MassARRAY and SABER Analyses of SNPs in Embryo DNA Reveal the Abscission of Self-Fertilised Progeny during Fruit Development of Macadamia ( Maiden & Betche).
Anushika L De Silva, Wiebke Kämper, Steven M Ogbourne, Joel Nichols, Jack W L Royle, Trent Peters, David Hawkes, Shahla Hosseini Bai, Helen M Wallace, Stephen J Trueman
Author Information
Anushika L De Silva: Centre for Planetary Health and Food Security, School of Environment and Science, Griffith University, Nathan, QLD 4111, Australia. ORCID
Wiebke Kämper: Functional Agrobiodiversity and Agroecology, Department of Crop Sciences, University of Göttingen, 37077 Göttingen, Germany. ORCID
Steven M Ogbourne: Centre for Bioinnovation, University of the Sunshine Coast, Maroochydore DC, QLD 4558, Australia. ORCID
Joel Nichols: Centre for Planetary Health and Food Security, School of Environment and Science, Griffith University, Nathan, QLD 4111, Australia. ORCID
Jack W L Royle: Australian Genome Research Facility, Gehrmann Laboratories, University of Queensland, Brisbane, QLD 4072, Australia.
Trent Peters: Australian Genome Research Facility, Gehrmann Laboratories, University of Queensland, Brisbane, QLD 4072, Australia.
David Hawkes: Australian Genome Research Facility, Gehrmann Laboratories, University of Queensland, Brisbane, QLD 4072, Australia.
Shahla Hosseini Bai: Centre for Planetary Health and Food Security, School of Environment and Science, Griffith University, Nathan, QLD 4111, Australia.
Helen M Wallace: School of Biology and Environmental Science, Queensland University of Technology, GPO Box 2434, Brisbane, QLD 4001, Australia.
Stephen J Trueman: Centre for Planetary Health and Food Security, School of Environment and Science, Griffith University, Nathan, QLD 4111, Australia. ORCID
Yield in many crops is affected by abscission during the early stages of fruitlet development. The reasons for fruitlet abscission are often unclear but they may include genetic factors because, in some crops, self-pollinated fruitlets are more likely to abscise than cross-pollinated fruitlets. Pollen parentage can also affect final fruit size and fruit quality. Here, we aimed to understand the effects of pollen parentage on fruitlet retention and nut quality in orchards of macadamia ( Maiden & Betche). We identified the pollen parent of macadamia 'cultivar '816' embryos by analysing single nucleotide polymorphisms (SNPs) in their DNA using customised MassARRAY and Single Allele Base Extension Reaction (SABER) methods. This allowed us to determine the proportions of self-fertilised and cross-fertilised progeny during premature fruit drop at 6 weeks and 10 weeks after peak anthesis, as well as at nut maturity. We determined how pollen parentage affected nut-in-shell (NIS) mass, kernel mass, kernel recovery, and oil concentration. Macadamia trees retained cross-fertilised fruitlets rather than self-fertilised fruitlets. The percentage of progeny that were cross-fertilised increased from 6% at 6 weeks after peak anthesis to 97% at nut maturity, with each tree producing on average 22 self-fertilised nuts and 881 cross-fertilised nuts. Three of the four cross-pollen parents provided fruit with significantly higher NIS mass, kernel mass, or kernel recovery than the few remaining self-fertilised fruit. Fruit that were cross-fertilised by '842', 'A4', or 'A203' had 16-29% higher NIS mass and 24-44% higher kernel mass than self-fertilised fruit. Nuts that were cross-fertilised by 'A4' or 'A203' also had 5% or 6% higher kernel recovery, worth approximately $US460-540 more per ton for growers than self-fertilised nuts. The highly selective abscission of self-fertilised fruitlets and the lower nut quality of self-fertilised fruit highlight the critical importance of cross-pollination for macadamia productivity.
