PTC Enhancement of Adventitious Shoot Regeneration in Cucumis sativus L. using AgNO3

The association of high frequencies of shoot regeneration with different concentrations of silver nitrate (AgNO3) added to both seed germination and regeneration media was investigated using proximal and distal cotyledons and hypocotyls of two cucumber (Cucumis sativus L.) cultivars, namely Spring Swallow and Tasty Green. Addition of AgNO3 to both seed germination and regeneration media had significant effect on high frequencies of shoot regeneration. The number of shoots induced per explant was also increased when AgNO3 added to both media. Its presence to both media up to 50 µM further showed significant effect on shoot regeneration from non-responsive explant, distal cotyledon, of both cultivars. The best regeneration response in relation to the optimum concentration of AgNO3 added to both media was found to be explant and cultivar dependent. The higher concentration negatively affected the regeneration capability as well as number of shoots induced per explant to some extent and remains unresponsive to distal cotyledon explant. Thus addition of AgNO3 to both seed germination and regeneration media up to a specific concentration is essential for enhancement of shoot regeneration from recalcitrant cucumber varieties.