Landraces-potential treasure for sustainable wheat improvement

Genetic Resources and Crop Evolution - Agricultural production is facing serious threat from various biotic and abiotic stresses specifically under climatic challenges. It is becoming increasingly...     

Storage and high conversion frequency of encapsulated protocorm-like bodies of Cymbidium devonianum (orchid)

Summary

A method for the storage and high frequency conversion of Cymbidium devonianum protocorm-like bodies (PLBs) is reported. To study the effect of nutrient level on storage, PLBs were encapsulated in calcium alginate beads supplemented with 1.0×, 0.5×, 0.25×, or 0.125× Murashige and Skoog (MS) basal medium containing 0.3% (w/v) sucrose, without agar in the encapsulating matrix, and stored at room temperature (25º ± 2ºC) in the dark. Beads containing 0.25× MS were also kept at different temperatures (0ºC, 4ºC, 8ºC, or room temperature) in the dark to ascertain the optimal temperature for storage. One set of controls (i.e., non-encapsulated PLBs) was maintained for each treatment. The survival and subsequent percentage conversion values of PLBs were assessed at 30 d storage intervals after culturing on MS regeneration medium. Compared to the controls, all encapsulated PLBs showed improved storage at room temperature. In all treatments, non-encapsulated PLBs did not survive, but turned brown and died. Encapsulated PLBs in 0.25× MS medium could be stored for 90 d at room temperature without any significant loss in viability. However, a significant decrease in the survival percentage was recorded after longer storage times. Encapsulated PLBs containing 0.25× medium could be stored at 4ºC and 8ºC for 120 d and 180 d, respectively, without loss of viability. As storage times increased beyond 180 d, the survival percentage of encapsulated PLBs decreased. The conversion of encapsulated PLBs led to the emergence of regenerated plantlets. Initially, small green globular outgrowths from the PLBs were observed on the surface of the beads. These outgrowths multiplied to form clusters of PLBs which then regenerated into plantlets. In both studies, more prolonged storage of encapsulated PLBs increased the time interval for germination and plantlet regeneration on MS regeneration medium. Similarly, decreases in both basal MS strength in the matrix, and in storage temperature, resulted in an increase in the time required for germination and plantlet regeneration. Plantlets that regenerated from stored, encapsulated PLBs were hardened-off, and a high survival percentage (90%) was obtained in a glasshouse.     

Characterization of the effect of a QTL for drought resistance in rice, qtl12.1, over a range of environments in the Philippines and eastern India

A large-effect QTL for grain yield under drought conditions (qtl12.1) was reported in a rice mapping population derived from Vandana and Way Rarem. Here, we measured the effect of qtl12.1 on grain yield and associated traits in 21 field trials: ten at IRRI in the Philippines and 11 in the target environment of eastern India. The relative effect of the QTL on grain yield increased with increasing intensity of drought stress, from having no effect under well-watered conditions to having an additive effect of more than 40% of the trial mean in the most severe stress treatments. The QTL improved grain yield in nine out of ten direct-seeded upland trials where drought stress was severe or moderate, but no effect was measured under well-watered aerobic conditions or under transplanted lowland conditions. These trials confirm that qtl12.1 has a large and consistent effect on grain yield under upland drought stress conditions, in a wide range of environments.     

Carbon and Nitrogen Amendments Lead to Differential Growth of Bacterial and Fungal Communities in a High-pH Soil

