Articles
Factors of difference in intra- and inter-ploid cross compatibility in asparagus
Article number
1376_3
Pages
15 – 22
Language
English
Abstract
To clarify the cause of the differences of cross compatibility among 2x, 3x and 4x asparagus, pollen fertility and pollen tube behaviors in the styles and ovaries were investigated.
Percentage of morphologically complete pollen was high in all the ploidies, but there was a large difference of the pollen germination rates (2x>4x>3x) on the artificial medium.
Differences in pollen tube elongation in the styles were observed due to differences in the ploidy of the pollen parent, but no differences in pollen tube elongation due to the ploidy of the seed parents were observed, indicating that differences in pollen tube behavior did not affect fruit set rate and number of seeds obtained.
Number of ovules in an ovary was six in all diploid female flowers, but it showed variation from six to nine with morphologically abnormal ones in higher ploids, especially triploid plants.
Embryos developed normally and vascular bundle formation was observed after 30 days of crossing in the cross between diploids, but most of the embryos were abnormal or degenerated in 2x×4x after 30 days of crossing.
When triploids were used as seed parents, a large number of embryos with abnormal morphogenesis were observed after 30 days of crossing.
A similar trend was recognized in the development of the endosperm.
From these results, it was suggested that most of the seeds of 2x×4x cross become empty because the embryo is not supplied with sufficient nutrients due to insufficient development of the endosperm.
The morphological abnormality of the ovules was also observed in many of the triploid and tetraploid female flowers, suggesting another factor of the difference in intra- and inter-ploid cross compatibility.
Percentage of morphologically complete pollen was high in all the ploidies, but there was a large difference of the pollen germination rates (2x>4x>3x) on the artificial medium.
Differences in pollen tube elongation in the styles were observed due to differences in the ploidy of the pollen parent, but no differences in pollen tube elongation due to the ploidy of the seed parents were observed, indicating that differences in pollen tube behavior did not affect fruit set rate and number of seeds obtained.
Number of ovules in an ovary was six in all diploid female flowers, but it showed variation from six to nine with morphologically abnormal ones in higher ploids, especially triploid plants.
Embryos developed normally and vascular bundle formation was observed after 30 days of crossing in the cross between diploids, but most of the embryos were abnormal or degenerated in 2x×4x after 30 days of crossing.
When triploids were used as seed parents, a large number of embryos with abnormal morphogenesis were observed after 30 days of crossing.
A similar trend was recognized in the development of the endosperm.
From these results, it was suggested that most of the seeds of 2x×4x cross become empty because the embryo is not supplied with sufficient nutrients due to insufficient development of the endosperm.
The morphological abnormality of the ovules was also observed in many of the triploid and tetraploid female flowers, suggesting another factor of the difference in intra- and inter-ploid cross compatibility.
Publication
Authors
Y. Ozaki, C. Fujita, K. Narikiyo, Y. Sakaguchi, K. Tomiyoshi, Y. Mizunoe, H. Okubo
Keywords
embryo, endosperm, fruit set, pollen germination, pollen tube growth
Groups involved
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