Breeding strategy and genetic gain in the Australian Strawberry Breeding Program

Abstract

The Australian Strawberry Breeding Program (ASBP) develops improved strawberry varieties tailored to the unique environmental conditions of Australia's primary strawberry production climates: temperate, subtropical, and Mediterranean. The program's strategic breeding objectives are to develop region-specific varieties that align with consumer demand and enhance grower profitability through higher yields per hectare and lower production costs. In recent years ASBP varieties have constituted approximately 90% of commercial strawberry plant sales for Australia's subtropical region and 50% at the national level.
To achieve its goals the ASBP applies classical breeding methodologies with quantitative genetic analysis and disease resistance screening, alongside genomic prediction and marker-assisted selection. Molecular markers for the presence of a flavour volatile and day-neutrality (ever-bearing phenotype) are routinely screened. A published marker for Colletotrichum crown rot resistance is also currently being trialled.
The ASBP additionally employs marker-assisted parental selection using single nucleotide polymorphism (SNP) markers on early-stage accessions. Through this process promising parents are identified prior to phenotypic data being collected, based on predicted performance for various key plant and fruit quality traits.
Over the past two decades, focused crossing and selection strategies have led to significant genetic gains in ASBP key traits. For example, since 2016 yield per plant in the subtropical population has significantly increased by an average of 24g each year, from a population average of 261g in the 2016 cohort to 411g in 2023. Average fruit weights have increased by 0.8g each year in the subtropical population, and by 0.5g in the temperate population, from 19.3g to 24.6g, and 19.3g to 21.5g between the 2016 and 2023 cohorts, respectively. Large fruit size is a major driver of production cost-efficiency in strawberry, and these genetic gains translate to over $20,000 in commercial labour savings per hectare.
Significant genetic gain has also been made in breeding for tolerance to Red Leaf Disorder (RLD), a major issue causing reduced yield and plant death in Australia. While a causal agent for RLD has yet to be identified, RLD tolerance demonstrates high heritability and most new ASBP varieties are resistant. Genetic studies to identify chromosomal regions associated with response to RLD are underway.