Endogenous Hormones in Seeds, Germination Behaviour and Early Seedling Characteristics in a Normal andoguraCytoplasmic Male Sterile Line of Rapeseed (Brassica napusL.)

Abstract

Endogenous hormones, namely cytokinins (CKs), indole-3-acetic acid (IAA) and abscisic acid (ABA) were quantified by specific enzyme-linked immunosorbent assay (ELISA) in the mature seed of normal (cv. Westar) and ogura (ogu) cytoplasmic male sterile (CMS) lines of rapeseed (Brassica napus L.). Dihydrozeatin (DZ) and dihydrozeatin riboside (DZR) were the major CK base and riboside, respectively, in seeds of both the normal and ogu CMS lines. The normal seed had more than 4-fold DZ levels in comparison to that of ogu CMS. On the other hand, the ogu CMS seed had higher levels of CK o-glucosides and CK. nucleotides than normal seed. Seeds of the normal line contained 5-fold more IAA but had one-quarter the level of ABA in comparison to those of the ogu CMS line. The normal line also had greater seed diameter and weight than the ogu CMS line and the normal seed germinated earlier than the male sterile seed. DZ (10−6 M) promoted the germination of ogu CMS seeds, but it was not comparable to that of the normal line. ABA (10−6 M) inhibited seed germination of ogu CMS but had little effect on the normal line. The normal seedlings had shorter primary roots, more lateral roots, longer hypocotyls, greater cotyledon fresh weight and higher chlorophyll levels in comparison to ogu CMS seedlings. Exogenously supplied DZ, IAA and ABA affected the various parameters of both the normal and ogu CMS seedlings, but in most cases did not fully restore the differences in the two lines. The results presented show that in the ogura cytoplasmic male sterile line of B. napus (1) a number of seed and seedling characteristics are affected, and (2) the altered seed morphology is accompanied by changes in the levels of various hormones.