Gaurab Gangopadhyay

Salt tolerance in rice in vitro: Implication of accumulation of Na+, K+ and proline

The implication of accumulation of both inorganic (Na+, K+) and organic (proline) solutes were evaluated in unadapted and NaCl-adapted callus of a salt-sensitive (Basmati 370) and a salt-tolerant (SR-26B) cultivar of rice (Oryza sativa L.) after a NaCl shock. Accumulation of Na+,K+ and/or proline in callus was co relatable and the relative presence of these components in tissues after shock treatment was found to be important factors to support differential regrowth capacities of the shock treated calluses. Presence or retention of K+ in rice callus was a key factor for salt tolerance as it was observed to be positively correlated with growth in both the varieties. The results indicated that K+ was the first candidate to counteract the negative water potential of outside milieu, while proline was probably the last metabolic device that rice calluses opted for when exposed to salt stress.

Enhanced rate of multiplication and rooting through the use of coir in aseptic liquid culture media

In the quest for cheap and suitable eco-friendly matrix with liquid culture to facilitate rooting three matrices, viz. paddy straw, jute and coir were chosen. Of the three matrices, coir was selected due to its higher water retention capacity compared to the other two matrices. Coir was used with aseptic liquid media for rooting of ten plant species, viz., Nicotiana tabacum, Andrographis paniculata, Chenopodium album (2n=54), C. album (Broad leaf diploid), C. album (Narrow leaf diploid), C. murale, Beta vulgaris (Sugar beet and Table beet), B. palonga (Indian spinach), Tectona grandis and Musa spp. Higher number of roots with profuse root hairs were recorded in all the plant materials in liquid medium with coir compared to conventional agar-gelled media. Apart from rooting, the rate of multiplication, maintenance and concomitant hardening were also found to be more effective in comparison to agar-gelled media. The economical aspect of use of coir instead of agar is also discussed.

Effects of salt and osmotic shocks on unadapted and adapted callus lines of tobacco

Growth, viability and proline content of adapted and unadapted calluses of Nicotiana tabacum L. var. Jayasri, affected due to osmotic stresses and particularly to stress-shocks treated with different osmotica like NaCl (ionic-penetrating), mannitol (non-ionic-penetrating) and polyethylene glycol, (PEG) (non-ionic-non penetrating) were studied to evaluate the physiological differences of stress effects. The tissues adapted to a low concentration of NaCl (85 mM) showed low growth with high proline content compared to the tissues adapted to a low concentration of mannitol (165 mM). Proline content was similar in tissues adapted to high concentrations of NaCl (171 mM) and mannitol (329 mM) but growth in the latter case was relatively low. Growth and viability were subsequently correlated with the pattern of retention in or diffusion of proline out of the tissues after shock-treatments. The loss of tissue viability of the adapted calluses was comparatively less than the unadapted callus even after shock-treatments with 1282 mM NaCl and 823 mM mannitol. The former calluses retained the capability of regrowth though at a slow rate. Such adapted tissues also retained more proline. The mannitol-adapted tissues, when shocked with PEG (200 g l-1), showed low viability with more diffusion and a very little retention of proline while, in the unadapted tissue, all the proline was leached out. The results indicated that the effects of different osmotica on plant tissue varied depending upon the physico-chemical nature of the compounds used as stress-inducing-agents, and retention and diffusion of proline was altered when the tissues were shocked with high concentrations of all these compounds.

Micropropagation of Tectona grandis: Assessment of Genetic Fidelity

Random amplified polymorphic DNA (RAPD) markers were used to analyze genetic fidelity of micropropagated teak (Tectona grandis L.) clones with respect to subcultural passage. Of the twenty primers screened, no variation in RAPD profiles was noticed in the in vitro clones of fifth, tenth, fifteenth and twentieth passage in comparison to the in vivo mother plants. Only one micropropagated plant of twenty-fifth subcultural passage, however, differed from the in vivo ones. It revealed the appearance of a new polymorphic DNA fragment (molecular mass 379 kb) in case of primer OPB-08. This primer, manifesting detectable variation, may be utilized as a diagnostic marker for assessing genetic fidelity of micropropagted teak plants.

