Agriculture Reference
In-Depth Information
tasty apple varieties that are highly susceptible to pest and disease problems
and necessitate enormous inputs of chemicals and labor to control. For sus-
ceptible varieties in humid areas, for example, a grower may need to apply
15 fungicide sprays per year to control apple scab.
In the 1990s, a group of some of the finest fruit scientists of the twentieth
century stated in
Genetic Resources of Temperate Fruit and Nut Crops
: “In
commercial apple orchards, spray chemicals plus their cost of application
can often be as much as a quarter of the total cost of production. Unfortu-
nately, sprays frequently do not give complete control of pests and therefore
there is often economic loss despite spraying.”
Alarmingly, the narrow genetic base is rapidly becoming narrower as
growers focus on a few varieties with strong market appeal. Despite the fact
that apples are grown on a large commercial scale in at least 63 countries
and we have thousands of varieties to choose from, only a few dozen vari-
eties are widely grown commercially worldwide, largely based on 'Delicious'
and 'Golden Delicious' strains. While newer varieties are beginning to domin-
ate the market, many of them also tend to be highly prone to diseases. Even
worse, many heirloom varieties are being lost as germplasm collections are
reduced due to budget shortages.
All is not gloom, however, and breeding programs are now producing
high-quality, disease-resistant apples. One of the best programs for apples
is the PRI Disease Resistant Apple Breeding Program, a cooperative among
Purdue University, Rutgers, and the University of Illinois. This program has
produced more than 1,500 selections and released 44 varieties, including
'Prima', 'Priscilla', 'Jonafree', 'Redfree', 'Dayton', 'William's Pride', 'Enterprise',
'GoldRush', and 'Pristine'. The Canadian Agricultural Research Station in
Kentville, Nova Scotia, has released 'Novamac' and 'Nova Easygro.' Unfortu-
nately, many of these fine apple varieties have yet to become accepted by
large-scale apple growers.
Pollination.
Most apple varieties require cross-pollination in order to achieve
an abundant and reliable fruit set. Cross-pollination involves the female or-
