Selecting the size of a diallel cross experiment

Summary The size of a diallel cross experiment can be determined by using statistical tables and past diallel cross results; this will provide more flexibility in planning experiments and increase the opportunity to detect real differences.Contribution No. R-015, Research Program Service, Research Branch, Agriculture Canada, Ottawa, Ont. K1A OC6     

Genetic studies of anther culture ability in rice (Oryza sativa)

Inheritance of three anther and culture characters, callus induction, green plant regeneration and culture efficiency was studied using incomplete diallel crosses with a gamete model. It was suggested that callus induction was mainly controlled by gametic additive effects and with less effect of the maternal effects. Green plant regeneration was mainly determined by maternal effects with less influence of gametic additive effects. Culture efficiency was controlled by gametic additive, maternal and cytoplasmic effects. Cultivar Lunhui 422 showed positive genetic effects for all three traits and was a very good parent for rice anther culture breeding. Significant positive heterosis was observed for callus induction. Both gametic additive and maternal correlations contributed to the significant genotypic and phenotypic correlations between callus induction and green plant regeneration suggesting these two traits to be linked.Abbreviations 2,4-d 2,4-dichlorphenoxyacetic acid - NAA -napthaleneacetic acid     

Serial analysis of combining ability in diallel and fractional diallel crosses in linseed

Summary An analysis of the nature of the gene action for seven characters influencing productivity and wide adaptation in Linum usitatissimum L. was undertaken in this investigation over three seasons based on diallel and fractional diallel crosses, among a set of ten genetically diverse parents. Estimation of combining ability and the nature of geno-type-environment interactions for the above characters was also examined.A comparison of the means of the parents and hybrids over three environments showed positive heterosis for height, number of tillers, fruit-bearing branches and capsules per plant while negative heterosis was observed for flowering time. The remaining two characters viz., height at branching and seeds per five capsules showed little differences due to mutual cancellation of the components of heterosis.A serial analysis of combining ability over three seasons using Griffing's model (1956) has revealed significant sea-sonal effects on the estimates of combining ability effects. Additive gene action was found to be predominant in most of the characters although non-additive variation due to s.c.a. was equally prominent for fruit-bearing branches and capsules per plant. On the basis of g.c.a. for all the characters, M. 10 and N. 55, both Peninsular types were the best followed by N.P. (R.R.) 45 and Mohaba Local.In the fractional diallel analysis the relative estimates g.c.a. and s.c.a. were similar for s=9 and 7. However, there was overestimation in favour of s.c.a. when s was reduced to 3. The serial analysis of fractional diallel had confirmed the results of full diallel. Significant genotype x environment interactions for flowering time, height, height at branching, fruit-bearing branches and capsules per plant were observed in this analysis also. The results have indicated that reduction of the diallel to a fraction with s=n/2 would vitiate the order and precision of estimates of combining ability.The analysis of genotype x environment indicated that the pattern of interactions among the parents of different geographical groups was not similar but varied with the character under study. Considerable interactions were observed for capsules per plant, fruit-bearing branches and flowering time in that order respectively. A comparison of the parental and hybrid populations for the degree of interaction for all the characters had revealed that heterozygosis might not at all be directly related to the degree of homeostasis. Actually, heterozygotes were found to show more interactions than homozygotes for flowering time, height at branching and tiller number and lower interactions for the other four characters. Significant seasonal effect on the degree of heterosis for vegetative as well as reproductive characters was observed in a majority of F₁'s with variable degree of dominance.

