Purification of maize streak virus and its relationship to viruses associated with streak diseases of sugar cane and Panicum maximum

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Abstract
SUMMARY: Maize streak virus (MSV) was purified by homogenising infected leaf tissue in 0·01 m pH 3·9 phosphate buffer and clarifying the extract with n‐butanol (7 ml/100 ml extract). Purified preparations contained particles 20 nm in diameter, some occurring singly, but most occurring in pairs, forming structures of 30 × 20 nm. The sedimentation coefficients of single and paired particles were 54 and 76 S respectively.When centrifuged in sucrose density gradients preparations made by extracting leaves at pH 3·9 gave a single intense light‐scattering zone containing paired particles. Preparations made at pH 5·9 or 7·9 gave one or two additional upper zones containing single particles and fragmented material. Preparations treated with 0·05 or 0·1 m ethylene diamine tetra‐acetic acid, disodium salt, (EDTA) contained no paired particles, few single particles and much fragmented material. In immunoelectrophoresis, the major component in preparations without EDTA migrated to the cathode whereas that in EDTA‐treated preparations migrated to the anode.Virus isolates from streak‐diseased sugarcane and guinea grass (Panicum maximum) were serologically related to MSV and had similar particles with identical sedimentation coefficients. No such particles were seen in purified preparations of healthy maize, sugarcane, or guinea grass. The viruses from sugarcane and guinea grass are probably host‐adapted and are referred to correctly as the sugarcane and guinea grass strains of MSV.MSV probably contains single‐stranded RNA, and the cryptogram is (R)/1:*/*:S/S:S/Au.