Effects of rootstock and crop load management on yield and fruit quality of early-season nectarine 'Rose Bright' and late-season peach 'September Sun'

The Australian summer fruit industry has identified that sales growth is impeded by low consumer satisfaction with fruit quality, leading to low prices and static consumption. The effect of rootstock and crop load on fruit production was studied in an experimental orchard at Tatura, Australia. The objective of the study was to identify combinations of rootstock and crop load management practices, under a vase training system, to enable peach LSQUOSeptember SunRSQUO and nectarine LSQUORose BrightRSQUO to maximise fruit quality. Crop loads were applied to induce a range of competitive source/sink responses between fruits and available assimilates. Different thinning regimes were implemented in season 2016/17 to establish the following crop load treatments: 1) high: minimally thinned; 2) medium (commercial standard as control): moderately thinned; and 3) low: heavily thinned. Rootstocks included Nemaguard (commercial standard as control), Elberta, Krymsk^® 86, Cadaman^® and Cornerstone. Crop load and rootstock did not affect flowering date. LSQUOKrymsk^® 86RSQUO produced smaller tree size measured as canopy radiation interception (f_PAR) for both cultivars. For nectarine, high crop load produced high yields, low fruit weight, reduced sweetness (°Brix), delayed maturity, increased firmness and lower pack-out percentage. Krymsk^® 86 outperformed Elberta rootstock in terms of fruit size, red skin coloration and pack-out. For peach, highest yield occurred on Cornerstone trees compared to Elberta. This yield difference was reflected in yield components (fruit number, fruit size), and attributed to the capacity of available fruiting wood and photosynthetic capability governed by tree size (f_PAR and branch size). Irrespective of cultivar, low crop load produced larger fruit and advanced maturity. Cornerstone produced sweeter fruit, while Krymsk^® 86 had lower sweetness with greater red skin coloration. In autumn, earlier leaf drop (senescence) occurred under high crop loads and on Elberta rootstock. Presence of rootstock suckers was greatest on Krymsk^® 86 and Nemaguard trees, while crop load did not impact suckers.