Anatomical observations of anther development of NCa, a cytoplasmic male sterile line in rapeseed( Brassica napus L.)

A cytoplasmic male sterile (CMS) line, named NCa, was obtained from the backcrossing descendents of hybridization between two amphidiploid species of Brassica napus L. (AACC, 2n =38) and B. carinata (BBCC, 2n =34), respectively. The anatomical observations on the anther development of NCa by light microscope and transmission electron microscope showed that the abortion of the anther development occurred at the later mono-nucleus microspore (MNM) stage. The microspore mother cell of NCa could pass through meiosis and form tetrads and then tetrads could release microspores as the same as the fertile line. The released microspores with one nucleus could continuously develop and form pollen wall soonly. The protoplast and nucleus of MNM degraded in succession and just left the empty pollen wall at last or with large vacuoles. The tapetum development was similar to that of the fertile anther up to tetrad stage but after that the protoplast of tapetal cell was rich in small vacuoles and degenerated gradually. Anther development of NCa sterile line was obviously different from all of the other kinds of CMS lines examined before, because its abortion stage revealed here was later than any of the examined CMS types and it formed pollen wall soon after microspores released and remained that until pollen degradation.