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Zusammenfassung Über einen Zeitraum von drei Vegetationsperioden wurde mit einem Material von 10 genetisch verschiedenen Eltern anhand von vollständigen und unvollständigen Diallelkreuzungen die Genwirkung bei 7 die Ertrags- und Anpassungsfähigkeit von Linum usitatissimum L. beeinflussenden Merkmalen geprüft. Außerdem wurde die Kombinationseignung dieser Merkmale und die Genotyp-Umwelt-Interaktion untersucht.Ein Vergleich der Durchschnittswerte der Eltern und Hybriden an drei verschiedenen Anbauorten ergab positive Heterosis bezüglich der Merkmale Höhe, Anzahl der Triebe, samentragende Zweige und Kapseln je Pflanze, negative Heterosis wurde dagegen bezüglich des Merkmals Blütezeit beobachtet. Die restlichen zwei Merkmale, Höhe der Verzweigung und Samenansatz von je 5 Kapseln, zeigten infolge gegenseitiger Aufhebung der Heterosiskomponenten geringe Unterschiede.Eine dreijährige Reihenanalyse hinsichtlich der Kombinationseignung nach dem Modell von Griffing (1956) ergab einen signifikanten Einfluß des Anbaujahres auf die Schätzung der Kombinationseignung. Bei den meisten Merkmalen konnte auf additive Wirkung der Gene geschlossen werden, obgleich nichtadditive Wirkung als Folge von spezieller Kombinationseignung bei den Merkmalen fruchtende Sprosse und Kapseln je Pflanze ebenso ausgeprägt war. Hinsichtlich der allgemeinen Kombinationseignung für alle untersuchten Merkmale erwiesen sich die beiden Halbinsel-Sippen, M 10 und N 55, als die besten, gefolgt von P.P. (R.R.) 45 und Mohaba Local.In den unvollständigen diallelen Analysen waren die relativen Schätzungen für allgemeine und spezielle Kombinationseignung für s=9 und 7 ähnlich. Wenn s jedoch auf 3 reduziert wurde, ergab sich eine Überschätzung der speziellen Kombinationseignung. Die Reihenanalysen des unvollständigen DiallelVersuchs bestätigten die Ergebnisse des vollständigen Diallel-Versuchs. Auch in diesem Fall wurden signifikante Genotyp-Umwelt-Interaktionen bezüglich Blütezeit, Höhe, Verzweigungshöhe, fruchtende Sprosse und Kapseln je Pflanze beobachtet. Die Ergebnisse deuteten an, daß eine Verringerung des Diallel-Versuchs auf einen Teil mit s=n/2 die Reihenfolge und Genauigkeit der Schätzung der Kombinationseignung beeinträchtigen würde.Die Analyse der Genotyp-Umwelt-Interaktion zeigte, daß die Art der Interaktion bei den Eltern verschiedener geographischer Gruppen nicht gleich war, sondern je nach dem untersuchten Merkmal variierte. Beträchtliche Interaktionen wurden für die Merkmale Kapseln je Pflanze, fruchtende Sprosse und Blütezeit — in dieser Reihenfolge — beobachtet. Ein Vergleich der Eltern- und Hybridenpopulationen bezüglich des Grades der Interaktion hat bei allen Merkmalen ergeben, daß Heterozygotie durchaus nicht unmittelbar mit dem Grad der Homeostasis in Beziehung zu stehen braucht. Tatsächlich wurde gefunden, daß Heterozygote bezüglich Blütezeit, Verzweigungshöhe und Zahl der Triebe größere Interaktionen und für die anderen 4 Merkmale geringere Interaktionen als Homozygote zeigen. Bei der Mehrzahl der F ₁-Nachkommen wurde sowohl für die vegetativen wie reproduktiven Eigenschaften ein signifikanter Einfluß des Anbaujahres mit verschiedenem Dominanzgrad auf den Grad der Heterosis beobachtet.

     

Multivariate statistical analysis of grain yield and agronomic characters in Durum wheat

Summary Correlation, stepwise multiple regression and factor analyses were conducted on grain yield and a number of agronomic characters in the parental, F ₁ and F ₂ families originating from a 10 X 10 diallel cross in durum wheat. For the F ₁ diallel, the correlation analysis indicated that the number of spikes and kernels per plant and 1,000 kernel weight had the highest correlations with grain yield; for the F ₂ diallel, the number of spikes and kernels per meter, 1000 kernel weight and plant height showed most striking correlations with same.Stepwise multiple regression analysis indicated that, for the F ₁ diallel, number of kernels per plant, 1000 kernel weight and days to maturity were the most potent predictor variables for grain yield, accounting for 78% of its variability. For the F ₂ diallel, the number of kernels and number of spikes per meter, 1000 kernel weight and number of kernels per spike were the most potent predictors for grain yield, accounting for 91 % of its variability. Five common factors were extracted which explained 98.8% and 98.1% of the total variance in the F ₁ and F ₂ diallel, respectively. However, the importance of each of the five factors and the characters which loaded highly on each of them differed from generation to generation.Contribution No. 323 from Plant Science Department, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada.     

