Diversity of salt tolerance in a germplasm collection of wheat (Triticum spp.).

A collection (5,072 lines) of wheat germplasm was screened at the seedling stage for tolerance to salinity concentrations having electrical conductivities of 0.8 (control), 12.5, 18.75 and 25.0 dS/m. Surviving seedlings were expressed for each line as a percentage of the control value. The 442 lines with greater than 70% surviving seedlings were tested for whole-life cycle survival under each salinity condition. The data of the reactions to salinity at both the seedling stage and maturity were used to classify the collection according to: (1) country of origin (2) species and ploidy level. The data were then subjected to a diversity analysis using the Shannon-Weaver information index. Seedling stage tolerance to 12.5 dS/cm salinity was widely distributed in the collection (79% of lines), whereas only 9% were tolerant at 25.0 dS/m salinity. The seedling stage tolerance was indicative of maturity tolerance. At the seedling stage, entries from USA and Egypt showed the largest proportions of tolerant lines. In addition, USA, Mexico and Egypt entries exhibited the widest variability. Diversity among regions was greater than among countries within regions, while the diversity among species was greater than among ploidy levels. Tetraploids exceeded hexaploids and diploids in the proportion of tolerant lines and diversity. Wheat-rye derivatives showed a good potential for salt tolerance at early stages. Screening more germplasm from the arid and semi-arid regions especially from countries with salt affected soils was recommended.

Determination of tetanus antitoxin levels in hyperimmunized volunteers.

A method is described using double diffusion with a perspex template for determining tetanus antitoxin levels in the plasma of volunteers who have been hyperimmunized with tetanus toxoid for the purpose of producing human tetanus immune globulin. This test is simple to perform, economical, sentitive, reproducible and is in excellent agreement with the standard toxin neutralization test in mice. Comparisons with the in vivo toxin neutralization test are presented for this test, the passive hemagglutination, radial immunodiffusion and counter electrophoresis methods.

Selection of a tetanus toxoid for hyperimmunization of human volunteers.

Five tetanus toxoids of different manufacture and of different concentrations were used to determine the most effective formulation and strength of toxoid for the production in human volunteers of sustained high levels of tetanus antitoxin suitable for the production of human tetanus immune globulin. The most satisfactory results were obtained with a fluid, low-protein, column-purified tetanus toxoid. 79% of volunteers injected with a 36 Lf dose of this material achieved antitoxin levels of greater than or equal to 10 antitoxin units/ml. The mean duration of these levels was 125 days.

Inheritance of five quantitative characters of bread wheat.

Heritability estimates of five characters of the wheat plant were studied in five crosses involving six cultivars of bread wheat. Parents, F1, F2 and backcrosses to both parents were used in the estimation of the genetic parameters.Heritability was low for number of fertile spikes/plant, moderate for number of spikelets/spike, number of kernels/spike, 1000-kernel weight and moderately high for number of kernels/spike. Evidence for mainly nonadditive gene effects were observed in the expression of number of fertile spikes and 1000-kernel weight. Although nonadditives contributed to a lesser degree to the gene action, additives seemed to be the most important genetic expression regulating number of spikelets/spike, number of kernels/spike, and number of kernels/spikelet. Except for number of fertile spikes/plant, selection in F2-populations seems to be promising.