ABSTRACT This study characterized resistance in pea lines PI 347295 and PI 378159 to Clover
yellow vein virus (ClYVV).
Genetic cross experiments showed that a single
recessive gene controls resistance in both lines. Conventional mechanical
inoculation did not result in
infection; however, particle bombardment with infectious
plasmid or mechanical
inoculation with concentrated viral inocula did cause
infection. When ClYVV No. 30 isolate was tagged with a
green fluorescent protein (GFP) and used to monitor
infection, viral cell-to-cell movement differed in the two pea lines. In PI 347595, ClYVV replicated at a single-cell level, but did not move to neighboring cells, indicating that resistance operated at a cell-to-cell step. In PI 378159, the
virus moved to cells around the
infection site and reached the
leaf veins, but viral movement was slower than that in the
susceptible line. The
viruses observed around the
infection sites and in the
veins were then recovered and inoculated again by a conventional mechanical
inoculation method onto PI 378159 demonstrating that ClYVV probably had
mutated and newly emerged
mutant viruses can move to neighboring cells and systemically
infect the plants. Tagging the
virus with GFP was an efficient tool for characterizing resistance modes. Implications of the two resistance modes are discussed.
