pdf wkg Dav.14-14 - Davidsonia

Davidsonia 14:4
147
chilling requirements necessary to break dormancy. Even in climates that
are optimal for present production, such as the Pacific Northwest, more
plantings are to be found on heavier, poorly drained soils where Phytophthorainfected
root rots can be devastating. The wide range of habitats, in which
plants of the wild species flourish, indicates the presence of variability that
can eventually meet the requirements of many of the diverse environments
in which red raspberry culture now takes place or will take place in the future.
Concomitant with the urgent need for more pest and disease resistances
and wider environmental adaptations, unique market outlets for red raspberry
fruit are being developed (Finn and Knight, 2002). There are few fruits that
give rise to as many popular processed products. For example, raspberry
juice by itself or in blends with other fruit such as cranberry, has become
popular. Raspberry jam has always been popular and fruits processed into
ice cream and yogurt and as whole “individual quick freeze” are equally
popular. Consumers demand that fresh red raspberries be available for 12
months of the year, just as strawberries and apples are. This has stimulated
production in the Southern Hemisphere, where fresh fruit is air-freighted to
the Northern Hemisphere from November through to April. Greenhouse
and tunnel production for “out-of-season” fruit has also increased (Pritts et
al., 1999). Recently there has been increased recognition of the health value
of red raspberries, which have high levels of antioxidants or “nutraceutical”
compounds such as anthocyanins, phenolics and ellagic acid, each of which
is reported to be effective against the effects of the degenerative diseases of
aging (Finn and Knight, 2002). Red raspberries figure prominently in
advertisements for cereals and other products that are equated with healthy
diets.
In recent years, the Agriculture and Agri-Food Canada red raspberry
breeding programme at the Pacific Agriculture Research Centre (PARC) has
been using selections from previously unexploited populations of R. strigosus
(Daubeny, 2002). Seedling populations of the species were obtained from
sites in BC, the Yukon, Ontario, Quebec, Nova Scotia, Washington,
Minnesota, Wisconsin, New York, and North Carolina. Most seedlings were
initially screened for reaction to the aphid, Amphorophora agathonica, a vector
of the raspberry mosaic virus complex. This complex can have a devastating
effect on growth and fruiting of susceptible cultivars and the easiest way to
control it is through vector resistance. Genes giving resistance to the aphid