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PubMed2005

The effect of nitrogen fertilizer application to maize and sorghum on the bionomics of Chilo partellus (Lepidoptera: Crambidae) and the performance of its larval parasitoid Cotesia flavipes (Hymenoptera: Braconidae).

Laboratory and field trials were conducted to evaluate the effect of plant species (maize, sorghum), plant age (young, middle, old) and four different nitrogen fertilization levels (N0-N3) on the bionomics of the invasive crambid Chilo partellus and the performance of its braconid larval parasitoid Cotesia flavipes. Plant N varied significantly between N0 and N1-N3, but the differences among the latter were not significant. Intrinsic rates of increase and net-reproductive rates of C. partellus followed the same trends: they were lowest with N0 and similar among the other treatments. On maize only, mortality of C. partellus and parasitism by C. flavipes tended to decrease with age of the plant while the percentage of borers reaching adulthood (i.e. pupation) increased. Borer mortality and parasitism was lower and pupation higher on sorghum than on maize. On both host plants, percent dry matter content of frass, which could affect ingress of the parasitoid into the borer tunnel, did not vary with nitrogen level but varied with age of the host plants: on maize, it was highest on young plants and on sorghum on old plants. Tunnels were shorter on young maize and sorghum plants; longer tunnels on older plants indicated compensatory feeding by the larva as a result of lower nutritive value of the food source. Consequently, larval weight was lower on older than younger plants. The level of nitrogen fertilization had no effect on food conversion efficiency of C. partellus. Nitrogen did not affect number of C. flavipes progeny while egg load of progeny increased significantly with nitrogen level, on both plant species. Differences in egg load between sorghum and maize were mostly not significant. It was concluded that on depleted soils only, an increase in nitrogen via mulching, rotation with a leguminous crop or fertilization would increase survival of C. partellus on both maize and sorghum and an increase in acreage of maize and in application of nitrogen fertilizer in an area would also increase the parasitism of C. flavipes.

Animals↗

PubMed2004

Fumonisin contamination of maize in Burkina Faso, West Africa.

Maize throughout the world is frequently contaminated with a family of mycotoxins, the fumonisins, produced by species of Fusaria. The study investigated the level of fumonisin contamination of maize samples from village farms and large market traders in Burkina Faso, West Africa. Maize samples (5 kg) from each of five to six large storage barns from farms in five villages in the district of N'Dorola, Kénédougou province, western Burkina Faso, were sampled (n = 26) in Jan 1999 (> 1 year storage), and a further 26 maize samples from the same farms were collected directly from the field in October 1999. In addition, 72 maize samples were obtained in July 1999 from large markets in Bobo Dioulasso. Fumonisins were extracted from dried maize, derivatized with o-phthaldialdehyde and quantified by reversed-phase high-performance liquid chromatography with fluorescence detection. All 26 samples from the first (mean 1170 microg kg(-1), range 110-3120 microg kg(-1)) and from the second (mean 130 microg kg(-1), range 10-450 microg kg(-1)) village collection were fumonisin positive. All 72 maize samples from the large markets were also positive for fumonisins, and had the highest levels of contamination (mean 2900 microg kg(-1), range 130-16,040 microg kg(-1)). As fumonisins were a ubiquitous contaminant of maize and given that this crop is a dietary staple in this region, chronic exposure is likely.

Agriculture↗

PubMed1994

Beet fed as such or ensiled with maize and fresh potatoes in diets for finishing bulls.

The use of beet for beef production after ensiling together with maize was studied in two experiments involving 112 and 114 White-blue bulls. In the first experiment maize silage (I) was compared with mixed silage of maize and fodder beet (II) or sugar beet (III) (ratio: 2/1, DM-basis). In the second experiment maize silage (I) was compared with mixed silage of 0.67 maize and 0.33 sugar beet (II) or maize silage and fresh sugar beet (ratio: 2/1, DM basis) (III) or fresh sugar beet and potatoes afterwards at 4% of the live weight and maize silage (IV). From day 113 onwards, mixed silage was also fed to group III and sugar beet were replaced by raw potatoes in group IV. The basic diet was always supplemented with concentrate at 0.75% of the live weight. In experiment 1 live weight gain was slightly but not significantly higher for the mixed silages, although daily net energy intake per kg metabolic weight was higher. Feed efficiency was not significantly different among groups. Mixed silages yielded more fat in the carcass. In the second experiment initial growth rates were not significantly affected by the use of sugar beet or mixed silages. Afterwards, they were increased in comparison with maize silage. Also in this experiment, daily net energy intake was increased by sugar beet, or by potatoes. Energy efficiency did not differ among groups. This experiment did not show significant differences for the carcass composition. However, EUROP fatness score was higher for diets containing one third sugar beet. Most meat quality parameters were not affected by the diets. Only the lightness was different between III and IV.

