Studies on in vitro chromosome doubling of haploid derived through androgenesis in marigold (Tagetes patula L.)

Local strain of Tagetes patula L. was used for in vitro androgenesis with floret size ranging from 2 to 4.5 mm. One haploid from anther derived regenerants was isolated and confirmed by cytological analysis and chloroplast counting. The isolated haploid was further multiplied and were subjected to colchicine treatment (0.005%, 0.01%, 0.02% for 36 and 48 hours) using nodal segment explants under in vitro conditions. The results revealed that treatment T1- Colchicine (0.005%) for 36 hours exposure was found good for parameters like percent survival (81.22%), percent diploidization (48.00%), leaf length (3.77 cm), leaf width (2.49 cm), number of shoots per plant (9.89) followed by treatment T2- Colchicine (0.005%) for 48 hours exposure for parameters like percent survival (69.67%), percent diploidization (37.22%), leaf length (3.56 cm), leaf width (1.97 cm), number of shoots per plant (8.67). Cytological analysis and chloroplast counting in stomatal guard cells was done for determination of ploidy level in colchicine treated haploid plantlets. The results revealed that in cytological analysis out of 38 plants screened, 26 plants (68.4%) were tetraploids and 12 plants (31.57%) were polyploids. Whereas through chloroplast counting, 38 plants screened out of which 26 plants (68.4%) were tetraploids with mean of 16 chloroplasts in the guard cells and 12 plants (31.57%) were polyploids with mean of 18 to 22 chloroplasts in the guard cells.