J. P. F. G. Helsper

The digestibility in piglets of faba bean ( Vicia faba L.) as affected by breeding towards the absence of condensed tannins

Seed samples from two near-isogenic faba bean (Vicia faba L.) lines were examined for the levels of so-called anti-nutritional factors (ANF). From the ANF known to be present in faba beans, trypsin inhibitor activity, functional lectins, condensed tannins and pyrimidine glycosides were analysed. It was concluded that the lines differed only in the content of condensed tannins being < 0.5 g/kg and 5.2 (SD 0.2) g/kg for the low (LT)- and high (HT)-tannin lines respectively. In addition, the level of pyrimidine glycosides in the LT line was slightly higher than that in the HT line. The LT line showed a reduced proportion of the seed coat (105 v. 119 g/kg) and a lower seed weight (0.85 v. 1.01 g). The apparent ileal and faecal digestibility values of dry matter and nitrogen from the HT and LT line were determined for piglets which were fed on diets containing chromium oxide as a marker. The mean apparent ileal and faecal digestibility values for dry matter for the LT line were 0.694 and 0.889 and for N 0.828 and 0.879 respectively. For the HT line, these values were approximately 0.05 and 0.10 lower (P > 0.05). A multienzyme technique was used to predict the in vitro protein digestibility (IVPD) of the two lines. The IVPD of the LT line was 0.965 and about 0.05 higher than the HT line, confirming the difference in digestibility as measured in vivo. The present study shows the positive effects on digestibility of removal of condensed tannins in faba beans which was achieved by plant breeding.

Characterization and trypsin inhibitor activity of proanthocyanidins from Vicia faba

Abstract In a chemical investigation epicatechin, epigallocatechin, the procyanidins B-1, B-3 and B-4, and the prodelphinidins gallocatechin-(4α,8)-catechin, gallocatechin-(4α,8)-epicatechin and gallocatechin-(4α,8)-epigallocatechin have been isolated from the testa of faba beans and characterized by means of spectroscopic methods. Proanthocyanidin samples were compared for their trypsin inhibitory activity. The results suggest that the degree of polymerization, the number of phenolic hydroxyl groups and the 2,3-stereochemistry of the constituent units affect remarkably the strength of the inhibition.

Phytate metabolism in Petunia pollen

Abstract Phytic acid has been detected in the anthers of young flower buds of Petunia hybrida , the amount increasing slowly as the flower develops until anther dehydration, when there was a more rapid increase in phytic acid content. In mature pollen, the phytic acid content was found to be 2.0 % by weight, of which 90 % was water soluble, while free myo -inositol was a relatively low 0.06 % by weight. Breakdown of phytic acid was initiated soon after pollen germination began, and its degradation products, myo -inositol and inorganic phosphate, were rapidly mobilized for phospholipid and pectin biosynthesis. Both are in high demand during pollen tube elongation. Utilization of myo -[2- 3 H]inositol for phospholipid biosynthesis was about five times that for pectin synthesis during the first few hours of pollen germination. The label in the phospholipid was identified as the myo -inositol moiety of phosphaltidylinositol, while the pectin material contained predominantly labelled arabinose, with smaller amounts of label in galacturonic acid, glucose and xylose. A chase experiment showed that the myo -inositol moiety of phosphatidylinositol was subject to a relatively rapid turnover, while the label in pectin was not. Labelling germinating pollen with [ 32 P]orthophosphate gave label in phosphatidic acid, phosphatidylinositol, phosphatidylethanolamine and phosphatidylcholine of the phospholipids. Phosphatidylinositol contained 30 % of this label initially, a proportion which declined to 10 % over longer periods of germination.

