No abstract

Summary At present, meiotic studies have been carried out on a population basis for assessing the genetic diversity in 38 accessions belonging to 6 species, namely S. barbata (n=18), S. glauca (n=9, 18, 36), S. megaphylla (n=18), S. palmifolia (n=18, 27), S. tomentosa (n=18) and S. verticillata (n=27), of the genus Setaria from different parts of India. For S. barbata and S. megaphylla, the chromosomal counts of n=18 represent the first reports from India. For S. glauca, 3 cytotypes occurring as diploids, tetraploids and octaploids are reported which also show some marked differences in their morphological features. The meiotic behavior in some populations of S. barbata and S. palmifolia (n=27) was found to be highly abnormal with low pollen fertility.

The chromosome numbers, meiotic course with pollen fertility and pollen size measurement of five species of Pedicularis were assessed: P. gracilis, P. hoffmeisteri, P. pectinata spp. bipinnatifida, P. porrecta and P. punctata. All the five species studied were diploid with 2n=16. The chromosome counts were the first report for P. pectinata spp. bipinnatifida, P. porrecta and P. punctata. Also the phenomenon of cytomixis was reported in these three species. All the chromosome counts reinforced x = 8 as the basic chromosome number for them.

ABSTRACT. Rheum, common name rhubarb is a source of number of chemical compounds like emodin, rutin and rhein. Plants are used as drugs, laxative and purgative. The two species of this genus viz R.emodi and R.webbianum grow wild in the Kashmir Himalaya. Keeping the threat status and the economic importance of these two species into consideration, an attempt was made to study their detailed meiotic course. Meiotic analysis revealed n=11 (2x) and n=22 (4x) as the chromosome numbers in R.emodi and R.webbianumi respectively. Cytological study for R.webbianum has been carried out for the fi rst time from the study area also it is the fi rst report of structural heterozygosity in R. emodi.

ABSTRACT. Natural variation in recombination frequency in Eclipta alba has been assessed by analyzing chiasma frequency variation among three morphologically diverse morphotypes i.e. erect, intermediate and prostrate. The study revealed that the chiasma frequency varied between 18. 8-21.4, 18.9-20.9 and 19.3-21.7 in the three morphotypes, respectively. It is found that the chiasmata frequency for prostrate type remain higher throughout the year in comparison to intermediate and erect types. There was no signifi cant variation in mean chiasma frequency between plants within accessions, but there was signifi cant variation between accessions. Presently observed the cyclic variation in the average chiasma frequencies, recombination index and excess chiasma in the three morphotypes of Eclipta alba clearly depict the infl uence of environmental factors on the process of recombination.