Graduate Thesis Or Dissertation


Effects of X-Ray Exposure on Seed Quality of Pear (Pyrus betulifolia) and Peach (Prunus persica) Public Deposited

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  • There is a perception that exposing seeds to x-ray in airports during export may affect the quality of seeds. This study was triggered when pear (Pyrus betulifolia) and peach (Prunus persica) grower reported that seeds quality was reduced after they were exposed to X-ray and tested in the final destination. Two studies were conducted to verify whether exposing pear and peach seeds to x-ray affect seed quality. In the first study, seeds of one pear and two peach varieties were exposed to x-ray radiation in an airport at 160 kV for 0.2 sec, for a total of 32 kV energy units). This is a common practice for exporting-importing seeds. Seeds were tested before and after exposure to x-ray. Both cracked and non-cracked seed were tested. Germination of peach var. 1 exposed to x-ray increased by 17% in non-cracked seeds and by 34% in var. 2 compared to non-exposed seeds. No significant difference in linear seedling length between exposed and non-exposed seeds were detected. In the second study, seeds of pear and peach were exposed to x-ray radiation 155 kV for 5 sec for total energy of 775 kV) which is considered relatively higher energy than the airport exposure. Germination of treated pear seeds with x-ray decreased compared to untreated seeds, however seeds of treated seeds germinated faster than untreated seeds (i.e., higher SGI). For peach, treated seeds of both varieties had lower viability and vigor than untreated seeds. However, extra 30 d of prechilling at 5˚C improved the treated peach germination significantly, indicating that seeds were dormant, not dead. In conclusion, X-ray dose of airport scanner stimulated germination and SGI. However, exposing seeds to higher x-ray energy 155 kV for 5 sec had negative effects on seed viability and vigor, probably because of the length of exposure because it has more exposures. The quality of treated peach seed var. 2 was negatively affected more than var. 1, with the exception of SGI which was higher in both treated varieties. Similarly, exposure to 155 kV for 5 sec affected seed quality of pear negatively. Longer exposure to x-ray may cause deep dormancy, but this dormancy can be overcome by longer prechilling treatment (extra 30 d, i.e., 45d + 30d). The study showed that x-ray airport scanner did not affect the quality of pear and peach seed used in the study. Longer exposure to x-ray may induce dormancy but did not have deleterious effect on seeds.
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