Phosphatidylinositol phospholipase C activity in pollen of Lilium longiflorum

Abstract Homogenates from pollen of Lilium longiflorum (cv. Arai) contain phosphatidylinositol phospholipase activity, which increased during germination. Analysis of radioactive products resulting from incubation of phosphatidylinositol, labelled in the myo -inositol, phosphate or glycerol moiety, showed that cleavage had only taken place between glycerol and phosphate. The activity is therefore of a phospholipase C-type (EC 3.1.4.10). It was stimulated by several divalent cations; Ca 2+ was the most effective. Zn 2+ , Cu 2+ and EDTA are inhibitory. The activity was found in both the cytosol and particulate fractions.

Characterization of galactosyltransferases in spinach chloroplast envelopes

Abstract Two galactosyltransferases involved in the galactolipid metabolism of spinach chloroplast envelopes were studied by specific assays: UDPgalactose: 1,2-diacylglycerol galactosyltransferase, which synthetizes monogalactosyldiacylglycerol from UDPgalactose plus diacylglycerol; and galactolipid: galactolipid galactosyltransferase (GGGT), which forms di- , tri- and tetragalactosyldiacylglycerol by dismutation of galactosyl groups between two galactosyldiacylglycerols. In the assay developed for UDPgalactose: 1,2-diacylglycerol galactosyltransferase, chloroplast envelope membranes were mixed with liposomes of phosphatidylcholine, and the mixture was treated with phospholipase C (from Bacillus cereus). The diacylglycerol produced from phosphatidylcholine is used by UDPgalactose: 1,2-diacylglycerol galactosyltransferase for synthesis of monogalactosyldiacylglycerol in the presence of UDPgalactose. Several characteristics of this enzyme were studied, including the effect of substrate concentrations, pH and temperature. UDPgalactose: 1,2-di-acylglycerol galactosyltransferase did not require cations for activity, but was stimulated by Mg2+ and Mn2+. Of the mono- and divalent cations tested only Zn2+, Cd2+ and Fe2+ were inhibitory. Specific inhibitors for UDPgalactose: 1,2-diacylglycerol galactosyltransferase were UDP and N-ethylmaleimide. In contrast to UDPgalactose: 1,2-diacylglycerol galactosyltransferase, galactolipid: galactolipid galactosyltransferase was strongly stimulated by a series of mono- and divalent cations, most stimulatory being Mn2+ Ba2+, Ca2+ and Mg2+. Galactolipid: galactolipid galactosyltransferase was specifically inhibited by low concentrations of Zn2+ (1 mM) and by chelating anions. UDPgalactose: 1,2-diacylglycerol galactosyltransferase synthetized monogalactosyldiacylglycerol from various molecular species of diacylglycerol; the highest activity was measured with distearoylglycerol and dioleoylglycerol. On the other hand, digalactosyldiacylglycerol synthesis by galactolipid: galactolipid galactosyltransferase proceeded most rapidly by galactosyl transfer to hexaene species of monogalactosyldiacylglycerol.

Rate and inheritance of cross-fertilization in faba bean (Vicia faba L.)

SummaryTo assess the feasibility for synthetic varieties of Vicia faba L., 108 faba bean genotypes were screened for cross-fertilization rate in five field experiments carried out in 1989 and 1990 at Wageningen.Significant genotypic differences were observed for outcrossing rate, which ranged from 1 to 55%. These percentages, however, are thought to be not high enough for a commercially feasible production of synthetic varieties.The inheritance of cross-fertilization rate, determined by testing the F4 generation of a cross between two inbreds, both with high outcrossing rates, appeared to be of a polygenic nature, as was indicated by the wide variation in, and the continous distribution of, the cross-fertilization rates. Among the F4 lines tested some had a significantly higher cross-fertilization rate than the parents. However, this difference was not found when these lines were retested, indicating that possibilities for successful selection for higher outcrossing rates might be limited.

