Risk analysis of non-native three-spot cichlid,Amphilophus trimaculatus, in the River Cauvery (India)

The three-spot cichlid Amphilophus trimaculatus (Günther) is an ornamental fish known to be invasive but has not been assessed for India. The present study confirmed this non-native species’ identity using conventional and molecular methods, as well as its occurrence in the River Cauvery, the first for this species in a lotic environment outside its native range. Gut content analysis indicated a diet of predominantly insects. The river's water quality and habitat were conducive for the species’ growth and reproduction. Using the Aquatic Species Invasiveness Screening Kit, A. trimaculatus was ranked as posing a “high” risk of being invasive in the River Cauvery, with climate match analysis showing 58% similarity with the species’ native range. Vector and pathway analysis found that A. trimaculatus was introduced to India via the aquarium trade, although consignment origin remains unknown, and the most likely means of entry into the river and its tributaries was the species’ escaping from holding facilities. Subsequent dispersal and impact of the species on native fauna are discussed. The study's outcomes demonstrate the importance of using risk analysis protocols to inform management of non-native species in India, with suggestions provided for immediate and long-term measures for the species’ management.     

Electrical wind force-driven and dislocation-templated amorphization in phase-change nanowires

Phase-change materials undergo rapid and reversible crystalline-to-amorphous structural transformation and are being used for nonvolatile memory devices. However, the transformation mechanism remains poorly understood. We have studied the effect of electrical pulses on the crystalline-to-amorphous phase change in a single-crystalline Ge(2)Sb(2)Te(5) (GST) nanowire memory device by in situ transmission electron microscopy. We show that electrical pulses produce dislocations in crystalline GST, which become mobile and glide in the direction of hole-carrier motion. The continuous increase in the density of dislocations moving unidirectionally in the material leads to dislocation jamming, which eventually induces the crystalline-to-amorphous phase change with a sharp interface spanning the entire nanowire cross section. The dislocation-templated amorphization explains the large on/off resistance ratio of the device.     

Long-term farmyard manure application effects on properties of a silty clay loam soil under irrigated wheat–soybean rotation

Increasing importance has been placed on the use of agricultural soils for the mitigation of atmospheric CO₂ through sequestration of soil C. Although crop productivity is sustained mainly through the application of organic manure in the Indian Himalayas, little information is available on C sequestration, C content in different aggregate size fractions and soil water transmission properties (infiltration and saturated hydraulic conductivity) as affected by long-term manure addition. We analyzed results of an 8-year experiment, initiated in 1995–1996 on a silty clay loam soil, to determine the influence of fertilizer and fertilizer + farmyard manure (FYM) application on those important soil properties. The overall increase in soil organic C (SOC) content in the 0–45 cm soil depth in NPK + FYM treatment as compared to NPK and control treatments was 11.0 and 13.9 Mg C ha⁻¹ at the end of 8 years, respectively. Application of FYM significantly reduced soil bulk density and increased mean weight diameter (MWD) and SOC contents in different aggregate size fractions. Soil organic C content in macroaggregates was greater than in microaggregates. The response of SOC content to FYM application was dependent upon inorganic fertilization and more upon balanced application of NPK than N only. Steady state infiltration rate under NPK + FYM (1.98 cm h⁻¹) was higher than under unfertilized (0.72 cm h⁻¹) and NPK (1.2 cm h⁻¹). Soil water sorptivity (calculated from Philip's equation) under NPK + FYM (1.06 cm min^−0.5) was higher than under NPK (0.61 cm min^−0.5). We conclude that hill farmers in northern India should be encouraged to use FYM along with chemical fertilizers to increase SOC content and improve soil physical properties.     

Modeling nitrate leaching and organic‐C build‐up under semi‐arid cropping conditions of N India

