Azhar Hussain Shah

Genomic affinity between Oryza sativa and Oryza brachyantha as revealed by in situ hybridization and chromosome pairing

Genomic affinity between Oryza sativa (2n = 24 AA), and Oryza brachyantha (2n = 24 FF) was assessed by using three strategies: genomic in situ hybridization (GISH), meiotic chromosome pairing, pollen and spikelet sterility. The chromosome pairing was examined in pollen mother cells of O. brachyantha, O. sativa and the hybrid between O. sativa and O. brachyantha. The hybrid was highly sterile with no pollen stain ability. Both parents showed regular meiosis with normal chromosome pairing. The F1 hybrid exhibited limited chromosome pairing. On an average, 0-2 bivalents and 20-24 univalents were recorded at metaphase-1 and 0 - 1 univalent at diakinesis. The most frequent configuration was two bivalents and twenty univalent. The meiosis was highly irregular showing unequal distribution of chromosomes at anaphase, formation of multipolar bodies and variation in the cell cycle of both genomes. GISH revealed unequivocal discrimination of O. brachyantha chromosomes as appeared red from O. sativa chromosomes that fluoresced yellow. No cross hybridization was examined between the labeled genomic DNA of O. brachyantha and the chromosomes of O. sativa. Mitotic chromosomes of O. brachyantha and O. sativa, in the hybrid, were discriminated by GISH. High sterility in this hybrid could be due to abnormal meiosis and lack of pairing.

Production and molecular characterization of wide cross derivatives in rice

The reduced genetic variability of modern rice varieties (Oryza sativa L.) is of great concern because it reduces the possibilities of genetic gain in breeding programs. Introgression lines (ILs) containing genetic fragment from wild rice can be used to obtain new improved cultivars. The objective of the present study was to develop ILs from the cross between O. sativa x O. longistminata aiming to be used in rice breeding program. In the present study, 12 ILs were produced. Among them, three ILs were highly resistant to all the isolates of bacterial blight from North West Frontier Province (NWFP) of Pakistan. A 900 bp DNA fragment linked to Xa21 was raised in these introgression lines and in O. longistminata by a pair of primers confirming the presence of Xa21 gene in these lines. Results indicated that Xa21 has broad spectrum of resistance to bacterial blight and wild species are the useful source for resistance.

The phenomenon of cross tolerance in osmotically and ionically adapted rice (Oryza sativa L.) cell lines

In the present study, cell lines of local rice ( Oryza sativa L.) cv. Swat-1 were incrementally adapted to osmotic [20% Poly ethylene glycol (PEG)] and ion specific (20 mM LiCl) stresses to investigate the phenomenon of cross tolerance. The tolerances of adapted lines were stable up to six generation on stress free medium. Both adapted cell lines were highly tolerant to either osmotic or ionic stresses while, the relative growth rates (RGR) of unadapted cells line decreased to about 95% at 20 mM LiCl and 20% polyethylene glycol, respectively. On subjection to temperature stress, the relative growth rates of unadapted cells line completely ceased, in contrast, both the adapted lines were found to be highly tolerant to low (18°C) and high temperature (36°C) stresses, respectively. At optimum temperature (27°C), proline content of unadapted and LiCl adapted lines were comparable (2 μmoles g -1 fresh weight), while polyethylene glycol adapted cell line had 17 time higher proline (35 μmole g -1 fresh weight) content. Under temperature stresses, the proline level of both the adapted lines increased significantly but the relative rate of increase was greater in LiCl adapted line than PEG adapted line. The tolerance of adapted cell lines to opposite stresses (osmotic or ionic) and to temperature stress (low and high) tangibly revealed that the presence of common stressor in the environment is not simply the cause of induction of cross tolerance, rather it seems to be the adaptations of software that facilitates induction of this phenomenon. Key words: Cross tolerance, growth, LiCl, polyethyleneglycol (PEG), proline.

Efficacy of Avicennia marina (Forsk.) Vierh. leaves extracts against some atmospheric fungi

Crude ethanolic extract of Avicennia marina leaves was tested against seven allergenic fungi viz., A lternaria alternata, Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Cladosporium herbarum, Penicillium notatum and Saccharomyces cerevisiae using five different solvents: dimethyl sulphoxide (DMSO), distilled water (DW), chloroform, ethanol and acetone at 2000, 4000 and 6000 ppm doses. Dose dependent tendency in the increase or decrease in the growth of fungi was observed. Two synthetic drugs miconazole and amphotericin-B were used as positive control. Miconazole was 100% effective against A. alternata, C. herbatum, P. notatum and S. cerevisiae with the concentrations of 95.00 ± 1.62, 78.00 ± 4.99, 100.00 ± 0.69 and 110.00 ± 2.33 (μg/ml of SDA medium), respectively. Amphotericin-B completely controlled the growth of A. flavus, A. fumigatus and A. niger in the concentration of 24.00 ± 17.00, 30.00 ± 15.66 and 18.00 ± 18.34 (μg/ml of SDA medium), respectively. Distilled water and DMSO were considered to be the most effective solvents preventing 83.00 ± 4.73% growth of A. niger , 80.33 ± 5.60% A. flavus , 78.58 ± 3.18% A. alternata , 72.91 ± 7.96% P. notatum , 65.25 ± 3.55% C. herbarum , 63.25 ± 4.52% A. fumigatus and 48.5 ± 7.89% S. cerevisiae. Statistically, the results were compared with negative control and found to be highly significant (p<0.01). Key words : Allergenic fungi, inhibition, dose dependent, growth control, synthetic drugs.

Co adaptation of LiCl tolerant Solanum tuberosum L. callus cultures to NaCl stress

In this research, co-adaptation of the Calli of Solanum tuberosum , raised from petioles, to the presence of lithium (LiCl) and sodium chloride (NaCl) was studied. The cultures were adapted with LiCl in the absence of an osmotic stress and the response of adapted and unadapted calli to salinity was investigated. Undifferentiated callus growth was induced in S. tuberosum by the addition of 2 mg/l 2,4 dichlorophenoxy acetic acid (2,4-D), 0.25 mg/l kinetin to Murashige and Skoog medium. Subcultures were subjected to an incremental increase in LiCl to obtain adapted lines. Adapted and undapted calli were grown with LiCl and NaCl and the tissue content of Na + , K + , Ca 2+ , Mg 2+ and proline levels were determined. Either 40 mM LiCl or 100 mM NaCl inhibited unadapted calli by more than 50%, while adapted calli grew normally under these conditions. The adapted calli exhibited a lower K