QTL mapping of soft scald in the RosBREED apple germplasm set

Soft scald is a postharvest disorder of apple (Malus domestica) characterized by distinct brown and often longitudinal lesions on the fruit that often extend into the flesh and can lead to secondary infections in the fruit. Fruit that develop soft scald are unmarketable for fresh eating. The disorder is economically important because it usually develops in storage multiple weeks after producers invest considerable resources into harvest and cold storage. Incidence of soft scald varies among cultivars and can vary depending on orchard and storage conditions. Many cultivars are susceptible to the development of soft scald, including cultivars commonly used extensively as parents in US breeding programs. Observations by breeders suggest the trait is heritable. The development of new cultivars with reduced potential for soft scald development would benefit the apple industry and this could be made more efficient through the use of marker assisted breeding.
A quantitative trait locus (QTL) detection study was conducted using FlexQTL software with data collected on soft scald incidence in 2011 and 2012 from the RosBREED apple germplasm set and additional data collected in 2013 at the University of Minnesota comprised of 4 half-sib families with ‘Honeycrisp’ as a common parent. Putative QTL were detected, though they were not consistently detected in all years and locations.