Novel genotypes of the subtropical grass Eragrostis curvula for the study of apomixis (diplospory)

The aim of this work was to obtain a series of genetically related lines of Eragrostis curvula with different ploidy levels and reproductive modes, which can be used for the discovery of genes associated to diplospory. E. curvula is a widely cultivated forage grass native to Southern Africa that reproduces naturally by obligate diplosporous apomixis (asexual reproduction by seeds) of the Antennaria type. In vitro culture of immature inflorescences of the apomictic cultivar Tanganyika led to the regeneration of a diploid plant with a particular morphology (plant UNST1122). Embryo sac analysis and progeny tests determined that plant UNST1122 reproduces by sexuality. UNST1122 was cloned by dividing its tillers and a R ₁ generation was obtained from seeds after open pollination among the diploid clones. A set of 500 seeds from a diploid R ₁ plant was treated with colchicine and two plants showing a duplicated chromosome number (2n = 4x = 40) were obtained (plants UNST1112 and UNST1131). Progeny tests using RAPDs indicated that these plants reproduce also by sexuality. The availability of sexual tetraploid genotypes of E. curvula will allow the production of hybrids with new interesting combinations of agronomic traits and the developing of mapping populations segregating for diplospory. Besides, these genetically related plants with different reproduction modes constitutes an excellent model for the identification of gen(es) involved in diplosporous apomixis by mRNA profiling as well as to study the genomic rearrangements and gene expression alterations associated to changes at ploidy levels.     

The response of Pisum sativum L. germplasm to high concentrations of soil boron

Summary Tolerance to high levels of boron in the soil is an important aspect of the adaptation of crop varieties to southern Australian conditions. This paper reports investigations aimed at exploring the extent of genetic variation in Pisum sativum and at defining appropriate selection criteria for selection for boron tolerance in breeding programs.A collection of 617 accessions of Pisum was screened in controlled conditions and visually assessed for symptoms of boron toxicity. A high proportion of accessions were sensitive with only 3.5% being more tolerant than any of the Australian varieties. Relatively high proportions of tolerant and moderately tolerant accessions originated from Asia and South America.In a second experiment the responses of selected tolerant accessions were evaluated with respect to different parameters. The objectives were to confirm the performance of the putative boron tolerant accessions and identify appropriate parameters for selecting boron tolerant genotypes. In addition to the visual assessment of boron toxicity, measurements at the time of harvest included dry matter yield and concentration of boron in tissues. Symptom expression was highly correlated with dry matter yield and concentration of boron in tissues under high boron conditions and so could be used as a non-destructive selection criteria. A low degree of symptom expression by tolerant accessions could usually be attributed to low levels of boron in the vegetative tissues. The results of this study indicate that considerable genetic variation exists among exotic accessions of Pisum sativum and tolerance to boron could be transferred to sensitive varieties.     

Major gene control of tolerance of bread wheat (Triticum aestivum L.) to high concentrations of soil boron

Summary The genetic control of tolerance of wheat to high concentrations of soil boron was studied for five genotypes. Each genotype represented one of five categories of response to high levels of boron, ranging from very sensitive to tolerant. Tolerance to boron was expressed as a partially dominant character, although the response of an F₁ hybrid, relative to the parents, varied with the level of boron applied. The F₁ hybrids responded similarly to the more tolerant parent at low B treatments and intermediate to the parents at higher treatments. Ratios consistent with monogenic segregation were observed for the F₂ and F₃ generations for the combinations (WI^*MMC) × Kenya Farmer, Warigal × (WI^*MMC) and Halberd × Warigal. The three genes, Bo1, Bo2 and Bo3, while transgressive segregation between two tolerant genotypes, G61450 and Halberd, suggested a fourth locus controlling tolerance to boron.     

The Importance of Having Zinc During In Vitro Maturation of Cattle Cumulus–Oocyte Complex: Role of Cumulus Cells

The aim of this study was to investigate the influence of zinc (Zn) on the health of cumulus–oocyte complex (COC) during in vitro maturation (IVM). Experiments were designed to evaluate the effect of Zn added to IVM medium on: DNA integrity, apoptosis, cumulus expansion and superoxide dismutase (SOD) activity of cumulus cells (CC). Also, role of CC on Zn transport during IVM was evaluated on oocyte developmental capacity. DNA damage and early apoptosis were higher in CC matured with 0 μg/ml Zn compared with 0.7, 1.1 and 1.5 μg/ml Zn (p < 0.05). Cumulus expansion did not show differences in COC matured with or without Zn supplementation (p > 0.05). Superoxide dismutase activity was higher in COC matured with 1.5 μg/ml Zn than with 0 μg/ml Zn (p < 0.05). Cleavage and blastocyst rates were recorded after IVM in three maturation systems: intact COCs, denuded oocytes with cumulus cells monolayer (DO + CC) and denuded oocytes (DO). Cleavage rates were similar when COC, DO + CC or DO were matured with 1.5 μg/ml Zn compared with control group (p > 0.05). Blastocyst rates were significantly higher in COC than in DO + CC and DO with the addition of 1.5 μg/ml Zn during IVM (p < 0.01). Blastocyst quality was enhanced in COC and DO + CC compared with DO when Zn was added to IVM medium (p < 0.001). The results of this study indicate that Zn supplementation to IVM medium (i) decreased DNA damage and apoptosis in CC; (ii) increased SOD activity in CC; (iii) did not modify cumulus expansion and cleavage rates after in vitro fertilization; (iv) improved subsequent embryo development up to blastocyst stage; and (v) enhanced blastocyst quality when CC were present either in intact COC or in coculture during IVM.     

