Intraspecific Cytotypes Research Articles

Genomic and epigenomic variation in Psidium species and their outcome under the yield and composition of essential oils

Diploid and polyploid species derived from the euploid series x = 11 occur in the genus Psidium, as well as intraspecific cytotypes. Euploidy in the genus can alter the gene copy number, resulting in several “omics” variations. We revisited the euploidy, reported genomic (nuclear 2C value, GC%, and copy number of secondary metabolism genes) and epigenomic (5-mC%) differences in Psidium, and related them to essential oil yield and composition. Mean 2C values ranged from 0.90 pg (P. guajava) to 7.40 pg (P. gaudichaudianum). 2C value is intraspecifically varied in P. cattleyanum and P. gaudichaudianum, evidencing cytotypes that can be formed from euploid (non-reduced) and/or aneuploid reproductive cells. GC% ranged from 34.33% (P. guineense) to 48.95% (P. myrtoides), and intraspecific variations occurred even for species without 2C value intraspecific variation. Essential oil yield increased in relation to 2C value and to GC%. We showed that P. guajava (diploid) possesses two and P. guineense (tetraploid) four copies of the one specific TPS gene, as well as eight and sixteen copies respectively of the conserved regions that occur in eight TPS genes. We provide a wide “omics'' characterization of Psidium and show the outcome of the genome and epigenome variation in secondary metabolism.

Milium effusum (Poaceae: Poeae: Miliinae): species of systematic and cytological interest with notes on polymorphic nature and cytogeography

Present communication records polymorphic and polyploid nature of the forest grass species M. effusum having wide distribution over different continents and countries. Globally the 4 x plants are widely distributed. The West Himalayan plants, collected at 3000 m alt. and more, are also sporting chromosome number of 2n = 28 based on basic number of x = 7. Further meiotic course analysis of Western Himalayan plants follows diploid like behaviour possibly directed by diploidization. This communication also calls the attention to cytogeography of intraspecific cytotypes of M. effusum, where diploid plants (2n = 14) have also been reported, but only 2 times – from the Kola Peninsula, Russia and from the Switzerland mountains. Perhaps these are relict populations, which deserve to be proved, studied and protected.

Why is reproductive isolation between intraspecific cytotypes so important? A commentary on: 'Strong post-pollination interactions govern cytotype isolation in a tetraploid-octoploid contact zone'.

This article comments on: Mariana Castro1, João Loureiro, Brian C. Husband and Sílvia Castro, The role of multiple reproductive barriers: strong post-pollination interactions govern cytotype isolation in a tetraploid–octoploid contact zone, Annals of Botany, Volume 126, Issue 6, 2 November 2020, Pages 991–1003, https://doi.org/10.1093/aob/mcaa084

Cytomorphological variations and new reports of B-chromosomes in the genus Plantago (Plantaginaceae) from the Northwest Himalaya

The genus Plantago is known with more than 200 species, used extensively all over the world as a promising source of functional foods and for various remedies. The present cytological study covers 24 populations of 5 species of the genus Plantago and intraspecific cytomorphological diversity in P. depressa from the Northwest Himalaya. Out of these, P. himalaica (n=12) is a first euploid report for the world. The B-chromosomes have been reported for the first time in 3 species, P. lanceolata (n=6+0−1B), P. major (n=6+0−1B), and diploid (n=6+0−1B) and tetraploid (n=12+0−1B) cytotypes of P. depressa. Beside this, intraspecific cytomorphological variations are also reported in P. depressa with three different cytotypes (2x, 4x, 6x). The detailed meiotic course of all the populations reveals the meiotic anomalies in the form of cytomixis, un-oriented bivalents, chromosome stickiness, laggards and chromatin bridges. The effect of these abnormalities on size and viability of the pollen grains is also discussed. The presence of B-chromosomes is found to be related with the reduction in the meiotic anomalies. Dendrogram constructed for the quantitative morphological features between the three intraspecific cytotypes of P. depressa, depicts the close relationship of diploid cytotype to the tetraploid one, rather than the hexaploid populations.

