Peter W. Jones

Bioactivities of glycoalkaloids and their aglycones from Solanum species.

Potatoes, tomatoes, and aubergines are all species of the Solanum genus and contain a vast array of secondary metabolites including calystegine alkaloids, phenolic compounds, lectins, and glycoalkaloids. Glycoalkaloids have been the subject of many literature papers, occur widely in the human diet, and are known to induce toxicity. Therefore, from a food safety perspective further information is required regarding their analysis, toxicity, and bioavailability. This is especially important in crop cultivars derived from wild species to prevent glycoalkaloid-induced toxicity. A comprehensive review of the bioactivity of glycoalkaloids and their aglycones of the Solanum species, particularly focused on comparison of their bioactivities including their anticancer, anticholesterol, antimicrobial, anti-inflammatory, antinociceptive, and antipyretic effects, toxicity, and synergism of action of the principal Solanum glycoalkaloids, correlated to differences of their individual molecular structures is presented.

Anti-inflammatory properties of potato glycoalkaloids in stimulated Jurkat and Raw 264.7 mouse macrophages.

AIMS The potato glycoalkaloids, α-chaconine, α-solanine and solanidine, along with potato peel extracts were investigated for potential anti-inflammatory effects in vitro. Their potential to reduce two biomarkers of inflammation, cytokine and nitric oxide (NO) productions, were assessed in the stimulated Jurkat and macrophage models, respectively. MAIN METHODS Cytokine and nitric oxide productions were stimulated in Jurkat and Raw 264.7 macrophages with Concanavalin A (Con A; 25 μg/ml) and lipopolysaccaride (LPS; 1 μg/ml), respectively. Selective concentrations of glycoalkaloids and potato peel extracts were added simultaneously with Con A or LPS for 24h to investigate their potential to reduce inflammatory activity. KEY FINDINGS α-Chaconine and solanidine significantly reduced interleukin-2 (IL-2) and interleukin-8 (IL-8) productions in Con A-induced Jurkat cells. The potato peel extracts did not influence cytokine production. In LPS-stimulated Raw macrophages, α-solanine, solanidine and two potato peel extracts significantly reduced induced NO production. SIGNIFICANCE Our findings suggest that sub-cytotoxic concentrations of potato glycoalkaloids and potato peel extracts possess anti-inflammatory effects in vitro and with further investigation may be useful in the prevention of anti-inflammatory diseases.

Flexural strain and crack width measurement of steel-fibre-reinforced concrete by optical grid and electrical gauge methods

A research programme is discussed, which has investigated the fracture of steel-fibre-reinforced sprayed concrete under flexural loading, with the aim of developing a stress-block model to predict flexural behaviour in the form of a load–deflection response. This paper reports the work associated with establishing the strain and crack width profiles in relation to mid-span beam deflection. A strain analysis technique is described, which combines the use of electrical strain gauges with a semiautomated grid method (using digital image processing) for measuring and monitoring the strain and crack width profile over the depth of a fibre-reinforced beam during a flexural test. This novel strain analysis technique has established strain/crack width data, which forms a key part of a stress-block approach for predicting residual flexural strength, an essential requirement of a much needed design rationale for steel-fibre-reinforced concrete.

Development of diagnostic markers for use in breeding potatoes resistant to Globodera pallida pathotype Pa2/3 using germplasm derived from Solanum tuberosum ssp. andigena CPC 2802

Quantitative resistance to Globodera pallida pathotype Pa2/3, originally derived from Solanum tuberosum ssp. andigena Commonwealth Potato Collection (CPC) accession 2802, is present in several potato cultivars and advanced breeding lines. One genetic component of this resistance, a large effect quantitative trait locus (QTL) on linkage group IV (which we have renamed GpaIVadgs) has previously been mapped in the tetraploid breeding line 12601ab1. In this study, we show that GpaIVadgs is also present in a breeding line called C1992/31 via genetic mapping in an F1 population produced by crossing C1992/31 with the G. pallida susceptible cultivar Record. C1992/31 is relatively divergent from 12601ab1, confirming that GpaIVadgs is an ideal target for marker-assisted selection in currently available germplasm. To generate markers exhibiting diagnostic potential for GpaIVadgs, three bacterial artificial chromosome clones were isolated from the QTL region, sequenced, and used to develop 15 primer sets generating single-copy amplicons, which were examined for polymorphisms exhibiting linkage to GpaIVadgs in C1992/31. Eight such polymorphisms were found. Subsequently, one insertion/deletion polymorphism, three single nucleotide polymorphisms and a specific allele of the microsatellite marker STM3016 were shown to exhibit diagnostic potential for the QTL in a panel of 37 potato genotypes, 12 with and 25 without accession CPC2082 in their pedigrees. STM3016 and one of the SNP polymorphisms, C237(119), were assayed in 178 potato genotypes, arising from crosses between C1992/31 and 16 G. pallida susceptible genotypes, undergoing selection in a commercial breeding programme. The results suggest that the diagnostic markers would most effectively be employed in MAS-based approaches to pyramid different resistance loci to develop cultivars exhibiting strong, durable resistance to G. pallida pathotype Pa2/3.

