REGENERATION AND AGROBACTERIUM-MEDIATED TRANSFORMATION OF WATERMELON

Abstract

In this study, a rapid regeneration system for two Egyptian watermelon cultivars
(Giza 1 and Giza 21) was developed using the proximal zone of the hypocotyls. An
Agrobacterium-mediated transformation system was also established for both
cultivars. Results showed that the highest regeneration frequency of both cultivars
(Giza 1 and Giza 21) was detected on explants that cultured on medium
5MSBAABA, as it revealed a percentage of 75 (Giza 1) and 72 (Giza 21) with 4-6
shoots/explants. It was also clearly observed that carbon source has an effect on the
shoot regeneration frequency. Data showed that the hypocotyls explant revealed a
regeneration percentage of 96.6 instead of 73.3 % when the sucrose was only used in
5MSAABA medium. Also, when 1.5g/L phytagel and 3g/L agar were used in
5MSBAABA medium the vitrification phenomenon of the developed shoots was
decreased. A percentage of ~80 % of the shoots formed roots on the medium
contained 40 μg/L NAA. At the level of transformation experiment, results showed
that a number of 20 (16.7%) explants out of 120 explants of both watermelon
cultivars were survived on the bialaphos- selection medium, and produced 42 (for
Giza 1) and 33 (for Giza 21) bialaphos-resistant shoots. The presence of gus-intron
(2070 bp) and bar (540 bp) genes was confirmed via polymerase chain reaction
while their expressions were detected by histochemical GUS assay and leaf painting
with 1 mg/L Basta herbicide.