Molecular cloning and characterization of phospholipase D from <Emphasis Type="Italic">Jatropha curcas</Emphasis>

Phospholipase D (PLD, EC 3.1.4.4) is a key enzyme involved in phospholipid catabolism, initiating a lipolytic cascade in membrane deterioration during senescence and stress, which was cloned from Jatropha curcas L., an important plant species as its seed is the raw material for biodiesels. The cDNA was 2,886 bp in length with a complete open reading frame of 2,427 bp which encoded a polypeptide of 808 amino acids including a putative signal peptide of 53 amino acid residues and a mature protein of 755 amino acids with a predicted molecular mass of 86 kD and a pI of 5.44, having two highly conserved ‘HKD’ motifs. Phylogenetic analysis indicated the J. curcas PLD alpha (JcPLDα) showed a high similarity to other PLD alpha from plants. Semi-quantitative RT-PCR analysis revealed that it was especially abundant in root, stem, leaf, endosperm and flower, weakly in seed. And the JcPLDα was increasedly expressed in leaf undergoing environmental stress such as salt (300 mM NaCl), drought (30% PEG), cold (4°C) and heat (50°C). The JcPLDα protein was successfully expressed in Escherichia coli and showed high enzymatic activities. Maximal activity was at pH 8 and 60°C.     

Parental and Heterotic Effects in <Emphasis Type="Italic">Jatropha curcas</Emphasis> L. Seedlings

Jatropha curcas L. (jatropha) is an important undomesticated perennial plant with high potential for sustainable production of food and fuel in tropical and subtropical regions. However, jatropha has no breeding history and genetic improvement of this novel crop is at an early stage. Therefore, it is of utmost importance to understand the significance of parental and heterotic effects that could be exploited in hybrid combinations. The main goal of this study was to assess the parental and heterotic effects at an early plant age in seedling traits. Our objectives were to (i) examine the variation of traits among genotypes, between genetic pools and fecundation types, (ii) investigate the parental and heterotic effects on these traits, and (iii) discuss the exploitation of parental and heterotic effects in jatropha breeding programs. Genotypes from two genetic pools were used to perform intra- and interpool crosses. Data on germination time, plant height, area of cotyledon and primary leaf, chlorophyll content of primary leaf, number of leaves, and shoot dry mass were investigated. Maternal and paternal effects affected the expression of traits at the seedling stage in jatropha. The level of influence depended on the trait and the parents under consideration. Heterotic effects were present for all seedling traits. The largest heterotic effect was found in an interpool cross.     

Molecular characterization and identification of markers for toxic and non-toxic varieties of <Emphasis Type="Italic">Jatropha curcas</Emphasis> L. using RAPD,AFLP and SSR markers

Jatropha curcas L., a multipurpose shrub has acquired significant economic importance for its seed oil which can be converted to biodiesel, is emerging as an alternative to petro-diesel. The deoiled seed cake remains after oil extraction is toxic and cannot be used as a feed despite having best nutritional contents. No quantitative and qualitative differences were observed between toxic and non-toxic varieties of J. curcas except for phorbol esters content. Development of molecular marker will enable to differentiate non-toxic from toxic variety in a mixed population and also help in improvement of the species through marker assisted breeding programs. The present investigation was undertaken to characterize the toxic and non-toxic varieties at molecular level and to develop PCR based molecular markers for distinguishing non-toxic from toxic or vice versa. The polymorphic markers were successfully identified specific to non-toxic and toxic variety using RAPD and AFLP techniques. Totally 371 RAPD, 1,442 AFLP markers were analyzed and 56 (15.09%) RAPD, 238 (16.49%) AFLP markers were found specific to either of the varieties. Genetic similarity between non-toxic and toxic verity was found to be 0.92 by RAPD and 0.90 by AFLP fingerprinting. In the present study out of 12 microsatellite markers analyzed, seven markers were found polymorphic. Among these seven, jcms21 showed homozygous allele in the toxic variety. The study demonstrated that both RAPD and AFLP techniques were equally competitive in identifying polymorphic markers and differentiating both the varieties of J. curcas. Polymorphism of SSR markers prevailed between the varieties of J. curcas. These RAPD and AFLP identified markers will help in selective cultivation of specific variety and along with SSRs these markers can be exploited for further improvement of the species through breeding and Marker Assisted Selection (MAS).     