Microbial Food Webs in Marine Sediments. II. Seasonal Changes in Trophic Interactions in a Sandy Tidal Flat Community

Abstract The role of grazing by marine sediment flagellates, ciliates, and meiobenthic animals in controlling production of their bacterial and diatom prey was investigated. At six selected time points, over the year, bacterial production and diatom standing stock were compared to grazing pressure exercised by proto- and micrometazoan consumers. The intensity of prey-predator relations showed pronounced yearly dynamics in which two stages could be distinguished. During the first phase, from the end of winter to mid-summer, the consumption of diatoms gradually increased, with possible overgrazing at the end of the period. This was followed by a collapse of diatom abundance, to the winter level. During the first stage, no appreciable bacterial consumption was observed in spite of the high abundance and production of bacteria. The second stage started in mid-summer and continued through the fall. During this period, the grazing on bacteria increased and reached the year's maximum. For at least a brief period (October), micrograzers removed the majority of bacterial production. In contrast, herbivory stayed at the year's lowest level, and diatoms appeared to be controlled by factors other than grazing. The observed ingestion rates seem to support the apparent energy requirements of flagellates and some ciliates (scuticociliates and hypotrichids). Other ciliates (pleurostomatids and karyorelictids) could not subsist on the observed diet and might have to complement it with other energy sources, possibly via dissolved organic matter absorption. Received: 27 August 1996; Accepted: 22 January 1997     

Cross habituation to feeding deterrents and acceptance of a marginal host plant byPieris rapae larvae

Sensitivity of the cabbage butterfly,Pieris rapae L. to feeding deterrents was compared for larvae reared on different food sources under laboratory conditions. Since cabbage-reared larvae normally reject nasturtium,Tropaeolum majus L., the effects of previous exposure to allelochemicals on larval acceptance or rejection of this plant were also examined. When compared with cabbage-reared larvae, nasturtium-reared larvae were less sensitive to feeding deterrents including cymarin, erysimoside and 2-O-β-d-glucosyl cucurbitacin E. Nasturtium-reared larvae were insensitive to chlorogenic acid, which was deterrent to cabbage-reared larvae. Feeding by larvae reared on a wheat germ diet was not deterred by these compounds. The results indicate that dietary experience can extensively affect larval sensitivity to feeding deterrents and that cross habituation of larvae to deterrents occurs in response to certain chemical constituents of nasturtium and wheat germ diet. Digitoxin, however, proved to be an exception. Larvae reared on either nasturtium or wheat germ diet were as sensitive to digitoxin as those reared on cabbage. Previous results have shown that rejectionof nasturtium by cabbage-reared larvae is due to the presence of strong feeding deterrents in this plant. However, more than 50% of 2nd instar larvae reared from neonate on cabbage leaves treated with strophanthidin, cymarin, erysimoside, digitoxigenin and digitoxin accepted nasturtium as a food source. 2-O-β-d-glucosyl cucurbitacin E, 2-O-β-d-glucosyl cucurbitacin I and rutin were also active in causing larvae to feed on nasturtium. Thus dietary exposure to unrelated plant chemicals can profoundly affect insect acceptance of a plant that contains feeding deterrents.     

Evaluation of circulant partial diallel crosses in maize

Summary The present study was conducted in maize (Zea mays L.) on crosses among 20 diverse parents. The materials were evaluated in four different environments for eight characters. Combining ability analysis was carried out following diallel and partial diallel crosses. The number of crosses per parent (s) varied from 3 to 19 and the results were studied to identify the critical value of s that would provide an adequate information with minimum resources. The S₅ partial diallel was as good as the S₁₉ for the detection of differences among general combining ability (GCA) effects. Even the S₃ gave adequate information in the case of characters with high heritability. However, partial diallel analysis was less efficient in detecting the differences due to specific combining ability (SCA) effects. These results varied with environments, and characters with low heritability were more prone to misinterpretation. GCA effects showed fluctuations in partial diallel analysis which were more pronounced in S₅ and S₃, particularly for characters with low heritability. The average standard error of difference between GCA effects increased with a decrease in s, with a steep slope for s < 7. The partial diallel analysis was more efficient for the estimation of the variance component of GCA than for SCA, as the estimate of SCA was biased upwards. Estimates of broad sense heritability obtained from the partial diallels agreed with the full diallel analysis better than the narrow sense estimates. Smaller partial diallels gave erratic estimates of heritability, particularly for the characters with low heritability.     

