The Female Fertility of Triploids in Lilium —Euploid and 5-Same-Genomes of Endosperm Are of Ensence

Triploid is usually sterile because it has abnormal meiosis and mainly produce aneuploid gametes with wide range of chromosomes. However, a special phenomenon was observed in Liliumhybridizations, i.e.,  most triploid lilies can be used as maternal parents to cross with diploid or tetraploid ones while the triploids are completely male sterile. By analysis, it is concluded that lily tetrasporic embryo sac is the reason for that. From tetrasporic embryo sac formation, we can deduce that triploid lilies usually produced aneuploid eggs but invariably hexaploid secondary nucleus. After double fertilization with diploid or tetraploid lilies, their embryos are usually aneuploid but endosperm inviarably euploid. Because euploid endosperm posses balanced chromosome numbers and then, it usually develops well, thus it could make aneuploid embryos survial. From more allotriploid x diploid/tetraploid lily hybridizations, we observed that the endosperm usually develops well when it contains at least 5-identical-genomes, otherwise, it aborts or hard develop. Based on the experimental results and analyses, we proposed a new hypothesis that five same genomes of endosperms are essential for its development in triploid x diploid/tetraploid crosses of Lilium. The hypothesis can explain the success or failure of 3x x 2x/4x crosses in Lilium and is of importance for lily breeders who need to know the likelihood of success when producing new cultivars of this economically important horticultural crop. For details, please refer to HortScience 2011 46(4), Euphytica 2012 184(3), JASHS 2013 138(2).

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