Common Bean: Experimental Indicator Plant for Citrus leprosis virus C and Some Other Cytoplasmic-Type Brevipalpus-Transmitted Viruses

Citrus leprosis (CL) caused by Citrus leprosis virus C (CiLV-C) is present in Latin America from Mexico to Argentina, where citrus plants are grown. CiLV-C is transmitted by the tenuipalpid mite, Brevipalpus phoenicis, causing localized lesions on citrus leaves, fruit, and stems. One limitation to study of the virus-vector-host relationship in this pathosystem is the lack of a suitable assay plant. On Citrus spp. used as susceptible hosts, symptoms may take weeks or months to appear after experimental inoculation by viruliferous mites. Common bean (Phaseolus vulgaris) was found to respond with localized necrotic lesions after inoculation with viruliferous B. phoenicis in 5 days. Thus far, 113 tested common bean varieties and lines and some recent accessions of varied genetic background behaved in a similar way. Black bean `IAC Una' was adopted as a standard test variety. When inoculated leaves were left at 28 to 30 C, the period for the lesion appearance was reduced to only 2 days. Confirmation that the lesions on common bean leaves are caused by CiLV-C were made by transmission electron microscopy, immunofluorescence, enzyme-linked immunosorbent assay, and reverse-transcription polymerase chain reaction specific for CiLV-C. Common bean plants mite-inoculated with some other cytoplasmic-type Brevipalpus-transmitted viruses (BrTVs) (Passion fruit green spot virus, Solanum violaefolium ringspot virus, Ligustrum ringspot virus, and Hibiscus green spot virus) also responded with necrotic local lesions and may serve as test plants for these viruses. Two nuclear types of BrTV (Coffee ringspot virus and Clerodend rum chlorotic spot virus) were unable to produce symptoms on common bean. (AU)