Genetic variation of the riparian pioneer tree species Populus nigra. II. Variation in susceptibility to the foliar rust Melampsora larici-populina

Abstract

Partial resistance of Populus nigra L. to three races of the foliar rust Melampsora larici-populina Kleb. was studied in a ®eld trial and in laboratory tests, using a collection of P. nigra originating from di erent places throughout France. No total resistance was found. The partial resistance was split into epidemiological components, which proved to be under genetic control. Various patterns of association of epidemiological components values were found. Principal components analysis revealed their relationships. Only 24% of the variance of the ®eld susceptibility could be explained by the variation of the epidemiological components of susceptibility. This variable was signi®cantly correlated with susceptibility to the most ancient and widespread race of the pathogen, and with the variables related to the size of the lesions of the di erent races. Analysis of variance showed signi®cant di erences in susceptibility between regions and between stands within one region. Up to 20% of variation was between regions, and up to 22% between stands, so that these genetic factors appeared to be more di erentiated than the neutral diversity (up to 3.5%; Legionnet & LefeÁ vre, 1996). However, no clear pattern of geographical distribution of diversity was detected.

Genetic and physical mapping of Melampsora rust resistance genes in Populus and characterization of linkage disequilibrium and flanking genomic sequence

“…and Melampsora spp. (Thielges & Adams, 1975;Lefevre et al, 1994;Legionnet et al, 1999). There are currently at least eight recognized species of Melampsora, with a large number of distinct physiological races varying in their specificity to individual poplar genotypes (Prakash & Thielges, 1987;Pinon, 1992).…”

Selection of clones of Populus nigra L. ssp. nigra for resistance to Melampsora larici-populina Kleb. Rust

“…In experiments with black poplar clones and with progenies of selected clones the infection was natural under field conditions where the origin of the species and race was not examined. Field sensitivity investigated on the basis of natural infection was also described by LEGIONNET et al (1999). Nevertheless, identical sensitivity to rust in field and laboratory conditions is important.…”

“…Most clones of the genus Populus grown in the last two centuries in Europe seem not to have ever been immune to rust; it indicates non-specific resistance of poplar to rust (PINON 1992), and as reported by LEGIONNET et al (1999), specific resistance was not detected in Populus nigra. On the contrary, some interspecific hybrids show immunity that may however be paralysed by the adaptation of physiological races, particularly of the rusts Melampsora larici-populina and M. medusae (PINON 1992).…”

“…Besides the oldest race E1 other races of this rust were identified (STEENACKERS 1982;PINON et al 1987;PINON, PEULON 1989;PINON, FREY 1997). These new races can infect poplar clones that are resistant to race E1 only (PINON, FREY 1997;LEGIONNET et al 1999).…”

The response of the poplar transcriptome to wounding and subsequent infection by a viral pathogen

“…Such pedigrees have proven to be particularly useful in uncovering Populus loci that confer resistance to fungal pathogens (Villar et al ., 1996). Most investigations into the defence mechanisms used by Populus have focused on fungal pathogens (Royle & Ostry, 1995;Newcombe, 1996;Villar et al ., 1996;Legionnet et al ., 1999;Ostry & Ward, 2003).…”