PATHOGENIC INTERACTIONS BETWEEN VARIANTS OF CAULIFLOWER MOSAIC-VIRUS AND ARABIDOPSIS-THALIANA

Pathogenic interactions between genetic variants of cauliflower mosaic virus (CaMV) and Arabidopsis thaliana were! characterized to identify combinations potentially useful in molecular genetic analysis. Infect ions 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 sy mptoms that varied between mild and very severe. Sl,me CaMV isolates p roduced symptoms in Arabidopsis that differed significantly in severit y or character from those produced in a standard host Brassica rapa (t urnip). A greater variety of symptom types was observed in a single Ar abidopsis ecotype infected with a range of CaMV isolates than was foun d in a range of Arabidopsis ecotypes infected with a single, typical C aMV isolate (Cabb B-JI). One isolate, Bari-1, that was asymptomatic bu t accumulated virus in Arabidopsis ecotype Col-0 g/1, caused mild symp toms 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, da rk-vein phenotype which had an altered symptom response to CaMV, was i solated. From this;, a phenotypically near-normal revertant (Col-0 dv1 R) spontaneously arose, but which showed altered responses to CaMV. In fection 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.