Plant regeneration of salt adapted callus of indica rice (var. Basmati 370) in saline conditions

NaCl adapted callus of a salt sensitive scented indica variety of rice (Oryza sativa var. Basmati 370) showed 55% regeneration in culture medium supplemented with IAA and kinetin. Regeneration was low in 85 mM NaCl but a concentration of 128 mM was inhibitory to regeneration. SEM study revealed organogenesis and somatic embryogenesis from the same callus. The rate of survival and endogenous free proline content of the plants regenerated from the NaCl adapted callus was significantly higher than for those obtained from unadapted callus in liquid maintenance media supplemented with NaCl.

In vitro selection and physiological characterization of NaCl- and mannitol-adapted callus lines in Brassica juncea

Na Cl (salt)- and mannitol (drought)- tolerant callue lines of Brassica juncea (L) Czern. Var. RW-85-59 were isolated by a plated cell suspension culture technique against 43 mM NaCl and 165 mM mannitol, respectively. Callus lines, adapted to a high concentration of Na Cl (171 mM) and mannitol (329 mM) were then established bv direct adaptation procedures. In the initial passages, the calluses showed severe reduction in tissue growth when grown on NaCl/mannitol-containing media but growth of adapted calluses recovered and was sustainable in the subsequent passages. Adapted calluses showed considerable accumulation of free proline in NaCl-/mannitol- containing media compared to the control callus grown on stress-free medium. A significant increase of intensity of one particular acid phosphatase isozymic band in the adapted calluses, irrespective of NaCl or mannitol stress, indicated that it may be used as an osmotic stress-marker in this system. Short-term salt/osmotic-shock-treatment with high concentrations of osmotica revealed that only the adapted lines retained the maximum amount of free proline within the cells for osmoregulation. This response probably helped the cells to restore their normal growth when the stress was withdrawn.

Speciation in Chenopodium in West Bengal, India

Two diploid cytotypes of Chenopodiumalbum have earlier been proposed as the probable ancestors ofhexaploid C. album in Gangetic Plainof West Bengal on the basis of cytomorphological data. The present study withthe diploid cytotypes of C. album (onebroad leaved, another narrow leaved), one wild species, C.murale and the hexaploid C.album utilizing parameters like seed protein, isozyme,RAPD, tissue culture along with conventional cytomorphological data supports ourearlier hypothesis of allopolyploid origin of hexaploid C.album. The results indicate that all the three diploidprogenitors have contributed for the evolution of present day semi-cultivatedhexaploid C. album. This study furthersuggests that the diploid cytotypes had been evolved sympatrically.

Trichomes: their Diversity, Distribution and Density in Acclimatization of Teak (Tectona grandis L.) Plants Grown in vitro

Diversity, distribution and density of trichomes were studied in relation to other morphological and physiological parameters of in vivo and in vitro teak (Tectona grandis L.) plants with the objective to understand their role in hardening and acclimatization of micropropagated plants. Less diversity and scanty distribution of trichomes of in vitro leaves in comparison to the in vivo ones were correlated with water loss of the former plants leading to low rate of survival after transplantation. The probable cause for absence of certain types of trichome in in vitro plants was also discussed.

Esterase as a Marker to Study the Genetic Fidelity of Micropropagated Banana

Isozymic profiles of different micropropagated banana (Musa spp.) cultivars (Giant Governor, Dwarf Cavendish, Robusta, Champa, Kachakel and Chatim) of West Bengal, India were assessed at different subcultural passages. Variation with respect to the banding pattern was noticed only in esterase but not in peroxidase and acid phosphatase. Of the six cultivars, four showed variation both at isozymic and yield level. Two cultivars (Kachakel and Chatim) maintained their esterase profile and genetic stability even after twenty subcultural passages.

Allele specific CAPS marker development and characterization of chalcone synthase gene in Indian mulberry (Morus spp., family Moraceae)

Chalcone synthase (CHS) is an essential enzyme in the phenylpropanoid pathway that catalyzes the first step in flavonoid biosynthesis in plants under diverse environmental stress. We have used CHS as a candidate gene in mulberry and developed Single Nucleotide Polymorphism (SNP) based co-dominant Cleaved Amplified Polymorphic Sequence (CAPS) marker associated with the CHS locus. The segregation pattern of the marker was studied in an F1 population derived from a hybridization program between two mulberry genotypes showing polymorphism for the CHS locus. Differential CHS activity of the recombinants has been correlated with the segregation pattern of the marker. Homology modelling and docking studies are performed for both the identified CHS alleles and correlated with respective CHS activity. Phenotyping of Powdery Mildew infected F1 population indicated a probable association with the CAPS marker.