BARRIERS TO INTERSUBGENERIC CROSSES BETWEEN MUSCADINIA AND EUVITIS

Fluorescence microscopy was used to examine the unilateral intersubgen eric incongruity of muscadine grape (Muscadinia Planch.) x bunch grape (Euvitis Planch.). Pollen grains of bunch grape hydrated and germinat ed on the stigmas of muscadine grape. Healthy pollen tubes of the bunc h grape also penetrated the stigma and entered into the style without obstacles. However, most bunch grape pollen tubes were arrested in the style near the stigma, and few bunch grape pollen tubes were found at the base of the style, Barriers to the intersubgeneric crosses appare ntly occurred before fertilization; abortion of pollen tubes in the st yle was the major cause of failure for the cross of V. rotundifolia Mi chx. x Euvitis.