Pear mutagenesis: in vitro treatment with gamma-rays and in field selection for productivity and fruit traits.

In vitro shoots of six pear (Pyrus communis L.) cultivars, Conference, Doyenné d'Hiver, Passe Crassane, Bartlett, Abbé Fetel and Butirra Precoce Morettini were irradiated with gamma rays (3.5 Gy). After three subcultures, microcuttings from the irradiated shoots and from additional non-irradiated microcuttings were rooted to establish plants for survey orchards. All trees were individually observed for variation in fruit traits and for productivity. Trees were selected for improved characters related to production such as early bearing and consistent productivity. Variations observed in fruit appearance concerned degree of russeting, fruit shape and size. The frequencies of the observed variations in fruit traits depended on the cultivar, ranging from 0.81% in Doyenné d'Hiver to 3.64% in Passe Crassane. Of the 97 variants selected, only two showed chimeral behavior.