PHYTOPLASMA ASSOCIATED WITH SYMPTOMS OF TRISTEZA-DEL-AJO (GARLIC DECLINE) IN GARLIC (ALLIUM-SATIVUM L.)

Garlic plants (Allium sativum L.) showing symptoms of decline, absence of cloves, leaf yellowing tin 'Rosado Paraguayo' and 'Colorado' type) and reddening tin 'Blanco' type), have been observed in certain areas around the city of Cordoba, Argentina. This syndrome was termed 'tris teza del ajo' (garlic decline) by growers. Symptoms appear during the second half of the growth cycle. Affected plants die, and have spongy bulbs with undeveloped cloves. When symptoms appear close to harvest t ime, plants show only a colour change in leaves, but bulbs appear norm al. Plants with symptoms showed abundant phytoplasma cells when observ ed under electron microscopy, and strongly reacted with an antiserum r aised against the phytoplasma associated with 'China-tree (Melia azeda rach L.) decline'. Using universal primers to phytoplasma, a DNA fragm ent from leaf and clove extracts of plants expressing symptoms was amp lified by PCR. The PCR amplified product was digested with the restric tion enzyme Alu I, and the generated restriction pattern was analysed in polyacrylamide gels. This allowed the location of the pathogen with in Group III of the classification proposed by Ahrens and Seemuller (1 992). These results confirm the association between the symptomatology described as 'tristeza del ajo' and a phytoplasma, supporting our fir st report from 1992, on the presence of this prokaryote in garlic.