DSpace Repository :: Browsing by Author "Nagarajan, P."

Browsing by Author "Nagarajan, P."

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Bulk Line Analysis in Coconut (Cocos nucifera L.) for Inferring Relationship between Talls, Dwarfs and Niu Leka Dwarf Forms
(2010) Manimekalai, R.; Nagarajan, P.
Coconut is an important an oil crop of India. Coconut (Cocos nucifera L.) is botanically classified in to two major groups based on its stature as Tall palms and as Dwarf palms. The Talls can also be referred to as var. Typica (Nav) and the Dwarfs as var. Nana (Griff). Further, intermediate forms of coconut referred to as Aurantiaca are also available. The technique Bulk Line analysis is employed for the identification of tall / dwarf bulk specific RAPD marker. Thirty random primers were used to amplify the DNA bulks of talls, dwarfs and intermediate coconut types. Out of 30 primers 22 primers showed polymorphism between the DNA bulks. The primers OPM 02, OPM 06, OPC 13 produced specific markers. Out of 40 polymorphic markers five markers were common to tall bulk and dwarf bulk; on the other hand 29 markers were common between the tall bulk and Niu Leka Dwarf. To reveal the overall relationship between the bulked samples presence or absence of RAPD marker data were analysed with the NTSYS software. Jaccard’s similarity coefficient was highest between talls and Niu Leka Dwarf. The resultant dendrogram showed clustering of talls and Niu Leka types together whereas, dwarf types were separated out.
DNA polymorphism among coconut (Cocos nucifera L.) cultivars and reciprocal cross derivatives differing in drought tolerance
(2004-12) Manimekalai, R.; Nagarajan, P.; Bharathi, M.; Naresh Kumar, S.
Coconut seedlings of Laccadive Ordinary Tall (LCT). Gangabondam Green Dwarf (GBGD) and their reciprocal cross combinations were analysed by molecular markers viz. Random Amplified Polymorphic DNA (RAPD) and Inter Simple Sequence Repeats (ISSR). These seedlings were evaluated for water stress tolerance based on leaf water potential measured during stress and non- stress periods. Thc leaf water potential decreased during stress period. The differences among the individuals for leaf water poteniial during stress were not significant. The molecular markers revealed the genetic structure of the cultivars and derivatives clearly. In the dendrogram. individuals of GBGD and GBGD X LCT formed one cluster and LCT and LCT X GBGD formed another cluster. The individuals of LCT and LCT X GBGD showed variation among themselves and they were scattered in the principal co-ordinate plot. Even though the parents are same. the reciprocal cross derivatives behaved differently for leaf water potential and showed polymorphism at DNA level. When the dwarf palm was used as female parent, the F, s were similar to female parent in their banding pattern.
Genetic survey of 10 Indian coconut landraces by simple sequence repeats (SSRs)
(Elsevier, 2008) Rajesh, M.K.; Arunachalam, V.; Nagarajan, P.; Lebrun, P.; Samsudeen, K.; Thamban, C.
A rich genetic diversity of coconut exists in farmer’s fields, which represent valuable genetic resource for breeding. The study was conducted to assess the pattern of diversity in 102 coconut palms representing 10 landraces from 3 coconut-growing communities of India using 14 simple sequence repeat (SSR) markers. A total of 90 alleles were detected with an average of 6.42 alleles per locus and an average polymorphism information content of 0.61. Expected heterozygosity (He) was highest for the two tall landraces from Pallikkara community, while the least heterozygosity was observed for the dwarf coconut landraces from Vayalar community. Mean fixation index (FST) of 0.42 indicates a high level of population differentiation. A low gene flow (Nm) of 0.37 was observed. Based on molecular data, genetic similarities were calculated. The unweighted pair group method with arithmetic averages (UPGMA) cluster analysis grouped the landraces according to their geographical locations and breeding behaviour. The practical implications of this study in farmer participatory evaluation and conservation of coconut genetic resources are highlighted.
Genetic variation of selected progney lines of coconut(cocos nucifera.L) based on simple sequence repeat markers
(2005) Manimekalai, R.; Nagarajan, P.; Bharathi, M.; Karun, A.; Kumar, S.N.; Kumaran, P.M.
Interrelationships among coconut (Cocos nucifera L.) accessions using RAPD technique
(Springer, 2006) Manimekalai, R.; Nagarajan, P.
The genetic relationships among 33 coconut germplasm accessions were analyzed using RAPD markers. The germplasm accessions were collected from various coconut growing regions viz. South Asia (SA), South East Asia (SEA), South Pacific (SP), Atantic and America, and Africa. Forty-five random primers produced a total of 399 polymorphic markers. The Polymorphism Information Content (PIC) ranged from 0.031 to 0.392 and the Marker Index (MI) ranged from 6.28 to 0.031 among the primers. Based on the MI a set of 5, 10 and 15 informative and reproducible primers were identified. The mantel matrix correlation was calculated to compare the similarity matrices of a set of reproducible informative primers and global primers. There was significant correlation among the similarity matrices (r‡ 0.50). The similarity matrix based on 399 polymorphic markers was used to construct the dendrogram to show the genetic relationship among the accessions. Similarity values ranged between 0.573 and 0.846. There was less genetic similarity (based on Jaccard’s coefficient) among South Pacific and South East Asian accessions. The clustering pattern obtained in the present study was in agreement with the earlier reports based on RFLP, SSRs and AFLPs.
