INHERITANCE OF RESISTANCE TO VIRUS-INDUCED LETHAL WILT IN ARROWLEAF CLOVER

Inheritance of the lethal wilt (LW) reaction in arrowleaf clover inoculated with a pea mosaic-type virus (PMV) isolate, 204-1, of the bean yellow mosaic virus (BYMV) subgroup was investigated. The expression of LW was found to be simply inherited and conditioned by a single dominant gene (L). Resistance to LW was conferred by the homozygous recessive form of the gene. Interaction of the L gene with five other BYMV subgroup isolates was also studied. Germ plasm tested included LW-resistant (family 3-97; ll) and -susceptible (Yuchi; approximately 20% LL or Ll) populations of arrowleaf clover. The LW reaction in arrowleaf clover is virus strain-specific, and only one other isolate, TX-22, induced LW in susceptible arrowleaf clover. Lethal wilt did not occur when susceptible arrowleaf clover was inoculated with BYMV-Scott, BYMV-RC, TX-3, and clover yellow vein virus (CYVV-Pratt) isolates. Plants in the family 3-97 did not express LW when inoculated with any of the six isolates. Plants resistant to the LW syndrome were susceptible to infection with all the virus isolates tested and developed symptoms consisting of varying degrees of nonlethal wilting and systemic mosaic.