Immunoassay and ultrastructural localization of isopentenyladenine and related cytokinins using monoclonal antibodies

Two hybridoma cell lines, J40-IV-A1 and J40-IV-C4 were obtained from a fusion of spleen cells of Balb/c mice immunized against an isopentenyladenosine-bovine serum albumin conjugate with X63. Ag 8.653 myeloma cells. These hybrids secrete monoclonal antibodies of the immunoglobulin G (IgG) class and share high affinities and specificities to isopentenyladenine and isopentenyladenosine suitable for the detection of femtomole amounts of these cytokinins in plant extracts by enzyme-linked immunosorbent assay (ELISA). One of the monoclonal antibodies (J40-IV-C4) has been employed to localize isopentenyladenine immunoreactivity in a cytokinin-over-producing mutant of the moss, Physcomitrella patens. After fixation and embedding at low temperature, immunoreactivity was visualized in protonemal filaments of the moss mutant by the use of indirect immunogold labelling. In the mutant, the labelling was predominantly in the wall of the protonemal cells. Neither the wild-type nor control treatments showed any labelling. The signficance of these observations is discussed with respect to the applicability of immunocytochemical techniques for the localization of low-molecular-weight compounds in plant tissue.Abbreviations ELISA enzyme linked immunosorbent assay - HPLC high-performance liquid chromatography - IP isopentenyladenine - IPA isopentenyladenosine - mAB monoclonal antibody - OVE cytokinin-over-producing mutant - RIA radioimmunoassay     

Studies on fungi associated with tomato fruits and effectiveness of some commercial fungicides against three pathogens

Among 39 fungal species and one variety belonging to 16 genera isolated from 116 healthy tomato fruits collected from markets in Assiut, Egypt, during 1994,Aspergillus niger was found to be the most prevalent, being isolated from 84.6% of the samples. Of 11 species recovered from 156 diseased tomatoes,Alternaria alternata, Rhizopus stolonifer andA. niger were the most common and isolated from 52.7%, 35.9% and 25.0% of the samples, respectively. Experiments for comparison of the effects of medium containing tomato juice with synthetic medium on the mycelial growth of nine fungal species indicated that, the tomato juice medium was more suitable for growth of all fungal species. The effect of five commercial fungicides and sodium hypochlorite when applied as post-harvest dips after inoculation was studied in laboratory againstA. alternata, A. niger andR. stolonifer. At 10 and 100 µg ml^–1, neither of the fungicide caused a noticeable inhibition ofAlternaria rot. At 1000 µg ml^–1 benlate, rovral and sumisclex completely preventedAlternaria andAspergillus rot, whereas cuprosan and ridomil were ineffective against rotting caused byA. niger. Rhizopus rot development was inhibited by over 50% with one treatment only (rovral at 1000 µg ml^–1). Sodium hypochlorite has good curative properties against fruit rots especially those caused byA. alternata andA. niger.     

Interrelationships Among Macrophomina phaseolina,Criconemella xenoplax,and Tylenchorhynchus annulatus on Grain Sorghum

Microplot experiments were established in 1992, 1993, and 1994 to investigate the relationships among Macrophomina phaseolina, Criconemella xenoplax, mad Tylenchorhynchus annulatus on grain sorghum in Louisiana. A factorial treatment arrangement of two grain sorghum hybrids (De Kalb DK 50 and Pioneer hybrid 8333), three levels of M. phaseolina (0, 10, and 100 colony-forming units (CFU)/g soil), and three nematode inoculum levels (0, 1x, and 2x) were used. Nematode inocula at 1x levels were 929, 1,139, and 1,445 C. xenoplax and T. annulatus/microplot in 1992, 1993, and 1994, respectively. Plants were harvested after 90-105 days. In all 3 years, grain sorghum root and head dry weights were suppressed as nematode inoculum level increased. These reductions were detected both in the absence and in the presence of M. phaseolina at 10 CFU/g. Reproduction of both nematode species was suppressed by M. phaseolina. Interactions between M. phaseolina and nematodes were antagonistic with regard to plant dry weights, yield, and nematode reproduction, so that combined effects were less than the sum of the effect of each pathogen alone.     

Two methods for the prediction of Mycocentrospora acerina infection on stored carrots

Carrot plants were collected from 26 fields located in different districts in Norway during 1985, 1986 and 1987. Leaves were sampled in the first two years, and roots were sampled in all years. Incidence of Mycocentrospora acerina on the leaves at harvest was correlated (r = 0.82) to the incidence of M. acerina on the roots after storage at 0–1°C for six months (long term storage). Incidence of M. acerina on roots sampled about six weeks before harvest (date c) and placed at 10°C for six weeks (test storage) was correlated (r = 0.84) to incidence of the pathogen after long term storage on roots sampled at harvest (date d). Test storage and long term storage data from parallel samples taken at date d was more strongly correlated (r = 0.90).     

