Genetic Determination for Susceptibility to CO2-Induced Injury In Apple

Use of CA storage is common in horticulture for extending the shelf life and quality attributes of fruits. However, maintaining CO₂ at levels low enough to avoid CO₂ injury is a major problem in the operation of CA facilities. This study was aimed at determining genetic basis for susceptibility to CO₂ injury in apple to facilitate 1) parental selection and development of new varieties with little or no susceptibility to CO₂ injury, and 2) setting up further genetic studies to dissect the underlying genetic mechanisms involved. We carried out studies in 2001 and 2002 with 41 and 35 seedling families respectively, selected from ‘breeding population 94’ of an apple recurrent selection programme well suited for genetic studies. Fruit from these families were harvested at or near physiological maturity and subjected to 3 CA treatments; air, 5% CO_{2 (+} balanced air) and 10% CO₂ (+ balanced air) for 10 weeks in 2001 or 6 weeks in air and at 5% CO₂ in 2002. The incidence and severity of CO₂ injury were assessed after storage and various statistical procedures including GLM, ANOVA, permutation tests, Monte Carlo simulations and Bootstrapping were used to explore the sources of variation for incidence of CO₂ injury. There was a significant family or genetic effect (p<0.001) on susceptibility to CO₂ injury. The results provide the basis for further studies to identify the underlying genetic mechanisms involved as well as selection of parents to develop new varieties with little or no susceptibility to CO₂ induced injury.