Biological Evaluation Of A Wax Deficient Mutant Of Newhall Navel Orange(Citrus Sinensis Osbeck’newhall’)

The cuticle is a layer of hydrophobic biological polymer membrane covered on the higher plants’ tissue surface, playing an important role in maintaining normal life activities of plants. When it changes, the biology traits, physiological function and anti-stress capability of plant may also change. In2005we found a mutant of Newhall navel orange in Anyuan, Ganzhou. Its leaves and fruits were clean, smooth and obviously shiny. Moreover it was proved to be wax deficient mutant and named as "Gannan No. I" and its resistance increased significantly compared to the wild type by preliminary analysis. In this study," Gannan No. I" was used as research material and the wild-type Newhall orange as a control, the differences of mature fruits’biological traits between them were compared systematically and the preliminary study on disease resistance of mutants was carried out.The main results were as follows:1." Gannan No. I " was experimentally identified as a spontaneous mutant of Newhall navel orange with stable traits by the morphological comparison, grafting and SSR analysis.2. The fruit color, gloss and firmness of "Gannan No. I" and the wild-type were compared by color-difference meter and TA-XT plus Texture Analyser. The results displayed that the "Gannan No. I" was redder and had shinier appearance than the wild-type, demonstrating "Gannan No. I" had improved the external quality and showed better commodity. The firmness of flavedos, segment, juice sacs and the whole fruit of "Gannan No. I" fruits was all dramatically higher than the wild-type.3. In pulp,the titratable acid content of "Gannan I" was significantly higher than the wild type; the soluble solid content, Vc content and juice rate of "Gannan I" were slightly higher than the wild type.4. The differences in physiological characteristic of fruits and leaves between the "Gannan No. I" and ordinary Newhall were compared. The results show that:There were no significant differences between "Gannan I" and wild-type on the respiration rate, but the mass loss rate of fruit and leaf of "Gannan I" is1time higher than that of the control. "Gannan I" fruit was more sensitive to the low temperature and it could suppress microbial growth on the surface on the cold storage.5. By observing in field,"Gannan I" trees were stronger than the wild-type and it showed stronger disease resistance during storage. Being inoculated fruits with penicillium digitatum, the disease incidence and the spot diameter were lower than the wild type. Moreover "Gannan I" was capable to inhibit the germination of spore and the elongation of hyphae observing the growth state of pathogen under scanning electron microscopy.6. There were no significant differences between "Gannan I" and wild-type on pericarp thickness and water content. The data revealed that the content of hemicelluloses and cellulose of "Gannan I" was remarkably higher than the wild-type, that was inferred to be the reason of the increase of peel’s hardness. And the content of lignin and pectin was slightly higher than the wild type.7. Essential oil content in flavedos of "Gannan I" and the wild-type was measured by GC-MS. The results found that there was no significant difference between them. However, the contents of10terpenes,3aldehydes,1saturated alkanes and2unknown substances in "Gannan I" were significantly higher than the wild type. The contents of octyl aldehyde and trans-β-ocimene which had significant antibacterial effect were significantly increased while the content of D-limonene which indicated maturation and senescence was significantly lower than that of wild-type.8. Hormone contents in flavedos, albedos, segment, juice sacs and leaves of "Gannan I" and the wild-type were determinated by HPLC-MS/MS.The results showed that the jasmonic acid content of "Gannan I" was higher than the wild type in each tissue layer. Moreover, the content of jasmonic acid in flavedos of "Gannan I" was almost twice higher than that of wild-type. And ethylene released amount of "Gannan I" fruits measured by GC was nearly twice lower than the wild type fruit.