Molecular characterization and genetic diversity analysis of <Emphasis Type="Italic">Jatropha curcas</Emphasis> L. in India using RAPD and AFLP analysis

Jatropha curcas L. belongs to family Euphorbiaceae, native to South America and widely distributed in South and Central America, attained significant importance for its seed oil which can be converted to biodiesel, a renewable energy source alternative to conventional petro-diesel. Very few attempts were made to understand the extent of genetic diversity that exists in J. curcas. Therefore, the present investigation was undertaken to asses the genetic diversity among 28 diverse germplasm collected from distinct geographical areas in India. The overall percentage of polymorphism (PP) was found to be 50.70 and 60.95 by RAPD and AFLP, respectively. The mean PP was found to be 9.72 and 20.57 by RAPD and AFLP, respectively. The mean genetic similarity was observed to be 0.89 by RAPD and 0.88 by AFLP. Among the germplasm JCI20 found to be the most diverged one. The dendrogram analysis of RAPD and AFLP data showed good congruence, but better resolution and more polymorphism was observed with AFLP. When the dendrogram of RAPD was compared with AFLP dendrogram, the major clustering pattern was found to be similar; however, changes in minor grouping were observed. In both RAPD and AFLP analysis clustering of germplasm did not show any correlation with the geographical area of collection. Low genetic diversity observed in J. curcas and the clustering pattern indicates that the distribution of species might have happened through anthropogenic activity and warrants the need for widening the genetic base. The present study will provide pavement for further intra-population studies on narrow geographical areas, to understand the population genetic structure, phylogeography, molecular ecological studies. The marker information and the characterized germplasm help in further improvement of the species through marker assisted breeding programs.     

Analysis of the genetic diversity of physic nut, <Emphasis Type="Italic">Jatropha curcas</Emphasis> L. accessions using RAPD markers

A sum of 48 accessions of physic nut, Jatropha curcas L. were analyzed to determine the genetic diversity and association between geographical origin using RAPD-PCR markers. Eight primers generated a total of 92 fragments with an average of 11.5 amplicons per primer. Polymorphism percentages of J. curcas accessions for Selangor, Kelantan, and Terengganu states were 80.4, 50.0, and 58.7%, respectively, with an average of 63.04%. Jaccard’s genetic similarity co-efficient indicated the high level of genetic variation among the accessions which ranged between 0.06 and 0.81. According to UPGMA dendrogram, 48 J. curcas accessions were grouped into four major clusters at coefficient level 0.3 and accessions from same and near states or regions were found to be grouped together according to their geographical origin. Coefficient of genetic differentiation (G_st) value of J. curcas revealed that it is an outcrossing species.     

Establishment of an <Emphasis Type="Italic">Agrobacteriuim</Emphasis>-mediated cotyledon disc transformation method for <Emphasis Type="Italic">Jatropha curcas</Emphasis>

Jatropha curcas contains high amounts of oil in its seed and has been considered for bio-diesel production. A transformation procedure for J. curcas has been established for the first time via Agrobacterium tumefaciens infection of cotyledon disc explants. The results indicated that the efficiency of transformation using the strain LBA4404 and phosphinothricin for selection was an improvement over that with the strain EHA105 and hygromycin. About 55% of the cotyledon explants produced phosphinothricin-resistant calluses on Murashige and Skoog (MS) medium supplemented with 1.5 mg l⁻¹ benzyladenine (BA), 0.05 mg l⁻¹ 3–indolebutyric acid (IBA), 1 mg l⁻¹ phosphinothricin and 500 mg l⁻¹ cefotaxime after 4 weeks. Shoots were regenerated following transfer of the resistant calli to shoot induction medium containing 1.5 mg l⁻¹ BA, 0.05 mg l⁻¹ IBA, 0.5 mg l⁻¹ gibberellic acid (GA3), 1 mg l⁻¹ phosphinothricin and 250 mg l⁻¹ cefotaxime, and about 33% of the resistant calli differentiated into shoots. Finally, the resistant shoots were rooted on 1/2 MS media supplemented with 0.3 mg l⁻¹ IBA at a rate of 78%. The transgenic nature of the transformants was demonstrated by the detection of β-glucuronidase activity in the primary transformants and by PCR and Southern hybridization analysis. 13% of the total inoculated explants produced transgenic plants after approximately 4 months. The procedure described will be useful for both, the introduction of desired genes into J. curcas and the molecular analysis of gene function.     

