Browsing by Author "Lekha Sreekantan"
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ArticleItem Open Access Evaluation of cowpea + fodder maize intercropping under varying fertilizer levels in summer rice fallows(Kerala Agricultural University, 1994) Sunitha, S; Lekha Sreekantan; KAUThesisItem Open Access Identification and characterization of flowering T (FT) gene in black pepper (Piper nigrum L.)(Department of Plant Biotechnology, College of Agriculture, Vellayani, 2016) Sooraj, J R; KAU; Lekha SreekantanThe study entitled “Identification and characterization of Flowering Locus T (FT) gene in black pepper (Piper nigrum L.)”, was carried out at the Integrated Biotechnology Block, College of Agriculture, Vellayani during 2015-2016. The main objective of the study was the isolation, cloning and sequencing of genes homologous to FT, a floral integrator gene from black pepper and functional characterization of the gene by studying its temporal and spatial expression patterns. The sample material used for this study was black pepper (Karimunda variety). Black pepper samples at different stages were collected from the Instructional Farm, College of Agriculture, Vellayani and RNA and DNA were extracted. cDNA was prepared from RNA by reverse transcription. PCR (Polymerase chain reaction) was done using both genomic DNA and cDNA with different degenerate primers and showed amplifications in nested reactions with expected size ~141 bp and ~256 bp. The amplicons were sequenced after elution and purification. Further sequence analysis using tBLASTx, NCBI conserved Domain Search and Clustal Phylogeny program showed that the sequence of the amplicons obtained around 124 bp and 230 bp were the partial fragments of flowering time and floral integrator gene named FT and inflorescence meristem identity gene named TERMINAL FLOWER 1 (TFL1) from black pepper. NCBI conserved Domain Search programme, showed that both the FT and TFL1 sequences belonged to PEBP (Phosphatidyl Ethanolamine- Binding Protein) super family and phylogenetic tree created from Clustal Phylogeny program also showed that the FT (124 bp) sequence was closer to FT mRNA of Cymbidium faberi and Oryza sativa. TFL1 (230 bp) sequence was closer to TFL1 mRNA of Solanum tuberosum. Semi quantitative analysis with FT primers showed that the FT gene was expressed in the mature spike with berries, spike with young berries, mature leaves, spikes with flowers, immature spikes and plagiotropic shoots. The expression of TFL1 gene was observed in mature leaves and slightly in spike with flowers. Microscopy studies were done including fixation of pepper spike tissues in the fixative FAA (Formaldehyde acetic acid alcohol) solution and Carnoy’s fluid, followed by sectioning of the tissues and staining with safranin and fast green to see the changes occurring in different development stages of spikes ranging from immature spike to mature spike with berries. Sequence analysis and expression studies confirmed that the isolated sequences were partial orthologues of PEBP genes from black pepper and this study has identified the flowering time and floral integrator gene (FT) and the inflorescence meristem identity gene (TFL1) from black pepper for the very first time.ThesisItem Open Access Identification and characterization of Suppressor of Overexpression of Constans1 (SOC1) gene in Black Pepper (Piper nigrum L.)(Department of Plant Biotechnology, College of Agriculture, Vellayani, 2016) Manu, K Venu; KAU; Lekha SreekantanThe present study entitled“Identification and characterization of Suppressor of Overexpression of Constans1 gene in Black Pepper (Piper nigrum L.)”was conducted at the Integrated Biotechnology Block, College of Agriculture, Vellayani, during 2015-2016.The study envisagedisolation and sequencing ofSOC1, a flowering integrator gene in black pepper (variety - Karimunda) and functional characterization of the gene by studying the expression patterns. Degenerate primers were designed for the above said gene based on the gene sequences from NCBI database (SOC1 forward and reverse primers) which were used to isolate and identify the gene. Total RNA of black pepper was isolated using modified CTAB method followed by synthesis of cDNA using AMV RT (Avian myeloblastosis virus reverse transcriptase). PCR (Polymerase chain reaction) with degenerate primers was done using cDNA as the template. However no amplifications were observed after the first reactions. Therefore nested PCR reactions were done using the PCR products of the first reaction as the template. Two bands of size 640 bp and 330 bp were produced in the nested reactions. Sequencing of the product yielded four sequences with each of the sequence showing similarity to the SOC1 gene, when done sequence analysis, thus