European pear

Abstract

Among the fruit tree species, the European pear (Pyrus communis L.) has the most stable cultivar structure. Although the selection activity in the last several centuries has produced several hundred cultivars, only a few pear cultivars are currently grown. Within the Pomoideae (Pyrinae) there are 22 Pyrus species, along with another ten or so that have been variously described and assignable to synonyms of the more important species. Perhaps the most widely known species, if not the most widely cultivated, is P. communis L. The European pear is essentially the only Pyrus species currently grown in Europe while in North America both the European and the Oriental pear are grown. The European pear and its ancestral species, P. pyraster Burgsd., grow wild throughout Europe, and it was here where it was domesticated as early as 300 bc. The pear and apple appear to be amphidiploid or allotetraploid species, i.e., those formed by the gametic union of two Rosaceae species of 8 and 9 chromosomes. The high level of genetic recombination combined with selection for fruit size, appearance, flavor, postharvest storability, and resistance to pathogens and diseases has resulted in a diverse array of cultivars. There has been major advances in fruit appearance (shape, color, attractiveness), size, ripening season (summer and fall are predominant) and postharvest traits. Much effort is being invested by researchers to find resistance genes to the main biotic adversities of pear: the fire blight bacterium (Erwinia amylovora), the European pear psylla (Cacopsilla pyri), which is the vector of the phytoplasma causing pear decline, the scab causing fungi Venturia pyrina, and the black spot fungus Stemphylium vesicarium.