Preliminary Assessment of G-755c Root Rot Resistant Avocado Rootstock on the Far North Coast of New South Wales, Australia

Root rot caused by Phytophthora cinnamomi is the main limiting factor to avocado production in most parts of the world. Control measures recommended in New South Wales (Allen 1984) have included close attention to site selection in regard to drainage, exclusion of the pathogen, judicious use of fertilizers and fungicides, and encouragement of biological antagonists through soil amelioration. Choice of rootstock has not been of great significance, even though sources of mild resistance have been identified in Californian research (Zentmyer and Schroeder 1951) and some of these sources have been available in New South Wales for many years. In 1984 however, a potentially highly resistant rootstock cultivar (G-755c) became available from California for evaluation under commercial conditions in New South Wales.