Molecular characterization and expression of 1-deoxy-<Emphasis Type="SmallCaps">d</Emphasis>-xylulose 5-phosphate reductoisomerase (DXR) gene from <Emphasis Type="Italic">Salvia miltiorrhiza</Emphasis>

1-Deoxy-d-xylulose 5-phosphate (DXP) reductoisomerase (DXR; EC 1.1.1.267) catalyzes the first committed step of the 2-C-methyl-d-erythritol 4-phosphate (MEP) pathway for isoprenoid biosynthesis in plants. The present study describes the cloning and characterization of a cDNA encoding DXR from Salvia miltiorrhiza (designated as SmDXR, GenBank Accession No. FJ476255). Comparative and bioinformatic analyses revealed that SmDXR showed extensive homology with DXRs from other plant species. Phylogenetic tree analysis indicated that SmDXR belongs to the plant DXR superfamily and has the closest relationship with DXR from Lycopersicon esculentum. Tissue expression pattern analysis revealed that SmDXR expressed strongly in leaves, followed by roots and stems, implying that SmDXR was a constitutively expressed gene. This is the first report on the mRNA expression profile of genes encoding key enzymes involved in tanshinone biosynthetic pathway in Salvia plants. The expression profiles revealed by RT-PCR under different elicitor treatments such as methyl jasmonate (MJ) and salicylic acid (SA) were compared for the first time, and the results revealed that SmDXR was an elicitor-responsive gene, which could be induced by SA in leaves and inhibited by exogenous MJ in three tested tissues. The functional color assay in Escherichia coli showed that SmDXR could accelerate the biosynthesis of lycopene, indicating that SmDXR encoded a functional protein. The characterization, expression profile and functional analysis of SmDXR gene will be helpful for further study in the role of SmDXR in tanshinones biosynthetic pathway and metabolic engineering to increase tanshinones production in S. miltiorrhiza.     

Estimation of genetic parameters in barley (Hordeum vulgare L.)

Summary Four exotic and four indigenous strains of barley were used for making diallel crosses. The sets of parents and crosses making full, half and quarter diallel were analysed in a randomized block design for plant height, number of effective tillers, ear length, grain yield per plant, 100 grain weight and number of grains per ear.The three alternatives of diallel were similar with respect to the estimates of degree of dominance, general combining ability and specific combining ability, indicating that all these three methods of diallel were equally efficient. However, as the number of entries are minimum in quarter diallel, it would be economical in terms of cost, time and labour to estimate genetic parameters by this method. Average degree of dominance was found in the range of overdominance. The ranking of parents on the basis of their array mean was similar to the ranking based on gca effects. Similarly, the ranking of crosses on the basis of per se performance was similar to the ranking based on sca effects. This suggests that the selection of best general combiner or best cross combinations may be easier and more effective through array mean for per se performance rather than through high gca and sea effects, respectively. From among 56 crosses, IB-226 X X C-164 was the one which showed superiority for maximum number of characters followed by AB-12/59 X PTS-57. High sea effect for plant height, ear length, grain yield, 100 grain weight and number of grains per ear was the result of cross between parents having high X low general combining ability, indicating additive X dominance type of gene interaction. For number of effective tillers, high sca was produced by low x low general combiners, indicating dominance x dominance gene interaction.Part of a Ph. D. thesis submitted by senior author to Haryana Agricultural University, Hissar.     

