Embryologic Mechanisms of Sterility in Triploid Loquat

Anther structure, anther dehiscence characteristics, pollen viability, pollen germination, pollen tube growth and ovule structure of triploid loquat (Eriobotrya japonica Lindl.) were studied. Most anthers were immature, and a few anthers, though mature, could not dehisce on time. Connective parenchyma cells were thick, the anther chamber was small, the amount of pollen was very small, and most pollen (up histo 83.7%) was abnormal. All this resulted in a high degree of male sterility in triploid loquat. Pollen germination and pollen tube growth were generally altered, indicating that the pre-fertilization barrier was strong in triploid loquat. Anatomical observations showed an atypical structure of most ovules, including small embryo sac, stigma and degeneration of style, embryo sac, and ovule. This resulted in a high degree of female sterility in triploid loquat. Fertilization and embryo development did not occur regularly in abnormal ovules of triploid loquat, which resulted in very low fruit set after cross-pollination, and no fruit production under open pollination and self-pollination probably as a result of lack of hormones from seeds.