Animals↗

PubMed1995

[Food intake of dairy cows and heifers in late pregnancy during feeding of maize silage].

The influence of restricted (covering requirements) or ad libitum supply of maize silage in late pregnancy on feed intake was tested in two experiments with totally 51 dairy cows with several calvings (V1, V2 and in one experiment with 14 heifers (V3). Experimental time were the last 8 weeks before the expected calving date and was equivalent to the dry period of the cows. With adjusted feeding for energy requirement as a restricted supply the cows in V1 and V2 consumed 5.73 vs. 5.64 kg DM maize silage/animal and day, with ad libitum supply the intake of maize silage was substantial higher with an average of 9.65 vs. 9.85 kg DM/animal and day. With adjusted feeding for energy requirement as a restricted supply the heifers in V3 consumed 4.77 kg DM maize silage/animal and day. With ad libitum supply, however, the daily maize silage intake of heifers was substantial more with 7.00 kg DM/animal. With ad libitum feeding the mean daily intake of maize silage was unchanged in the weeks 8 to 3 before calving and decreased very strong in the cow experiments (V1, V2) in the last two weeks before calving and in the heifers experiment (V3) in the last week before calving. With restricted feeding the intake of maize silage was nearly unchanged until calving, only the cows in V1 showed a slight decrease in the last week before calving. With ad libitum feeding of maize silage in late pregnancy until 2 weeks before calving the cows and heifers reached a net energy intake of about 80 vs. 62 MJ NEL/day, which corresponded to 160% (V1, V2) vs. 135% (V3) of the energy requirement. The overconsumption for the crude protein was slighter with 120 to 140% of requirement.

Animals↗

PubMed2005

Absorption of calcium from tortilla meals prepared from low-phytate maize.

BACKGROUND: Calcium fortification of maize has been achieved for millennia in Central America by the process of nixtamalization. Bioavailability of calcium is, however, compromised by phytate, which is present in large quantities in maize kernels and is only modestly reduced by nixtamalization. OBJECTIVE: The objective was to compare the absorption of calcium from tortilla meals prepared from low-phytate maize with that from meals prepared from maize with typical phytate content. DESIGN: At 1-mo intervals, 5 healthy adult women were fed 2 test meals of approximately 140 g tortillas in lieu of breakfast. On one occasion, the tortillas were prepared from maize with approximately 60% phytate reduction, and, on the other occasion, they were prepared from the matching isohybrid wild-type maize. Beginning midway through the test meal, (44)Ca (0.3 mg/kg body wt) was administered in water as an extrinsic label; (42)Ca (0.06 mg/kg body wt) was administered intravenously immediately after the test meal. Isotope ratios of (42)Ca to (43)Ca and of (44)Ca to (43)Ca were measured by inductively coupled plasma mass spectrometry in urine collected as an 8-h pool from the period 16-24 h after intravenous tracer administration and prepared by the oxalate precipitation method. Fractional absorption of calcium was determined by using a dual-isotope ratio technique. RESULTS: Mean fractional absorption of calcium from tortillas prepared from the low-phytate maize (0.50 +/- 0.03) was significantly (P = 0.003) greater than that from tortillas prepared from the control maize (0.35 +/- 0.07). CONCLUSION: The increase in the quantity of calcium absorbed could be of practical importance for calcium nutriture when the intake of dairy products is limited.

Adult↗

PubMed1993

Inheritance of the morphological differences between maize and teosinte: comparison of results for two F2 populations.

