Disease Resistance in Polyploid Strawberry

Abstract

Strawberries are produced commercially in 76 countries. China is the largest producer and the top five producing nations also include USA, Mexico, Turkey and Spain. Production continues to increase, particularly in Asia, North and Central America, and North Africa with a matching increase in demand in many parts of the world. The development of the strawberry industry in California in the twen- tieth century was followed by rapid expansion of local industries in many other parts of the world including the Mediterranean region, Central and South America, Australia and China. In all of these regions, it was possible to identify the areas where a combination of short days with warm or mild temperatures made it possible to produce high yields over a long season. Plant breeding has had a very significant role in increasing the geographical adaptation of strawberries. The most notable achievement has been to transform the crop from a plant with a short season of production and a modest yield of small, soft berries to a highly productive plant capable of cropping over a long period with large, firm berries suitable for shipping over long distances. Berries have been grown for food for over 2000 years and before that would have been an important part of the human diet when harvested from the wild. Commercial production of berries began to become important in the early part of the nineteenth century following the breeding of improved cultivars of the cultivated strawberry (Fragaria ? ananassa), while raspberries fol- lowed several decades later in the century after the hybridisation of the European and North American sub-species of the red raspberry (Rubus idaeus). Both types of berry became important crops initially in western Europe and North America but were characterised by short seasons of only a few weeks. During the twen- tieth century, production gradually spread to many other parts of the world and berry crops steadily increased in their economic importance, particularly in the post-war period when improved cultivars and new agronomic practices resulted in an extension of the production season.