Abstract
Pathogenic interactions between genetic variants of cauliflower mosaic virus (CaMV) and Arabidopsis thaliana were! characterized to identify combinations potentially useful in molecular genetic analysis. Infections of a glabrous mutant (g/1) of Arabidopsis ecotype Columbia (Col-0 g/1) by 30 CaMV isolates were assessed by recording symptom character. Thirteen isolates failed to cause symptoms; the remainder induced symptoms that varied between mild and very severe. Sl,me CaMV isolates produced symptoms in Arabidopsis that differed significantly in severity or character from those produced in a standard host Brassica rapa (turnip). A greater variety of symptom types was observed in a single Arabidopsis ecotype infected with a range of CaMV isolates than was found in a range of Arabidopsis ecotypes infected with a single, typical CaMV isolate (Cabb B-JI). One isolate, Bari-1, that was asymptomatic but accumulated virus in Arabidopsis ecotype Col-0 g/1, caused mild symptoms in ecotype Ler g/1. A hybrid virus constructed from CaMV isolates Cabb B-JI and Bari-1 produced symptoms; in Arabidopsis variants that were more severe than in either parental isolate. From a screen of EMS-mutagenized Arabidopsis, one mutant (Col-0 dv1) with a pale-green, dark-vein phenotype which had an altered symptom response to CaMV, was isolated. From this;, a phenotypically near-normal revertant (Col-0 dv1R) spontaneously arose, but which showed altered responses to CaMV. Infection of Col-0 dv1R by CaMV isc,late Bari-l elicited symptoms unlike the parent Arabidopsis ecotype (Col-0 g/1. Also, Col-0 dv1 and Col-0 dv1R expressed an uncharacteristic necrotic reaction to CaMV.