An update on apple scab resistance breeding in New Zealand

Genetic gain in fruit quality of scab-resistant breeding populations was observed in the HortResearch apple breeding programme. In the past, the introduction of resistance into high quality varieties has proved to be a time-consuming effort, in many cases spanning seven or more generations of crossing. It is expected that through the systematic evaluation of the HortResearch Apple Genetics Population, the timespan for the introduction of new resistances can be reduced by simultaneous selection for large fruit size, fruit quality and scab resistance. This process includes the evaluation of our Malus sieversii germplasm collected from wild progenitors of modern apples in Kazakstan, which appeared to be highly resistant to scab. Research has been initiated to investigate the potential role this germplasm may play in the development of cultivars with durable resistances to apple scab. Marker assisted selection is now an important technique for our programme, as epistatic interactions between loci for scab resistance have been shown to be a limiting factor in screening for resistance based on phenotype. Our intention is to develop resistant cultivars; by coupling the genetic transformation of natural resistances with marker assisted selection.