Molecular marker loci (MMLs) were employed to map quantitative trait loci (QTLs) in an F2 population derived from a cross of maize (Zea mays ssp. mays) and its probable progenitor, teosinte (Z. mays ssp. parviglumis). A total of 50 significant associations (putative QTLs) between the MMLs and nine key traits that distinguish maize and teosinte were identified. Results from this analysis are compared with our previous analysis of an F2 population derived from a cross of a different variety of maize and another subspecies of teosinte (Z. mays ssp. mexicana). For traits that measure the architectural differences between maize and teosinte, the two F2 populations possessed similar suites of QTLs. For traits that measure components of yield, substantially different suites of QTLs were identified in the two populations. QTLs that control about 20% or more of the phenotypic variance for a trait in one population were detected in the other population 81% of the time, while QTLs that control less than 10% of the variance in one population were detected in the other population only 28% of the time. In our previously published analysis of the maize x ssp. mexicana population, we identified five regions of the genome that control most of the key morphological differences between maize and teosinte. These same five regions also control most of the differences in the maize x ssp. parviglumis population. Results from both populations support the hypothesis that a relatively small number of loci with large effects were involved in the early evolution of the key traits that distinguish maize and teosinte. It is suggested that loci with large effects on morphology may not be a specific feature of crop evolution, but rather a common phenomenon in plant evolution whenever a species invades a new niche with reduced competition.

Chromosome Mapping↗

PubMed2003

Maize phytoene desaturase and zeta-carotene desaturase catalyse a poly-Z desaturation pathway: implications for genetic engineering of carotenoid content among cereal crops.

Carotene desaturation, an essential step in the biosynthesis of coloured carotenoids, has received much attention (1) as a target of bleaching herbicide action, (2) as a determinant of geometric isomer states of carotenoids and their metabolites, and (3) as a key modulator of accumulation and structural variability of carotenoids. Having previously isolated and functionally characterized the cDNA encoding the first enzyme in maize carotene desaturation, phytoene desaturase (PDS), the isolation and functional characterization of the second desaturase, a maize endosperm cDNA (2265 bp) encoding zetacarotene (zeta-carotene) desaturase (ZDS) is reported here. Functional analysis of the concerted actions of maize PDS and ZDS ex situ showed these enzymes to mediate a poly-Z desaturation pathway to the predominate geometric isomer 7,9,7',9'-tetra-Z-lycopene (poly-Z-lycopene or prolycopene), and not the all-trans substrate required of the downstream lycopene cyclase enzymes. This finding suggests a rate-controlling isomerase associated with the carotene desaturases as a corollary of a default poly-Z carotenoid biosynthetic pathway active in planta for maize. Comparative gene analysis between maize and rice revealed that genes encoding PDS and ZDS are single copy; the Zds cDNA characterized here was mapped to maize chromosome 7S and vp9 is suggested as a candidate locus for the structural gene while y9 is ruled out. Classical genetic resources were used to dissect the desaturation steps further and hydroxyphenylpyruvate dioxygenase was linked to the vp2 locus, narrowing candidate loci for an obligate isomerase in maize to only a few. Since the first functional analysis of the paired carotene desaturases for a cereal crop is reported here, the implications for the genetic modification of the pro-vitamin A content in cereal crops such as rice and maize, are discussed.

Amino Acid Sequence↗

PubMed2005

Estimating a nucleotide substitution rate for maize from polymorphism at a major domestication locus.

To estimate a rate for single nucleotide substitutions for maize (Zea mays ssp. mays), we have taken advantage of data from genetic and archaeological studies of the domestication of maize from its wild ancestor, teosinte (Z. mays ssp. parviglumis). Genetic studies have shown that the teosinte branched1 (tb1) gene was a major target of human selection during maize domestication, and sequence diversity in the intergenic region 5' to the tb1-coding sequence is extraordinarily low. We show that polymorphism in this region is consistent with new mutation following fixation for a small number of tb1 haplotypes during domestication. Archeological studies suggest that maize was domesticated approximately 6,250-10,000 years ago and subsequently the size of the maize population is thought to have expanded rapidly. Using the observed number of mutations within the region of selection at tb1, the approximate age of maize domestication, and approximations for the maize genealogy, we have derived estimates for the nucleotide substitution rate for the tb1 intergenic region. Using two approaches, one of which is a coalescent approach, we obtain rate estimates of approximately 2.9 x 10(-8) and 3.3 x 10(-8) substitutions per site per year. We also show that the pattern of polymorphism in the tb1 intergenic region appears to have been strongly affected by the mutagenic effect of DNA methylation. Excluding target sites of symmetric DNA methylation (CG and CNG sites) from analysis, the mutation rate estimates are reduced by approximately 50%-60%, while the rates for CG and CNG sites are nearly an order of magnitude higher. We use rate estimates from the tb1 region to estimate the timing of expansion of transposable elements in the maize genome and suggest that this expansion occurred primarily within the last million years.

Base Sequence↗

PubMed2006

The TIGR Maize Database.

