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Breeding a psyllid-resistant Leucaena hybrid for northern Australia - Phase 2
Leucaena (Leucaena leucocephala) pastures for beef cattle production are productive and sustainable but susceptibility to the psyllid insect (Heterospylla cubana) has limited expansion of current commercial cultivars into more humid areas (>800 mm/yr) (Shelton & Dalzell 2007). Psyllids also cause intermittent damage in lower rainfall regions during humid periods. The psyllid, which arrived in Australia in 1986, is a leaf sucking insect specific to the Leucaena genus, feeding on the growing tips of susceptible cultivars (Bray 1994). Psyllid damage can reduce production by 50-70% in humid regions and 20-50% in sub-humid environments (Bray 1994, Mullen and Shelton 2003).
Control of the insect is possible by aerial spraying but breeding for resistance is a more desirable approach. Work on psyllid resistance in the Leucaena genus through the 1990s showed that several Leucaena species including the tetraploid L. pallida were resistant (Mullen et al. 2003). A breeding program to develop psyllid resistant varieties began in 2002 at The University of Queensland (UQ) based on the F1 inter-specific hybrids between L. leucocephala and L. pallida (KX2) developed at the University of Hawaii in the 1980s and 1990s.
Between 2002 and 2005, UQ initiated a program of recurrent selection in an attempt to produce stable outcrossed KX2 lines but inbreeding depression for yield and poor forage quality led to a change in the breeding strategy, and a backcrossing program was implemented between 2005 and 2008. Two cycles of backcrossing to elite L. leucocephala ssp. glabrata material were completed. Phase 2 of the breeding program required two cycles of progeny testing and selection for self-compatibility to achieve stability and uniformity (2009 to 2013). The objective was to select the best line (s) for release to industry.
This page was last updated on 29/06/2017
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