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  • Author or Editor: A. Shukla x
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An impact of temperature, light and relative humidity were studied on root colonisation by mycorrhizal fungi and on pine seedling growth. Moderate and high light intensities favoured mycorrhizal colonisation and seedling growth. Pine seedlings inoculated with Pisolithus tinctorius compared to other fungi attained maximum growth. Survival of pine seedlings was higher under moderate light intensity than low and high light intensity. Seedling growth and mycorrhizal colonisation was better at 25°C than 10°C. Variation in humidity did not show much difference in mycorrhizal colonisation and seedling growth. However, seedling survival was greater at high than at low humidity. Pine seedlings showed best survival with 0.5 P level (46.153 mg P/kg soil) of phosphorus at 25 °C temperature and under moderate light intensity. Among the mycorrhizal fungi used P. tinctorius was the most effective endophyte and was followed by Laccaria laccata, Rhizopogon luteolus and Collybia radicata under various physical factors.

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Yellow mosaic and leaf curling symptoms were observed on Ageratum conyzoides plants in a survey made during 2007–09 at Gorakhpur and nearby locations of North-Eastern Uttar Pradesh, India. The incident of disease was significantly high with severe symptoms. Due to presence of whiteflies in the field, begomovirus infection was suspected. Therefore, polymerase chain reaction (PCR) was performed with begomovirus specific primers (TLCV-CP). Total genomic DNA was isolated from infected as well as healthy leaf samples. In gel electrophoresis an ∼800 bp amplicon was obtained in diseased leaf samples as expected, while no amplicon was found in healthy plants.Amplicons obtained were directly sequenced and submitted to the GenBank with the accession number GQ412352 and a phylogeny tree was constructed with the available sequences in the Genbank. Based on the highest nucleotide similarity (98%), amino acid similarity and close relationship with isolates of Ageratum enation virus, the present isolate was considered as an isolate of Ageratum enation virus.

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Nitrogen use efficiency, more specifically physiological nitrogen use efficiency depends primarily on management of N, one of the major essential nutrients. It is required in increased agricultural production and may possibly cause soil toxicity if fed in excess. Rate of N fertilizer application in fertile agricultural field and improved productivity in sterile soils require the improvement of NUE. A field experiment was therefore conducted to evaluate the effect of different N levels (N0, N50, N100 and N200) on rice genotypes. Vegetative plant growth was found to be reduced under N0 while improved at N200 level. Among the genotypes, highest PNUE (34.94) and correspondingly higher yield (7.15 ton ha−1) was observed for Krishna Hamsa. The other traits viz. plant height, no. of productive tillers and LAI exhibited higher values for Krishna Hamsa as well. Hence these can be utilized as physiological markers for the selection of rice genotypes efficient in N use.

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Global warming is rising as a serious concern affecting agricultural production worldwide. Rice is a staple food crop and the threshold temperature for its pollination is 35 °C. A rise in temperature above this value can cause pollen sterility and may severely affect fertilization. Therefore, a study emphasizing the rise in temperature with respect to pollen viability was conducted with eleven rice genotypes during kharif seasons of 2010 and 2011 in indigenous field conditions. Increasing mean temperature by 12 °C at full flowering was found to severely affect the spikelet attributes of the crop. All genotypes showed spikelet sterility above 90% during both seasons. The study indicated that increased temperature may limit rice yield by affecting spikelet fertility and grain filling. The net reduction in grain yield was 30.4% and 27.6% in 2010 and 2011, respectively. A clear reduction in pollen size under high temperature was shown by scanning electron microscopy.

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The paper deals with morphological and physiological variability of Colletotrichum falcatum Went on different temperature, pH, medium, nitrogen sources, carbon sources and also first time reporting of the two National Pathotypes from North East Zone of Uttar Pradesh, India. Thirty-four isolates were isolated from infected samples of different sugarcane varieties during survey and maintained on Oat Meal Agar (OMA) slants as well as on the Petri dishes at 30±1 °C. These isolates showed the variability in their optimum radial growth pattern. The optimum radial growth of all isolates was recorded at 8, 10 and 12 days. Six isolates exhibited maximum radial growth (90 mm diam) in 8 days, while the other 10 isolates attained same growth in 10 days. Remaining 14 isolates took 12 days to attain same growth. Pathogenecity of 34, isolates has been tested on 12 host differentials of sugarcane genotypes only SES594 was found resistant and others showed the variable response, while highly susceptible reaction to be found in three isolates (R0704, R0720 and R0728). These three isolates gave maximum spores on OMA followed by PDA medium and higher dry mycelium weight was observed in Richard’s liquid medium as compared to others. The maximum growth was recorded for these three isolates on potassium nitrate and sodium nitrate as nitrogen sources. Growth regulators like IAA and IBA at lower concentration enhances the growth while higher concentration showed adverse affect. When these three isolates were compared with the national level pathotypes, viz. Cf01 (Co1148), Cf08 (CoJ64) and Cf09 (CoS767) reaction in differential and spores inoculation technique it was found that isolates showed similar reaction like National Level pathotypes. Hence, it was concluded that these three isolates are belonging to new pathotypes.

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A set of 286 recombinant inbred lines (RILs) along with the parents and a popular wheat variety in India were grown for two consecutive years at three locations belonging to the two major wheat growing zones of India and evaluated for four grain quality traits. Rare recombinants with high trait value appeared for protein content (PC), thousand-kernel weight (TKW), sedimentation value (SV), and kernel hardness (KH). The magnitude of environmental effects was more pronounced than genotypic effects and genotype-environment interaction (GEI). The cumulative contribution of environment and GEI components to the total variance was highest in the expression of PC followed by TKW, SV, and KH. The top five percent (14 RILs) of genotypes with high trait value were subjected to Eberhart and Russell (1966) (ER), genotype and genotype-environment (GGE) and additive main effects and multiplicative interaction (AMMI) stability models. Five RILs were identified as stable in all the three stability models. RIL61 with 38.8%, RIL101 with 8.9%, RIL226 with 26.1% superiority over check variety were the most stable genotypes in all the three stability models for PC, TKW and KH, respectively. RIL113 was found to be stable genotype in ER and GGE models, whereas, RIL231 was the most stable genotype in AMMI and GGE models in the expression of SV. These common stable genotypes with high trait value identified through ER, AMMI and GGE models could be potential donors in active breeding programs to develop high yielding wheat varieties with improved PC, TKW, SV and KH.

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