AN IMPROVED PURIFICATION PROCEDURE FOR GRAPEVINE LEAFROLL ASSOCIATED VIRUSES

Higher yields of purified grapevine leafroll associated viruses (GLRaV ) types 1 and 2 were consistently realized when an acidic extraction b uffer [0.5 M potassium phosphate, pH 6.4; 4% polyvinyl polypyrrolidone (PVPP), without bentonite] was used. In contrast, yield of purified v iruses was problematical using 0.5 M Tris-HCl buffer, pH 8.2, PVPP, ei ther with or without bentonite. Relative virus yields were determined by ELISA. The consistency in virus yields was probably due to increase d activity of the polyphenol absorbent, PVPP, when it was suspended in a slightly acidic solution. For GLRaV-3, yields of purified virus wer e somewhat comparable irrespective of extraction buffer or bentonite.