A CLADE-BASED SEARCH FOR GENOME REARRANGEMENTS AND USEFUL DIVERSITY IN SOLANUM

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: TERMINATED
• Funding Source: NRI COMPETITIVE GRANT
• Reporting Frequency: Annual
• Accession No.: 0187459
• Grant No.: 00-35300-9411
• Project No.: WISR-2000-01394
• Proposal No.: 2000-01394
• Project Start Date: Sep 15, 2000
• Project End Date: Sep 30, 2004
• Grant Year: 2000

Project Director
Spooner, D. M.

Recipient Organization
UNIV OF WISCONSIN
21 N PARK ST STE 6401
MADISON,WI 53715-1218

Performing Department
HORTICULTURE

Non Technical Summary
The wild relative of potato present an exceedingly rich and yet largely unexplored resource for potato improvement. Vastly conflicting taxonomies of different workers have hindered a logical search for complimentary sources of resistances, however, especially considering the size of the collections (about 5000 accessions of 200 wild potato species). Recent molecular studies have shown that potato is composed of four well-defined phylogenetic groups (clades). We will conduct a systematic approach to capturing this diversity from one of these four clades (Solanum Piurana), through an examination of comparative genome rearrangements and identification of quantitative trait loci (QTL) for late blight resistance. The long-range goals of the research are the breeding of potato cultivars that harbor diverse resistances and other valuable genes. We construct a low-density genetic map the Solanum Piurana clade, based on universal RFLP markers that permit the use of this map in comparisons with other taxa of potatoes and tomatoes, and for QTL analysis. Unique technical strategies (comparative sibship analysis and ploidy manipulation) are proposed, to exploit the unusual opportunities and challenges for the use of these wild potato species. This research draws on the complimentary expertise in basic and applied research in taxonomy, genetics, and potato breeding, to locate and use valuable genetic diversity for crop improvement. It will establish an approach to examine consensus and distinction among phylogenetically diverse sources of disease resistance, through comparative genetic

Animal Health Component

(N/A)

Research Effort Categories

Basic

50%

Applied

50%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
202	1310	1060	100%

Knowledge Area
202 - Plant Genetic Resources;

Subject Of Investigation
1310 - Potato;

Field Of Science
1060 - Biology (whole systems);

Keywords

plant disease resistance

germplasm

phytophthora infestans

late blight (potatoes)

quantitative genetics

gene loci

traits

solanum

plant genetics

genetic diversity

potatoes

wild plants

plant evaluation

alleles

comparative analysis

genetic mapping

plant accessions

genetic markers

rflp

data analysis

Goals / Objectives
1) Investigate members of a group of wild relatives of potato taxonomically classified in the Solanum Piurana clade, as potentially important sources of resistance to potato late blight through quantitative trait loci and candidate gene approaches. 2) To contribute to the recognition, characterization, and use of conserved and complementary alleles conferring durable resistance to potato late blight through comparison with quantitative trait loci maps of other solanum species.

Project Methods
Quantitative trait loci of potato late blight resistance will be mapped in an intra-Solanum series Piurana cross involving a late blight susceptible accession of Solanum chomatophilum and a late blight resistant accession of S. paucissectum, backcrossed to the late blight susceptible S. chomatophilum parent. Resistance will be determined in two field locations, one in Wisconsin, and one in Peru, using the area under the disease progress curve, and by an in-vitro detached leaf test. Quantitative trait loci will be mapped using heterologous RFLP markers previously mapped in tomato. Tomatoes and potatoes are sister groups, and conservation of markers allow for this efficient mapping tool. Mapmaker software will be used for data analysis.

Progress 09/15/00 to 09/30/04

Outputs
The cultivated potato, Solanum tuberosum, is affected by a variety of diseases with late blight, caused by Phytophthora infestans, being the most severe. Wild potato species have proven to be a continuing source of resistance, sometimes of an extreme type, to this disease. The present study constructed a genetic map of a previously uncharacterized wild, tuber-bearing South American relative of potato, Solanum paucissectum, using probes for conserved sequences from potato and tomato. Eight probes mapped to unexpected linkage groups, but syntenic differences with prior maps of potato were not supported by any blocks of rearranged chromosome segments. All 12 linkage groups were resolved, and significant associations with late blight resistance were found on chromosomes 10, 11 and 12. A major quantitative trait locus on chromosome 11 accounts for more than 25% of the phenotypic variance measured in a field trial. Crossing of S. paucissectum with cultivated potato resulted in very few seeds indicating partial reproductive barriers. Differential reactions of accessions of this potential donor species with simple and complex isolates of P. infestans suggest that it carries major resistance genes that are not those previously described from the Mexican species, S. demissum. However, the additivity of the quantitative trait loci effects argues for the quantitative nature of resistance in this cross.

Impacts
Late blight, caused by the oomycete Phytophthota infestans (Mont.) de Bary is one of the most important diseases affecting the potato crop (Solanum tuberosum L.) worldwide. Late blight destroys the foliage, stems, and tubers of growing plants, causing severe losses in cultivated potato. The first and most devastating late blight outbreak ever recorded occurred in Ireland in the 1840s, resulting in famine and migration of more than a million people. Control of the disease relies on fungicide application, which increases agricultural inputs and environmental and health risks. Where fungicides are not affordable, total crop loss can result. Resistance to late blight was incorporated into cultivated potato during the first decades of the 20th century by repeated backcrossing with the resistant wild species Solanum demissum. These crosses resulted in the incorporation of at least 11 R (resistance) genes into cultivated potato. Potato has a narrow genetic base and wild species have great potential to improve the crop for a range of traits. Researchers are actively screening additional wild species for sources of new resistance genes and there is a need to continuously develop new sources to keep pace with the dynamic pathogens like P. infestans. This paper reports the first genetic map and late blight resistance loci involving species from a member of the wild potato group Solanum series Piurana, and shows a potential new source of late blight resistance.

Publications

• No publications reported this period