Effect of cultivar and fertilization on garlic yield and allicin content in bulbs at harveand during storage

Abstract

Allicin, one of the most important flavor compounds in garlic bulbs, is affected by genotypic characteristics modified by ontogenesis, environmental conditions, fertilization practices, and storage duration. Therefore, the effects of fertilization practices and cultivar on garlic yield and allicin content in garlic bulbs were evaluated at harvest and during storage. One autochthonous (Ptujski spomladanski) and three commercial cultivars (Garcua, Gardacho, and Gardos) were used, and three fertilization treatments (N90S0 – 90 kg N ha−1, N90S60 – 90 kg N ha−1 +60 kg S ha−1, and N0S0 – control) were performed during two growing seasons. After the harvest, 32 bulbs per treatment were stored for 4 months at a constant temperature of 15–18 °C and relative humidity of 45% in a shaded and ventilated room. A representative subsample of 8 bulbs per treatment was taken immediately after harvesting, and then 45, 90, and 120 days after harvest (DAH). Clear effects of nitrogen (N) and sulfur (S) supply were expressed, with measurements of the yield being higher on fertilized plots compared to the unfertilized ones, and the impact was cultivar-dependent. N and S fertilization significantly increased the allicin content of Gardos bulbs, while for other cultivars, the allicin content was dependent on weather conditions, revealed in decreased allicin in the year with lower temperature and excessive precipitation. When garlic was stored at 15–18 °C for 120 days, a sharp increase was observed in allicin content between 45 and 90 DAH, while the S status in garlic bulbs was unchanged, which indicated a conversion effect of γ-glutamyl peptides to sulfoxides, a precursor compound for allicin. Changes in the allicin content during storage showed an N fertilization-related pattern, being correlated with the modification of bulb dormancy.