Stress-induced curcin-L promoter in leaves of <Emphasis Type="Italic">Jatropha curcas</Emphasis> L. and characterization in transgenic tobacco

Ribosome-inactivating proteins (RIPs) represent a type of protein that universally inactivates the ribosome thus inhibiting protein biosynthesis. Curcin-L was a type I RIP found in Jatropha curcas L.. Its expression could be activated in leaves by treatments with abscisic acid, salicylic acid, polyethylene glycol, temperature 4, 45°C and ultraviolet light. A 654 bp fragment of a 5′ flanking region preceding the curcin-L gene, designated CP2, was cloned from the J. curcas genome and its expression pattern was studied via the expression of the β-glucuronidase (GUS) gene in transgenic tobacco. Analysis of GUS activities showed that the CP2 was leaf specific, and was able to drive the expression of the reporter gene under stress-induction conditions. Analysis of a series of 5′-deletions of the CP2 suggested that several promoter motifs were necessary to respond to environmental stresses.     

<Emphasis Type="Italic">Amycolatopsis endophytica</Emphasis> sp. nov., a novel endophytic actinomycete isolated from oil-seed plant <Emphasis Type="Italic">Jatropha curcas</Emphasis> L.

A novel actinomycete, designated KLBMP 1221^T, was isolated from the surface-sterilized seeds of an oil-seed plant Jatropha curcas L. collected from Sichuan Province, south-west China and was characterized taxonomically by using a polyphasic approach. Phylogenetic analyses based on 16S rRNA gene sequence showed that this strain formed a distinct phyletic line within the radiation of the genus Amycolatopsis. The 16S rRNA gene sequence similarity indicated that strain KLBMP 1221^T was most closely related to Amycolatopsis eurytherma NT202^T (98.9%), Amycolatopsis tucumanensis ABO^T (98.8%), Amycolatopsis thermoflava N1165^T (98.6%) and Amycolatopsis methanolica IMSNU 20055^T (98.5%). Strain KLBMP 1221^T had morphological and chemotaxonomic properties that were consistent with its classification in the genus Amycolatopsis. However, DNA–DNA relatedness data and phenotypic differences clearly distinguished the isolate from its closest relatives. Based on the combined genotypic and phenotypic evidence, it is proposed that strain KLBMP 1221^T be classified as representative of a novel species for which the name Amycolatopsis endophytica sp. nov. is proposed. The type strain is KLBMP 1221^T (= KCTC 19776^T = CCTCC AA 2010003^T).     

Changes in DNA methylation levels during seed development in <Emphasis Type="Italic">Jatropha curcas</Emphasis>

The antiviral action of natural killer (NK) cells is regulated by a wide repertoire of germ-line encoded membrane receptors which recognize the expression of certain self-molecules on target cells. Among the receptors, killer cell immunoglobulin-like receptor (KIR) which recognizes the expression of human leukocyte antigen (HLA) class I has a predominant role in regulating the effector functions of NK cells, particularly in viral infections. We studied a total of 128 hepatitis B virus (HBV) patients (15 acute, 43 asymptomatic, 27 chronic and 43 with other liver diseases) while attending the Department of Medical Gastroenterology, Government Rajaji Hospital, Madurai, India, and 128 ethnic matched control to find the association between the KIR : HLA genes and differential manifestations of HBV. KIR and its ligand HLA polymorphism were identified by DNA-PCR methods. The activatory receptor KIR-2DS1 was significantly elevated in various disease categories, namely asymptomatic, chronic and other HBV, except acute HBV infection. Whereas, KIR 2DS3 in acute and chronic patients and KIR 2DS5 and 3DS1 in asymptomatic individuals. Among various KIR–HLA combinations, homozygous 2DS2:C1 and individuals with 3DSI:BW4 (OR = 3.23, CI = 1.55–6.7, Pc = 0.02) are associated with HBV asymptomatism, while most of the two domain inhibitory receptors with their ligands showed significant risk in other liver diseases. Further, KIR3DL1 : HLA Bw4Iso80 (OR = 3.89, 95% CI = 1.58–9.55, Pc = 0.004) is related with higher risk for asymptomatic infection when compared with chronic HBV. Thus, the select KIR : HLA alleles and combinations seem to direct the NK cell activities and immune response in different directions resulting in varied symptoms and manifestations in the subgroups of HBV-infected patients studied.     

