Flower morphology of Nashi pear in regions of intermediate and high chilling units in southern Brazil

This work had the objective of comparing the flower morphology of three Nashi pear (Pyrus pyrifolia var. culta) cultivars grown under two different climatic conditions in Santa Catarina State, Brazil. These different climatic conditions were a medium chilling units (MCU) site at Cacador (with 1.000 CU) and a high chilling units (HCU) site at Sao Joaquim (with 2.000 CU) during the winter of 2007. The three cultivars evaluated at each site were 'Housui', 'Kousui' and 'Nijisseiki'. At the coldest site, lateral buds on 1-year-old branches produced larger numbers of scales per flowering bud. Conversely, at the warmer site, larger numbers of sepals and petals were produced in individual flowers. Furthermore, larger numbers of long stigmas and larger numbers of anthers were produced at this warmer site. Under these warm climatic conditions, the flowers thus showed abnormal development, with potential implications for reduced fruit productivity. The three cultivars responded differently, with 'Kousui' producing more petals, pistils (stigmas and styles) and anthers than 'Housui' and 'Nijisseiki'. In Nashi pear breeding for regions with inadequate chilling units (CU), such as Cacador, the length of the peduncle does not seem a useful selection criterion for climatic adaptation.