The progamic phase, embryo and endosperm development in an intraspecific Tulipa gesneriana L. cross and in the incongruent interspecific cross T. gesneriana × T. agenensis DC.

Abstract

The development of the embryo and endosperm has been investigated in an intraspecific Tulipa gesneriana cross and in the incongruent cross T. gesneriana × T. agenensis at intervals of 10 days, from 12 to 82 days after pollination (DAP). In both tulip crosses, the zygote gives rise to an apparently undifferentiated cell mass, the proembryonal cell mass, on which a suspensor then develops. Subsequently, a globular embryo is formed on top of the suspensor. This embryo finally elongates, giving rise to a spindle-shaped embryo. The cellular endosperm fills the whole embryo sac in mature seeds, except for a region immediately around the embryo. In both crosses, aberrant developments were found. In the intraspecific T. gesneriana cross, the pollen tubes did not open in a number of ovules. In other ovules, the pollen tubes seemed to have opened, but an embryo or endosperm was not found or only endosperm was observed. In the cross T. gesneriana × T. agenensis, fewer pollen tubes entered the ovules than in the intraspecific T. gesneriana cross. The ovules with embryo and endosperm formation of the incongruent interspecific cross showed, in general, retarded development in comparison with the intraspecific T. gesneriana cross. The first globular embryos and spindle-shaped embryos were found at the later fixation dates and the relatively lower number of spindle-shaped embryos at 82 DAP had a shorter average length. The number of ovules with deformations in embryo and/or endosperm development was also higher in the cross T. gesneriana × T. agenensis in comparison with the intraspecific T. gesneriana cross. Between 87% and 100% of the ovules with embryo and endosperm development showed normal development in the intraspe-cific T. gesneriana cross, while in the incongruent interspecific cross, from 22 DAP, between 17% and 56% of the ovules showed normal development. Of those ovules with aberrations in embryo and/or endosperm formation, about 80% had a deformed endosperm, of which more than 50% also contained a deformed embryo. Embryos of the incongruent cross might be saved by the application of embryo rescue techniques.& k w d : Key words Interspecific hybridization · Embryo development · Endosperm development · Tulipa& b d y :

Hybridisation between Brassica napus L. and Raphanus raphanistrum L. under agronomic field conditions

“…The successful formation of an embryo is not only dependent on fertilisation but also on normal development of the endosperm. The endosperms of intraspecific and interploidy crosses often develop abnormally when there is a deviation from a 2:1 maternal to paternal ratio (Masuelli and Camadro 1997;Vancreij et al 1997;Scott et al 1998). Interspecific crosses are more complex and have led to the development of the EBN hypothesis (Johnston et al 1980;Ehlenfeldt and Ortiz 1995;Carputo et al 1999).…”

New Aspects of Tulip Breeding: Embryo Culture and Polyploid

“…T. fosteriana belonging to section Leiostemones, subsection Eichleres is second position in commercial markets. Wide interspecific hybridization has attempted to improve agronomic trait such as disease resistance, strong growth vigor and special flower colors (Upcott and Philp, 1941;Kho and Baër, 1971;Hagiya, 1971;Van Eijk et al, 1991;Van Creij et al, 1997a, b, 1999. Crosses between species of the two sections have not succeeded thus far, but crosses between subsection Gesnerianae and subsection Eichleres are partially compatible.…”