Maize is a staple crop of the grass family and also an excellent model for plant genetics. Owing to the large size and repetitiveness of its genome, we previously investigated two approaches to accelerate gene discovery and genome analysis in maize: methylation filtration and high C(0)t selection. These techniques allow the construction of gene-enriched genomic libraries by minimizing repeat sequences due to either their methylation status or their copy number, yielding a 7-fold enrichment in genic sequences relative to a random genomic library. Approximately 900,000 gene-enriched reads from maize were generated and clustered into Assembled Zea mays (AZM) sequences. Here we report the current AZM release, which consists of approximately 298 Mb representing 243,807 sequence assemblies and singletons. In order to provide a repository of publicly available maize genomic sequences, we have created the TIGR Maize Database (http://maize.tigr.org). In this resource, we have assembled and annotated the AZMs and used available sequenced markers to anchor AZMs to maize chromosomes. We have constructed a maize repeat database and generated draft sequence assemblies of 287 maize bacterial artificial chromosome (BAC) clone sequences, which we annotated along with 172 additional publicly available BAC clones. All sequences, assemblies and annotations are available at the project website via web interfaces and FTP downloads.

Chromosome Mapping↗

PubMed2001

A complete set of maize individual chromosome additions to the oat genome.

All 10 chromosomes of maize (Zea mays, 2n = 2x = 20) were recovered as single additions to the haploid complement of oat (Avena sativa, 2n = 6x = 42) among F(1) plants generated from crosses involving three different lines of maize to eight different lines of oat. In vitro rescue culture of more than 4,300 immature F(1) embryos resulted in a germination frequency of 11% with recovery of 379 F(1) plantlets (8.7%) of moderately vigorous growth. Some F(1) plants were sectored with distinct chromosome constitutions among tillers of the same plant and also between root and shoot cells. Meiotic restitution facilitated development of un-reduced gametes in the F(1). Self-pollination of these partially fertile F(1) plants resulted in disomic additions (2n = 6x + 2 = 44) for maize chromosomes 1, 2, 3, 4, 6, 7, and 9. Maize chromosome 8 was recovered as a monosomic addition (2n = 6x + 1 = 43). Monosomic additions for maize chromosomes 5 and 10 to a haploid complement of oat (n = 3x + 1 = 22) were recovered several times among the F(1) plants. Although partially fertile, these chromosome 5 and 10 addition plants have not yet transmitted the added maize chromosome to F(2) offspring. We discuss the development and general utility of this set of oat-maize addition lines as a novel tool for maize genomics and genetics.

Avena↗

PubMed1973

Alternate pathways of glycolate synthesis in tobacco and maize leaves in relation to rates of photorespiration.

After a preliminary period in light, leaf disks floated on 10 mm alpha-hydroxy-2-pyridinemethanesulfonic acid to inhibit glycolate oxidase accumulate glycolate at average initial rates of 67 micromoles in tobacco and 8 micromoles per gram fresh weight per hour in maize under optimal conditions in air. In the presence of (14)CO(2), the glycolate synthesized has a high specific radioactivity in illuminated tobacco and a low one in maize. Isonicotinic acid hydrazide also inhibits glycolate oxidation and causes a slow accumulation of glycolate in maize but not in tobacco, while it inhibits glycolate synthesis in tobacco but not in maize. Radioactive carbon in acetate-2-(14)C and especially pyruvate-3-(14)C is incorporated predominantly into the C-2 of glycolate in both species, but the specific radioactivity is much greater in maize. Glyoxylate-2-(14)C is readily converted to glycolate-2-(14)C in both species. The addition of phosphoenolpyruvate stimulated glycolate formation in maize and inhibited its synthesis in tobacco, and in the presence of (14)CO(2) the specific radioactivity in glycolate-(14)C was decreased greatly by the added phosphoenolpyruvate only in maize.Thus, unsymmetrically labeled glycolate is mainly synthesized from pyruvate-3-(14)C by a slow pathway in maize. Tobacco possesses an additional rapid pathway that produces equally labeled glycolate more directly from fixed CO(2) during photosynthesis. Glycolate is believed to be the primary substrate of photorespiration, and sufficiently rapid rates of glycolate synthesis have been observed in tobacco to account for this function. Hence the high rates of photorespiration observed in tobacco leaves compared with maize result partly from differences between these species in the pathway of glycolate synthesis.

Journal Article↗

PubMed1989

Immunological comparison of the starch branching enzymes from potato tubers and maize kernels.