Chromosomal variation in some members of Malvales Juss. from Rajasthan, India

The present paper deals with the meiotic study of 15 species belonging to 7 genera of 3 families of order Malvales i.e. Malvaceae, Sterculiaceae and Tiliaceae from different geographical areas of Rajasthan. Out of 15 species, intraspecific cytotypes at tetraploid and diploid level of Triumfetta rhomboidea has been reported for the first time. The chromosome numbers of 6 species i.e. Abutilon pannosum, Sida ovata, Sida rhombifolia, T. rhomboidea are reported for the first time from India. Whereas, chromosome studies on Melhania magnifolia have been worked out for the first time, also the occurrence of new cytotypes of Abutilon ramosum (2n = 42) are the first record in global context. Meiotic course is found to be abnormal in case of T. rhomboidea, A. pannosum and A. ramosum with the presence of laggards, chromatin bridges, unoriented bivalents and cytomixis, leading to the reduced pollen fertility and heterogenous sized pollen grains.

Altitudinal variability in anthraquinone constituents from novel cytotypes of Rumex nepalensis Spreng—a high value medicinal herb of North Western Himalayas

Rumex nepalensis is a reputed medicinal herb of North Western Himalayas. It owes its pharmacological significance to an active class of compounds known as anthraquinones. In the present study four different intraspecific cytotypes with varying ploidy level ranging from tetraploidy (4×, 2n=40) to octaploidy (8×, 2n=80) were discovered, hitherto unreported. The investigation also included the evaluation of chemical variability in four major anthraquinone constituents of different cytotypes from five altitudinal habitats of Himalayas using standard HPLC method. There was significant increase in the aglycone components of anthraquinones with the increase in ploidy status, except for dodecaploid type (12×, 2n=120) that showed a decreasing trend in their accumulation. However, the overall concentration of anthraquinones, both glycone and aglycone constituents was found to be highest (33.95%) in the dodecaploid type from Lidderwatt location. Polyploidy, an important driver of eukaryotic evolution is a prevalent feature among angiosperm species providing dynamic genome flexibility to them. Polyploids can undergo rapid structural and functional alterations, allowing them to adapt and persist across heterogeneous landscapes in the long run. It is reflected in the robust adaptability of different cytotypes of R. nepalensis. These display appreciable chemical variability, and ecological plasticity possibly because of the intraspecific polyploidization in response to different ecological niches of a geographical region. The scope of present investigation also extends to identify elite cytotypes in terms of their desirable chemoprofiles for pharmaceutical and commercial purposes.

High Pollen Sterility and 2<i>n</i> Pollen Grains in an Asynaptic 4<i>x</i> Cytotype (2<i>n</i>=48) of <i>Solanum nigrum</i> L.

Cytological investigations have been carried out on the 9 wild accessions of Solanum nigrum L., a medicinally important species having wide-range therapeutic properties. Male meiotic studies performed in 9 accessions revealed the presence of 3 intraspecific cytotypes, 2x (n=12), 4x (n=24) and 6x (n=36) in the species. The course of meiosis in 8 of the 9 accessions among the 2x, 4x, 6x cytotypes was noticed to be perfectly normal resulting in very high pollen fertility (95–100%). However, 1 accession of 4x cytotype scored from Palchan (Solang Valley, Kullu, Himachal Pradesh) depicted irregular chromosomal behaviour during meiosis due to the presence of all 48 chromosomes as univalents. The further course of meiosis in this individual was highly irregular with the presence of large number of lagging and unoriented chromosomes, eccentric positioned univalents in the PMCs and unequal distribution of chromosomes at anaphase-I. Microsporogenesis was also abnormal which is characterized by the presence of irregular sporads, such as dyads, triads and polyads. Lagging chromosomes constituted micronuclei at sporad stages. Consequent to all these meiotic irregularities, 95% of the pollen grains were observed to be sterile. Pollen grains were also recorded to be of different sizes. In meiotically abnormal 4x accession, pollen grains were of 2 different types compared to normal 4x plants showing perfectly normal meiosis. The large pollen grains, which were measured to be 1.25–1.5 times bigger than normal sized pollen grains, were considered as unreduced or 2n pollen grains. The role of such 2n (unreduced) pollen grains in producing polyploid genotypes through sexual polyploidization in a chromosomally variable S. nigrum (2x, 3x, 4x, 5x, 6x, 8x, 9x, 12x) has also been discussed.

