The Preliminary Research Of The Development Of Navel Orange's Secondary Fruit

Studies on the development of floral organs have become a hot point in modern molecular biology researches. There has been recently a significant progress in this area with model plants, such as Arabidopsis, Snapdrogen. However, related areas are less concerned in woody plants. The experimental materials included Jin Cheng, Cutter Valencia Orange, Dream Navel Orange, Skaggs Bonanza Navel Orange. By Morphological observation and gene expression analysis, this experiment aimed at origin of navel structure in the orange fruit. The main results are summarized as follows:1. Through the observation of paraffin sections and Scanning electron micrographs, the floral bud morphodifferentiation of navel orange and common orange was compared. The results showed that the undeterminate floral meristem of navel orange after pistil primordia appearance produced excess stem cells, which might be the direct reason of navel. As seems to mean that the critical period of the formation of navel was the time when pistil primordia appeared.2. Based on previous researches in model plants, many presumptive genes were chosed to test their expression patterns, using semi-quantitative RT-PCR and Real time RT-PCR. The results showed that WUS2,LFY,AP1,KNU expressed significantly higher in navel than in common orange, which inferred those genes might have a relation to the generation of navel structure. Especially when connected with researches in model plants, the rise of WUS2 in navel orange meant it had a close relationship with the navel's generation. WUS/AG pathway might play an important role in the navel's emergence.3. The full cDNA/DNA sequences of AG and WUS were isolated from navel oranges and the common oranges. The sequence comparison between them showed there were little differences, as suggested that the emergence of navel might not be caused by the sequence differences of WUS and AG.