Location: Vegetable Research
Project Number: 6080-22000-025-09
Start Date: Sep 01, 2012
End Date: Jul 31, 2015
The University of Florida tomato breeding program has vast experience in developing improved germplasm with multiple disease resistance as well as other traits such as improved flavor and heat-tolerant fruit setting ability. Examples of resistance genes that were discovered in wild species, introgressed into tomato, genetically characterized, and incorporated into tomato varieties include the I-3 gene conferring resistance to fusarium wilt race 3 (Scott and Jones, 1995), and the Ty-3 and Ty-4 genes conferring resistance to tomato yellow leaf curl virus (TYLCV) and other begomoviruses. Recently they discovered the begomovirus resistance gene from ‘Tyking’ was recessive and located on chromosome 4. Other resistance genes not yet in varieties are the Sw-7 Tomato Spotted Wilt Virus (TSWV) resistance gene and numerous genes conferring resistance to various races of bacterial spot caused by Xanthomonas species. The linkage of high levels of bacterial wilt (Ralstonia solanacearum) with small fruit size was broken in developing the breeding line Fla. 8109. In addition, the Ty-3 and Ty-1 genes have been fine mapped and breeding lines without linkage drag have been developed that should dramatically improve future resistant varieties. Current research involves using SNP genotyping from SolCAP (http://solcap.msu.edu/) and other sources to identify genes of interest and conduct fine mapping. These projects include: fine mapping of TYLCV resistance genes Ty-2 and Ty-4 and locating genes for resistance to Bemisia tabaci, the sweet potato whitefly that vectors begomoviruses, and locating bacterial spot resistance genes from PI 114490 where we have just found six genes. Specifically in the current project, Dr. Scott will generate near isogenic lines (NILs) with resistance to TYLCV and TSWV. For TYLCV screening and phenotyping on the ty-5 gene from Tyking, viruliferous whitefly (B. tabaci) will be used for inoculation and the resistant rating system will be based on symptom expression. For NIL for TSWV, the process will be the same using the Sw-7 gene. TSWV screening and phenotyping will be done following inoculation by thrips on test plants, as well as resistant and susceptible controls. These plant materials or their RNAs will be provided to Ling’s lab for RNA-Seq analysis. Genes involved in tomato responding to virus (TYLCV and TSWV) infection will be identified through differential expression profiling.