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Integrated screening for resistance to diseases and pests in lucerne breeding

Kaehne, J.A. Horsnell, E.T. Kobelt and B.M. Martin

Department of Agriculture, Northfield Research Laboratories, GPO Box 1671, Adelaide SA 5001

The persistence, productivity and quality of lucerne is limited in many regions of Australia by susceptibility to groups of identified pests and diseases. Lucerne performance is being improved by selecting individual parent plants by sequential exposure of seedlings to diseases and pests in an integrated screening programme, which is developed in five steps: (i) a known or suspected disease or pest is isolated; (ii) a reliable culturing technique is developed; (iii) a reliable inoculation technique for screening seedlings is developed; (iv) the inoculation technique is incorporated with inoculations with other diseases and pests, and (v) the integrated set of screens is tested for effectiveness against the identified diseases and pests. The integrated screening procedure is presented in Figure 1. Two temperature regimes are used so that lucerne seedlings can be challenged by each disease and pest within an optimum range for effectiveness.

Figure 1. The flow of lucerne seedlings through two temperature regimes during integrated screening.


Experimental cultivars developed from this procedure are more persistent, productive and less affected by foliar diseases than current commercial cultivars. The procedure ensures that previously achieved levels of frequency of resistance to factors in the screening sequence are not lost by genetic drift and may be further increased by selection when a new factor is added. The procedure has required the construction of breeding populations from which individuals which are resistant through all steps of the sequences may be selected.


This project has been supported by the Meat, Dairy and Wool Research and Development Corporations.

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