Factors of intersectional unilateral cross incompatibility between several evergreen azalea species and Rhododendron japonicum f. flavum

Abstract

The mechanism of unilateral cross incompatibility in the reciprocal crossings between several evergreen azalea species and R. japonicum f. flavum behavior of pollen tube growth in the styles was studied. In crossings using evergreen azalea as seed parents, straight, thin pollen tubes elongated into the lower portion of style within 96 hr after pollination, but in those using R. japonicum f. flavum as seed parents, the pollen tube with abnormal morphology were arrested in the upper portion of the styles. These results indicate that the cross incompatibility of R. japonicum f. flavum x evergreen azaleas is accompanied by abnormal pollen tubes and a restriction of their growth in the upper portion of the style.