Agriculture Reference
In-Depth Information
Storage technology is now cultivar-specific and is designed not just to extend
the time for which the apples will remain firm and juicy but also to extend
the period over which they retain their flavour and aroma. The characteristic
aromaof'Cox'sOrangePippin',forexample,wasreducedbyultra-lowoxygen
(
%O
) storage even though this improved firmness. A brief raising of
storage O
concentration to
.
% was found to maintain aroma without loss
of firmness (Smith,
). Similar development of 'dynamic' storage regimes
has been done to extend the period of storage over which 'Gala' can retain
its capability to emit its characteristic aroma volatiles (Mattheis and Fellman,
). Such developments are likely to add weight to the concept of flavour
being a major discriminant between cultivars.
Apple cultivar yield
High yields, beginning in the early years after planting and continuing on a
regular basis without excessive biennial bearing, are an important but not a
sufficient criterion to establish the popularity of a cultivar. Many production
costs,e.g.thoseofpruning,pesticidespraying,grass-mowingandherbicideuse,
are effectively on a per-hectare basis independent of yield as are most farm
overhead costs. The cost of production per kilogram therefore rises markedly
as yields fall. However, many costs, e.g. storage and transport, are post-harvest
and per kg of fruit and, most importantly, the volume of apples which can
be sold at any given price depends on customer demand for the particular
cultivar, i.e. on customer perceptions of its quality (O'Rourke,
). It is
notable that the very popular apple cv. 'Red Delicious' is classed as only fair
for precocity and productivity (on a scale of poor, moderate, fair, good and very
good) and shows a moderate degree of alternate bearing (Westwood,
).
Much can be done to improve productivity by choice of rootstock, selection
of improved clones and development of appropriate cultural practices. Large-
fruited cultivars may give higher sustainable yields because the adverse effect
of heavy cropping on yield in the following year is largely due to seed and
hence fruit numbers, not yield
per se.
Climatic factors may determine which
cultivars yield well in different areas (cf. pp.
-
).
Apple cultivar tree vigour and growth habit
Orchards of large trees are slow to come into cropping and are expensive to
manage at maturity. In general this problem is solved by the use of dwarf-
ing rootstocks (see pp.
) and no cultivar has attained importance in
commercial fruit growing because of its compact habit or high ratio of yield to
tree size. However, there has been very effective selection of compact or spur-
type mutants within many of the important cultivars, usually giving trees about
two thirds of the size of the original cultivar. Also, compact habit has been the
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