GLOBAL PEAR BREEDING PROGRAMMES: GOALS, TRENDS AND PROGRESS FOR NEW CULTIVARS AND NEW ROOTSTOCKS

Fruit crops rely on the introduction of new cultivars to revitalise and provide consumers with superior products. Consumers and growers have been slow to adopt new pear cultivars compared with many competing fruit crops. This is in part because of the long juvenility period and long time frame to introduce a new cultivar from conception to market, but could also reflect the lack of real novelty of new products. Pear breeders have to take a long-term view of what consumers and growers require. In the future, breeders will use a combination of traditional methods and aspects of biotechnology including the development of molecular markers to increase the speed of development of new cultivars. Consumer trends and demands are increasing for more environmentally friendly products. This fits very well with the current emphasis of many pear breeding programmes on pest and disease resistance, which will reduce chemical inputs into the crop. Fire blight and psylla resistance breeding have received special attention in North America and Europe because of the devastating effects they can have on crops, the difficulty of their control and the cost to growers. Resistance to pear scab, Venturia pirina Aderh., which infects European pear and Venturia nashicola, which affects Asian pear, is also important worldwide. Fruit quality and appearance are important to all breeding programmes. In the New Zealand interspecific hybridisation programme incorporating European and Asian species, fruit quality is combined with convenience to develop fruit with high flavour that do not require chill induction for ripening in addition to pest and disease resistance. Breeding targets that are especially important to growers include spread of harvest season, adaptation, self-fertility, yield and growth habit.
Pears still lag behind apples in the availability of a wide range of growth-controlling rootstocks that are easy to propagate and fully graft compatible. Although some encouraging reports have emerged of Pyrus rootstocks that might provide progress in this area, more widespread testing has often failed to support the early promise. Lack of resistance to pear decline may be part of this failure. Europe continues to rely heavily on quince rootstocks for high density planting systems, except in areas of high soil pH. Other pear-growing areas with colder winters are not so fortunate, and the limited range of size-controlling Pyrus rootstocks has held back intensification of production. Pear rootstock breeding programmes are seeking to fill these gaps, but progress to date has been slow.