Summary Micronuclei are extra nuclear structures, formed by the exclusion of chromosomes during cell division. The genotoxicity of a compound and its impact on the genome can be assessed via micronuclei formation. The present study has been undertaken to evaluate the mutagenic effect of the alkylating agent EMS on the meiotic behavior of pollen mother cells of Phaseolus vulgaris L. The cytological analysis revealed the induction of micronuclei at all the three administered concentrations of EMS, viz. 0.1, 0.3 and 0.5%. Besides micronuclei formation, other meiotic abnormalities associated with chromosomal segregation, such as stickiness, laggard, bridge, multivalent, etc., were also reported at metaphase I/II and anaphase I/II. The micronuclei formed would have two fates either it remains until the tetrad stage or is expelled out in the form of microcytes which will give rise to sterile pollen grains affecting the pollen fertility. The present study also documents the first instance of nuclear budding in Phaseolus vulgaris L. It is contemplated that these nuclear buds will later on convert into micronuclei. The micronuclei formation results in partial elimination of the genome, which could be efficiently utilized in breeding programmes for the production of addition and substitution lines. Similarly, haploid lines could also be produced by the complete loss of genome. It is therefore essential to understand the biological aspects of micronuclei formation, its consequences on the cell carrying it and other factors related to it so that in the future, it could be used as a marker of genetic damage and also be utilized in breeding programmes.

The present study documents the mutagenic efficacy of gamma ray and sodium azide on the chromosomal association pattern of bivalents and meiotic behavior in Phaseolus vulgaris L. The seeds were irradiated with different doses of gamma rays viz.10 krad, 20 krad, and 30 krad from a 60 Co source and thereafter, the seeds were treated with 0.3% of freshly prepared sodium azide solution for three hours, respectively. The results clearly show the formation of various types of secondary chromosomal association among bivalents. Secondary association is defined as the tendency of bivalents to lie in pairs having diffused connections. The phenomenon of secondary pairing manifested from metaphase I stage and persisted upto metaphase II stage. The bivalents lie side by side and end to end to form secondary pairing. A secondary association between bivalents is considered to be of great significance as it is being taken as an indicator of ploidy in plants. Apart from secondary chromosomal association, other meiotic abnormalities were also noticed. These include precocious movement of chromosomes at metaphase I/II (2.83%), stickiness at metaphase I/II (3.45%), stickiness at anaphase I/II (2.20%), bridge (1.25%), unorientation (0.94%), micronuclei (1.88%) etc. This phenomenon, along with other meiotic aberrations affects the pollen fertility considerably.

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The cytological screening of gamma ray treated plants revealed few desynaptic plants where an enhanced frequency of univalents were found at metaphase I along with few bivalents. The desynaptic plants were obtained at 200 Gy dose of gamma rays and were characterised as weak and medium strong type. The univalents remained unpaired till later meiotic stages and resulted in the unequal separation of chromosomes at anaphase I. The unequal separation of chromosomes as a consequence of desynapsis lead to the formation of micronuclei and gametes with imbalanced chromosomes, thus affecting the post-meiotic stages also. The desynaptic plants possess very few pods and acquire high pollen inviability. The study suggests the ability of gamma rays in the creation of male sterile lines in Phaseolus vulgaris L. The gamma rays either act on the genes responsible for synapsis and chiasma formation or disrupt the synaptonemal complex affecting chiasmate dissociation. The desynaptic mutants could be used as a potential source for gathering information on chiasma maintenance mechanism as well as to study the genetic mechanism and consequences of male sterility in plants. Further, the male sterile lines could also be profitably utilized in hybridization breeding programmes to produce hybrid seeds.

This study contributes to a better understanding of Grangea maderaspatana (L) Poir. a species of the Asteraceae family, as a pharmaceutical plant for its phytochemicals. Extracts from leaves analysed for phytochemicals. Methanol and hexane were used to prepare the extracts from the leaf. Spectrophotometric techniques were used to determine the total phenolics, total flavonoids, total tannin and total antioxidants contents. The phytochemical screening was also carried out by means of thin layer chromatography.