S01 - Session O9 - II - Rapid papaya crop improvement through accelerated in vitro breeding and molecular diagnostics

Authors: Puthiyaparambil Josekutty *, Candy MacLaughlin, Mark MacLaughlin, Paul Fagg, Marion MacLaughlin, Ian MacLaughlin, Nitin Mantri

Skybury farms located in tropical Queensland (17° 00' 21.456" S and 145° 20' 18.24" E) is a major, diversified farm producing papaya, coffee, avocados, citrus, banana and passionfruit. The unique Skybury Red Papaya is a market leader with over 50% of the Australian market share. Skybury strives for excellence in all areas of innovative farming and value addition, like award winning papaya vodka and coffee liquors, as well as marketing fresh fruits. Skybury engages in applied research using biotechnology tools to achieve rapid crop improvement through accelerated in vitro breeding. Papaya has very limited genetic variability. Therefore, we developed novel, high yielding, more flavoursome Skybury papaya lines with high brix through accelerated in vitro breeding using a high-throughput somatic embryogenesis system. We induced genetic variability among the embryogenic cell lines, regenerated variant papaya through a non-GM method (mutagenesis), conducted large-scale field trials, and recovered unique variants with better agronomic and fruit qualities. We generated several mutant lines free of the dreaded Papaya Sticky Disease (PSD) caused by the Papaya Meleira Virus. We developed a rapid and reliable molecular diagnostic test (PCR test) and LDF kit for rapid screening for PSD, and verified the PSD-free status of several of the mutant lines using the PCR test. We conducted a large-scale field trial of the PSD-free lines and recovered highly improved Skybury papaya lines in a short period by combining in vitro breeding with molecular technologies. Limited genetic variability is the major bottleneck for papaya crop improvement through conventional breeding, hence the accelerated in vitro breeding approach is the best way for rapid papaya crop improvement in the non-GM agriculture system of Australia. Gene editing technology, such as CRISPR technology, can be useful for further rapid papaya crop improvement.