ARS | Publication request: Confirmation By QTL mapping Of The Malus Robusta (Cv. Robusta 5) derived powdery mildew resistance gene Pl1

Submitted to: Acta Horticulturae
Publication Type: Proceedings
Publication Acceptance Date: December 15, 2010
Publication Date: N/A

Technical Abstract: The Geneva® apple rootstock breeding program has made extensive use of Malus robusta cv. Robusta 5 as a source of resistance to fire blight. Robusta 5 has also been used as the source of powdery mildew resistance by other breeding programs and a single locus Pl1 has been associated with this resistance and recently mapped on LG12 of the European Apple Framework Map [Plant Breeding 126:476-481, 2007] using a qualitative approach. We collected quantitative data on field powdery mildew resistance in 2006 and 2007 on a segregating population made up of 186 individuals from a cross between Ottawa 3 (a susceptible apple rootstock) and Robusta 5; the correlation between the two years was 0.84 (p=0.000). This quantitative data were used in combination with a molecular marker linkage map derived from the same cross to scan the genome using interval and MQM mapping in MapQTL 5 software. The result was the identification of a large QTL on the distal end of LG12 with a peak near the SSR marker CH01b12z. No other regions in the apple genome had any significant effects on resistance in this population when using Interval Mapping procedure. MQM mapping revealed a . Future plans include scanning of a BAC library containing Pl1 and utilizing existing markers for marker assisted breeding.