MSc

An investigation entitled “Artifical induction of polyploidy in Cucumis sativus L. was carried out as two separate experiments. Experiment I, was (in-vivo study) was carried out at the College of Agriculture, Vellayani during the period September 1991 to February 1991. Experiment II (in-vitro study) was carried out at the Tissue culture laboratory attached to Department of Pomology, College of Horticulture, Vellanikkara during the period January 1991 to july 1991. The main objective of Experiment I was to study the effect of colchicine for inducing polyploidy in seed, seedling and apical bud treatments. Objectives of Experiment II were to standardise a suitable medium for embryo culture and to study the effect of colchine on proembryos, mature embryos and dry seed embryos under in - vitro conditions. Experiment I was laid out in RBD with two replications. Experiment II was carried out in CRD with three replications. The two varieties of Cucumis sativus used for the present study were Seethal and Delila. The abstract of results is given below.
Experiment I
Survival of plants in both Seethal and Delila was significantly affected by increasing colchicine concentration 0.2 to 0.4 per cent and with increasing period of treatment from two to six hours. Survival was significantly low in apical bud treatment. Maximum survival was noticed in seed treatment of colchicine 0.2 per cent for a period of four hours. At early growth stage significant reduction was noticed in length of vine, number of branches per plant and number of leaves per plant along with the increase in colchicine concentrations, from 0.2 to 0.4 per cent, and period of treatment, from two to six hours. Seed treatment gave maximum value for these parameters in both varieties except number of leaves in Delila. These variations seen during early growth stages were found to be diminishing at later growth stage (60 days growth stage). Delay in both male and female flower opening along with significant reduction in number of male and female flowers was noticed in higher colchicine concentrations and in lower period of treatments. Mode of treatment did not exert any significant influence on number of days taken for flower opening and total number of flowers produced per plant in both varieties except on number of days taken for female flower opening in Seethal in which by apical bud treatment maximum delay was noticed. With increasing colchicine concentration from 0.2 to 0.4 per cent and period of treatment from two to six hours significant increase in stomatal length was noticed in both varieties. Mode of treatment exerted no significant influence on stomatal length. All the fruit characters ie. Number of fruits per plant, length of fruit, girth of fruit and weight of fruit studied, were not significantly influenced by the treatments tried. In both varieties pollen size and sterility increased considerably with increasing colchicine concentration. Apical bud treatment gave significantly high values for pollen size and pollen sterility in Delila. Seed treatment recorded minimum pollen size and pollen sterility. Cytological studies were conducted in the root tips of colchicine treated seeds and metaphase and anaphase stages were obtained in the normal diploid cells. But the enlarged colchicine affected cells showed very poor stainability.
Eepeiment II
Standardisation of a suitable medium was carried out by using MS medium as the basal medium. MS medium supplemented with 0.1 mg/L of IAA was found suitable for embryo culture. Three types of embrayo viz., pro-embryo, mature embryo and dry seed embryo were used for embryo culturing.
Embryogenesis was delayed significantly with increase in colchicine concentration from 0.02 to 0.04 per cent in both varieties. When pro-embryos were used for inoculation significant delay was noticed for embryogenesis in both varieties. Regeneration of calli was reduced significantly with increase in colchicine concentration. Pro-embryos gave lowest and dry seed embryo gave highest regeneration percentage in both varieties. Length of plantlet and number of leaves produced per plantlet in culture tubes were reduced significantly in the higher levels of colchicine concentration. Pro-embryos gave lowest and dry seed embryos gave highest values with respect to these parameters. Plantlets from pro- embryo showed lowest survival under green house conditions in both varieties. Colchicine concentration exerted no significant influence in Seethal. But in Delila with increasing colchicine concentration from 0.02 to 0.04 percent, survival of plants in green house reduced significantly. Day of treatment had no significant influence in all the parameters studied.
On the basis of present study it can be concluded that different concentrations of colchicine, different periods of treatment and different modes of colchicine treatment can induce significant changes in the survival of plants, cytomorphological characters of the plants and pollen sterility. With increasing colchicine concentration and period of treatment the variations increased progressively. But considering the lethal effects as reflected on the survival of plants, 0.2 per cent colchicine application for two hours by seed treatment is desirable under in-vivo condition. Under in-vitro condition use of dry seed embroyo is best for embryo culture which can be successfully carried out by using MS medium modified with 0.01 mg/L of IAA. Colchicine 0.02 per cent can be used for the induction of polyploidy under in-vitro conditions. Since it is effective in producing variations with minimum deleterious effects.