Transfer of late blight resistance genes in tomato via marker-assisted selection and phenotypic selection
Open Access
- Author:
- Reibson, Anna Dahl
- Graduate Program:
- Horticulture
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- May 09, 2013
- Committee Members:
- Majid R Foolad, Thesis Advisor/Co-Advisor
- Keywords:
- late blight
tomato
marker-assisted selection
breeding - Abstract:
- Late blight (LB), caused by the oomycete Phytophthora infestans, is a devastating disease of many species in the Solanaceae family, including tomatoes and potatoes. Previously, the use of cultural practices and frequent use of fungicides were sufficient to manage the disease. Up until recently, predominant genotypes of P. infestans were characterized as being resistant to the systemic fungicide metalaxyl. This and other factors such as the negative environmental impact of heavy chemical applications and limited availability of commercially acceptable LB resistant tomato cultivars have prompted the identification and use of genetic resistance to complement other management practices in an integrated pest management program for LB. Three useful LB resistance genes in tomato have been identified; Ph-2 and Ph-3, which have been incorporated into several commercially available inbred lines and hybrids, and Ph-5, which was recently discovered in Foolad lab at The Pennsylvania State University. The objective of this project is to continue the transfer of these LB resistant genes into Penn State fresh market and processing tomato lines, which have been bred for other desirable horticultural characteristics. The resistance genes were traced through a combination of phenotypic selection (PS) and marker-assisted selection (MAS). Tomato families containing at least one resistance gene were inoculated with a LB isolate and screened for LB resistance under greenhouse conditions. Plants exhibiting the most phenotypic resistance were genotyped using CAPS and SSR markers. Plants selected based on PS and MAS were grown under field conditions and evaluated for other desirable horticultural characteristics, including fruit quality and yield. The selected plants were hybridized with other Penn State inbred lines for further improvement. The phenotypic and genotypic screening process was repeated to develop further advanced populations. The ultimate goal of this project is to develop advanced breeding lines with LB resistance and other desirable horticultural characteristics suitable for production in PA and the Northeast. The increased availability of LB-resistant tomato cultivars will potentially reduce the frequency of fungicide applications and the negative economic impact of crop loss.