Uptake and conversion of <Emphasis Type="SmallCaps">d</Emphasis>-amino acids in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

The d-enantiomers of proteinogenic amino acids fulfill essential functions in bacteria, fungi and animals. Just in the plant kingdom, the metabolism and role of d-amino acids (d-AAs) still remains unclear, although plants have to cope with significant amounts of these compounds from microbial decay in the rhizosphere. To fill this gap of knowledge, we tested the inhibitory effects of d-AAs on plant growth and established a method to quantitate 16 out of 19 proteinogenic amino acids and their d-enantiomers in plant tissue extracts. Therefore, the amino acids in the extracts were derivatized with Marfey’s reagent and separated by HPLC–MS. We used two ecotypes (Col-0 and C24) and a mutant (lht1) of the model plant Arabidopsis thaliana to determine the influence and fate of exogenously applied d-AAs. All of them were found in high concentrations in the plant extracts after application, even in lht1, which points to additional transporters facilitating the import of d-AAs. The addition of particular amino acids (d-Trp, d-Phe, d-Met and d-His) led to the accumulation of the corresponding l-amino acid. In almost all cases, the application of a d-AA resulted in the accumulation of d-Ala and d-Glu. The presented results indicate that soil borne d-AAs can actively be taken up and metabolized via central metabolic routes.     

Burnt sacrificial plant offerings in Hellenistic times: an archaeobotanical case study from Messene, Peloponnese, Greece

Messene, situated on the southwest Peloponnese, Greece, was founded in 369 B.C. by Epaminondas, after the liberation of Messenia from Spartan rule. During the 2001 excavation campaign on the site, large numbers of carbonised fruits were recovered from a sacrificial context, dated to the end of the 3rd century B.C. This material was very rich thanks to the remarkable preservation of the plant remains. Cones and seeds of stone pine, olives, grape and almonds were present in the samples. A particularly interesting find was the presence of five whole chestnuts, the first find of carbonized fruits of Castanea sativa in Greece. The comparison of the Messene finds with other plant offerings recorded in Classical times in Greece and in Archaic and Roman Italy provides useful information about the composition of sacrificial offerings in antiquity. An erratum to this article can be found at     

Epistasis in maize (Zea mays L.)

Summary Three flint and three dent maize (Zea mays L.) inbred lines, their possible F₁ crosses, F₂ and backcross progenies, and all possible three-way crosses were evaluated in a three-year experiment for yield, ear moisture, and plant height. The purpose was to estimate genetic parameters in European breeding materials from (i) generation means analysis, (ii) diallel analysis of generation means, and (iii) analysis of F₁ and three-way cross hybrids. Method (i) was based on the F-metric model and methods (ii) and (iii) on the Eberhart-Gardner (1966) genetic model; both models extended for heterotic maternal effects.Differences among generation means for yield and plant height were mainly attributable to dominance effects. Epistatic effects were significantly different from zero in a few crosses and considerably reduced heterosis in both traits. Additive x additive and domiance x dominance effects for yield were consistently positive and negative, respectively. Significant maternal effects were established to the advantage of generations with a heterozygous seed parent. In the diallel analysis, mean squares for dominance effects were greater than for additive effects for yield and plant height but smaller for ear moisture. Though significant for yield and plant height, epistatic variation was small compared to additive and dominance variation. Estimates of additive x additive epistasis for yield were significantly negative in 11 of 15 crosses, suggesting that advantageous gene combinations in the lines had been disrupted by recombination in the segregating generations. The analysis of hybrids supported the above findings regarding the analysis of variance. However, the estimates of additive x additive epistasis for yield were considerably smaller and only minimally correlated with those from the diallel analysis. Use of noninbred materials as opposed to materials with different levels of inbreeding is considered the main reason for the discrepancies in the results.     

Generation and analysis of expressed sequence tags from the salt-tolerant mangrove species Avicennia marina (Forsk) Vierh

Salinization poses an increasingly serious problem in coastal and agricultural areas with negative effects on plant productivity and yield. Avicennia marina is a pantropical mangrove species that can survive in highly saline conditions. As a first step towards the characterization of genes that contribute to combating salinity stress, the construction of a cDNA library of A. marina genes is reported here. Random expressed sequence tag (EST) sequencing of 1,841 clones produced 1,602 quality reads. These clones were classified into functional categories, and blast comparisons revealed that 113 clones were homologous to genes earlier implicated in stress responses, of which the dehydrins are the most predominant in this category. Of the ESTs analyzed, 30% showed homology to previously uncharacterized genes in the public plant databases. Of these 30%, 52 clones were selected for reverse Northern analysis: 26 were shown to be up-regulated and five shown to be down-regulated. The results obtained by reverse Northern analysis were confirmed by Northern analysis for three clones.     

