Otimização de protocolo para obtenção in vitro de microbulbos de Allium sativum das cultivares Ito e Quitéria livre de virus

Abstract

The objective of this study was to optimize the protocol for obtaining virus-free garlic in vitro developed for the garlic cultivars Caçador and Amarante, described by Torres et al. (2001), for the noble garlic cultivars Ito and Quitéria. Evaluating the effect of luminosity, microenvironments, sucrose concentrations, vernalization temperatures and thermotherapy time in order to obtain a lower rate of hyperhidricity and higher productivity of the cultivars Ito and Quitéria via meristem culture. Four experiments were conducted in an entirely randomized design. In the first experiment, three types of lamps were tested: blue, red and white LEDs. In the second, the impact of three types of microenvironments was verified: lids without a filter, lids with a filter, and lids containing two filters. In the third experiment, five concentrations of sucrose were analyzed: 0, 2, 4, 6, 8, and 10%. In the fourth experiment, the effect of the vernalization temperatures combined with different days of thermotherapy at 37ºC were evaluated. Two temperature ranges: -1 to -3ºC (vernalization at negative temperature) and 2 to 4ºC (vernalization at positive temperature), and four periods of thermotherapy: 0, 10, 20 and 30 days were used. The results showed that the blue LEDs provided superior results for all parameters evaluated, except for the characteristic bulb diameter (DB). In addition, the microenvironment with caps containing a filter promoted a lower rate of hyperhidricity in both cultivars. Sucrose provided increased productivity of the reserve organs. The lower the number of days of thermotherapy, the higher the average productivity of microbulbs, especially with the negative vernalization temperature when compared to the positive temperature for both cultivars. However, a minimum therapy time of 20 days is necessary for bulbs vernalized at a negative temperature to produce in vitro with adequate reduction of the virus pool. Regarding the quality of meristem donor materials, as the days in which the bulbs are submitted to thermotherapy went by, the percentage of viable materials decreases, especially for bulbs that were vernalized at positive temperatures.