<Emphasis Type="Italic">Ty</Emphasis>1<Emphasis Type="Italic">/copia</Emphasis>- and <Emphasis Type="Italic">Ty</Emphasis>3<Emphasis Type="Italic">/gypsy</Emphasis>-like DNA sequences in <Emphasis Type="Italic">Helianthus </Emphasis>species

Two repeated DNA sequences isolated from a partial genomic DNA library of Helianthus annuus, p HaS13 and p HaS211, were shown to represent portions of the int gene of a Ty3 /gypsy retroelement and of the RNase-Hgene of a Ty1 /copia retroelement, respectively. Southern blotting patterns obtained by hybridizing the two probes to BglII- or DraI-digested genomic DNA from different Helianthus species showed p HaS13 and p HaS211 were parts of dispersed repeats at least 8 and 7 kb in length, respectively, that were conserved in all species studied. Comparable hybridization patterns were obtained in all species with p HaS13. By contrast, the patterns obtained by hybridizing p HaS211 clearly differentiated annual species from perennials. The frequencies of p HaS13- and p HaS211-related sequences in different species were 4.3x10(4)-1.3x10(5) copies and 9.9x10(2)-8.1x10(3) copies per picogram of DNA, respectively. The frequency of p HaS13-related sequences varied widely within annual species, while no significant difference was observed among perennial species. Conversely, the frequency variation of p HaS211-related sequences was as large within annual species as within perennials. Sequences of both families were found to be dispersed along the length of all chromosomes in all species studied. However, Ty3 /gypsy-like sequences were localized preferentially at the centromeric regions, whereas Ty1/ copia-like sequences were less represented or absent around the centromeres and plentiful at the chromosome ends. These findings suggest that the two sequence families played a role in Helianthusgenome evolution and species divergence, evolved independently in the same genomic backgrounds and in annual or perennial species, and acquired different possible functions in the host genomes.     

Leaf-residing <Emphasis Type="Italic">Methylobacterium</Emphasis> species fix nitrogen and promote biomass and seed production in <Emphasis Type="Italic">Jatropha curcas</Emphasis>

Background

Jatropha curcas L. (Jatropha) is a potential biodiesel crop that can be cultivated on marginal land because of its strong tolerance to drought and low soil nutrient content. However, seed yield remains low. To enhance the commercial viability and green index of Jatropha biofuel, a systemic and coordinated approach must be adopted to improve seed oil and biomass productivity. Here, we present our investigations on the Jatropha-associated nitrogen-fixing bacteria with an aim to understand and exploit the unique biology of this plant from the perspective of plant–microbe interactions.

Results

An analysis of 1017 endophytic bacterial isolates derived from different parts of Jatropha revealed that diazotrophs were abundant and diversely distributed into five classes belonging to α, β, γ-Proteobacteria, Actinobacteria and Firmicutes. Methylobacterium species accounted for 69.1 % of endophytic bacterial isolates in leaves and surprisingly, 30.2 % which were able to fix nitrogen that inhabit in leaves. Among the Methylobacterium isolates, strain L2-4 was characterized in detail. Phylogenetically, strain L2-4 is closely related to M. radiotolerans and showed strong molybdenum-iron dependent acetylene reduction (AR) activity in vitro and in planta. Foliar spray of L2-4 led to successful colonization on both leaf surface and in internal tissues of systemic leaves and significantly improved plant height, leaf number, chlorophyll content and stem volume. Importantly, seed production was improved by 222.2 and 96.3 % in plants potted in sterilized and non-sterilized soil, respectively. Seed yield increase was associated with an increase in female–male flower ratio.

Conclusion

The ability of Methylobacterium to fix nitrogen and colonize leaf tissues serves as an important trait for Jatropha. This bacteria–plant interaction may significantly contribute to Jatropha’s tolerance to low soil nutrient content. Strain L2-4 opens a new possibility to improve plant’s nitrogen supply from the leaves and may be exploited to significantly improve the productivity and Green Index of Jatropha biofuel.

     

Biosynthesis and characterization of copolymer poly(3HB-<Emphasis Type="Italic">co</Emphasis>-3HV) from saponified <Emphasis Type="Italic">Jatropha curcas</Emphasis> oil by <Emphasis Type="Italic">Pseudomonas oleovorans</Emphasis>