Polyphenol oxidase activity in dormant saffron (<Emphasis Type="Italic">Crocus sativus</Emphasis> L<Emphasis Type="Italic">.</Emphasis>) corm

Crocus sativus L., cultivated since ancient times as the source of saffron, is a triploid plant that can be propagated only via its corms which undergo a period of dormancy. Understanding the processes taking place in the corm is essential to preserve the plant and improve its quality. Color and taste being of prime importance in the quality of the saffron spice, knowledge on polyphenol oxidase (PPO) activity in the plant is of particular interest given the role of the enzyme in fruit and vegetable browning during processing and during the storage of processed food. In this paper, PPO activity was investigated for the first time in extracts obtained from dormant C. sativus L. corms. PPO activity was detectable using l-DOPA, pyrogallol, catechol or p-cresol as substrate, each being oxidized to its corresponding o-quinone; no activity was detectable with l-tyrosine, tyramine or phenol as substrate. Two pH optima, respectively at 4.5 and 6.7, were observed with all substrates and a third one, at 8.5, was found with l-DOPA and p-cresol. Kinetics parameters studied at pH 6.7 indicated the highest catalytic efficiency (in units mg⁻¹ prot mM⁻¹) with pyrogallol: 150, then catechol: 39, l-DOPA: 6.4 and p-cresol: 4.6. The enzymatic activity was inhibited by 50% in the presence of 0.22, 0.35, 0.5 and 0.7 mM kojic acid with, respectively, catechol, pyrogallol, p-cresol and l-DOPA as substrate. When stained for PPO activity, non-denaturing gel electropherograms of extract revealed three distinct bands, indicating the presence of multiple isoenzymes in dormant C. sativus L. corms.     

A test of homology between the B chromosome of maize and abnormal chromosome 10, involving the control of nondisjunction in B's

Summary Nondisjunction of B and B-translocation chromosomes occurs regularly in maize at the second pollen mitosis (Roman, 1947; Blackwood, 1956). The mechanism of nondisjunction was studied using the A-B interchange, TB-9b. The B⁹ chromosome of the interchange undergoes nondisjunction at the second pollen mitosis, while the 9^B chromosome does not (Roman, 1947). It was shown that the 9^B chromosome must be present in a plant for nondisjunction of the B⁹ to occur. This is consistent with the reports of Roman on TB-4a (1949) and Longley on TB-10a (1956). It was also demonstrated that the influence of the 9^B chromosome is limited to pollen grains containing it, and does not extend to all the pollen of a plant.A test of homology between the B chromosome and abnormal chromosome 10 was also made. The ability of abnormal 10 to substitute for the 9^B chromosome and induce nondisjunction of the B⁹ was tested. Nondisjunction did not occur at a detectable rate in the presence of abnormal 10, and the results failed to support Ting's proposal (1958) concerning the origin of abnormal 10.     

Betulinic and oleanolic acids isolated from Forsythia suspensa Vahl inhibit urease activity of Helicobacter pylori

Sixteen medicinal herbs were selected from a database on traditional herbal materials as well as literature on Korean plant resources. Then ethanol (70%, v/v) extracts of these herbs were tested for inhibition of the urease activity of Helicobacter pylori. The urease activity of H. pylori was strongly (82%) inhibited by extract of Forsythia suspensa Vahl. Active compounds in extract of Forsythia suspensa Vahl were first separated by batch mode solvent extraction, followed by purification by silica gel and octadecyl silica gel column chromatography using solvents of different polarity. According to NMR analysis of the last chromatographic fraction, we identified the presence of betulinic acid and oleanolic acid, which are known to have anti-inflammatory, anti-cancer, and anti-HIV viral activities.     

