GENETIC CHARACTERIZATION AND MAPPING OF PARTIAL RESISTANCE TO EARLY BLIGHT IN DIPLOID POTATO
Open Access
- Author:
- Zhang, Ruofang
- Graduate Program:
- Plant Pathology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- April 26, 2004
- Committee Members:
- Barbara Jane Christ, Committee Chair/Co-Chair
John Ayers, Committee Member
John Edward Carlson, Committee Member
Frederick Eugene Gildow Jr., Committee Member
Seogchan Kang, Committee Member
Kathleen Haynes, Committee Member - Keywords:
- Potato
Early blight
Resistance
QTL mapping - Abstract:
- ABSTRACT Early blight (EB), caused by Alternaria solani Sorauer, is one of the main foliar diseases of potato (Solanum tuberosum L.). Yield losses up to 40% occur in some years. Plant protection by fungicide application is possible but planting a disease resistant cultivar would be preferable. A diploid hybrid family of 219 clones from Solanum phureja „e Solanum stenotomum was evaluated for EB resistance over three years in Pennsylvania. Disease severity was assessed for each clone throughout the development of the epidemic and area under disease progress curves (AUDPC) were calculated. There were significant differences among the clones for AUDPC. Resistance to EB appears to be inherited quantitatively based on the distribution of AUDPC values. Broad-sense heritability of EB resistance in this family was estimated as 0.77 with a 95% confidence interval of 0.71 to 0.82. There were significant clone „e year interactions. Further partitioning of the clone „e year interaction revealed that 75 clones made significant contributions to this interaction, and therefore, their resistance to EB was not stable. In this family, a negative correlation (r ƒ ¡V0.448, pƒ¬ 0.0001) was observed between mean AUDPC and earliness in maturity, indicating that plant maturity explained about 20% of the variation in disease reaction. However, some clones were identified with considerable EB resistance and early or mid-season maturity, suggesting that resistance from the parental clones might be useful for breeding early-maturing as well as EB resistant cultivars. This partial resistance has been genetically characterized by quantitative trait loci (QTL) mapping. Fluorescence-based, semi-automated amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) marker techniques were used to generate a genetic map. 170 AFLP and 47 SSR polymorphic markers were developed and analyzed for this full-sib family and 15 linkage groups were identified. Thirty eight of common AFLP markers and 44 of SSR markers were used to anchor 12 of the 15 linkage groups to 12 potato chromosomes. The markers covered 925 centiMorgan (cM) of genome with an average distance of 4.5 cM between adjacent markers, and less than 15% of the genome lies more than 20 cM from the nearest marker. Quantitative trait loci (QTLs) for partial resistance to EB and for foliage maturity were mapped using the "Multiple-QTL models" (MQM) method with putative QTL markers from interval mapping as cofactors. Five QTLs on chromosome IV, V, IX, XI and XII were identified for EB resistance that collectively explained 62.2% of the total phenotypic variation. Three QTLs on chromosome IV, V and VI were identified for foliage maturity that collectively explained 97.5% of the total phenotypic variation. Two QTLs for EB resistance and foliage maturity on chromosome IV and V were mapped in the same or closely linked regions. The other three QTLs for EB resistance on chromosome IX, XI and XII, which accounted for 33.1% of the total phenotypic variation and were not linked to foliage maturity, have the potential to improve EB resistance using marker-assisted selection (MAS) in a breeding program.