Psyllid resistant leucaena to market

Summary

​The leucaena psyllid (Heteropsylla cubana) is a serious insect pest of commercial leucaena (Leucaena leucocephala ssp.glabrata) in Australia especially in areas with average annual rainfall > 800 mm. Availability of a psyllid-resistant variety would increase the range of adaptation of leucaena by 30%, from 4.4 M ha to 5.7 M ha.

An MLA-supported breeding program was initiated in 2002 to develop a psyllid-resistant variety developed from inter-specific hybrids between the susceptible species L. leucocephala and the resistant species L. pallida. Forty breeding lines of the psyllid-resistant leucaena were produced following three generations of mass selection, two generations of backcrossing to L. leucocephala, and two generations of self-pollination, progeny testing and selection among backcrossed breeding lines. Selection for psyllid resistance was carried out at each stage of the breeding program.

Four of these breeding lines were then selected for possible release to industry. The lines were chosen for their psyllid resistance, moderate seed production and high in vitro digestibility comparable to that of the existing commercial cultivars.  To move to commercialisation, it was necessary to gain Plant Breeders Rights (PBR) for these varieties, bulk up seed, and conduct a final assessment of psyllid resistance and forage yield, and test palatability to animals.

This project involved fieldwork required to achieve PBR, and selection of one or more lines to be commercially released based on a final comparison of psyllid resistance, forage yield and forage quality. The field trial gathered data to prove the distinctness, uniformity and stability of the new variety. Part 1 documentation for QPBR was obtained giving provisional protection for two lines (#12 and #39) in 2014.

In parallel, additional work in conjunction with QDAF, a grazing preference trial was established at Whitewater Station in north Queensland to compare the grazing preference of the 4 breeding lines with commercial cultivars L. leucocephala cvv Cunningham and Wondergraze. Overall, there were no major differences in preference among the breeding lines. Although animals displayed a preference for commercial cultivars under light grazing when not psyllid damaged, all entries were well eaten with approximately 10% of leaf remaining at the end of the grazing period. Psyllid damage reduced the palatability of the commercial cultivars compared to the psyllid resistant breeding lines.

Breeding line #12 was ultimately selected for advancement to Stage 2 of the PBR application and has now been approved by IP Australia (reference 2014/112) (28/9/2017) and given the name cultivar Redlands.

Prior to final selection of #12 for release, seed orchards of each of the four selected lines were established at 3 locations in order to obtain breeder's seed for distribution to the commercial companies chosen to multiply and market the new variety. Seed of all of the non-selected breeding lines has been retained and placed into cold storage at the University of Queensland. Field plots of non-selected breeding lines have been destroyed, or are in the process of being destroyed.

About 40 kg of breeding line #12 was provided to Leuc Seeds PTY LTD as the first successful licensee to grow and distribute the new psyllid-resistant leucaena. In November 2015, 5 kg of seed was given to the second licensee, Bandana Station Carnarvon Pastoral with an additional 35 kg supplied in June 2016.

Commercial seed of cv. Redlands has now been harvested and is available for purchase by graziers.