The effect of mycorrhizal fungi on the hatch of potato cyst nematodes

In the presence of potato plants cv. Golden Wonder, Globodera pallidaexhibited delayed in-soil hatch compared to that of G. rostochiensis, with significantly fewer G. pallida second-stage juvenile nematodes hatching in the first two weeks, though the difference disappeared after four weeks. Inoculation of potato plants with arbuscular mycorrhizal fungi eliminated this delay in G. pallida hatch, so that the two potato cyst nematode (PCN) species exhibited similar in-soil hatch rates. When the corresponding in vitro hatching activities of root leachate from uninoculated and mycorrhiza-inoculated plants were compared, similar effects were revealed. G. pallida hatch in root leachates from uninoculated plants increased significantly from one-week-old to two-week-old plants, but this increase was not significant in the mycorrhizal-inoculated plants. When the in-soil experiment was repeated using the potato cyst nematode non-host plant strawberry, mycorrhizal inoculation induced no significant increase in G. pallidahatch. The results indicate that mycorrhizal inoculation of potato plants stimulates production of G. pallida-selective hatching chemicals, either hatching factors or hatching factor stimulants.

The influence of in-egg mortality and spontaneous hatching on the decline of Globodera rostochiensis during crop rotation in the absence of the host potato crop in the field

The decline of Globodera rostochiensis (Woll.) populations in two fields was 57% during the first and 40.3% during the second year of crop rotation in the absence of a potato crop in Co. Cork, Ireland. The decline was found to be due to both spontaneous hatch and in-egg mortality. Spontaneous hatch accounted for between 75.8 and 80.2% of the decline experienced during rotation. In-egg mortality was found to be responsible for a reduction of approximately 10% in the total number of viable eggs in both fields, and was positively correlated with soil temperature in the field. The number of culturable bacteria and the composition of the bacterial microflora in the cysts was found to change with increasing soil temperatures. The increase in cellulase-positive isolates reflected the effect of temperature on egg degradation. Der Einfluss von Absterben im Ei und spontanem Schlupfen auf die Abnahme von Globodera rostochiensis im Feld im Laufe des Fruchtwechsels bei Abwesenheit des Wirtes Kartoffel - In Co. Cork, Irland, betrug die Abnahme der Populationen von Globodera rostochiensis (Woll.) in zwei Feldern in einer Fruchtfolge ohne Kartoffeln im ersten Jahr 57% und im zweiten Jahr 40,3%. Es wurde festgestellt, dass die Abnahme durch spontanes Schlupfen und durch Absterben im Ei verursacht wurde. Spontanes Schlupfen war fur 75,8 und 80,2% des wahrend des Fruchtwechsels beobachteten Ruckganges verantwortlich. Etwa 10% der Gesamtzahl infektionsfahiger Eier in den beiden Feldern gingen durch Absterben im Ei zugrunde. Dieser Ruckgang war positiv korreliert mit der Bodentemperatur im Feld. Der Anteil der kulturfahigen Bakterien und die Zusammensetzung der Bakterienflora in den Zysten nahmen mit steigenden Bodentemperaturen zu. Der Anstieg der zellulase-positiven Isolate spiegelte die Wirkung der Temperatur auf die Zersetzung der Eier wider.

Nuclear and cytoplasmic gene control of resistance to loose smut (Ustilago tritici (Pers.) Rostr.) in wheat (Triticum aestivum L.)

