VIRUS FREE GARLIC (ALLIUM-SATIVUM L) PLANTS OBTAINED BY THERMOTHERAPY AND MERISTEM TIP CULTURE

Virus infection in garlic considerably reduces yield and quality in Argentina. The production of virus free "seed" was attempted by means of thermotherapy and meristem tip culture. A hot water treatment was employed to determine the lethal temperature/time cobmination for clonal type (c.t.) Blanco cloves. It was established that 50-degrees-C x 20 min, 50-degrees-C x 15 min and 55-degrees-C x 5 min were the limit thermal/time combinations which garlic could withstand. Those treatments were employed followed by meristem tip culture, however, none of the successfully developed plants after culture (only 13 %) were virus-free. Hot air treatments in a growth chamber at 36-degrees-C lasting for 30, 40 and 60 days, and at 25-degrees - 32-degrees-C for 30 days in a greenhouse were tested on c.t. Blanco. Cloves kept at room temperature throughout the experiment were employed as controls. In the 25-degrees - 32-degrees-c treatment, 73 % of meristems produced plants and, of these, 33 % were virus free. After 30 and 40 days at 36-degrees-C, 62 % and 67 % of the meristems developed into plantlets, of which respectively 51 % and 50 % were virus-free. Very few meristems (10 %) developed into plants when cloves had been kept at 36-degrees-C for 60 days but the resulting plantlets were all virus free. Controls produced 78 % of plants, of which 14 % were virus free. Results of hot air treatments of 36-degrees-C for 40 days performed on c.t. Colorado, Rosado, Paraguayo, Espanol and Hilario Ascasubi were similar to those obtained with c.t. Blanco. In Espanol and Hilario Ascasubi, no virus-free plants were detected among control specimens (no thermotherapy treatment). The only virus (from up to 3 that infected the plants) that persisted in some plants after thermotherapy and meristem tip culture was garlic yellow streak.