Browsing by Author "Mallika, V K"

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Characterisation of field established tissue culture derived black pepper (piper nigrum L.) plants using morphological, cytological and molecular markets
(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2001) Sujatha, R; Mallika, V K
Universally acclaimed as the ' King of Spices', black pepper (Piper nigrum L.) enjoys a unique position as a commercial crop of historical importance and assumes great economic importance to several nations of the world. Efforts to evolve high yielding types of black pepper through selection as well as hybridisation started as early as in 1953 (Nambiar et al., 1978) and by now, about ten improved varieties were evolved and released. In order to meet the insatiable demand from farmers for the planting materials of high yielding pepper varieties, mass multiplication protocol through micro-propagation has been standardised (Joseph et al., 1996). Babu (2000) tested the fidelity of TC plantlets of black pepper during the hardening stage using RAPD assay. A thorough evaluation and characterisation of these 'I'C plants in relation to their performance in the field is a prerequisite to establish their heritage and usefulness. In this background, the present study was taken up with the main objectives of establishing the genetic identity of TC derived black pepper plants in field; testing the intra-group, inter-clonal and inter- varietal polymorphism and obtaining a thorough and fool proof finger print of the TC plants using a combination of molecular marker techniques and conventional markers. Each of the experimental vines was characterised using morphological traits (biometric as well as qualitative) based on the descriptor formulated by NBPGR. The cytological studies ruled out any variation caused by a change in the chromosome number, which is possible in in vitro cultured plants. The somatic chromosome number was found uniform in all the vines with 2n = 52, which is characteristic of the species. The molecular markers provided a more specific identity for each of the experimental vines. The , zymogram based on peroxidase as well as RAPD banding pattern has given a very clear fingerprint characteristic of each vine. The biometric observations and visual assessment of the vines based on qualitative traits brought out the intra group (within conventional clones or within TC clones), inter- clonal (CC vs. TC clones) and inter varietal variation of the different characters. Among the 22 biometric observations, 17 were found homogenous within clonal groups and also within the TC groups irrespective of varieties. The remaining five traits were discussed with respect to each variety. Most of the qualitative observations also showed uniformity in. the clones as well as TC plants. The estimation of inter-clonal variablity proved the uniformity and better vigour of TC plants compared to the conventional clones. Another interesting observation was the great variablity in qualitative and quantitative traits between TC Subhakara and clonal Subhakara indicating a possible error in labelling. The molecular markers brought out the variablity in the different vines more specifically. In both isozyme and RAPD analysis, the clones under each variety were found to be monomorphic whereas certain variants could be detected within TC plants with respect to a few bands. The vines TC P2-7 and TC P1-1 were separated out as variants by both isozyme and RAPD markers. Other TC vines, which showed polymorphism with respect to either of these markers were Pl-I, PI-2, P2-10, P4-9, Su-9, Su-lO, P4-4 and P4-8. The assessment of inter clonal variability using molecular markers clearly pointed out the distinctly different traits of TC clones and conventional clones Subhakara. Morphological observations too supported this finding. Using RAPD, it was conclusively proved that the vines labelled as TC Su were in fact TC P 4. This confirmed the possibility of an error in labelling while the TC plantlets were transported from Vellanikkara to Panniyur. The inter-varietal polymorphism brought out by morphology and molecular markers was useful in discriminating the four black pepper varieties and to asses the genetic distance between them, which is an important criterion in the selection of parents for hybridisation. The results exposed the genetic proximity between PI and P2 and between P 4 and Suo The standardisations of various protocols for cytological and molecular marker analysis in black pepper as well as the relative efficiency of the different marker systems were also discussed. The RAPD technique was found most effective in assessing the genetic constitution of the individual vine.
Flower bud anatomy of 'kokkan' affected banana
(Kerala Agricultural University, 1993) Estelitta, S; Suma Luckins, A; Babu, C; Mallika, V K
Genome analysis in the genus Amatanthus
(Department of Olericulture, College of Horticulture, Vellanikkara, 1987) Mallika, V K; Peter, K V
Plantlet regeneration through somatic embryogenesis in cocoa (Theobroma cacao L.)
(Department of Agricultural Botany, College of Horticulture, Vellanikkara, 1994) Jiji Joseph; Mallika, V K
Investigations on 'Plantlet regeneration through somatic embryogenesis in cocoa' were undertaken in the Department of Agricultural Botany, College of Horticulture, Kerala Agricultural University, Vellanikkara during 1992-94. Studies were made to identify the most suitable medium, the most responsive genotype and most favourable conditions for embryogenesis in cocoa. Conditions for germination of embryoids to plantlet were also standardised. Among the different media tested for embryogenesis namely, MS, WPM and B5, MS medium was found to be the most ideal. Embryoids could be induced only from the tender cotyledon and embryonal axis of immature embryos of 100 days old pods. Other vegetative tissues like leaf, stem, petal, gynoecium, integumant etc. Yielded only non-embryogenic calli in media for somatic embryogenesis. An important finding in the present study was the standardisation of an ideal medium which favoured maximum embryogenesis from embryonic tissues. This medium was MS+ NAA 1.8 + thiamine 1 mg 1-1 + CW 15 per cent + sucrose 4 per cent. This is a modification of medium proposed for cocoa somatic embryogenesis by Adu-Ampomah et al. (1988). As already reported by other workers, the maximum embryogenesis occurred under dark incubation. The ideal incubation temperature was 30±20C. The embryoids originated singly or in clusters from the cotyledon explants. Most of the embryoids lacked a suspensor but some of them did have a suspensor. A typical embryoids had an embryonic axis and two cotyledons. However, aberrant forms were not uncommon with excessive proliferation of cotyledons as well as with disproportionate axes and cotyledons. The study helped to identify some genotype which showed maximum degree of embryogenesis. The Series I hybrid H 6.5 was found to be the ideal source of explant giving high frequency and intensity of embryogenesis as well as with larger sized embryoids having lesser percentage of abnormalities. The selfed progeny (S1) of this out-breeding crop exhibited minimum degree of embryogenesis. This indicates that the degree of embryogenesis may be associated with the vigour of the explant. Germination of embryoid to plantlet was a difficult process. Liquid media with 1/2 MS salts and 5 per cent sucrose was found to favour germination. A pretreatment was required to remove the inhibitors by washing and desiccation. Only embryoids of larger size (>4 mm) germinated properly to plantlet. The recovered plantlets were too small for field establishment. The most significant achievement in the present study was the plantlet regeneration from somatic embryoids and its planting out in the nursery. This was achieved by micrografting the embryoid derived plantlet to a three week old seedling rootstock. The presence of cotyledons was found to be inhibitory and at least a small leaflet in the embryoid derived plantlet was essential for success in micrografting.
Standardisation of in vitro techniques for rooting,hardening and micrografting in cocoa (Theobroma cacao L.)
(Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 1997) Bindu, M R; Mallika, V K