In vitro induction and assessment of tetraploid plants from shoot cultures of diploid Niger (Guizotia abyssinica (L.f.) Cass.): a multipurpose oilseed crop

Agronomic traits improvement in crop plants can be accomplished by induction of polyploidy. Niger (Guizotia abyssinica (L.f.) Cass.) is an important edible oil yielding diploid crop (2n = 30). In the present study, the tetraploidization in niger plants was attempted by treating apical portion (about 2 cm length) of in vitro raised shoots with colchicine and their confirmation by chromosome counting and flow cytometry. The in vitro shoots were raised from leaf explants excise from in vitro germinated seedlings and cultured on MS medium supplemented with 1.0 mg/l BAP (6-benzylaminopurine). The survival and nature of growth of treated shoots was variable with colchicine concentration (0.0, 0.005, 0.01, 0.02, 0.03, and 0.04%) and exposure time (4, 8, 12, and 16 h). The maximum tetraploid induction ratio (38%) was recorded with 0.02% colchicine treatment for 8 h. The chromosome number in root cells of tetraploid plantlets was 2n = 4x = 60 and the DNA content in leaf cells was 10.44 pg which was double to the diploid plant (5.32 pg) cells. In addition, there was significant difference in leaf characteristics of diploid and tetraploid plantlets. Compared to diploid, the tetraploid plantlets showed larger leaves, larger stomatal size, low stomatal index, larger capitula, larger seeds, and a higher number of seeds per capitula. The oil content in seeds was higher and associated with altered fatty acid profile. The results demonstrated that the tetraploid plantlets obtained in this study exhibited some superior agronomical traits (as mentioned above) compared to diploid. The developed protocol and produced tetraploid plantlets will open the new door in improvement of edible oil yielding crop Guizotia abyssinica (L.f.) Cass. Key message Tetraploid plantlets of Niger (Guizotia abyssinica Cass.) produced for the first-time using colchicine and in vitro technique exhibited superior agronomical traits compared to parent diploid. Tetraploidization could increase the dimensions of leaf, stomata, inflorescence, seed and seed oil.