Genetic engineering offers an alternative method to the conventional
breeding of 'W. Murcott' mandarin (Citrus sp.), one of the most commercially
important cultivars grown in the world. Ahmad Omar from the University of
Florida and Zagazig University in Egypt used genetic engineering to confer
citrus canker resistance in W. Murcott mandarin.

Transformation of W. Murcott mandarin was achieved by protoplast
transformation system using Xa21, a Xanthomonas resistance gene from rice.
Ten transgenic lines were developed from the transformation and were
subjected to the citrus canker pathogen by syringe inoculation under
laboratory conditions. The transgenics showed a reduction in lesion number
and bacterial populations within lesions compared to wild type control
plants.

This study presents a new approach to confer canker resistance to mandarin
oranges. However, the transgenic W. Murcott mandarin lines require further
evaluation under field conditions to validate the level of resistance.

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