Relationships between Camellia. japonica and C. reticulata were studied to assess whether C. reticulata inherited the genome complements from C. japonica. Genomic in situ hybridization (GISH) was used to get the hybridization signalpatterns in mitotic interphase nuclei and metaphase chromosomes of three polyploid types in root-tip cells in C. reticulata using the whole genomic DNA of C. japonica as probe. Most of the hybridization signals were located at the terminal region of the chromosomes, whereas weak signals were found in whole parts of chromosomes. Numbers of hybridization signals in interphase nuclei had a tendency that higher numbers were correlated with higher ploid levels, however, no correlation between the hybridization signals and the ploidy level was seen in the metaphase chromosomes in C. reticulata. The results confirmed that the polyploids of C. reticulata were allotetraploid and allohexaploid. The results also showed that C. reticulata and C. japonica were closely related to each other, and C. japonica had partly contributed to the origin of the polyploid C. reticulata.
Detailed meiotic course and pollen fertility studies have been carried out in 23 species belonging to 14 families from the Indian cold deserts of Lahaul-Spiti. Out of these, new chromosome counts have been made in the three species, Chrysanthemum pyrethroides (2n=3x=27, 2n=4x=36), Waldhemia stoliczkai (n=9) and W. tomentosa (n=9). Meiotic course is abnormal in both the triploid and tetraploid cytotypes of C. pyrethroides which include univalents at metaphase, late disjunction of bivalents, formation of restitution nuclei at anaphase-I and chromatin bridges. Subsequently, microsporogenesis is also abnormal and is characterized by the occurrence of high frequency of monads, diads, triads, polyads, and micronuclei. These meiotic irregularities lead to high pollen sterility in both the cytotypes. Six species, Aquilegia fragrans (n=7), Astragalus bicuspis (n=8), Cicer microphyllum (n=8), Bergenia stracheyi (n=17), Sedum ewersii (n=11), Datisca cannabina (n=11) and Silene vulgaris (n=12) are worked out chromosomally for the first time from India. An additional/varied intraspecific aneuploid cytotype has been recorded in Hypericum elodeoides (n=9) against the earlier report of 2n=16 from other parts of India and elsewhere. The phenomenon of cytomixis involving inter PMC migration of chromatin material has been recorded in Anemone rivularis (n=8), Caltha palustris (n=16), Meconopsis aculeata (n=28) and Potentilla fruticosa var. rigida (n=7). Cytomixis in Anemone rivularis (n=8) and Caltha palustris (n=16) resulted into high percentage of pollen malformation and heterogenous sized fertile pollen grains. In the remaining species, the meiosis is perfectly normal leading to very high pollen fertility. Our counts for rest of the species substantiate the previous chromosome reports by other workers.
PCR-amplified DNA using the random primer OPB-06 was used as a probe for Fluorescence in situ hybridization (FISH). Signals of hybridized sites were observed in both interphase and metaphase plates after hybridization. The FISH signals of the metaphase chromosomes were confirmed as two yellow-color signals hybridized with the probe on two adjacent loci at interphase of the control plates. FISH analysis of the metaphase plates of 25μg/ml deoxynivlenol (DON) and aflatoxin B1 (AFB1) treated plants revealed 85.7% and 89.3%, respectively had no signals. Of the metaphase plates of plants treated with AFB1, 3.6% had one terminal signal while 7.1% revealed two signals and no signals were observed in 89.3% plates. Regarding the interphase nuclei, only one signal was observed in 42.1% of the plates where two signals were observed in 57.8% interphase plates. 10.7% metaphase plates of plants treated with DON had one terminal signal while 3.6% exhibit two signals and no signals were observed in 85.7% plates of metaphase. 44.1% of the interphase nuclei had one signal while 53.2% plates reveal two signals and four signals were observed in 2.7% interphase nuclei. Disappearance of FISH signals in some metaphase plates of plants treated with the two investigated toxins indicates the toxigenic effect of these mycotoxins on metaphase chromosomes of wheat.
The positions of heterochromatic bands, 45S and 5S rDNA regions were detected on the chromosomes in three cultivars of cucumber (Cucumis sativus L.). The post-heated DAPI bands, which revealed heterochromatic region, were observed on the both terminal and pericentromeric regions of most of the chromosomes in three cultivars. However, these band patterns were different between European and Eastern Asian cultivars. The major 45S rDNA sites were found around the centoromeric region of the chromosomes 1, 2 and 5, and the minor 45S rDNA sites were found around centoromeric region of the chromosomes 3 and 7. The positional variation of this region was not found among three cultivars, but size difference was observed in the chromosome 5. The 5S rDNA site was observed on the interstitial region of the chromosome 6 in all of the cultivars studied. These results indicated that the variation of chromosome structure among cucumber cultivars occurred in the heterochromoatic region and suggested that the genetic variation in cucumber cultivars would be revealed by strict analysis and comparison for the position and size of heterochromatic region.