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- Author or Editor: Zora Singh x
- HortScience x
Particle bombardment seems to be a promising method for genetic transformation of mango and the information on various factors affecting transient gene expression is inconclusive. Pro-embryonic masses (PEMs) of mango (Mangifera indica L. cv. Kensington Pride) used for particle bombardment were established and maintained in vitro using various liquid and semisolid media containing 2,4-D. Various factors affecting the biolistic transformation efficiency in mango and subsequent transient gene expression were optimized using β-glucuronidase (GUS) as a reporter gene driven by CaMV 35S promoter. Our results show that bombardment pressure significantly affects transient gene expression with the best results obtained from PEMs bombarded at 1200 kPa of helium pressure under vacuum. The application of osmoticum pre and post-bombardment also significantly increased the transient gene expression in the PEMs as compared to the controls. Mannitol (0.2 m) proved to be the best osmoticum in improving transient GUS expression as compared to sorbitol. The duration of exposure of PEMs to mannitol (0.2 m) both pre and post-bombardment also played a significant role in improving transient gene expression. The transient GUS expression was significantly highest with a pre-treatment of 0.2 m mannitol for 4 hours as compared to 0, 8 and 12 hours. The post-bombardment treatment of 0.2 m mannitol for 16 hours resulted in significantly highest transient gene expression as compared to 0, 4, 8, 12, 20 and 24 hours. In conclusion, PEMs of `Kensington Pride' mango bombarded at 1200 kPa, which were exposed to mannitol (0.2 m) for 4 and 16 hours pre and post bombardment respectively, resulted in the highest transient GUS expression (25.1 GUS foci/mg PEMs).
Growth and maturation of `Pink Lady' (Malus domestica Borkh.) apples with special emphasis on ethylene biosynthesis and color development were monitored in Western Australia during 2002-2003. Changes in fruit growth, respiration rate, ethylene production, anthocyanin accumulation and development of red blush were evaluated between 60 days after full bloom (DAFB) and commercial harvest (191DAFB). Fruit diameter, length and fresh weight showed the typical single sigmoid growth curve, with linear increases until 158 DAFB. High respiration rate and ethylene production were recorded 60 DAFB followed by rapid decrease until 144 DAFB and then a steady increase, which peaked between 172 and 179 DAFB. Red blush on the fruit surface showed steady increase from 167 DAFB and corresponded to concomitant decrease in hue angle. Total anthocyanin increased from 167 DAFB till harvest and synchronized with increasing ethylene and maturity of apples. There were significant (P ≤ 0.001), direct linear relationships between ethylene production and total anthocyanin (r = 0.63, y = 7.6032x + 2.4756), total anthocyanin and red blush (r = 0.74, y = 0.5082x -1.54). Significant (P ≤ 0.001) negative direct linear relationships between total anthocyanin and hue angle (r = -0.89, y = -0.5973x + 110.14), and ethylene and hue angle (r = -0.69, y = -5.37x + 109.60) were recorded. Increasing anthocyanin content and red blush also coincided with decreasing daily temperatures in the orchard. Reduction in fruit firmness and acidity and increase in TSS from 167DAFB were good indicators of advancing maturity of apples. Our experimental results indicate that red blush in `Pink Lady' apples develops a few weeks before harvest and is regulated by ethylene biosynthesis and temperature.
The effects of preharvest application of AVG and ethephon alone, or in combinations, on color development, fruit quality and shelf life were tested in `Pink Lady' apples (Malus domestica Borkh.) in Western Australia during 2002.The experiment aimed at improving color without adversely affecting fruit quality at harvest and after long term cold storage. Treatments included 124.5 g·ha-1 AVG only [148 Days after full bloom (DAFB)]; 280 g·ha-1 ethephon only (148 DAFB); AVG (148 DAFB) followed by ethephon (166 DAFB); and control. Fruit were evaluated for color development, internal ethylene concentration (IEC) and quality at commercial harvest(181DAFB) and 45, 90, and135 days after cold storage (1 °C ± 0.5 °C). At harvest, ethephon with or without AVG significantly (P ≤ 0.05) improved red blush and total anthocyanin in fruit skin. AVG+ethephon treated-fruit had higher total anthocyanin and TSS compared to AVG alone and control fruit. There were no significant differences among different AVG and ethephon treatments for fruit firmness and IEC. During different storage periods, fruit treated with AVG alone and AVG+ethephon had significantly lower IEC compared to fruit treated with ethephon only and the control, however the interactions between treatments and storage periods were not significant for fruit firmness. AVG + ethephon and ethephon alone did not significantly affect fruit color during different storage periods, which showed that the subsequent ethephon spray on AVG-treated fruit had overcome the inhibitory effect of AVG. Our experimental results showed that application of AVG followed by ethephon improved color in `Pink Lady' apples without compromising fruit quality including firmness during extended cold storage.