Elimination of Citrus psorosis virus using shoot tip grafting and electrotherapy techniques

Abstract

During the spring of 2020, Citrus psorosis virus isolate was identified in citrus orchards in Qalyubia Governorate, displaying typical virus symptoms such as bark scaling lesions and ringspot on the leaves and fruits. Using chip buds from the donor plant grafted into Madam Vinous and Navelina sweet orange as indicator plants, the isolated virus was identified using biological indexing. DAS-ELISA and RT-PCR were used to test the plants that yielded positive results. RT-PCR employing virus-specific primers revealed single amplified fragments of the appropriate size (434 bp) in infected plants, while no bands in healthy plants were detected. Electrotherapy was used to eliminate the infection. Stem cuttings from infected plants were subjected to electric currents of 10, 20, and 40 mA for 10 and 20 minutes, respectively, before being grafted on the indicator plants. The treatment of 40 mA for 20 minutes was shown to be more effective in developing virus-free plants (85%). Also, for the elimination of Citrus psorosis virus, small shoot tip explants (0.1-0.2 mm) from virus-infected shoots were grafted onto a young rootstock of troyer citrange, growing in vitro on Murashige and Skoog medium with a success rate of 3%, after which the grafted plants were transferred to the greenhouse for acclimatization. The micrografted plants were successfully regrafted on potted sour orange seedlings in the greenhouse. DAS-ELISA was used to test all plants which survived for Citrus psorosis virus.