Additional Hosts of Alfalfa Mosaic Virus and Its Seed Transmission in Tumble Pigweed and Bean. Walter J. Kaiser, Research Plant Pathologist, Regional Plant Introduction Station, USDA, ARS, Washington State University, Pullman 99164. Richard M. Hannan, Laboratory Technician, Regional Plant Introduction Station, USDA, ARS, Washington State University, Pullman 99164. Plant Dis. 67:1354-1357. Accepted for publication 16 June 1983. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1983. DOI: 10.1094/PD-67-1354.

Alfalfa mosaic virus (AMV) was isolated from naturally infected tumbleweed (Amaranthus albus) (AMV-P) and chickpea (Cicer arietinum) (AMV-CP) at Pullman, WA, and from A. albus (CF) at Central Ferry, WA. Infected tumble pigweed plants at both locations were stunted and the foliage showed yellow mosaic symptoms. Incidence of virus-infected A. albus was <1%. The host ranges of the two AMV isolates from tumble pigweed differed significantly, particularly in pathogenicity and symptomatology in different legumes, including bean (Phaseolus vulgaris) and cowpea (Vigna unguiculata). In experimentally inoculated plants, AMV-CF was seedborne in A. albus (15.5%) and in three of 12 bean lines (0.7–4.9%). This isolate, when seedborne, induced yellow mosaic symptoms in A. albus seedlings but was symptomless in infected bean plants. AMV-P was seedborne in 1.9% of the seeds of naturally infected A. albus. Transmission in seed of different plant species was confirmed by back-inoculation to sensitive indicator hosts and by immunodiffusion serology tests. Seed transmission of AMV undoubtedly aids in spread and survival of some isolates of the virus, particularly in the absence of such perennial reservoir hosts as alfalfa (Medicago sativa). Seed yields of chickpea mechanically inoculated in the field with isolates AMV-CF and AMV-CP at prebloom and full bloom were reduced by 100 and 78.8%, respectively. Most plants artificially inoculated at prebloom with both virus isolates were killed within 2–4 wk of inoculation.