ABSTRACT. Assessment of the cytogenetical and biochemical studies in two varieties of Stevia rebaudiana Bertoni were performed. The effect of EMS (ethyl methane sulphonate) on mitotic, meiotic analysis and amount of sugar contents were analysed indicating that EMS caused various mitotic and meiotic abnormalities as well as sugar contents were enhanced. Significant dose dependent increase in total soluble sugars, reducing sugars and non-reducing sugars were recorded.

Haworthia limifolia is a xerophytic plant belonging to the family Liliaceae and is indigenous to Africa. It is use extensively for its medicinal properties like antibacterial, antifungal properties and used for the treatment of sores, superficial burns, as a blood purifier and to promote pregnancy in women and cattles. In present investigation chromosomal behaviour of H. limifolia in meiosis was studied. In diplotene stage chiasmata was observed showing the possibilities of genetic recombination. Chromosome clumps were observed in diakinesis indicating sticky nature of chromosomes. Meiotic abnormalities like stickiness, precocious movement, formation of bridges and laggards were also reported in both meiosis I and II. A fairly high percentage of pollen sterility that is 73.41% was recorded resulting in failure of fruit formation. This plant could be designated as facultative apomict (Swanson, 1957) as the only means of reproduction found was asexual or vegetative.

Mutation can be beneficially utilized for tailoring crop plants. Chemical mutagen become one of important tools in crop improvement. Each mutagen has its important role as positive or negative effects on crops. Cytological abnormalities during meiosis has also been regarded one of the dependable parameters for estimating mutagenic sensitivity of a species. Studies undertaken in M 1 and M 2 generations on pink flower and white flower strains of Catharanthus roseus showed EMS elicit various chromosomal aberration in meiosis. Different types of meiotic abnormalities such as fragments, univalents, stickiness and unorientation of bivalents could be observed at metaphase I and bridges, laggards, unequal separation, unorientation of bivalents and stickiness could be seen at anaphase I. Meiotic abnormalities increased along with the increase in concentration in mutagens. The percentage of meiotic abnormalities was recorded maximum in M 1 generation as compared to M 2 generation. Contrary to pink, white flower strain exhibited maximum meiotic abnormalities and pollen sterility and hence, more sensitive to EMS. The highest pollen fertility was recorded in 0.2% concentration of EMS in pink flower strain of C. roseus.