Cryptic Viruses in Hop Trefoil (Medicago lupulina) and Their Relationships to Other Cryptic Viruses in Legumes

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Abstract
Three double-stranded (ds) RNA-containing viruses, named hop trefoil cryptic virus (HTCV) 1, 2 and 3, were found in apparently healthy seedlings of hop trefoil (Medicago lupulina). Only 1–2% of plants tested were virus-free. The particles occurred in the cytoplasm, nuclei and nucleoli of parenchyma cells. They were purified as a mixture (HTCV-M) with a mean yield of 50–100 µg/kg fresh tissue, and an antiserum was obtained. HTCVl was serologically related to one component (ACV1) of a mixture of alfalfa cryptic viruses (ACV-M) present in alfalfa (M. sativa), and was separated by immunoprecipitation from HTCV-M; its particles, about 30 nm in diameter, contained two dsRNAs (Mr 1.27 × 106 and 1.15 × 106) comigrating in PAGE with two RNAs of ACV-M. Particles of HTCV2, about 38 nm in diameter and with distinct morphological subunits, were serologically closely related to particles of similar morphology (RCCV2) present in a mixture of cryptic viruses (RCCV-M) from red clover (Trifoliumpratense), and were distantly related to white clover cryptic virus 2, also of similar morphology. HTCV3 had particles 30 nm in diameter, morphologically similar to those of HTCVl, and reacted with an antiserum to vicia cryptic virus. HTCV2 and 3 could not be individually separated. The RNAs of HTCV-M, in addition to the two bands attributed to HTCVl, gave, upon electrophoresis, three bands of estimated Mr 1.34, 1.08 and 0.95, all × 106, and up to five minor bands of Mr ranging from 1.45 to 0.98, all × 106.