Cytomorphological studies of genus Saxifraga L. from Western Himalaya

Cytomorphological studies have been carried out for analysing the cyto-genetic diversity in 14 populations covering 5 species belonging to the genus Saxifraga L. (fam. Saxifragaceae) from Western Himalaya. New intraspecific cytotypes in Saxifraga diversifolia Wall. ex Ser. (n = 8 and n = 16), S. filicaulis Wall. ex Ser. (n = 8) and S. siberica Linn. (n = 16) are added on world-wide basis. Cytotypes of S. flagellaris Willd. (n = 8), S. ligulata Wall. (n = 17) and S. siberica Linn. (n = 8) although worked out earlier from other countries are being reported for the first time from India. Further, comparison of the different cytotypes studied at present for Saxifraga diversifolia Wall. ex Ser and S. siberica Linn. show significant variation in their morphology, and also increased size for morphphological features in the polyploids. The course of meiosis has been observed to be abnormal in all the populations of S. filicaulis Wall. ex Ser., S. flagellaris Willd. and S. siberica Linn., but in S. diversifolia Wall. ex Ser. it exhibited patterns of normal to abnormal behaviour in different populations.

233 INVITED Single nucleotides in the p53 pathway

Rumex nepalensis is a reputed medicinal herb of North Western Himalayas. It owes its pharmacological significance to an active class of compounds known as anthraquinones. In the present study four different intraspecific cytotypes with varying ploidy level ranging from tetraploidy (4×, 2n = 40) to octaploidy (8×, 2n = 80) were discovered, hitherto unreported. The investigation also included the evaluation of chemical variability in four major anthraquinone constituents of different cytotypes from five altitudinal habitats of Himalayas using standard HPLC method. There was significant increase in the aglycone components of anthraquinones with the increase in ploidy status, except for dodecaploid type (12×, 2n = 120) that showed a decreasing trend in their accumulation. However, the overall concentration of anthraquinones, both glycone and aglycone constituents was found to be highest (33.95%) in the dodecaploid type from Lidderwatt location. Polyploidy, an important driver of eukaryotic evolution is a prevalent feature among angiosperm species providing dynamic genome flexibility to them. Polyploids can undergo rapid structural and functional alterations, allowing them to adapt and persist across heterogeneous landscapes in the long run. It is reflected in the robust adaptability of different cytotypes of R. nepalensis. These display appreciable chemical variability, and ecological plasticity possibly because of the intraspecific polyploidization in response to different ecological niches of a geographical region. The scope of present investigation also extends to identify elite cytotypes in terms of their desirable chemoprofiles for pharmaceutical and commercial purposes.

Cytology of genus Sporobolus R. Br. from North India (Punjab plain).

As a result of chromosomal analysis of various populations of five species of genus Sporobolus it has been found that (i) morphologically distinct tetraploid (n=12) and hexaploid (n=18) cytotypes for S. diander and diploid (n=9) and tetraploid (n=18) cytotypes for S. marginatus exist in nature, (ii) cytomixis leading to aneuploid numbers characterises S. helvolus and (iii) abnormal meiosis results in reduced pollen fertility in S. indicus.All the five species are polyploids. On the basis of cumulative world wide data 83% of the species of genus Sporobolus are polyploids and intraspecific cytotypes exist in a large number of species. This calls for taxonomic revision of the genus in the light of cytomorphological evidence.