Microbial growth in soil is mostly limited by lack of carbon (C). However, adding fresh, C-rich litter can induce nitrogen (N) limitation. We studied the effect of alleviating C and N limitation in high-pH (> 8) soils, soils expected to favor bacterial over fungal growth. Nitrogen limitation was induced by incubating soils amended with C-rich substrate (starch or straw) for 4 weeks. Limiting nutrients and the effects of alleviating limitation were then studied by adding C (as glucose) or N (as NH₄NO₃) and measuring microbial growth and respiration after 4 d. In non-amended, C-limited soils, adding C but not N increased both microbial respiration and bacterial growth. In N-limited, substrate-amended soils, adding C increased respiration, whereas adding N increased both microbial respiration and growth. Inducing N limitation by amending with straw was most easily detected in increased fungal growth after the addition of N, whereas with starch, only bacterial growth responded to alleviating N limitation. Compared to earlier results using a low-pH soil, the effect of substrate used to induce N limitation was more important than pH for inducing bacterial or fungal growth after alleviating N limitation. Furthermore, we found no evidence that alleviating N limitation resulted in decreased respiration concomitant with increased microbial growth in soil, suggesting no drastic changes in C use efficiency.     

Removal of Trinitrotoluene with Nano Zerovalent Iron Impregnated Graphene Oxide

Nano zerovalent iron (nZVI) impregnated reduced graphene oxide (nZVI-rGO) hybrid was prepared via gaseous hydrogen reduction of anhydrous iron(III) chloride (FeCl₃) on the surface of thermally exfoliated reduced graphene oxide (rGO) nanosheets without using any toxic reducing agent, surfactant, or stabilizing agent. Characterization of prepared samples was carried out using various techniques. Morphological study showed that prepared rGO possesses a few-layered wrinkled paper-like structures and nZVI particles of ~?30 nm size were homogeneously dispersed on the surface of rGO nanosheets. Fourier transform infrared (FTIR), X-ray diffraction (XRD), and energy dispersive X-ray spectrometry (EDS) analyses indicated that oxygen-containing functional groups decreased in the order of graphite oxide (GO) > rGO > nZVI-rGO. Removal studies of trinitrotoluene (TNT) were carried out using graphite (G), GO, rGO, and nZVI-rGO with the aid of high-performance liquid chromatography (HPLC). Kinetic models were applied to establish the rate and mechanism of adsorption of TNT on different adsorbents, and intraparticle diffusion model based on initial adsorption characteristics was employed to ascertain mechanism of film and intraparticle diffusion in the adsorption process. The removal rate and adsorption capacity was found to be highest for nZVI-rGO, which renders this adsorbent to be a potential futuristic adsorbent for removal of explosives.

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Long term performance study of glass reinforced composites with different resins under marine environment

For marine structural applications which poses significant challenges to the choice of materials due to presence of corrosive seawater, polymer matrix based fiber reinforced composites are increasingly becoming the material of choice. However the performance properties of composites are greatly influenced by the moisture absorbed by the composite. In the current study, the long term performance is assessed by determining the amount of moisture absorbed and the reduction of mechanical properties over 12 months in a simulated sea-water environment at different temperatures. Three commonly used thermoset resins with different chemistry such as unsaturated polyester (USP), epoxy resin (EP) and vinylester (VE) are chosen. The effect of fiber reinforcement on the long term performance is investigated. A suitable method for manufacturing glass reinforced composite with good interfacial bonding and high volume fraction is also developed in current study. It is observed that vinylester plaques and composites absorb lesser moisture compared to USP and Epoxy systems resulting in lesser reduction in flexural strength and making the best performing among polymers studied. It is also found that sea-water diffusion into the composite follows non-Fickian behaviour and diffusion relaxation model fits well with the experimental data and corresponding model parameters are evaluated.     

Definitive Callose Deposition in Tapping Panel Dryness Affected Bark of Hevea brasiliensis

