Responses of Citrus medica var. sarcodactylis during Xanthomonas citri subsp. citri Infection

Asiatic citrus canker [Xanthomonas citri subsp. citri; (Xcc)] is a serious bacterial disease that can causes economic losses in citrus production and marketing throughout the world. In the present investigation, canker lesion development was examined in Buddha Hand (Citrus medica var. sarcodactylis), which is an ornamental tree. Basal matured leaves (fully expanded) were inoculated using a tuberculin syringe (1 cc) without a needle. Citrus canker inoculum (1.1 x 10(6) cfu/cm(2)) was slowly infiltrated into the abaxial leaf surface on both sides of the mid vein to produce a zone of water-soaked tissue. The highest Xcc population (1.9 x 10(11) cfu/cm(2)) was observed at 8 days after inoculation (dai) and thereafter declined. This decline was associated with higher oxidative redox of host tissue. These results showed that Buddha Hand represents a delayed type of hypersensitive-like response. Buddha Hand may serve as an important citrus species for resistance to citrus canker that might be exploited through transgenic and hybrid plants.