SummaryUsing disomic chromosome substitution lines based on the susceptible wheat cultivar ‘Chinese Spring’, loose smut resistance of wheat cultivars ‘Hope’ and ‘Thatcher’ was shown to be conferred in each case by a single dominant major gene carried on chromosome 7 A (‘Hope’) or 7 B (‘Thatcher’). Partial resistance was determined by genes on an additional eight ‘Hope’ or seven ‘Thatcher’ chromosomes, and similarities were evident between the partial resistance genotypes of‘Hope’ and ‘Thatcher’. ‘Chinese Spring’ exhibited a mean infection value of approximately 50%, indicating a significant level of partial resistance, which was found to be due, in part, to genes on the homoeologous chromosome arms 1 As, 1 Es and 1 Ds, and to cytoplasmic genes. Substitution of the ‘Chinese Spring’ nucleus into the cytoplasm of Aegilops squarrosa, Ae. variabilis or Ae. mutica resulted in increased susceptibility to Ustilago tritici. Several alloplasmic lines of the resistant wheat cultivars ‘Selkirk’ and ‘Chris’ exhibited race-specific susceptibility to U. tritici.

Interrelationships Between the Enzymes of Ethanolamine Metabolism in Escherichia coli

The activities of the enzymes ethanolamine ammonia-lyase, CoA-dependent and CoA-independent aldehyde dehydrogenases, and isocitrate lyase were assayed in Escherichia coli which had been grown on various sources of carbon and nitrogen. Induction of ethanolamine ammonia-lyase and of maximal levels of both aldehyde dehydrogenases required the concerted effects of ethanolamine and vitamin (or coenzyme) B12. Molecular exclusion chromatography revealed that, in the absence of one or both co-inducers, two repressible isoenzymes of CoA-dependent aldehyde dehydrogenase (mol. wts 900000 and 120000) were produced, these being replaced by two inducible isoenzymes (mol. wts 520000 and 370000) in the presence of both co-inducers. A similar inducible repressible series of isoenzymes was also observed for CoA-independent aldehyde dehydrogenase. No evidence was found for structural relationships between ethanolamine ammonia-lyase, CoA-dependent aldehyde dehydrogenase and CoA-independent aldehyde dehydrogenase, but mutant and physiological studies demonstrated that the induction of the first two enzymes is under common control. Evidence is presented for the operation of a previously unreported pathway of ethanolamine metabolism in E. coli.

Isolation of wheat mutants with increased resistance to powdery mildew from small induced variant populations

Small variant wheat populations created by induced mutagenesis (n = 69) or adventitious regeneration (n = 66) were intensively screened for an altered response (compared to the parent variety ‘Guardian’) to the causal pathogen of powdery mildew in wheat, Blumeria graminis f. sp. tritici. Intensive field screening following natural infection of replicated plots of wheat lines over two years revealed a total of 13 mutants exhibiting significantly greater resistance than ‘Guardian’: eight from induced mutagenesis (11.6%) of the M2 population and five from adventitious regeneration (7.6%). Complete resistance was identified in two lines, (one (M66) developed following induced mutagenesis, and the other (SC240) by adventitious regeneration). The complete resistance in the induced mutant was stable over two generations and was associated with a high frequency of leaf flecking, and consequently a low grain yield. Resistance in SC240 proved to be unstable; SC240 exhibited complete resistance to powdery mildew in the SC2 and SC3 generations, but only 20% of the SC4 plants were completely resistant, while the remainder were indistinguishable in mildew response to ‘Guardian’. The mildew response of all the SC5 generation of SC240 was not significantly different from ‘Guardian’. Yield analysis of the thirteen mutants with increased resistance in the presence of powdery mildew indicated that eleven exhibitedgrain yields at least as high as that of ‘Guardian’, while the mutant M19 exhibited a yield significantly higher than that of ‘Guardian’.

Criteria for decision making in crop improvement programmes — Technical considerations

Plant breeding involves three stages: namely, creation of variation, selection of desired genotypes and trialling to confirm characteristics. Since the 1900s, plant geneticists and plant breeders have worked together to develop methods to increase the options and efficiencies of the different stages in plant improvement. During the intervening years, inputs from plant pathologists and plant physiologists have been assimilated. Recently, new techniques for plant improvement have been developed by molecular biologists and plant tissue culturists. The challenge is to incorporate these and other non-conventional methods efficiently into the development of strategies for plant improvement.