Progress 09/15/01 to 09/30/04
Outputs
L. hirsutum-derived early blight resistance, available in lines good horticultural type, provides useful levels of Early Blight control. Field tests were first performed using Alternaria tomatophila light strain, and repeated the following year using the more aggressive Alternaria tomatophila dark strain. The results are generally in agreement. Heterozygous hybrids are not sufficiently resistant under severe disease pressure. Disease levels in susceptible and heterozygous plants can be reduced by chemical control agents. However varieties incorporating this resistance should be homozygous, rather than heterozygous for optimal levels of resistance. One difference between the results of the two years was that under the more stressful conditions of the second year, and using the more aggressive strain of the pathogen, defoliation was not fully controlled by the homozygous resistance. Overall, the best control of defoliation due to early blight was obtained by the
combination of homozygous resistance and alternating sprays of Cabrio and the Serenade + Kocide 2000 mix. The treatment alternating Cabrio with the Serenade + Kocide 2000 mix also significantly reduced stem lesion scores compared to that of the water control for all genotypes. The response of the homozygous resistant parent always had the lowest stem lesion scores, and the heterozygous F1 hybrids had lesions scores intermediate to the susceptible and resistant parents. The best levels of stem lesion control are clearly obtained by the combination of the homozygous resistant genotype and the treatment alternating Cabrio with the Serenade + Kocide 2000 mix. The results of the Late Blight trials show that the L pimpinellifolium L3708-derived resistance, in the homozygous or heterozygous genotypes, performs very well against US-11 in field trials. This is promising, since US-11 is the major isolate in the west coast. However caution is strongly urged in using this resistance in the
heterozygous genotype, since the same assays with other isolates (such as US-7 and US-17) indicate that resistance to these isolated is only provided by the homozygous genotypes. There was no difference of resistance between early maturity CU LBR homozygote line and late maturity CU LBR homozygote line. Furthermore, crosses between early maturity CU LBR and late maturity CU LBR acted like a homozygote, so there is no effect of maturity on disease resistance. The results of these trials were immediately shared with seed companies developing resistant tomato varieties, with the strongest suggestion that new varieties in development should be homozygous for the early blight resistance, and homozygous for the full level of late blight resistance. This information was critical to the companies, since prior expectations had been that heterozygous resistance for early blight and monogenic (incomplete) late blight resistance would be sufficient for disease control. The information was also
presented at meetings of extension agents and university and USDA associated plant pathologists and plant breeders, to inform them of the use of the control agents in the presence and absence of early blight resistance.
Impacts
Late blight (caused by Phytophthora infestans) is a significant problem in tomato production. Use of resistant processing tomato lines could materially reduce use and reliance on chemical sprays for control of this disease. We released a series of tomato lines fixed for the resistance from L3708 in backgrounds approaching that of processing tomato hybrids. The first commercial processing tomato hybrids containing this resistance may be on the market for the 2006 season. Freshmarket breeding lines combining this resistance and early blight resistance were also released in 2004. The goal of this project was to use late blight resistant inbred lines, as well as available source of resistance to early blight, to develop a sustainable coordinated total disease control program using this new resistance and low risk alternatives to agrochemical to significantly reduce reliance on chemical control. The results of the test have indicated the need for homozygous resistance for
optimal control of early blight and of late blight, and the roles of protective compounds when resistant varieties are used. The recommendations have been presented at meetings, sent in reports to seed companies using the resistance, and published on a popular extension website dedicated to plant disease control. Publications will also be submitted in the near future.The combination of materials and information will permit creation and effective use of resistant varieties, for reduction of use of pesticides.
