Commercial development of subtropical mandarin hybrids

Abstract

Mandarin growers operating in subtropical Australia need better varieties if they are to remain competitive on both domestic and international markets. There is a significant gap between consumer expectations and the mandarin fruit they actually consume, and new improved varieties can close this gap. The problem is long-standing, and more than 20 years ago Queensland grower organisations approached their state Department of Agriculture and Fisheries to collaborate in a private mandarin breeding program to start tackling the problem; the Mandarin Hybridisation Project. More than 50,000 hybrids resulted and were carefully tested to identify a few that showed the most promise. This project aimed to progress this high quality material toward commercial production.
More than 16,000 original hybrids remained to be assessed and this was completed during the project, with the last progeny block bulldozed in May 2014. No new hybrids were produced, focussing instead on existing material and getting it ready for commercial production. Although close to 500 individual hybrids showed commercial potential when originally selected from the progeny blocks, an extensive period of stage-two testing using conventional rootstocks and wider spacing gradually identified faults with most of these and less than 20 were finally considered worthy of testing in commercial orchards. With such an exhaustive list of essential traits, it is hardly surprising that such a small fraction of the original hybrid population (<0.05%) had all the necessary characteristics in the one cultivar.
A major obstacle to commercial production of the selected cultivars was the presence of very high seed numbers (20-30 per fruit) and this was successfully solved by this project. Through the production and screening of large numbers of variants, we were able to obtain low-seeded selections of the best quality hybrids. These were then carefully compared as daughter trees to ensure undesirable changes had not occurred in other traits such as acidity and productivity, and to identify the best few to go into a final stage of commercial testing.
Commercial test blocks of low-seeded variants of three high quality hybrids were planted at the end of the project, and will provide fruit for test marketing and production testing ahead of full-scale commercialisation.
The project was successfully guided by a management committee comprising representatives of the contributing organisations. Important issues such as a commercialisation strategy module and an open tender process for commercial-scale testing were undertaken by this committee. Industry engagement activities occurred in every year of the project, providing opportunities for growers, marketers and contributing organisations to inspect and taste the new mandarin cultivars as they progressed toward commercialisation. Feedback from this engagement was critical to identifying which hybrids had the best commercial potential.
Improving the profitability of commercial mandarin growing in the subtropics, via the availability of better quality mandarin cultivars, was the key objective of this breeding project. With new high quality low-seeded mandarins now established in commercial quantities, and industry players eager to gain access, this goal is within reach.