Producing super sweet and firm peaches and nectarines

Abstract

New systems are being developed to produce super-sweet peaches and nectarines under subtropical conditions of Australia. Currently most low-chill stone fruit, because of their short fruit development period (FDP), exhibit low sugar concentrations between 9-10° Brix, whereas a minimum acceptable °standard would be 11° Brix. Evaluation of total orchard exclusion netting (2 mm spacing microfilament mesh) as an environmentally friendly means of preventing pest damage to stone fruit has been proven to be highly effective. Additional benefits of the exclusion netting were the change in microclimate. Higher maximum temperatures (5°C) compared with ambient generated °additional heat units producing fruit with 30% greater Brix concentrations (15° Brix). New management tools and techniques have also increased sugar concentrations of fruit by an additional 10 to 20%. These tools and techniques include: applying foliar growth retardants of pro-hexiodione-Ca or paclobutrazol during early fruit development to restrict shoot extension growth to less than 10 cm by stone-hardening; and applying ethylene inhibitors such as aminoethoxyvinylglycine (AVG) one week before first harvest. Ethylene inhibitors have the effect of delaying fruit maturity. Further studies are being conducted on new hybridised low-chill germplasm with longer FDPs and genetically higher sugar concentrations. Various combinations of these new varieties and management factors are being assessed.