Isolation and characterization of WRKY genes in coconut (Cocos nucifera L.)
(2006) Rajesh, M.K.; Bharathi, M.; Nagarajan, P.
WRKY proteins are plant-specific transcriptional factors associated with regulation of defense responses to both biotic and abiotic stresses. in the present study, degenerate PCR primers were designed to the highly conserved WRKY DNA binding domain and these were used to isolate putative WRKY genes from coconut. Six DNA fragments were isolated using five pairs of degenerate primers and these Were cloned. Sequencing of these cloned fragments was done and their amino acid sequences deduced. Homology search of the deduced amino acid sequences against non-redundant GenBank protein database revealed significant sequence similarity of two of the cloned fragments to known WRK Y genes. The other four cloned fragments showed homology to known stress responsive genes. Cluster analysis based on neighbour-joining method was carried out using the putative coconut WRKY genes with other known WRKY genes. These results demonstrate that PCR amplification with appropriately designed degenerate primers is an efficient approach for cloning WRKY genes.
Microsatellite variability of coconut accessions (Cocos nucifera L.) from Andaman and Nicobar Islands
(2008) Rajesh, M.K.; Nagarajan, P.; Jerard, B.A.; Arunachalam, V.; Dhanapal, R.
The extent of genetic diversity in 26 coconut accessions from the Andaman and Nicobar (A&N) Islands was determined using 14 microsatellite markers. A total of 103 alleles were detected by the microsatellite markers with an average of 7.35 alleles per locus. The average observed and expected heterozygosity was 0.29 and 0.66 respectively. A mean fixation index (FST) of 0.49 was observed, indicating a high level of population differentiation among the coconut accessions. Heterozygosity was highest in tall coconut accessions. Majority of rare alleles were observed in tall accessions from the Nicobar Islands. The UPGMA dendrogram revealed clustering of majority of tall and dwarf accessions separately. This study using microsatellites confirms the rich genetic diversity of coconut accessions from A&N Islands.
Molecular diversity among South East Asian coconut (Cocos nucifera L.) germplasm accessions based on ISSR markers
(2005-01) Manimekalai, R.; Nagarajan, P.; Bharathi, M.; Anitha Karun; Kumaran, P.M.; Parthasarathy, V.A.
Optimization of DNA Isolation and RAPD Technique in Arecanut (Areca catechu L.)
(2007) Rajesh, M.K.; Bharathi, M.; Nagarajan, P.
A simple and efficient protocol for extracting high quality DNA from arecanut (Areca catechu L.) leaves is presented. DNA yield and purity were monitored by gel electrophoresis and by determining absorbance at UV (A260/A280). The ratio was between 1.7 to 1.9 indicating that the presence of contaminating metabolites was minimal. The quantities of DNA obtained were 100- 400 ig/g starting material. The isolated DNA proved amenable to PCR amplification and restriction digestion. DNA was completely digested with the three restriction enzymes (EcoR I, EcoR V and Hind III) confirming the purity of the extracted DNA. Using the isolated DNA, the parameters for randomly amplified polymorphic DNA (RAPD) protocol was standardized.
SSR and ISSR Markers based Population Genetic Structure of Coconut (Cocos nucifera L.) Germplasm Accessions
(2010) Manimekalai, R.; Nagarajan, P.
The coconut palm (Cocos nucifera L.) is one of the major perennial oil crops of tropics. Population genetic structure was assessed among 33 accessions (4 individuals per accession) with ISSR and SSR markers. The molecular marker data were analyzed with POPGENE and ARLEQUIN software. The parameters derived were, Shannon’s index, differentiation indices (Fst and Gst) and molecular variances. The diversity was partitioned into ‘within population’ (59.82% and 68.56% based on ISSR and SSR markers, respectively) and ‘between populations’ (40.18% and 31.44% based on ISSR and SSR markers, respectively). Relatively high ‘between populations’ diversity was present in the accessions belonging to South Pacific region reflecting higher population differentiation. Dwarfs and intermediate coconut types also maintained high ‘between populations’ diversity due its autogamous behaviour. There was overall reduction in the number of markers (ISSR and SSR) among the dwarfs and intermediate populations. The study provided useful information regarding the genetic makeup of the coconut germplasm accessions and their utilization in breeding.

Browsing by Author "Nagarajan, P."

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