TITLE:
Phytopigments, Proline, Chlorophyll Index, Yield and Leaf Nitrogen as Impacted by Rootstock, Training System, and Girdling in “Aztec Fuji” Apple
AUTHORS:
Esmaeil Fallahi, Shahla Mahdavi, Clive Kaiser, Bahar Fallahi
KEYWORDS:
Canopy Architecture, Cambium Ringing, Growth Control, High Density Orchards, Malus x domestica
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.10 No.9,
September
17,
2019
ABSTRACT: World overpopulation, scarcity
of water and finite arable land mandate a more efficient use of these natural resources. To
remain sustainable, modern-day apple (Malus domestica Borkh.) fruit production utilizes high-density orchards on semi-dwarfing, precocious rootstocks. Nonetheless, little attention has been paid to the
use of size-controlling practices such as trunk girdling in these modern
orchard systems. The impact of two rootstocks, two tree architecture (training) systems, and three levels of girdling (in
spring) on chlorophyll index (CI), proline,
chlorophyll content (Chl; a, b, a + b),
carotenoids, anthocyanin, yield, fruit weight and leaf nitrogen (N) in “Aztec
Fuji” were studied in 2015 and 2016. Trees on “Bud 9” had up
to 5% higher chlorophyll indices in leaves on side branches than those on “Nic
29” at each sampling time in 2015 and 2016. However, trees on “Nic 29” had up
to 5.5% chlorophyll index in terminal branches, 14% higher Chl b, 54% higher leaf
proline in 2015, up to 5% higher leaf nitrogen
(N) in 2015 and 2016, 82% higher yields in 2015, and up to 7% higher fruit
weight in 2015 and 2016 than those on “Bud 9”. Trees trained into a central
leader (CL) architecture had up to 6% higher chlorophyll index and 4%
higher leaf N in terminal branches 2015 and 2016, 43% more terminal leaf
proline content in 2015, but 13% less yield in 2016 than those with a tall spindle training (TS). Terminal leaves from trees receiving a bark girdling in 2015 (BG15) had up to 6.5% lower leaf N, 7% less chlorophyll index, and between 27% to 56% lower proline content than those from the ungirdled check and
score girdled treatment in 2015 (SG15). Also,
trees with BG15 and a bark girdling in both 2015 and 2016 (BG1516) treatments
had significantly less leaf N concentration than all other treatments or the ungirdled check.
Trees that were score girdled in 2015 and repeat score girdled in 2016 (SG1516) had 21% higher yield and 12%
higher fruit weight than those that were ungirdled.