making it the first flowering integrator gene to be identified in black pepper. Microscopy studies were carried out to see the floral characters of black pepper in detail. Microscopy studies were done using FAA fluid as fixative, sectioning the tissues and staining with safranin and fast green were carried out to see the changes occurring in different development stages of spikes from immature spike to complete spike with berries.ThesisItem Open Access Seed production of potential Stylosanthes gracilis(Department of Agronomy, College of Agriculture, Vellayani, 1981) Lekha Sreekantan; Madhavan Nair, K PFactorial experiment in Randomised Block Design with three replications was conducted in the College of Agriculture, Vellayani to study the effect of levels and methods of phosphorus application and number of cuts of green fodder taken, on the seed production potential of Stylosanthes gracilis. The phosphorus treatments were 40, 80 and 120 kg P2O5/ha as soil applications, 40 kg P2O5/ha as soil application + 40 kgP2O5/ha foliar and 80 kg P2O5/ha soil application+ 40 kg P2O5/ha foliar. The cutting treatments were two, three or four cuts. Increasing the level of soil applied phosphorus significantly increased height, spread, leaf stem ratio, nodular weight and number, greenmatter and drymatter yields in each cut and the cumulative greenmatter and drymatter yields.ThesisItem Open Access Spatial arrangement & nutrient management of grain cowpea - Fodder maize intercropping in summer rice fallows(Department of Agronomy, College of Agriculture, Vellayani, 1990) Sunitha, S; KAU; Lekha SreekantanAn investigation was carried out during the summer season of 1988-'89 in the Instructional Farm attached to the College of Agriculture, Vellayani to determine the best crop arrangement for a grain cowpea + fodder maize intercropping system in summer rice fallows under different fertility levels. The different crop arrangements tried were pure crop of cowpea at normal row arrangement, pure crop of maize at normal row arrangement, cowpea and maize in alternate rows, paired row of cowpea with one row of maize in between and triple row of cowpea with one row of maize in between. The fertilizer levels tried were 100, 75 and 50 per cent of the recommended doses of nutrients of cowpea, maize and cowpea+ maize, depending on the crop arrangement and the area occupied by each crop. The experiment was laid out in split plot design with four replications. The crop arrangements were allotted to main plots and the fertility levels to the subplots. Plant height of cowpea was maximum in the crop arrangement where cowpea was alternated with one row of maize where as the pure crop of cowpea produced the maximum number of leaves. In the case of maize, plant height and number of leaves were maximum when cowpea and maize were grown in alternate rows. Pure crops of cowpea and maize recorded the highest for their respective LAI values at flowering. Plant height, number of leaves and LAI of both cowpea and maize were affected by different fertility levels. Higher doses of fertilizers were found to be the best. The crop arrangements did not show pronounced variation in the uptake of nutrients by cowpea except potassium. Potassium uptake by cowpea and maize were maximum for their respective sole crops. For maize, nitrogen and phosphorus uptake were maximum when grown in alternate rows with cowpea plants. Full dose of fertilizers recorded the highest uptake values. Number of pods per plant, length of pods, number of seeds per pod, hundred grain weight, pod yield as well as grain yield of cowpea were not affected by different crop arrangements or fertilizer levels. The fodder yield of maize was affected by different crop arrangements and the pure crop of maize was on par with the crop arrangement where cowpea and maize were alternately grown. Hundred per cent recommended dose of fertilizers recorded the highest value for fodder yield of maize. The treatment where cowpea and maize were grown in alternate rows resulted in the greatest protein content of cowpea grains. Seventy five percent dose of fertilizers resulted in the highest crude protein content of maize fodder. The various indices like LER, LEC, IER, net profit, benefit/cost ratio, return per rupee invested on labour and return per cropping day were found to be superior in the crop arrangement where cowpea and maize were grown in alternate rows and at full dose of fertilizers. Hundred per cent and seventy five per cent dose of fertilizers were on par with regard to LER, LEC, IER, net profit and benefit/ cost ratio. From a detailed analysis it is seen that cowpea alternated with one row of fodder maize under 75 per cent of the recommended level of nutrients, is the best in providing higher profit to the farmer.