Identification of susceptible lime and lemon genotypes and determination their relative response severity to Citrus yellow vein clearing virus

Citrus yellow vein clearing virus (CYVCV), is the causal agent of a destructive disease that has been spreading in Iran and a number of countries in the region in recent years. To identify susceptible hosts of the disease, the budwoods of the important lime and lemon genotypes of Iran were collected from asymptomatic mother trees. Then the samples were confirmed to be CYVCV-free by biological indexing using the indicator plant. The buds of the genotypes were then propagated on sour orange (Citrus aurantium) rootstocks and the plants were simultaneously graft-inoculated with the Iranian LEN isolate (GenBank accession number: KX902488). The inoculated and control plants were maintained under controlled temperature conditions (24°C during the day and 18°C at night). Persian lime (C. latifolia) and nine lemon (C. limon) varieties were identified as disease-susceptible cultivars among the 21 studied genotypes. To confirm infection in symptomatic inoculated plants, total RNA was extracted from the bark and midrib of new flushes and a two-step RT-PCR was performed. No symptoms were observed in the other genotypes studied until one year after inoculation. Disease severity in susceptible genotypes was graded from 0 to 4 based on the severity of symptoms on the lateral veins and cultivars were divided into three groups according to the intensity of the response. The relationship between ancestral affinity of lemon cultivars and susceptibility to Citrus yellow vein clearing virus was discussed.