Mapping QTL involved in powdery mildew resistance of the apple clone U 211

Abstract

Scab and powdery mildew, caused by Venturia inaequalis (Cke.) Wint. and Podosphaera leucotricha (Ellis et Ev.) Salm. are the most important apple diseases. The apple clone U 211 is resistant to scab and is also highly resistant to powdery mildew under field conditions. The interval mapping method was applied for the identification of genomic regions conferring U 211 resistance to powdery mildew. The genetic maps of the ÔIdaredÕ and U 211 genome sectors were constructed using amplified fragment lenght polymorphism and simple sequence repeat markers and 98 individuals from the progeny of the cross ÔIdaredÕ · U 211. On the basis of the phenotypic and molecular marker data 10 powdery mildew resistance quantitative trait loci (QTL) were identified in U 211 and ÔIdaredÕ. One of the QTL in the clone U 211 explained 48-72% of the phenotypic variation and its effect was stable over years.

Mapping of the apple powdery mildew resistance gene Pl1 and its genetic association with an NBS‐LRR candidate resistance gene

“…Several major genes for powdery mildew and apple scab as well as QTLs for both diseases have previously been mapped in this region: Pld as a major powdery mildew resistance gene (James et al. 2004), a stable QTL for mildew resistance from the apple clone U211 (Stankiewicz‐Kosyl et al. 2005), the scab resistance gene Vg conferring resistance to scab race 7 (Durel et al.…”

“…The position of the Pl1 locus together with the AT20-SCAR and the RGA 15G11 at the bottom part of apple LG 12 indicate that Pl1 might be a further gene of an important resistance gene cluster located in this region of the apple genome. Several major genes for powdery mildew and apple scab as well as QTLs for both diseases have previously been mapped in this region: Pld as a major powdery mildew resistance gene ), a stable QTL for mildew resistance from the apple clone U211 (Stankiewicz-Kosyl et al 2005), the scab resistance gene Vg conferring resistance to scab race 7 (Durel et al 2000), and, as a recent result, the Vb major scab resistance gene (Erdin et al 2006). The comparison of the positions of the SSRs CH01g12, CH01f02, CH03c02 and CH01d03 in the Pl1 maps and in the Vg map published by Calenge et al (2004) indicates that Pl1 and Vg could be tightly linked.…”

Development of apple powdery mildew on sources of resistance to Podosphaera leucotricha, exposed to an inoculum virulent against the major resistance gene Pl‐2

“…1995, Evans and James 2003, James et al. 2004) and the detection of quantitative trait loci will be useful in apple breeding programmes to improve the selection of genotypes for durable resistance to powdery mildew (Stankiewicz‐Kosyl et al. 2005, Calenge and Durel 2006).…”