Type II callus production and plant regeneration in tropical maize genotypes

A total of 113 maize inbreds adapted to tropical conditions were evaluated for their tissue culture response. Additionally, four media combinations of 15 or 30 μm dicamba with or without 88 μm AgNO₃ were used to study the effect of dicamba and AgNO₃ on type II callus production and plant regeneration from 42 of the inbred lines. Inbreds 48, 389 and 1345 of the populations BR 105, BR 112, and Catete, respectively, showed a high capacity for type II callus production and plant regeneration. The production of type II calli increased significantly when the concentration of dicamba was changed from 15 to 30 μm and when AgNO₃ was added to the medium. A synergistic effect between 88 μm AgNO₃ and 30 μm dicamba (CM-30Ag medium) was observed, leading to additional production of type II callus. Medium CM-30Ag allowed the best tissue culture performance and plant regeneration capacity. Received: 5 October 1996 / Revision received: 21 April 1997 / Accepted: 9 May 1997     

Fermentation of seaweed sugars by Lactobacillus species and the potential of seaweed as a biomass feedstock

It is known that seaweeds differ greatly from land plants in their sugar composition. The current research on the L-lactic acid fermentation process focuses on land plant sugars as a carbon source, with the potential of seaweed sugars being largely ignored. This study examined the feasibility of seaweed biomass as a possible carbon source for the production of l-lactic acid, by comparing the fermentation of seaweed sugars (d-galactose, d-mannitol, l-rhamnose, d-glucuronic acid, and l-fucose) and land plant sugars (d-glucose, d-xylose, d-mannose, and l-arabinose). The experiments were repeated with 2 sugar acids (d-gluconic acid, d-glucaric acid) in order to investigate the effect of the degree of reduction of carbon source on the fermentation yield. This research also examined the effect of bacterial strain on the characteristics of fermentation reactions, by conducting l-lactic acid fermentation with 7 different Lactobacillus species. Taking into account the sugar composition of seaweed and the levels of lactic acid production from each pure sugar, it was possible to predict the lactic acid production yield of various seaweeds and land plants. From comparative analysis of the predicted lactic acid production yield, it was found that seaweeds are already comparable to lignocellulosics at the current stage of technology. If new technologies for the utilization of non-fermentable seaweed sugars are developed, seaweeds show promise as an even more useful biomass feedstock than lignocellulosics.     

Globba unifolia andG. corneri stat. et nom. nov. (Zingiberaceae; Peninsular Malaysia)

Based on personal collections ofGlobba unifolia Ridl. andG. unifolia var.sessiliflora Holtt., the latter is recognized as a distinct species. As the nameG. sessiliflora is already occupied, the nomen novumG. corneri is proposed in honour of Prof. DrE. J. H. Corner, who was the first collector of the plant.Dedicated to Prof. DrE. J. H. Corner (Cambridge) on the occasion of his 85th birthday on January 12th, 1991.     

Fungal arabinan and <Emphasis Type="SmallCaps">l</Emphasis>-arabinose metabolism

l-Arabinose is the second most abundant pentose beside d-xylose and is found in the plant polysaccharides, hemicellulose and pectin. The need to find renewable carbon and energy sources has accelerated research to investigate the potential of l-arabinose for the development and production of biofuels and other bioproducts. Fungi produce a number of extracellular arabinanases, including α-l-arabinofuranosidases and endo-arabinanases, to specifically release l-arabinose from the plant polymers. Following uptake of l-arabinose, its intracellular catabolism follows a four-step alternating reduction and oxidation path, which is concluded by a phosphorylation, resulting in d-xylulose 5-phosphate, an intermediate of the pentose phosphate pathway. The genes and encoding enzymes l-arabinose reductase, l-arabinitol dehydrogenase, l-xylulose reductase, xylitol dehydrogenase, and xylulokinase of this pathway were mainly characterized in the two biotechnological important fungi Aspergillus niger and Trichoderma reesei. Analysis of the components of the l-arabinose pathway revealed a number of specific adaptations in the enzymatic and regulatory machinery towards the utilization of l-arabinose. Further genetic and biochemical analysis provided evidence that l-arabinose and the interconnected d-xylose pathway are also involved in the oxidoreductive degradation of the hexose d-galactose.