Genetic improvement of summer fresh market tomatoes
2003
REP.TM-1296
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Title
Genetic improvement of summer fresh market tomatoes
Publication Date
2003
Call Number
REP.TM-1296
Summary
Tomato occasionally incurs poor grown and fruit-set under hot-dry or hot-wet season in the tropics and sub-tropics. It is a major bottleneck impeding summer production, along with many tropical diseases, such as bacterial wilt, bacterial spot, fusarium wilt, root-knot nematode, and several viruses. In order to overcome these production problems as well as improve the quality of tomatoes for the tropics, a multidisciplinary team at the Asian Vegetable Research and Development Center (AVRDC) has worked on varietal improvement for heat tolerance and multiple diseases resistance in tomato, and over the past 30 years. One hundred nineteen AVRDC tomato varieties have been released, among them eight varieties which have been released in Taiwan. Five major strategies have been important in AVRDC tomato improvement: 1. Germplasm collection AVRDC holds 7225 Lycopersicon accessions, including 9 species which are utilized as breeding materials of disease resistance, heat tolerance and other major horticultural traits. 2. Understanding the genetic basis of heat tolerance - previous screenings for heat tolerance revealed only 41 tomato heat tolerant accessions out of thousands that were tested. The inheritance of heat tolerance is controlled by a few dominant genetic factors with major effects on the trait, and an undefined number of minor modifiers. 3. Identification of disease resistance sources and determination of the inheritance of disease resistance - three dominant genes control tomato mosaic virus, one gene Tm-2a gives a high level of resistance to the three most commonly occurring strains 0, 1, and 2. Ten stocks resistant to tomato leaf curl virus have been identified; and two dominant genes for resistance to tomato leaf curl virus (Ty-1 and Ty-2) have been introgressed from two wild species L. chilense and L. hirsuturn, respectively; One hundred forty one bacterial wilt resistant stocks have been identified, and resistance is polygenic and tends to show incomplete dominance; many fusafium wilt resistant stocks have been identified, and three dominant genes, I-1, I-2, and I-3, provide race-specific resistance, but the I-2 gene condition resistance to races 1 and 2; two late blight resistant accessions, L 3708 (L. pinpinellifolium) and LA 1033 (L. hirsutum) have been identified; one single dominant gene (Ph-3) originating from L 3708 provides race spcific resistance; black leaf mold resistance is controlled by two recessive genes; resistance to common rootknot nematode is controlled by a single dominant gene, Mi, which was derived from a wild species L. peruvianum, and is tightly linked to the gene Aps-1, an isozyme locus for acid phosphatase. 4. Breeding strategies to incorporate heat tolerance and multiple disease resistance - Two breeding methodologies, hybridization and backcrossing have utilized of AVRDC, along with two selection methods: single seed descent and pedigree. A stepwise improvement of tropical tomato has been pursued, particularly for high levels of heat tolerance and bacterial wilt resistance and other disease resistances in order to develop heat tolerant and multiple disease resistant inbred lines. 5. Development of commercial Fl hybrid varieties - To combine heat tolerant and multiple disease resistant inbred lines to develop the commercial Fl hybrid varieties.
Journal Citation
v.4(1):83-102, AGRICULTURAL ASSOCIATION OF CHINA, JOURNAL
Contact Information
harvest@worldveg.org
Record Appears in
Research > Staff Publications