Identification of non-TIR-NBS-LRR markers linked to the Pl5/Pl8 locus for resistance to downy mildew in sunflower

Abstract

The resistance of sunflower, Helianthus annuus L., to downy mildew, caused by Plasmopara halstedii, is conferred by major genes denoted by Pl. Using degenerate and specific primers, 16 different resistance gene analogs (RGAs) have been cloned and sequenced. Sequence comparison and Southern-blot analysis distinguished six classes of RGA. Two of these classes correspond to TIR-NBS-LRR sequences while the remaining four classes correspond to the non-TIR-NBS-LRR type of resistance genes. The genetic mapping of these RGAs on two segregating F2 populations showed that the non-TIR-NBS-LRR RGAs are clustered and linked to the Pl5/ Pl8 locus for resistance to downy mildew in sunflower. These and other results indicate that different Pl loci conferring resistance to the same pathogen races may contain different sequences.

Can Pl Resistance Gene in Sunflower Line D4 be Used to Differentiate the Pathogenicity in Four Plasmopara halstedii (Sunflower Downy Mildew) Races 304, 314, 704 and 714?

“…Our results confirmed that the two sunflower lines XRQ and RHA340 were resistant to all P. halstedii isolates used in this study because they carry effective Pl genes against all races tested in the present study. This type of resistance may be controlled by non-TIR-NBS-LRR (Toll/interleukin-1 receptor (TIR) nucleotide-binding site leucine-rich repeat class) which clustered and linked to the Pl5/Pl8 locus for resistance to downy mildew in sunflower (Radwan et al, 2003).…”

Toward Marker Assisted Selection for Fungal Disease Resistance in Sunflower. Utilization ofH. Bolanderias a Source of Resistance to Downy Mildew

“…The NBS region is forwarded by either a coiledcoil (CC) or Toll-interleukin1 receptor (TIR) domain, which divides the NBS-LRR genes in two classes, CC and TIR-NBS-LRR. The clusters of NBS-LRR genes were identified in PL1 locus (9), in PL6 (TIR-NBS-LRR class) (3) and in PL5/PL8 (CC-NBS-LRR class) (29,30). The cloned genes were used for development of 13 RGA based markers within PL6 (3) and 14 STS (sequence tag sites) markers within the Pl5/Pl8 locus (29,30).…”

“…The clusters of NBS-LRR genes were identified in PL1 locus (9), in PL6 (TIR-NBS-LRR class) (3) and in PL5/PL8 (CC-NBS-LRR class) (29,30). The cloned genes were used for development of 13 RGA based markers within PL6 (3) and 14 STS (sequence tag sites) markers within the Pl5/Pl8 locus (29,30). SSR markers, closely linked to PL6, PL13 and PLarg genes were also identified (8,23,25).…”

“…It spanned 1363 cM with a mean density of 3.1 cM per locus, providing framework for cross-reference between already established genetic maps. Further, it was saturated, resulting in what is presently the most comprehensive framework map, developed (4,29), that corresponds to the LG13 of the map of Yu et al (42); PL6 was mapped on LG1 (38), which corresponds to LG8 of Yu et al (42). The genetic analysis showed that the Pl6 locus from wild H. annuus is split in two distinct genetic loci, one conferring resistance to races 100 and 300, and the secondto races 700, 703 and 710 (38).…”

Quelles perspectives pour la lutte génétique vis-à-vis du mildiou du tournesol ?

“…Cette dernière stratégie semble avoir été expé-rimentée avec succès par Zhu et al [20] dans le cas des maladies du riz. Ces stratégies (assemblage, combinaison de gènes et alternance) sont aujourd'hui envisageables chez le pathosystème mildiou/ tournesol du fait de la découverte de plusieurs gènes Pl efficaces vis-à-vis des principales races présentes en France et de leur localisation sur la carte chromosomique [16,17,[21][22][23][24][25], ce qui a permis le développement d'outils (marqueurs) d'aide à la sélection. Dans cet article, nous présenterons les résultats d'un essai pluriannuel mettant en évidence l'impact de l'assemblage, de l'alternance ou de la combinaison de gènes sur les taux de plantes malades et sur l'évolu-tion d'une population de Plasmopara halstedii dans un dispositif contrôlé proche des conditions de culture agricoles.…”