Production and characterization of alien chromosome addition lines in Allium fistulosum carrying extra chromosomes of Allium roylei using molecular and cytogenetic analyses

Allium roylei was employed for the production of alien chromosome addition lines in A. fistulosum. Interspecific hybridization between A. fistulosum and A. roylei successfully produced F₁ hybrids. Chromosome doubling of an F₁ hybrid was carried out to produce amphidiploids. After two times backcrossing of the amphidiploids with A. fistulosum, a BC₂ generation was obtained with chromosome numbers (2n) ranging from 16 to 23. Alien monosomic addition lines (AMAL, FF + nR, 2n = 17) appeared with the highest frequency. Furthermore, multiple addition lines (MAL, 2n = 18–23) were also observed with lower frequencies. Five AMALs (FF + 1R, +3R, +4R, +5R, and +8R) and ten MALs (2n = 18–23) were characterized using isozyme and DNA markers. The extra chromosomes from A. roylei clearly altered the biochemical characteristics of the MALs. Variations in sugar, cysteine sulfoxide, and flavonoid contents were observed among the MALs in various amounts. Allium fistulosum–A. roylei allotriploids (2n = 24, FFR) showed significantly higher saponin content and antifungal activities of saponin extracts against isolates of Fusarium oxysporum f. sp. cepae in comparison with A. fistulosum. This first report of A. fistulosum–A. roylei addition lines opens the possibility of developing novel A. fistulosum cultivars with enhanced nutritional value and disease resistance.