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Abstract: Fluorescence in situ hybridization based physical localization of 45S ribosomal DNA in eight horticulturally important species of Cymbidium (Orchidaceae) from north-east India (South-East Asia) has been carried for the first time. Observations revealed only one pair of chromosomes had NOR loci. Three, out of eight Cymbidiums showed decondensed, dispersed, extended form of hybridization signals of rDNA as dots of fluorescence (transcriptionally active), where as the rest of the Cymbidiums revealed condensed (non-active) forms, hence demonstrated the heteromorphism in size, intensities and their appurtenance which may be under epigenetic control. Except for the ribosomal genes, no other active genes have been reported to reside within the nucleoli. Such observations provide useful chromosome landmarks and provide valuable evidence about the genome evolution, speciation and ploidy both at molecular and chromosomal levels which is more or less highly ambiguous in family Orchidaceae. [Copyright &y& Elsevier]

Abstract: Genetic variability in the wild genotypes of Jatropha curcas L., collected from different parts of Northeast India, was analyzed using two different single primer amplification reactions (SPAR) methods, viz., inter-simple sequence repeats (ISSR) and directed amplification of minisatellite DNA (DAMD). A total of 36 genotypes were used to investigate the existing natural genetic variation at intra-specific level. One hundred forty nine (149) amplification products were scored by ISSR and DAMD, both of which collectively showed 75.83% polymorphism with a mean intra-population genetic diversity (HS ) of 0.1309. However, their level of diversity at inter- and intra-population levels was significant, with the percentage of polymorphic loci (P) ranging from 22.82% to 44.30%, Shannon’s information index (Hpop ) from 0.1302 to 0.2541 and Nei’s gene diversity (HE ) from 0.0831 to 0.1723 with mean Nei’s gene diversity (HT ) 0.2202 and the overall estimate of gene flow being (Nm) 0.8085. Analysis of molecular variance (AMOVA) showed that 68.88% of variation at intra-population level, whereas 31.12% variation was recorded at inter-population level. Cluster analysis also supported the existence of genetic diversity in the genotypes of J. curcas collected from Assam and Meghalaya provinces of Northeast India. Present investigation suggests the efficiency of SPAR methods to estimate the genetic diversity precisely which can define genetic relationship and population genetics of J. curcas. [Copyright &y& Elsevier]