-2-3 (parents, M82 and Gc9).          

15 November 2004

[Breeding tomatoes for resistance-GT project]  [Projects for Breeding Tomatoes for Begomovirus Resistance]