Polyhydroxyalkanoates (PHAs) are naturally occurring biodegradable polymers with promising application in the formulation of plastic materials. PHAs are produced by numerous bacteria as energy/carbon storage materials from various substrates, including sugars and plant oils. Since these substrates compete as food sources, their use as raw material for industrial-scale production of PHA is limited. Therefore, efforts have been focused on seeking alternative sources for bacterial production of PHA. One substrate that seems to have great potential is the seed oil of Jatropha curcas plant. Among other favorable properties, J. curcas seed oil is non-edible, widely available, and can be cheaply produced. In this study, Pseudomonas oleovorans (ATCC 29347) was grown in a mineral salt medium supplemented with saponified J. curcas seed oil as the only carbon source under batch fermentation. Optimum PHA yield of 26.06% cell dry weight was achieved after 72 h. The PHA had a melting point (T _m) between 150 and 160°C. Results of polymer analyses by gas chromatography/mass spectrometry (GC/MS) identified only the methyl 3-hydroxybutanoate monomeric unit. However, electrospray ionization–time of flight mass spectroscopy (ESI–TOF MS) confirmed that the PHA was a copolymer with the characteristic HB/HV peaks at m/z 1155.49 (HB) and 1,169, 1,184–1,194 (HV). The data were further supported by¹H and ¹³C NMR analysis. Polymer analysis by gel permeation chromatography (GPC) indicated a peak molecular weight (MP) of 179,797, molecular weight (M _W) of 166,838, weight number average mass (M _n) of 131,847, and polydispersity (M _w/M _n) of 1.3. The data from this study indicate that J. curcas seed oil can be used as a substrate to produce the copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3HB-co-3HV).     

Isolation and characterization of microsatellite DNA markers for the flagfish <Emphasis Type="Italic">Jordanella </Emphasis><Emphasis Type="Italic">floridae</Emphasis>

The flagfish (Jordanella floridae) is commonly used in studies of wetlands ecology. Here we describe the isolation of ten microsatellite loci, six of which were polymorphic. The observed number of alleles ranged from 4 to 24 and observed heterozygosities ranged from 0.59 to 0.81 for the polymorphic loci. The isolation of these markers will enable estimations of genetic diversity in natural populations.     

Stimulation of the growth of <Emphasis Type="Italic">Jatropha curcas</Emphasis> by the plant growth promoting bacterium <Emphasis Type="Italic">Enterobacter cancerogenus</Emphasis> MSA2

A novel Enterobacter cancerogenus MSA2 is a plant growth promoting gamma-proteobacterium that was isolated from the rhizosphere of Jatropha cucas a potentially important biofuel feed stock plant. Based on phenotypic, physiological, biochemical and phylogenetic studies, strain MSA2 could be classified as a member of E. cancerogenus. However, comparisons of characteristics with other known species of the genus Enterobacter suggested that strain MSA2 could be a novel PGPB strain. In vitro studies were carried for the plant growth promoting attribute of this culture. It tested positive for ACC (1-aminocyclopropane-1-carboxylic acid) deaminase production, phytase, phosphate solubilization, IAA (Indole acetic acid) production, siderophore, and ammonia production. The isolate was then used as a inoculant for the vegetative study of Jatropha curcas plant. Enterobacter cancerogenus MSA2 supplemented with 1% carboxymethylcellulose showed overall plant growth promotion effect resulting in enhanced root length (124.14%), fresh root mass (81%), fresh shoot mass (120.02%), dry root mass (124%), dry shoot mass (105.54%), number of leaf (30.72%), chlorophyll content (50.41%), and biomass (87.20%) over control under the days of experimental observation. This study was designed for 120 days and was in triplicate and the data was collected at every 30 days.     

Molecular Detection of <Emphasis Type="Italic">Streptococcus pyogenes</Emphasis> and <Emphasis Type="Italic">Streptococcus dysgalactiae</Emphasis> subsp. <Emphasis Type="Italic">equisimilis</Emphasis>

We developed molecular diagnostic assays for the detection of Streptococcus pyogenes (GAS) and Streptococcus dysgalactiae subsp. equisimilis (SDSE), two streptococcal pathogens known to cause both pharyngitis and more invasive forms of disease in humans. Two real-time PCR assays coupled with an internal control were designed to be performed in parallel. One assay utilizes a gene target specific to GAS, and the other utilizes a gene target common to the two species. Both assays showed 2–3 orders of magnitude improved analytical sensitivity when compared to a commercially available rapid antigen test. In addition, when compared to standard culture in an analysis of 96 throat swabs, the real-time PCR assays resulted in clinical sensitivity and specificity of 91.7 and 100%, respectively. As capital equipment costs for real-time PCR can be prohibitive in smaller laboratories, the real-time PCR assays were converted to a low-density microarray format designed to function with an inexpensive photopolymerization-based non-enzymatic signal amplification (NESA™) method. S. pyogenes was successfully detected on the low-density microarray in less than 4 h from sample extraction through detection.     

