Summary of Field Evaluations of Tomato Germplasm in Sanarate Guatemala, September 2003

Luis Mejía, Universidad de San Carlos, and Douglas Maxwell, University of Wisconsin-Madison

Goals:  To evaluate the segregating (F1, F2, F3) populations from the diverse crosses of begomovirus-resistant lines by other germplasm with desirable characteristics of shape, size, firmness, disease resistance, etc.

                    Most resistant F1 population!!

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 to a particular begomovirus species.

   From the initial field trials, the following points were established:

• The TY52 (Ty1 gene resistance) and line H24 were susceptible.
• TY197, TY198, FAVI 9, FAVI 12 and lines from Scott 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, GP10.
• Combining different sources of resistance increased the level of resistance, eg, hybrid H5.
• At least six 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.  This time some of the areas of the field were "hot spots" and most if not all plants were killed by 90 days after transplanting.  Amilcar Sanchez at Universidad de San Carlos and Caitilyn Allen at the University of Wisconsin-Madison are involved in studies of the races associated with tomatoes.

Conclusions from September 2003 field evaluation:

            208 populations (7,600 plants) were evaluated at 90 days after transplanting by the research team, and all had mature fruit.  The field test was severe and the commercial cultivar, Marina, had a DSI of 3.  During the dry season, Marina has a DSI of 3.5 to 4.   A commercial planting of Marina, which was about 400 meters away from our field plot, was a total loss, and the grower did not harvest any fruit.

            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.

• Most resistant hybrid:   The F1 hybrid (175) from GS16 (L. chilense resistance) x GF13 (L. hirsutum resistance)   was the most resistant and DSI was 0.5  -- no symptoms were evident.  Fruit is round and medium firm at about 120 g.

• Progress: 

            Large round (>150 g):  Number of plants selected for F2, F3, F4, and F6 populations were 6, 3, 5, and 1, respectively.

            Medium round (ca. 120 g): Number of plants selected for F2, F3, and F4 populations were 16, 11, and 3.

            Blocky types ( ca. 80-120 g): Number of plants selected for F2, F3, and F4 populations were 6, 4, and 11.

            Saladette types (120 g):  Number of plants selected for F2, F3, F4, F5, and F6 populations were 2, 6, 6, 1, and 2.

            "Cucumber" shape (ie, long and slender): Three F3 plants were selected.

            Cherry type:  Number plants selected for F2 and F3 populations were 1 and 1.

            Mandarina cross:  Three F1 plants were selected.  Mandarina is local "land race" type OP from Guatemala.  There was a slight indication that these crosses might have some resistance to BW.

            (For more information on these selections, please contact Dr. Luis Mejia at Universidad de San Carlos -- because of spam mail first contact, Douglas Maxwell, dum@plantpath.wisc.edu, and he will send you Dr. Mejia's email address.)

• Selection for parental lines for hybrid production:  F4, F5, and F6 plants will be used in crosses to create hybrids of potential interest.  These hybrids will include the saladette types, the Sheriff-types, and the large round types.  Currently, the plan is to have the crosses made at Pilones de Antigua and this company will give the seed to our program, plus assisted in the field evaluation of these crosses.

• Problems with Gray Leaf Spot: 

The populations with TY197 or TY198 in their background had indeterminate growth and relative low yields and showed susceptibility to gray leaf spot.  The parental plants (F2) were selected because of there vigor and this was during the dry season.  Also, some of these parental lines (F2) had excellent flavor. Selections of resistant and susceptible plants for gray leaf spot were made to use in our marker assisted selection studies.

• Problem with bacterial wilt in the plot:  Over the past three growing seasons, several plants had shown severe wilting and had died.  This time it was the most serious and about 10% of the plants were lost.  Jay Scott identified the problem as bacterial wilt.  The next planting will be in a different field, which does not have a history of this bacterial wilt problem.

• Problems with disorders on the fruit:  Jay Scott pointed out several disorders on the fruit.

• Crosses of Scott’s lines (L. chilense) with susceptible lines: 

A new line called, GS173-1, has the saladette shape and excellent resistance.  It will be used in crosses with lines with L. hirsutum resistance to create several hybrids.

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).  AgroVida (a Bayer Co. and GTZ sponsored IPM program in Salama Valley) included Llanero 7 (a GF line x susceptible line) in their field evaluation.  It was highly resistance to the begomoviruses and the chocolate spot.  Currently, 100 g of this hybrid were produced in Israel and ready for testing in grower’s fields.

           Follow up from March 2003, a large field (2.8 ha) with 35-day-old transplants of Silverado, which had 100% incidence of begomoviruses, was observed in March.  The yield from this field was 100 boxes of 50 lb of tomatoes.  The break even point would have been 2,800 boxes and the expected yield was 8,000 boxes.  Price of tomatoes varies, but about $10/box could be used. Thus, there was a $28,000 investment and a return of $1,000.  Expected return was $80,000.  Again this September 2003, the  tomato fields in this area had a high incidence of geminivirus infection.

        AgroVida, Salama, Guatemala will be collecting data for development of an economic threshold for percentage of plants infected with geminiviruses and predicted yield.

Seedling production and hybrid seed production:

            100 g of Llanero 7 (GF1 x commercial breeding line) was produced by a commercial company in Israel at 1.5 cents/seed and is being sent to Guatemala for field testing.  In March2003, two of the three large tomato seedling producing companies, Pilones de Antigua and Agropecuana Popoyan, in Guatemala were contacted and managers of both companies indicated that they are interested in producing the seedlings and helping us locate growers for field testing.

            Also, very initial discussions were made with Pilones de Antigua about producing hybrid seed.  The general manager, Richard Rotter, was the general manager for Asgrow Seed Co. in Salama and has considerable experience in hybrid tomato seed production.  This discussion with R. Rotter continued and he has agreed to participate in the production of seedlings and hybrid seed.  The intellectual property issues were discussed with the Dean of the Faculty of Agronomy, Universidad de San Carlos and with representative of AGROCYT.  Bacterial wilt was detected on the tomato lines in the greenhouse at Universidad de San Carlos, thus it is extremely helpful to have Pilones de Antigua willing to make hybrids for the program. 

5 October 2003

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