Studies on indicator plants for citrus viruses. 1

Mechanical inoculation on legumincus plants with sap from Satsuma dwarf tree

Abstract

1. Thirty two species of leguminous plants were inoculated with the sap from the young shoots of Satsuma orange showing symptoms of Satsuma dwarf. Nine species including cowpea (Vigna sinensis Endl.), asparagus bean (Vigna sesquipedalis Wight), kidney bean (Phaseolus vulgaris L.), Crotalaria spectabilis Roth, peanut (Arachis hypogaea L.), garden pea (Pisum sativum L.), Chinese milk vetch (Astragalus sinicus L.), sword bean (Canavalia gladiota DC.), and Japanese clover (Microlespedeza striata Makino) were proved to be susceptible to a virus present in the affetced trees. Two species of Chenopodiaceae and three species of Cucurbitaceae were not subject to it. The authors temporarily propose the name “Satsuma dwarf virus” to this legume infecting virus.
2. Among the susceptible plants listed above, Blackeye cowpea and kidney bean (Satisfaction) showed the most characteristic symptoms. The former showed mottling and vein clearing on the leaves, and necrotic streaks on the petioles as well as on the stems. The latter also developed clear mottling and vein clearing on the foliage of most plants that were infected by sap-inoculation. These two species appear to be good indicator plants. However, retransmission from infected legume plants to Satsuma orange has not been successful in the tests so far conducted.
3. Higher percentages of infection resulted when the expressed sap was buffered with about an equal volume of 0.05-0.1mol solution of K₂HPO₄.
4. One-month old shoots of affected Satsuma orange were demonstrated to carry highly active virus in the leaves, bark and wood portions. One-year old shoots and relatively old current shoots carried active virus in the wood, but not in the bark of twigs or the leaves.