Molecular cloning and characterization of the <Emphasis Type="Italic">MsHSP17.7</Emphasis> gene from <Emphasis Type="Italic">Medicago sativa</Emphasis> L.

Heat shock proteins (HSPs) are ubiquitous protective proteins that play crucial roles in plant development and adaptation to stress, and the aim of this study is to characterize the HSP gene in alfalfa. Here we isolated a small heat shock protein gene (MsHSP17.7) from alfalfa by homology-based cloning. MsHSP17.7 contains a 477-bp open reading frame and encodes a protein of 17.70-kDa. The amino acid sequence shares high identity with MtHSP (93.98 %), PsHSP17.1 (83.13 %), GmHSP17.9 (74.10 %) and SlHSP17.6 (79.25 %). Phylogenetic analysis revealed that MsHSP17.7 belongs to the group of cytosolic class II small heat shock proteins (sHSP), and likely localizes to the cytoplasm. Quantitative RT-PCR indicated that MsHSP17.7 was induced by heat shock, high salinity, peroxide and drought stress. Prokaryotic expression indicated that the salt and peroxide tolerance of Escherichia coli was remarkably enhanced. Transgenic Arabidopsis plants overexpressing MsHSP17.7 exhibited increased root length of transgenic Arabidopsis lines under salt stress compared to the wild-type line. The malondialdehyde (MDA) levels in the transgenic lines were significantly lower than in wild-type, although proline levels were similar between transgenic and wild-type lines. MsHSP17.7 was induced by heat shock, high salinity, oxidative stress and drought stress. Overexpression analysis suggests that MsHSP17.7 might play a key role in response to high salinity stress.     

Development of new molecular markers for the <Emphasis Type="Italic">Colletotrichum</Emphasis> genus using <Emphasis Type="Italic">RetroCl1</Emphasis> sequences

A nonautonomous element of 624 bp, called RetroCl1 (Retroelement Colletotrichum lindemuthianum 1), was identified in the plant pathogenic fungus Colletotrichum lindemuthianum. RetroCl1 contains terminal direct repeats (223 bp) that are surrounded by CTAGT sequences. It has a short internal domain of 178 bp and shows characteristics of terminal-repeat retrotransposon in miniature (TRIM) family. We used RetroCl1 sequence to develop molecular markers for the Colletotrichum genus. IRAP (Inter-Retrotransposon Amplified Polymorphism) and REMAP (Retrotransposon-Microsatellite Amplified Polymorphism) markers were used to analyze the genetic diversity of C. lindemuthianum. Fifty-four isolates belonging to different races were used. A total of 45 loci were amplified. The Nei index showed significant differences among the populations divided according to race, indicating that they are structured according to pathotype. No clear correlation between IRAP and REMAP markers with pathogenic characterization was found. C. lindemuthianum has high genetic diversity, and the analysis of molecular variance showed that 51% of variability is found among the populations of different races. The markers were also tested in different Colletotrichum species. In every case, multiple bands were amplified, indicating that these markers can be successfully used in different species belonging to the Colletotrichum genus.     

Cytogenetic characterization of <Emphasis Type="Italic">Amaranthus caudatus</Emphasis> L. and <Emphasis Type="Italic">Amaranthus hybridus</Emphasis> subsp<Emphasis Type="Italic">. cruentus</Emphasis> (L.) Thell.

The present study is aimed to identify genetic variability between two species of Amaranthus viz., A. caudatus and A. hybridus subsp. cruentus, two economically important species, cultivated mainly for grain production. Karyomorphological studies in Amaranthus are scarce, probably due to higher number of small sized chromosomes. Karyomorphological studies were conducted using mitotic squash preparation of young healthy root tips. Karyological parameters and karyotypic formula were established using various software programs and tabulated the karyomorphometric and asymmetry indices viz., Disparity index, Variation coefficient, Total forma percentage, Karyotype asymmetry index, Syi index, Rec index, Interchromosomal and Intrachromosomal asymmetry index and Degree of asymmetry of karyotypes. The mitotic chromosome number observed for A. caudatus was 2n = 32 with a gametic number n = 16 and A. hybridus subsp. cruentus was 2n = 34 with a gametic number n = 17. In A. caudatus the chromosome length during somatic metaphase ranged from 0.8698 to 1.7722 μm with a total length of 39.1412 μm. In A. hybridus subsp. cruentus the length of chromosome ranged from 0.7756 to 1.9421 μm with a total length of 44.9922 μm. Various karyomorphometry and asymmetry indices analyzed revealed the extend of interspecific variation and their evolutionary status.