BREEDING COMMERCIAL APPLE CULTIVARS IN NEW ZEALAND WITH RESISTANCES TO PESTS AND DISEASES

In the HortResearch apple breeding programme, three phases can be recognised which reflect the course of the development of pest and disease resistant cultivars: (1) germplasm evaluation and genetics; (2) development of parents with multiple resistance, and (3) commercial cultivar breeding. In phase 2 of the breeding programme, most of the lines that are fruiting currently carry either V_f for apple scab resistance, or Pl₁ or Pl₂ for powdery mildew resistance, while four families carry major gene resistances to both diseases. From these, over 100 selections have been made. Nearly all of the more recently developed lines carry resistance to both apple scab and powdery mildew. Some carry additional resistances to fire blight, woolly apple aphid and/or collar rot. In phase 3, there are now eight fruiting families, most of which have either apple scab or powdery mildew resistance, and from which over 100 selections have been made for further evaluation on clonal rootstocks at three sites around New Zealand. Last year, one selection from a ‘Granny Smith’ x A679–2 cross carrying both V_f and Pl₂ was chosen for its high fruit quality, and bulked up for trialling as a potential commercial cultivar. This year, several resistant selections from crosses involving ‘Braeburn’, ‘Royal Gala’ and ‘Prima’ were identified as having commercial potential.