Studies on in vitro chromosome doubling of haploid derived through androgenesis in marigold

Abstract

A 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 multiplied and 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 good for parameters like per cent survival
(81.22%), per cent 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 per cent survival
(69.67%), per cent 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 were done to determine ploidy
levels in colchicine-treated haploid plantlets. Cytological analysis of 38 plants revealed that 26 (68.42%) were
tetraploids and 12 (31.57%) were polyploids. Whereas through chloroplast counting, 38 plants were screened,
out of which 26 plants (68.42%) were tetraploids with a mean of 16 chloroplasts in the guard cells and 12 plants
(31.57%) were polyploids with a mean of 18 to 22 chloroplasts i n the guard cells.