Yearly variation in glucosinolate content in inflorescences of broccoli breeding lines

This study aimed to evaluate yearly variation in individual glucosinolate (GSL) profiles and content in inflorescences of 42 broccoli genotypes (9 commercial cultivars, 16 F₁ hybrids, and 17 inbred lines) grown at the same location for two consecutive years (2014 and 2015). Broccoli heads were harvested at the marketable stage, and individual GSLs were analyzed using high performance liquid chromatography (HPLC). Eight GSLs, namely glucoiberin (IBE), progoitrin (PRO), epiprogoitrin (EPI), glucoraphanin (GRA), sinigrin (SIN), gluconapin (NAP), glucoerucin (ERU), and glucobrassicin (BRA) were identified in broccoli breeding lines grown in both 2014 and 2015. BRA was the most dominant GSL, followed by GRA and ERU, in both 2014 and 2015. The GSL content and profiles were dependent on both the genotype and the growing year. In total, five F1 hybrids (A311, 5022, 5036, 5075, and 5078) and three inbred lines (5401, 5402, and 5409) showed similar levels of BRA in both years. In addition, the levels of GRA in genotypes 5078, 5079, 5075, and 5308, and levels of IBE in 5078, 5079, and 5312 were stable between 2014 and 2015. Total GSL content varied from 3.32-16.92 μmol·g^-1 in 2014 and 3.83-14.20 μmol·g^-1 in 2014. The average total GSL content was higher in 2015 (8.18 μmol·g^-1 DW) than in 2014 (7.66 μmol·g^-1 DW). This trend was positively correlated to climatic factors such as relative humidity, temperature, and radiation, which were also higher in 2015 than in 2014. The genotypes 5035, 5402, and 5409 had the highest total GSL content among all genotypes in both years. Altogether, two F₁ hybrids (5078 and 5079) and two inbred lines (5308 and 5409) showed stable and high GSL contents under two different climatic conditions. Therefore, these genotypes could be used for breeding functional materials for commercialization in the future.