Publications
- Mutschler, M.A., Min-Jea Kim, T.A. Zitter. 2004. Deployment Considerations for Late Blight and Early Blight Resistances in Tomatoes http://vegetablemdonline.ppath.cornell.edu/NewsArticles/Tom_Deploy.ht m
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Progress 01/01/03 to 12/31/03
Outputs
The L. hirsutum-derived early blight resistance, now available in lines with horticultural type close to cultivated tomato, provides useful levels of Early Blight control. Varieties incorporating this resistance should be homozygous, rather than heterozygous for optimal levels of resistance. Heterozygous hybrids are not sufficiently resistant under severe disease pressure. Disease levels in susceptible and heterozygous plants are affected by additional factors, such as chemical control agents. Field tests should be repeated using Alternaria tomatophila light strain, which may show different response than the dark strain of this pathogen The results of the Late Blight trials show that the L3708-derived resistance, in the homozygous or heterozygous genotypes, performs very well against US-11 in field trials. This is promising, since US-11 is the major isolate in the west coast production areas. However caution is strongly urged in using this resistance in the
heterozygous genotype, since the same assays with other isolates (such as US-7 and US-17) indicate that resistance to these isolated is only provided by the homozygous genotypes. These results of these trials were immediately shared with seed companies developing resistant tomato varieties, with the strongest suggestion that new varieties in development should be homozygous for the early blight resistance, and homozygous for the full level of late blight resistance. This information was critical to the companies, since prior expectations had been that heterozygous resistance for early blight and monogenic (incomplete) late blight resistance would be sufficient for disease control. The information was also presented at meetings of extension agents and university and USDA associated plant pathologists and plant breeders, to inform them of the use of the control agents in the presence and absence of early blight resistance.
Impacts
New tomato varieties with resistance to late blight and/or early blight will be released, reducing risk of crop loss or damage, and reducing reliance on pesticides from control of this disease. Many seed companies have requested the Cornell lines incorporating this resistance. The information provided to the private breeders will allow them to more rapidly the resistance to their own lines and produce a commercial resistance. The first commercial processing tomato with late blight resistance should be on the market for the 2005 season.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
Late blight (caused by Phytophthora infestans) is an increasingly significant problem in processing tomato production. Transfer of resistance into processing tomato lines could materially reduce reliance on chemical sprays for control of this disease. High-quality processing tomato lines fixed for the late blight resistance from L. pimpinellifolium accession L3708 were produced. Resistance to late blight is also incorporated into other tomato lines. Current breeding efforts focus on pyramiding an additional late blight resistance in these lines, to further extend and strengthen the resistance, and to add early blight resistance to the lines. The goal of this project is to determine the best strategy to deploying the resistance to late and early blight and to determine the interaction of the best use of these resistances and other control mechanisms in a coordinated IPM based strategy for total disease control in tomato. The results of 2002 lab/field tests indicate
that the late blight resistance holds against some isolates of the pathogen, but not others, when in the heterozygous form in F1 hybrids. Therefore, for greatest control of the disease, varieties released using the resistance should be homozygous for the resistance trait. These results have been reported in the Dec 2002 tomato disease meeting in Sacramento CA, and will be supplied to all seed companies who have obtained the resistant lines. Results of the early blight test indicate that under conditions very conducive to early blight, the plants must be homozygous for the resistance to control the disease expression on the stems. Disease is not fully suppressed on leaves, so some additional control means is needed. Two publications will be submitted by Mar 2003.
Impacts
The control of late blight and of early blight in regions affected by either/both of these tomato diseases involves heavy use of fungicide, which is both costly and incomplete in efficacy. Despite heavy intervention, a major late blight outbreak resulted in loss of nearly 25 percent of the California processing tomato crop in 1998, and periodically causes similar losses in other production areas. Early blight is largely controlled by use of chemicals either on a fixed (weekly or alternate week) schedule, or as indicated by use of a weather based blight forecast method. Deployment of strong broadly effective late blight resistance and or early blight resistance would reduce production cost, reduce use of chemical, and reduce the likelihood of crop loss due to these diseases.
Publications
- No publications reported this period
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Progress 01/01/01 to 12/31/01
Outputs
This project only started fall of 2001. Seed lots needed for 2002 season trials were produced at Cornell and for the project as a gift of in kind service by Campbells'. The first late blight trial of test hybrids is currently growing in Sinaloa, Mexico. We expect that the disease will spread in susceptible check and spreader rows within February to March of 2002. Efforts to map the two genes postulated as controlling this resistance to late blight is progressing. A tentative location for the first gene has been identified.
Impacts
Major losses can occur in tomato crops due to Late BLight, despite heavy use of fungicide, which is both costly and incomplete in efficacy. A major late blight outbreak resulted in loss of nearly 25% of the California processing tomato crop in 1998, and periodically causes similar losses in other production areas. Deployment of strong broadly effective late blight resistance would reduce production cost, reduce use of chemical, and reduce the likelihood of crop loss due to this disease. This interregional program will not only determine the best means for deploying the resistance, but due to interregional cooperation, will distribute the information needed to tomato growers and processors in diverse regions across the US.
Publications
- No publications reported this period
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