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  • Author or Editor: M. Zaidi x
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The Juniperus excelsa is considered an important medicinal plant by the local population of Balochistan, Pakistan. The species is facing a grave threat by a parasitic and epiphytic angiosperm, dwarf mistletoe, Arceuthobium oxycedri (DC.) M. Bieb. (Viscaceae). The methanolic extract of A. oxycedri was studied for its chemical composition and biologically active compounds for the first time. The extract was assayed for antibacterial, antifungal, phytotoxic, cytotoxic and insecticidal activities. The antibacterial and antifungal activities of the extract were determined against ten bacterial and ten fungal strains by agar well diffusion and disc diffusion assay. The extract was highly effective against three bacteria Pseudomonas aeruginosa, Escherichia coli, Bacillus subtilis and a fungus Candida albicans . The phytotoxic effects showed that it was extremely toxic for Lemna acquinoctialis . It showed high cytoxicity for brine shrimps at all concentrations and was found to be significantly cytotoxic against Candida albicans when checked by flow cytometer. However, the extract was not effective against the pests tested.

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A total of 32 bacterial isolates including Mesorhizobium (N=10), Azotobacter (N=12) and phosphate-solubilizing bacteria (N=10) were isolated and tested for siderophore, HCN, ammonia, indole acetic acid production and phosphate solubilization in vitro . The bacterial cultures were positive for siderophore, HCN and ammonia. Among the isolates, M. ciceri RC3 and A. chrococcum A4 displayed 35 and 14 μg ml −1 of IAA, respectively, whereas Bacillus produced 19 ( Bacillus PSB1) and 17 μg ml −1 ( Bacillus PSB10) of IAA in Luria Bertani broth. The diameter of the P solubilization zone varied between 4 ( Bacillus PSB1) and 5 mm ( Bacillus PSB10) and a considerable amount of tricalcium phosphate (7 and 8 μg ml −1 by Bacillus PSB1 and Bacillus PSB10, respectively) was released in liquid medium, with a concomitant drop in pH. The effects of N 2 -fixing and PS bacteria on the growth, chlorophyll content, seed yield, grain protein and N uptake of chickpea plants in field trials varied considerably between the treatments. Nodule number and biomass were significantly greater at 90 days after sowing (DAS), decreasing by 145 DAS. Seed yield increased by 250% due to inoculation with M. ciceri RC3 + A. chroococcum A4 + Bacillus PSB10, relative to the control treatment. Grain protein content ranged from 180 ( Bacillus PSB1) to 309 ng g −1 ( M. ciceri RC3 + A. chroococcum A4 + Bacillus PSB10) in inoculated chickpea. The N contents in roots and shoots differed considerably among the treatments.

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To understand the molecular details of T-DNA integration, the left border (LB) sequences and flanking plant DNA of 16 independent T-DNA insertions in transgenic cry1Ab rice were analyzed by an inverse PCR approach. DNA sequencing indicated that five of the 16 fragments (31%) were found to have simple or rearranged tandem repeats of right border sequences in a head to tail fashion. Mirror truncations of LB of the T-DNA, as well as mirror rearrangements, such as point mutations, small deletions and inversions were found in the region close to the LB breakpoints in some inserts. Host plant DNA flanking the T-DNA endpoints were also sequenced. The A+T contents in the plant DNA within 50 bp adjacent to the T-DNA endpoints were between 30–76% (average 52.5%), not different from the average genome value. Despite minor mutations and some rearrangements, it appears that T-DNA, harbouring a synthetic cry1Ab coding sequence of 49% GC (as well as uidA and hph ), still carries such a foreign gene into ‘transcriptionally active regions’ of the rice genome, which are 55.8% GC on average as predicted from the rice genome sequence.

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Selection on the basis of grain yield per se for improved performance under excessive moisture stress has often been misleading and considered inefficient. We assessed the importance of secondary traits of adaptive value under waterlogging stress. During the 2000–2004 summer-rainy seasons twelve trials were conducted and a total of 436 tropical/subtropical inbred lines (S 4 –S n ) were evaluated under excessive soil moisture stress. Excessive moisture treatment was applied at V 6–7 growth stage by flooding the experimental plots continuously for seven days. Different phenological and physiological parameters were recorded before, during and either immediately or 1–2 weeks after exposure to stress. Excessive moisture conditions significantly affected all the morphological and physiological traits studied. However, there was significant genetic variability for various traits, especially for root porosity and brace root development that were induced under excessive moisture. Across the trials, significant genetic correlations (p<0.01) was obtained between grain yield and different secondary traits, including ears per plant, root porosity, brace root fresh weight, number of nodes with brace roots and anthesis silking interval. Broad-sense heritability decreased under excessive moisture stress conditions for most of the traits; however, it increased significantly for root porosity, nodal root development and ears per plant. Our findings suggest that consideration of these second-ary traits during selection of maize germplasm for excessive moisture tolerance can improve selection efficiency and genetic gains.

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