Nitrate leaching, overall N balance, and organic‐C build‐up in a semi‐arid agro‐ecosystem in NW India was estimated from the results of a long‐term manurial trial with farmyard manure (FYM) and mineral‐N fertilizer in operation since 1967 at the Research Farm of CCS Haryana Agricultural University, Hisar, India. The model LEACHN was calibrated for the wheat‐growing period November 2000 to April 2001 and the leaching of nitrate during this period was predicted to 48 kg N ha^–1 without mineral‐N fertilization and 59 kg N ha^–1 with addition of 120 kg mineral‐N fertilizer, both with the addition of 15 t ha^–1 FYM. The N balance for the simulation period showed that the 120 kg N ha^–1–mineral N fertilization compared to zero mineral N, both plus FYM, resulted in only slightly higher crop uptake, leaching losses, and NH₃ volatilization, and a negligible increase of N in organic matter. The largest amount remains as an additional build‐up of mineral N in the profile (84.3 kg N ha^–1) which is prone to losses as ammonia or nitrate. The model was used to simulate organic‐C build‐up with FYM and a decrease of organic C without FYM for a period of 33 y (1967–2000). The simulated C build‐up to about 0.1 g kg^–1 agreed very well with the measured values and showed that additional mineral‐N fertilization will not have any significant effect on organic‐C content. Simulations with the assumption of no FYM application showed a gradual decrease of organic C from its starting value of 0.046 g kg^–1 in 1967 down to almost half of this. This agreed well with the observed organic‐C values of 0.028 g kg^–1 as measured for unmanured plots.     

Heterosis for leaf photosynthesis,grain yield and yield components in maize

Summary One of the primary avenues of improving the biological efficiency of crop plants is through the improvement of the leaf and canopy photosynthetic rates. However, the question whether the superiority of hybrids in respect of productivity potential could be traced, in retrospective fashion, to the photosynthetic parameters should be answered first. Once established and standardized, such indices could be streamlined in innovative breeding to predict the heterotic combinations for final yield formation. To answer this question, the photosynthetic rate and other components of photosynthetic efficiency were monitored among eight inbred stocks of maize (selected for variable photosynthetic rate from a previous study) and their all possible one-way crosses. The results demonstrated extensive heterosis in respect of photosynthetic rate and other photosynthetic indices which, in turn, was also realized in terms of higher biomass productivity and yield. Nonetheless, high leaf photosynthesis alone did not result in higher grain yield. On the contrary, component interaction among the photosynthetic indices like photosynthetic rate, leaf area/plant, number of leaves and chlorophyll content on one hand and the complementary gene action on the other, could be held responsible for higher yields in hybrids. Since the components of photosynthetic efficiency can predict heterosis for biomass and grain yield upto a reasonable extent, judicious incorporation of such indices in selection parameters for applied genetic protocols can add yet another dimension to the strategies for future yield improvements.     

In vitro somatic embryogenesis in callus cultures of Azadirachta indica A. Juss.—a multipurpose tree

Plant regeneration via somatic embryogenesis was achieved in embryogenic callus cultures derived from immature zygotic embryos 40 days after anthesis of Azadirachta indica A. Juss. on semisolid basal Murashige and Skoog (MS) salts and vitamins supplemented with 1.11 µM 6-benzylaminopurine (BA) and 4.52–6.78 µM 2,4-dichlorophenoxyacetic acid (2,4-D). The globular-stage embryos were induced when the callus was transferred to medium with 1.11 µM BA and 0.45 µM 2,4-D. The highest average number of somatic embryos per 200 mg of callus was 152.8 after 8 weeks of culture on the medium. Maturation and germination of the somatic embryos were achieved on half-strength MS salts and vitamins supplemented 0.38–0.94 µM abscisic acid (ABA) and 2% (w/v) sucrose. The maximum percentage (64.2%) of germination was obtained with 0.94 µM ABA within 2 weeks of culture. Somatic embryo-derived plantlets were acclimatized in a greenhouse and subsequently showed normal growth. This efficient protocol will be helpful for propagating elite clones on a mass scale and will also be useful for genetic transformation study.     

Epidemiological study of parasite infection in a cow-calf beef herd in Quebec.

The patterns of gastrointestinal and pulmonary nematode infections in a previously untreated Aberdeen Angus cow-calf herd were observed between May 1988 and December 1990. The cow-calf herd and replacement heifers were on separate pastures. The relatively high mean faecal egg counts of cows and heifers at the time of turnout were mainly owing to the maturation of hypobiotic worms. The strongyle egg counts of calves began to rise soon after turnout onto pasture and reached peak levels at the end of the grazing season. The number of infective larvae on pasture was highest during September/October. Ostertagia, Cooperia and Nematodirus were the most prevalent genera found at necropsy and on pasture. Larvae of these nematodes were able to overwinter on pasture and Ostertagia larvae, additionally, were able to overwinter in the host as arrested early fourth stage larvae. The high egg output of cows at the time of turnout may serve as a source of infection for their calves and be responsible for the late-season rise in pasture larval counts.     