Behavioural and EEG changes in sheep in response to painful acute electrical stimuli

Objective To measure acute pain in sheep, based on a human pain model, and examined changes in both electroencephalogram frequency spectrum and behavioural responses to increased electrical stimulation in sheep. Design Analysis of variance (treatment and animal effects) for stimulus intensity where each animal received each electric shock treatment given in the order 0, 5,10 and 20 mA. Procedure Eight sheep with electrodes implanted over the surface of the brain were examined for escape-avoidance and electroencephalogram responses to four levels of electrical stimulation from 0–20 mA. Results With increasing stimulus intensity at the time of feeding, the sheep were more hesitant to return to the feeder or remain near the feeder following stimulation. There was little difference between the 0 and 5 mA stimuli for any of the behaviour variables (P > 0.05). However, there were marked increases in the time taken to re-approach the feeder after receiving an electric shock of 5 mA and of 20 mA (P < 0.05; mean values 3 and 119 s, respectively) and remaining near the feeder for 5 s (P < 0.001; mean values 10 and 167 s, respectively). Following the stimulus, there was an overall increase in the electroencephalogram power spectrum in the first four seconds, which then rapidly returned to normal. In particular, the 20 mA stimulus resulted in higher absolute power values than in the control (0 mA) treatment for delta 2 (P < 0.001), theta 1 (P < 0.05), theta 2 (P < 0.05), alpha 1 (P < 0.001), alpha 2 (P < 0.001) and beta 1 (P < 0.01) band-widths. Similarly, for the 10 mA stimulus, the absolute power values were greater than the control treatment for delta 2 (P < 0.05), alpha 1 (P < 0.01), alpha 2 (P < 0.001) and beta 1 (P < 0.01) bandwidths. Conclusion The experiment suggests that a human acute pain model is applicable to sheep and that these electroencephalogram changes may provide a good measure of acute pain in sheep.     

Effect of adjuvants on antibody responses of sheep immunised with recombinant pili from Dichelobacter nodosus

Objective To compare the effects of two oil emulsion adjuvants (incomplete Freunds adjuvant and a proprietary oil adjuvant), DEAE-dextran, L-tyrosine particles and Quil A on the humoral immune responses of sheep immunised with recombinant pili of Dichelobacter nodosus (strain A).
Procedure Antibody titres were studied for up to 32 weeks and were measured by bacterial agglutination and ELISA. The relative avidity of antibodies for pili was determined and the incidence and severity of adverse reactions at the site of injection of vaccines were recorded.
Results The oil emulsion adjuvants and Quil A were more effective than either DEAE-dextran or L-tyrosine at stimulating antibodies in sheep. The incidence and severity of adverse reactions was lower in sheep which received vaccines containing either Quil A or DEAE-dextran than in sheep which received vaccines containing oil emulsion adjuvants. L-tyrosine had no adverse effects.
Conclusion Quil A was as effective as oil adjuvants at stimulating high levels of antibodies against recombinant pili in sheep and had the significant advantage of being less irritant after subcutaneous injection.     

Grain quality and yield characteristics of D-genome disomic substitution lines in 'Langdon' (Triticum turgidum var. durum)

Sets of D-genome disomic substitution lines of ‘Langdon’ (Triticum turgidum var. durum) were used to study the effect of chromosome substitutions on grain yield and flour technological properties. In general, the substitution of any D-genome chromosome had a detrimental effect on grain yield and growth vigour (some lines were sterile). SDS-sedimentation, SE-HPLC and two-gram mixograph procedures were used to measure dough strength of the lines studied. Significant correlations were observed between protein concentration and grain yield and other quality parameters such as SDS-sedimentation value, the proportion of glutenin, dough mix time and peak resistance. Most of the quality characters were highly correlated with each other. Substitution of chromosomes 1D, 5D, 2D and 7D resulted in positive responses to SDS-sedimentation values, but only chromosome 1D had positive effects on the proportion of peak 1 (P₁%), measured by SE-HPLC. Besides the major influence of chromosome 1D on three major mixograph parameters (mixing time, peak resistance and resistance breakdown), chromosome 5D also exhibited significant effects on these mixing parameters. Principal-component analysis showed that the predominant effect on durum-wheat rheological properties was from chromosome 1D, whereas chromosome 5D had a major effect on grain hardness (50%) and increased the whiteness of the flour.