Sustainable deployment of QTLs conferring quantitative resistance to crops: first lessons from a stochastic model

Quantitative plant disease resistance is believed to be more durable than qualitative resistance, since it exerts less selective pressure on the pathogens. However, the process of progressive pathogen adaptation to quantitative resistance is poorly understood, which makes it difficult to predict its durability or to derive principles for its sustainable deployment. Here, we study the dynamics of pathogen adaptation in response to quantitative plant resistance affecting pathogen reproduction rate and its carrying capacity. We developed a stochastic model for the continuous evolution of a pathogen population within a quantitatively resistant host. We assumed that pathogen can adapt to a host by the progressive restoration of reproduction rate or of carrying capacity, or of both. Our model suggests that a combination of QTLs affecting distinct pathogen traits was more durable if the evolution of repressed traits was antagonistic. Otherwise, quantitative resistance that depressed only pathogen reproduction was more durable. In order to decelerate the progressive pathogen adaptation, QTLs that decrease the pathogen's ability to extend must be combined with QTLs that decrease the spore production per lesion or the infection efficiency or that increase the latent period. Our theoretical framework can help breeders to develop principles for sustainable deployment of quantitative trait loci.

FROM STRAWBERY BANKE TO PUDDLE DOCK: THE EVOLUTION OF A NEIGHBORHOOD, 1630-1850 (URBAN COMMUNITY, MARITIME; NEW HAMPSHIRE)

This dissertation examines the evolution of a site from 1630 to 1850. Until 1690 the site was part of a large farmstead; during the eighteenth century it became a thriving commercial area in the seaport town of Portsmouth, New Hampshire; after 1820 it became an old waterfront neighborhood serving primarily as a residential area. The study first places the site within the context of the larger community, and then looks at spatial arrangements and structural forms within the site itself. Finally it follows the changing reputation of the area. The local economy was the strongest influence on the way people organized and built a neighborhood at the site. The importance of other factors, such as the natural environment, aesthetics and population density, varied from time to time. The way the site evolved was a result of the interplay of such factors

Estimation of the average effects of specific alleles detected by the pseudo-testcross QTL mapping strategy

International audienc

Construction of an integrated consensus map of the Apple genome based on four mapping populations

An integrated consensus genetic map for apple was constructed on the basis of segregation data from four genetically connected crosses (C1¿=¿Discovery × TN10-8, C2¿=¿Fiesta × Discovery, C3¿=¿Discovery × Prima, C4¿=¿Durello di Forli × Fiesta) with a total of 676 individuals using CarthaGene® software. First, integrated female¿male maps were built for each population using common female¿male simple sequence repeat markers (SSRs). Then, common SSRs over populations were used for the consensus map integration. The integrated consensus map consists of 1,046 markers, of which 159 are SSR markers, distributed over 17 linkage groups reflecting the basic chromosome number of apple. The total length of the integrated consensus map was 1,032 cM with a mean distance between adjacent loci of 1.1 cM. Markers were proportionally distributed over the 17 linkage groups (¿ 2¿=¿16.53, df¿=¿16, p¿=¿0.41). A non-uniform marker distribution was observed within all of the linkage groups (LGs). Clustering of markers at the same position (within a 1-cM window) was observed throughout LGs and consisted predominantly of only two to three linked markers. The four integrated female¿male maps showed a very good colinearity in marker order for their common markers, except for only two (CH01h01, CH05g03) and three (CH05a02z, NZ02b01, Lap-1) markers on LG17 and LG15, respectively. This integrated consensus map provides a framework for performing quantitative trait locus (QTL) detection in a multi-population design and evaluating the genetic background effect on QTL expression

Book Reviews

Reviews of the following books: The Living Past, Being the Story of Somesville, Mount Desert, Maine and Its Relationship with Other Areas of the Island.By Virginia Somes-Sanderson; Voice on the Kennebec, 1941-1981, edited by Kathleen A. Martin; Nathan A. Cushman: A Rugged Individualist edited by Franklin P. Cole; and Portsmouth and the Piscataqua by Peter E. Randall