A mutant chlorophyll‐reduced (Cr) seedling with yellow‐green cotyledons and leaves was obtained from the Brassica napus inbred line 3529 induced by fast neutron and diethyl sulphate (DES). Genetic analysis revealed that the Cr seedling marker trait was controlled by a pair of recessive genes. A randomized complete block design was used to evaluate its agronomic performance. Results from 2 years of tests indicated that the seed yield of Cr lines was significantly lower than that of normal green plants; however, when the Cr gene was in the heterozygous condition, no deleterious effects on yield characteristics and disease resistance were observed. The Cr seedling marker trait was introduced into male‐sterile lines, and Cr male‐sterile lines revealed the same superior combining ability as normal chlorophyll (Nc) lines. The Cr trait can therefore be used as a marker to produce hybrid seed.
The floral organ morphogenesis of the apetalous flower mutant Apet33-10 in Brassica napus was investigated and the result showed that all the floral organ morphogenesis was normal except that petal primordium was not observed during flower development. Eighteen genes were found to be down regulated in early floral buds (less than 200 mum in length) of Apet33-10 at the stage of floral organ initiation by means of suppressive subtraction hybridization (SSH) and RT-PCR. These genes were involved in petal identity, calcium iron signal transduction, mRNA processing, protein synthesis and degradation, construction of cytoskeleton, hydrogen transportation, nucleic acid binding, alkaloid biosynthesis and unknown function. Three overall coding region cDNAs of APETALA3 (AP3) gene, BnAP3-2, BnAP3-3 and BnAP3-4 were obtained by RT-PCR, respectively. Real-time quantitative PCR analysis showed that the expression ratio among BnAP3-2, BnAP3-3 and BnAP3-4 was 3.67:3.68:1 in early floral buds of wild type Pet33-10. The expression level of BnAP3-2, BnAP3-3 and BnAP3-4 in early floral buds of Apet33-10 was down-regulated to 36.6, 28.3 and 66.8% with the comparison of that of wild type, respectively, and the overall expression level of AP3 genes in apetalous mutant amounted to 45.0% of that in wild type. The difference in the expression level of each AP3 gene in stamen between apetalous and wild type lines was not significant. It is suggested that lower abundant expression of AP3 genes during the early flower development might be enough for stamen primordium initiation, but not enough for petal primordium initiation in the apetalous line Apet33-10.
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