Monomorphic Banding Pattern Research Articles

Genetic variability and phytogeography of <i>Miscanthus sinensis</i> var. <i>condensatus</i>, an apomictic grass, based on RAPD fingerprints

DNA fingerprinting using random amplified polymorphic DNA (RAPD) markers was employed to investigate the genetic variation within and among populations of Miscanthus Anderss. sinensis var. condensatus (Hack.) Makino, an apomictic grass distributed along the coasts of Taiwan and Ryukyu Islands. A total of 250 plants from three Tai- wanese populations (Southeast Coast, Orchid Islet, and Green Islet) and two populations from Ryukyu (Ishigaki and Amami-O-Shima Islets) were sampled. The amplified products of 40 random primers showed monomorphic banding patterns within all populations as well as among the three populations from Taiwan. Low genetic variation (with only two polymorphic loci), but significant differentiation, was detected between populations from Taiwan and Ryukyu (ΦCT = 0.864) and between populations (ΦST = 1.0) from Ishigaki and Amami-O-Shima Islets. In contrast, a high level of variation was exhibited in the outcrossing Miscanthus sinensis var. glaber (Nakai) Li. In addition to apomictic repro- duction, low genetic variation across populations of M. sinensis var. condensatus may be a result of high salinity acting as a selective agent. With the cost of reduced genetic heterogeneity, apomixis may have provided a mechanism for avoiding the transmission of endophytic fungi. The phytogeographic pattern of M. sinensis var. condensatus ,a s re- flected by the RAPD data, likely represents isolation between Taiwan and Ryukyu since the mid-Pleistocene.

RAPD Analysis of Lathyrus sativus Somaclones

RAPD patterns were studied in seven somaclones of Lathyrus sativus having contrasting characteristics alongwith the parent cultivar P-24. Out of 81 decamer random primers used, 5 did not amplify and 24 revealed DNA polymorphism while the rest generated monomorphic banding patterns. Eight unique bands were amplified with different primers in four different somaclones. With most of the informative primers differences were observed between somaclones and also between some of the somaclones and parent cultivar P-24. More than 90% similarity in the RAPD patterns was evident among the somaclones and the parent cultivar P-24. Though it was not possible to identify a particular somaclone with a single primer, a combination of two or more primers could be employed to identify a somaclone.

Abundance and polymorphism of di-, tri-and tetra-nucleotide tandem repeats in chickpea (Cicer arietinum L.)

The abundance and polymorphism of 38 different simple-sequence repeat motifs was studied in four accessions of cultivated chickpea (Cicer arietinum L.) by in-gel hybridization of synthetic oligonucleotides to genomic DNA digested with 14 different restriction enzymes. Among 38 probes tested, 35 yielded detectable hybridization signals. The abundance and level of polymorphism of the target sequences varied considerably. The probes fell into three broad categories: (1) probes yielding distinct, polymorphic banding patterns; (2) probes yielding distinct, monomorphic banding patterns, and (3) probes yielding blurred patterns, or diffused bands superimposed on a high in lane background. No obvious correlation existed between abundance, fingerprint quality, and the sequence characteristics of a particular motif. Digestion with methyl-sensitive enzymes revealed that simple-sequence motifs are enriched in highly methylated genomic regions. The high level of intraspecific polymorphism detected by oligonucleotide fingerprinting suggests the suitability of simple-sequence repeat probes as molecular markers for genome mapping.

Electrophoretic evidence for the origin ofDryopteris yakusilvicola (Dryopteridaceae)

To investigate the origin of the triploid agamosporous speciesD. yakusilvicola, an electrophoretic analysis was made for five enzymes of theD. sparsa complex.Dryopteris yakusilvicola showed a monomorphic banding pattern for the five enzymes and was heterozygous in all six gene loci coding them. Comparison of enzyme banding patterns suggests that the genome ofD. yakusilvicola was derived through hybridization betweenD. sabaei and either a sexual tetraploid or an agamosporous triploid ofD. sparsa. Cytological evidence (Darnaediet al., 1989) supports the idea that of the two types ofD. sparsa the sexual tetraploid is a parent. The monomorphic pattern implies thatD. yakusilvicola originated from a single hybrid between the parental species, and that it is a neo-endemic of Yakushima Island.