The structural and functional aspects of sieve elements in Tapping Panel Dryness (TPD) affected bark of Hevea brasiliensis, with special reference to definitive callose deposition, have been studied using histochemical methods. The effect of ethephon in definitive callose deposition in TPD affected bark also has been investigated, as the ethylene is reported to have a major role in TPD. The phloem of Hevea is characterized by sieve elements with compound sieve plates. The deposition of definitive callose on the sieve areas following TPD limits the translocation of sap through sieve elements. The amount of functional phloem was narrow and the accumulation of definitive callose was more in the sieve elements of TPD affected bark compared to that of unaffected bark of the same tree and of healthy trees. The affected area showed an increment in deposition of definitive callose in both vertical and horizontal extent of sieve areas; and there was a reduction in length of sieve plate, density of sieve pores, length of inter-sieve area wall, and number of sieve element rows in the inner bark. The lateral walls of non-functional sieve elements became thick and lignified. The anatomical changes in the sieve elements of TPD affected bark suggest that the translocation of phloem sap is regulated by deposition of definitive callose and less differentiation of sieve elements from vascular cambium. The external application of ethephon on bark enhanced the definitive callose deposition on sieve elements. The findings from the study reveal that ethylene plays a major role in the senescence of sieve elements.     

Isolation of arbuscular mycorrhizal fungi and Azotobacter chroococcum from local litchi orchards and evaluation of their activity in the air-layers system

Soil samples were collected from rhizosphere of litchi-growing areas of North-Western Himalayan Region (NWHR) of India, for finding qualitative and quantitative differences in arbuscular mycorrhizal (AM) fungi and Azotobacter chroococcum. These samples were taken from plants being grown in different cultivation types namely, weed control with weedicides or tillage; orchard floor either clear or with cover crops; intercropping with cereals and legumes. Qualitative and quantitative differences were noticed with different cultivation types and a marked reduction in the AM fungi was observed in orchards where chemicals were used for weed control and intensive farming system was used on the orchard floor. AM fungi were generally abundant in the soils with range pH 5.5–6.6. Among different AM fungi retrieved from the soils, Glomus spp. was most dominant. Fifteen AM fungal species were isolated, identified and characterized and along with their ability to colonize the roots. In the soil samples, a marked variation in viable bacterial count of A. chroococcum was also noticed due to varied physico-chemical characteristics of the orchard soils. The changes in AM fungal species composition can be attributed to changes in soil chemical properties resulting from cultural practices such as ploughing, application of chemical fertilizers and weedicides. An experiment was also conducted to study the comparative efficacy of four dominant and frequently occurring indigenous AM species namely, Glomus fasciculatum (Thaxter sensu Gerdemann), G. magnicaulis (Hall), G. mosseae (Nicol. & Gerd.), Gigaspora heterogamma (Nicol. & Gerd.) and two A. chroococcum strains viz., AZ₁ and AZ₂ singly and in dual combination to evaluate their effect in air-layers system. Dual inoculation of G. fasciculatum and AZ₁ increased total root length of air-layered shoots by 81.39% over uninoculated control. These studies indicated that indigenously isolated AM fungal species and A. chroococcum strains can be used for air-layering for better adaptation under specific agro-climatic and ecological zone conditions.     

Anatomical changes in the cell-wall structure of Leucaena leucocephala (Lam.) de Wit as caused by the decay fungi Trametes versicolor and Trametes hirsuta

The structural changes in the cell wall and delignification pattern caused by Trametes versicolor and Trametes hirsuta in the sap wood of Leucaena leucocephala were examined by light and confocal laser scanning microscopy. The in vitro decay test was conducted for 12 weeks. Both species of Trametes used in this study caused anatomical characteristics specific to simultaneous white rot. Formation of boreholes, erosion troughs, erosion channels with U-shaped notches in tangential sections and thinning of cell walls were evident in the wood inoculated with each of the fungal species. Cell separation due to removal of middle lamellae occurred at the early stages of infection (30 d) with T. versicolor. In contrast, middle lamellae remained intact in wood inoculated with T. hirsuta and showed cell separation due to degradation of the outer layer of the secondary wall and degradation of the middle lamellae observed only in severely decayed wood at late stages. Confocal microscopy revealed the delignification pattern particularly from cell corners and vessel walls at an advanced stage of decay, indicating strong ligninolytic activity of both species in the sapwood of L. leucocephala.