The importance of induced mutations in pear improvement

Pear production is firmly established on a limited number of well-known cultivars that appear to fulfill the requirements of the market. The pear consumer accepts more easily improvements in a standard cultivar than those that are completely new. Spontaneous and induced mutations can be of importance for pear breeding in the improvement of single traits of an already outstanding cultivar. But on the other hand, since the most appreciated pear cultivars have high degrees of heterozygosity, cross-breeding leads to high degrees of variability in the progenies, thus making troublesome the selection of new genotypes using this traditional method. Many important traits have been introduced through mutagenesis such as plant size reduction, early ripening, fruit color change, changes in blooming time, and changes in fruit quality, despite the low number of cultivars that became established commercial varieties. Variations in vegetative and fruit traits were observed in experimental orchards planted with about 5,000 self-rooted trees derived from in vitro gamma-ray irradiated shoots. Some of the observed changes improved the original cultivars allowing for an easier size control (variants for reduced size). Variants for increased sugar content and for extended shelf-life have also been found, showing that mutagenesis can change various economically important traits, thus contributing to pear breeding. The use of in vitro methodologies, the exploiting of somaclonal variation, and the setting up of early selection methods could make induced mutation techniques more reliable. The current interest in the development of induced and spontaneous interesting pear mutants is attested by a number of recent reports originated from most pear-growing countries in the world. Induced-mutation breeding has intrinsic limitations, but also offers good prospects for further contributions to pear cultivar development and improvement.