Production and characterization of an amphidiploid line between Brassica rapa and a wild relative Diplotaxis tenuifolia

Intergeneric hybridization was performed between Brassica rapa and Diplotaxis tenuifolia following embryo rescue. Twenty-three F₁ hybrid plants were developed from the cross B. rapa  ×  D. tenuifolia and confirmed to be amphihaploids with 21 chromosomes in mitosis. Chromosome doubling of F₁ hybrids by colchicine treatment resulted into five amphidiploid plants which exhibited (20–21)_II + (0–2)_I at metaphase I (MI) of pollen mother cells. Sib-crossing and/or open-pollination among amphidiploid plants for more than four generations resulted in the development of an ADt-06 line with reproductive systems capable of maintaining an amphidiploid line. The ADt-06 line was intermediate in some morphological traits between two parental species, and was characterized by a slightly pungent taste as a physiological trait. Analyses for genomic DNA confirmed that this line was a hybrid between two species. This new amphidiploid ADt-06 line could be a useful genetic resource for the breeding of new leafy salad vegetables.