A serological test for detecting Botrytis allii, the cause of neck rot of onion bulbs

Polyclonal antisera for the immunological detection of Botrytis allii, the cause of onion neck rot, were raised from cell wall and cytoplasmic fractions of the fungus, and from surface plate washings of two isolates of the pathogen. These antisera were used to develop an indirect ELISA for the detection of latent B. allii infection in stored onion bulbs. The antisera did not react with healthy onion tissue and showed only minimal recognition of fungi from other genera. Some cross-reactivity was observed with B. cinerea but not with other Botrytis spp. tested. In many instances following infection, fungal antigen could be detected earlier by ELISA than by direct culture. In tests on bulbs from a commercial store, the level of B. allii infection was found to be 3.3% by both ELISA and direct plating, but this result was achieved 7 days sooner by ELISA. In field tests, the indirect ELISA gave a good indication at harvest of the probable incidence during storage of neck rot in untreated and artificially inoculated plants, whilst culturing gave results consistently lower than the ELISA until bulbs had been in store for several months, when results for ELISA and culturing were the same. Spores applied to growing plants during the growing season led to greater levels of neck rot than did infested seed, indicating that field debris and waste from cold stores may be more important sources of inoculum in some years than seed contamination.     

Diurnal changes in the radius of a subalpine Norway spruce stem: their relation to the sap flow and their use to estimate transpiration

Diurnal changes in the stem radius of a subalpine mature Norway spruce were measured simultaneously with the flow of sap in xylem. Matric potentials in the soil were > -35 kPa. The kinetics of the flow were closely related to the changes in the radius of the stem resulting from depletion of its extensible tissues. The radius of the stem oscillated daily and, fairly independently of this, fluctuated over several days. The daily shrinkage (_d) was correlated with the daily flow through its base (Q_d). When the crown transpired little and was nearly saturated during rainy days, ASd tended to increase relative to Q_d. Using a linear relation, the estimates of flow by _d deviated less than ± 10% from the values measured by heat balance, provided that the periods of calibration in their ratio of dry to rainy days were comparable to those estimated. If the two periods differed in this respect, the estimates of flow deviated up to 42%. A quadratic relation yielded estimates that depended less on weather. It reduced maximal deviations to ±22%. Since _d additionally may represent the time pattern of the daily transpiration better than Q_d, analysing changes in the radius of stems may supplement or partly replace measurements of sap flow in stems.     

Influence of exogenous ethylene on ipomeamarone accumulation in black rot infected sweet potato roots

Ipomeamarone accumulation in sweet potato (Ipomoea batatas) roots infected with Ceratocystis fimbriata (black rot) was decreased by one-third when roots were stored under 100 ppm ethylene. This effect of ethylene was not observed when infected tissue was also treated with benzylisothiocyanate. Ethylene treatment and long term infection were associated with the accumulation of 4-ipomeanol and 1-ipomeanol.     

Mass spectrometric measurement of zeatin glycoside levels in Vinca rosea L. crown gall tissue

The range of zeatin glycosides found in crown gall tissue of Vinca rosea L. has been quantified using a mass spectrometric isotope dilution procedure. Problems in the quantitative analysis of cytokinins in plant extracts are discussed.Abbreviations GC/MS coupled gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - Me methyl - Z zeatin - Z9G zeatin 9-glucoside - ZOG zeatin O-glucoside - ZR zeatin 9-riboside - ZROG zeatin 9-riboside O-glucoside     

Effect of moisture stress, plant population density and pathogen inoculation on charcoal stalk rot of sorghum

The effects of moisture deficit stress, plant population density and pathogen inoculation technique on charcoal stalk rot in the sorghum hybrid CSH 6 were studied in the 1980–81 and 1981–82 post-rainy seasons at three locations in India. Incidence and severity of charcoal rot caused by Macrophomina phaseolina were compared in three plant population densities, subjected to different moisture stress regimes created by withholding irrigation at various plant growth stages. Natural infections were compared to artificial inoculation with M. phaseolina. Combinations of moisture stress, plant population and inoculation treatments were compared to identify the combination most likely to develop maximum disease. Lodging, the first external symptom of charcoal rot, was significantly correlated with other disease symptoms used to measure charcoal rot, such as soft stalk, number of nodes crossed by M. phaseolina infection, root damage and plant senescence. In both seasons the highest incidence of lodging occurred when moisture stress was induced at the 'flag leaf visible in the whorl' growth stage. The greatest incidence of the disease was recorded in the highest plant population (266 700 plant ha^-) at all three locations. No significant differences were found between artificially and naturally inoculated treatments. The maximum number of lodged plants was found at a density of 266 700 plants ha^-1 when moisture stress was induced at the 'flag leaf visible in the whorl' growth stage.     

Evaluation of ash from some tropical plants of Nigeria for the control of Sclerotium rolfsii Sacc. on wheat ( Triticum aestivum L.)

Eleven ash samples, from organs of nine tropical plants, were screened for their abilities to inhibit mycelial growth and sclerotial germination of a Nigerian isolate of Sclerotium rolfsii on agar and in the soil. Ten ash samples showed some activity against mycelial growth of S. rolfsii in vitro. Ash samples from Delonix regia stem wood, Mangifera indica leaf and Vernonia amygdalina leaf were most effective as each totally inhibited mycelial growth of S. rolfsii in vitro. Ocimum gratissimum leaf ash, D. regia wood ash and Musa paradisiaca flower bract ash inhibited sclerotial germination on agar. Nine ash samples protected seeds against pre-emergence rot. Ash from M. indica leaf, V. amygdalina leaf and Azadirachta indica leaf protected seedlings against post-emergence infection. Eichornia crassipes ash, which was ineffective in vitro, offered some protection to seeds in soil against pre-emergence rot. The study demonstrates potentials of ash samples from tropical plants in control of S. rolfsii on wheat. This revised version was published online in June 2006 with corrections to the Cover Date.