Marker assisted breeding of papaya to develop new commercial lines (PP10005)

What was it all about?

The Australian papaya industry needs new varieties of both yellow and red papayas, with high uniformity, disease resistance, good eating qualities and consistent yield.

This project, which ran from 2011 to 2015, set out to breed new commercial lines with favourable characteristics. This breeding program evaluated twenty-seven lines and breeding selections were made on the basis of 11 productivity traits and 13 characteristics related to fruit quality, based on both grower and consumer preferences.

Trees were evaluated at three different harvesting times, April 2012, October 2012 and May 2013, to separate out the effects due to differences in the environment, rather than the genetics of the trees. Trees were selected as parents for the next phase of a breeding program if they were judged favourably across the three time points.

The traits sought included flavour, skin quality, eating quality of red papaya, eating quality of yellow papaya and yield.  

Twenty-three representative trees were selected as parental lines and 17 crosses were made for the breeding programs to develop improved commercial lines.

The researchers also developed genetic markers for a wide range of character traits to speed up future seedling selection.

Fruit flavour was improved in both red and yellow fleshed papaya and trees with better flavoured fruit and high yield were crossed back to commercial varieties to keep improving the Australian genetics.

A potential new variety of yellow papaya was established in tissue culture for field testing in different regions in the following phase of breeding program.