Effects of acclimation on chilling tolerance in Asian cultivated and wild rice

Tolerance to low temperature can be enhanced by pre-exposure to low, non-harmful temperatures, a process known as acclimation. The effects of acclimation on chilling tolerance in species from tropical and subtropical regions are not well understood. Therefore, we investigated whether acclimation improved chilling tolerance at the plumule and seedling stages in Asian rice. A comparison of the effect of acclimation between chilling tolerance scores from a tolerant (A58) and a susceptible (W107) strain demonstrated that acclimation enhances chilling tolerance especially in the tolerant strain, indicating that considerable genetic variation in acclimation capacity exists. The genetic variation in chilling tolerance in acclimated plants was investigated using 57 strains derived from cultivated (Oryza sativa L. ssp. japonica and ssp. indica) and wild (O. rufipogon Griff.) rice. The genetic differentiation of the japonica and indica subspecies of cultivated rice with regard to chilling tolerance was more prominent in the presence than in the absence of acclimation. Furthermore, latitudinal clines for chilling tolerance were observed in both acclimated plumules and seedlings of wild rice, whereas without acclimation, a latitudinal cline was observed only at the plumule stage. This suggests that acclimation capacity, as well as intrinsic chilling tolerance, might contribute to local adaptation. QTLs involved in acclimated chilling tolerance at the plumule stage are different from those involved in intrinsic chilling tolerance. The present results indicate that the maximum genetic potential for chilling tolerance is achieved by acclimation, giving cautions for evaluation of genetic resources in rice.     

Top working method and bloom density of pollinizers as productive determinant for spur type apple (Malus x domestica Borkh.) cultivars

Apple (Malus x domestica Borkh.) shows gametophytic self incompatibility and requires cross pollination by suitable pollinizers. Gradual decline in natural pollinators and insufficient proportion of pollinizers have been observed in the apple orchards over the years across the North Western Himalayan region. This situation resulted in considerable pollination problem in the region. The present study was undertaken (during the years 2006–2010) to examine the effect of top working methods and time as well as type of pollinizers on different growth parameters for efficient pollination management. Chip budding performed in fall, late winter and summer gave significantly higher success rate (90.0, 89.8 and 80.9%, respectively). Other methods viz., side rind graft (85.6%) and cleft graft (71.2%) during February–March, and T-bud (71.7%) during July–August also gave better success. The highest shoot numbers (4.1) and length (92.8 cm) were recorded when chip budding was performed during September–October and February–March, respectively. In 4th year, chip budded scion branches of all the pollinizers recorded significantly higher number of spurs/m twig length with a range of 22.8 (December–January) to 24.7 (September–October). Significantly the highest bloom density (22.1) was recorded on chip budded (February–March) branches of pollinizers in 4th year. Fruit set on top worked trees of ‘Oregon Spur’ was only in the range of 18.0–20.1% in 1st year and reached to the range of 35.6–41.5% in 4th year. Seed numbers/fruit also increased to the range of 7.3–7.9 in 4th year from 2.9 to 4.6 in 1st year. All these factors resulted in better yield efficiency (2.6–3.8) of ‘Oregon Spur’ in 4th year. ‘Manchurian’ crab produced significantly higher shoot length of 86.5–87.2 cm and 146.1–149.2 cm in 1st and 4th years, respectively. However, ‘Stark Spur’ produced the highest number of spurs/m twig length of 28.9 when grafted/chip budded during December–January or February–March, and 27.1 when chip/T-budded during September–October or July–August. Top working with ‘Manchurian’ crab also resulted in significantly higher fruit set (44.2–45.4%) and yield efficiency (3.6–3.8) on ‘Oregon Spur’ in 4th year. This was followed by ‘Stark Spur’ as pollinizer (37.1–38.2% and 2.9–3.1, respectively). Highly significant positive correlation of shoot numbers, spur density and bloom density of pollinizers with fruit set and yield efficiency of ‘Oregon Spur’ were observed. ‘Manchurian’ crab was found to be very efficient as pollinizer, followed by ‘Stark Spur’ for spur type ‘Oregon Spur’ apple cultivar on the basis of higher bloom density and fruit set parameters.