Glasshouse studies of inherent root growth of seedling avocado rootstock cultivars

Abstract

In order to mimic loss of root function caused by Phytophthora cinnamomi, differences in inherent root growth of avocado seedlings of ten different rootstock cultivars across the three ecological races were investigated. A 2-pot root harvesting system was used and roots were harvested at three different intervals to assess tolerance to root removal. Seedling 'Velvick' produced the largest amount of harvested roots. However, when results were standardised by the total area of mature leaves, there were no significant differences found between rootstock cultivars in cumulative, root growth. Relative to total photosynthetic area, cultivars 'Kidd' and 'Fuerte' (produced the most roots in the absence of root trimming. Overall, increased trimming decreased cumulative root output (P<0.001). For root growth of harvested roots, significant interactions were observed between cultivars and trimming treatment, with the cultivar 'A10' best able to withstand regular mechanical root removal. Significant interactions were also observed between cultivars and trimming treatment for the parameter of root diameter. Most cultivars generally produced thicker roots over time, except for varieties 'Reed' and 'Velvick', for which the average thickest roots were the youngest. Regressing dry weight of harvested roots with projected area in root images, 'Velvick' seedlings had the steepest relationship while 'Edranol' roots had the flattest.