A new method for differentiation in the screening of similar avocado selections in the quest for tolerance to Phytophthora cinnamomi
2014
Bijzet, Z. | Sippel, A. D.
The avocado rootstock-breeding programme of the ARC-Institute for Tropical and Subtropical Crops aims to develop a range of avocado rootstocks tolerant to Phytophthora root rot. A detached root inoculation method (Van der Merwe, 1995) was only able to eliminate 45 of 91 original selections. An additional method was needed, as the remaining number of selections was still too high to be promoted to the field. The 46 seedling selections, remaining after the detached root inoculation method, were clonally multiplied by the method of Moll and Wood (1980). Of the 46, only 14 selections could be etiolated successfully and thus be multiplied for the trial. Comparison of feeder root percentage in non-inoculated and inoculated treatments was insufficient to facilitate the final selection of candidate rootstocks from a large number of potential selections with initial characteristics similar to that of the standard rootstock Duke 7. A new method for differentiation of the apparently similar selections on the assumption that a larger root system will be a better forager and thus enhance the horticultural aspects of the rootstock scion combination is discussed. The four best selections were identified. This method will identify the selections with an ability to maintain root regeneration in the face of P. cinnamomi pressure over time.
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