Effect of the absence of condensed tannins in faba beans ( Vicia faba ) on resistance to foot rot, Ascochyta blight and chocolate spot

The effect of breeding for the absence of condensed tannins in the testa of Vicia faba L. on resistance to foot rot, Ascochyta blight and chocolate spot diseases was investigated in 1988–92 at Wageningen, The Netherlands. For this purpose the disease development in tannin-free and tannin-containing partners of six near-isogenic pairs was compared after exposure to causative pathogens. Except for one near-isogenic pair, in which both partner lines showed a relatively high resistance, the tannin-free lines were more susceptible to foot rot than the tannin-containing partners of the same pair. This observation indicates that the presence of condensed tannins in the testa prevents infection of the plant by the causative pathogens. Fusarium oxysporum and F. solani , isolated from faba bean tissues showing foot rot symptoms, were shown to be primary foot rot pathogens, while F. avenaceum caused wilting of young plantlets. No pathogenic isolates were obtained from F. tabacinum . Resistance to Botrytis fabae (chocolate spot disease), scored on leaves and stems under glasshouse and field conditions in 1992, was not influenced by selection for the absence of condensed tannins which occur in the testa of mature seeds. Under the same environmental conditions, leaves, stems, pods and seeds of tannin-free lines showed similar levels of damage due to Ascochyta fabae (Ascochyta blight) as the tannin-containing partner lines of the same near-isogenic pair. These results indicate that condensed tannins do not play a role in resistance to both B. fabae and A. fabae , probably because, except for the seeds, these polyphenols do not accumulate in the tissues affected by these pathogens.

Genetic factors controlling outcrossing in faba bean (Vicia faba): effects of pollen donor and receptor genotypes and estimates of inter-receptor cross-fertilization

For the production of hybrid and synthetic varieties, high rates of cross-fertilization are needed. Two aspects of cross-fertilization in Vicia faba L. were studied at Wageningen in 1989 and 1990. The occurrence of cross-fertilization between pollen receptor lines in large-scale assays for cross-fertilization was determined. Furthermore, the contribution of the genotype of the donor, of the receptor, and of their specific interactions in terms of cross-fertilization rate were studied. Inter-receptor cross-fertilization may represent from 2 to 70% of the total cross-fertilization. Inter-receptor cross-fertilization increases when donors and receptors do not match for flowering height

Inheritance of seedling colour in faba bean (Vicia faba L.)

SummaryThe inheritance of purple seedling colour was studied, in relation to the genetic control of flower colour. It was found that purple seedling colour is likely to be controlled by a single gene and that the trait is dominant over green seedling colour. White flowering prohibited the expression of the purple seedling colour, and is therefore thought to be epistatic.This character can be used to estimate rate of outcrossing in breeding programmes, as well as contribute to our knowledge of the biosynthesis of plant pigments and secondary metabolites such as tannins.

Studies on l-ascorbic acid biosynthesis and metabolism in Parthenocissus quinquefolia L. (vitaceae)

Abstract Parthenocissus quinquefolia (L.) Planch., commonly known as Virginia Creeper, is a vitaceous tartrate-accumulating vine that exhibits C-4/C-5 cleavage of l -ascorbic acid (AA) to produce l -tartaric acid (TA) from the C4 fragment and carbohydrate pool material from the C2 fragment. Experiments in which detached leaves were supplied d -[5-3H,1-14C]glucose or d -[5-3H,6-14C]glucose yielded AA devoid of 3H whereas the l -threonic acid (ThA) and TA recovered from the same tissues still retained some 3H. These comparative experiments also indicated that the ThA was derived from carbons 3 through 6 of d -glucose. ThA was shown to be a natural constituent of P. quinquefolia but apparently not an intermediate between AA and TA. Results are consistent with a biosynthetic pathway from d -glucose to AA that involves a hydrogen-exchanging epimerization at C-5 as reported earlier for the geraniaceous plant Pelargonium crispum, but differing from P.crispum in biosynthesis and metabolism of ThA. When l -[6-14C]idonate or its lactone was supplied to P. quinquefolia leaves, about 80% of the 14C appeared in the carbohydrates, an observation remarkably similar to previous observations with [6-14C]AA-labeled leaves. l -Idonate and its lactone appear to have an intermediate role in AA metabolism in vitaceous plants.