Starch branching enzyme was purified from potato (Solanum tuberosum L.) tubers as a single species of 79 kilodaltons and specific antibodies were prepared against both the native enzyme and against the gel-purified, denatured enzyme. The activity of potato branching enzyme could only be neutralized by antinative potato branching enzyme, whereas both types of antibodies reacted with denatured potato branching enzyme. Starch branching enzymes were also isolated from maize (Zea mays L.) kernels. All of the denatured forms of the maize enzyme reacted with antidenatured potato branching enzyme, whereas recognition by antinative potato branching enzyme was limited to maize branching enzymes I and IIb. Antibodies directed against the denatured potato enzyme were unable to neutralize the activity of any of the maize branching enzymes. Antinative potato branching enzyme fully inhibited the activity of maize branching enzyme I; the neutralized maize enzyme was identified as a 82 kilodalton protein. It is concluded that potato branching enzyme (M(r) = 79,000) shares a high degree of similarity with maize branching enzyme I (M(r) = 82,000), in the native as well as the denatured form. Cross-reactivity between potato branching enzyme and the other forms of maize branching enzyme was observed only after denaturation, which suggests mutual sequence similarities between these species.

Journal Article↗

PubMed1990

Characterization and distribution of a maize cDNA encoding a peptide similar to the catalytic region of second messenger dependent protein kinases.

Maize (Zea mays) roots respond to a variety of environmental stimuli which are perceived by a specialized group of cells, the root cap. We are studying the transduction of extracellular signals by roots, particularly the role of protein kinases. Protein phosphorylation by kinases is an important step in many eukaryotic signal transduction pathways. As a first phase of this research we have isolated a cDNA encoding a maize protein similar to fungal and animal protein kinases known to be involved in the transduction of extracellular signals. The deduced sequence of this cDNA encodes a polypeptide containing amino acids corresponding to 33 out of 34 invariant or nearly invariant sequence features characteristic of protein kinase catalytic domains. The maize cDNA gene product is more closely related to the branch of serine/threonine protein kinase catalytic domains composed of the cyclic-nucleotide- and calcium-phospholipid-dependent subfamilies than to other protein kinases. Sequence identity is 35% or more between the deduced maize polypeptide and all members of this branch. The high structural similarity strongly suggests that catalytic activity of the encoded maize protein kinase may be regulated by second messengers, like that of all members of this branch whose regulation has been characterized. Northern hybridization with the maize cDNA clone shows a single 2400 base transcript at roughly similar levels in maize coleoptiles, root meristems, and the zone of root elongation, but the transcript is less abundant in mature leaves. In situ hybridization confirms the presence of the transcript in all regions of primary maize root tissue.

Amino Acid Sequence↗

PubMed2000

The complete sequence of 340 kb of DNA around the rice Adh1-adh2 region reveals interrupted colinearity with maize chromosome 4.

A 2.3-centimorgan (cM) segment of rice chromosome 11 consisting of 340 kb of DNA sequence around the alcohol dehydrogenase Adh1 and Adh2 loci was completely sequenced, revealing the presence of 33 putative genes, including several apparently involved in disease resistance. Fourteen of the genes were confirmed by identifying the corresponding transcripts. Five genes, spanning 1.9 cM of the region, cross-hybridized with maize genomic DNA and were genetically mapped in maize, revealing a stretch of colinearity with maize chromosome 4. The Adh1 gene marked one significant interruption. This gene mapped to maize chromosome 1, indicating a possible translocation of Adh1 after the evolutionary divergence leading to maize and sorghum. Several other genes, most notably genes similar to known disease resistance genes, showed no cross-hybridization with maize genomic DNA, suggesting sequence divergence or absence of these sequences in maize, which is in contrast to several other well-conserved genes, including Adh1 and Adh2. These findings indicate that the use of rice as the model system for other cereals may sometimes be complicated by the presence of rapidly evolving gene families and microtranslocations. Seven retrotransposons and eight transposons were identified in this rice segment, including a Tc1/Mariner-like element, which is new to rice. In contrast to maize, retroelements are less frequent in rice. Only 14.4% of this genome segment consist of retroelements. Miniature inverted repeat transposable elements were found to be the most frequently occurring class of repetitive elements, accounting for 18.8% of the total repetitive DNA.

Alcohol Dehydrogenase↗

PubMed1990

Antibody response reveal differences in oral tolerance to wheat and maize grain protein fractions.

The influence of diet on humoral immune responses to gluten- and maize-derived proteins was examined using ELISA and protein blotting techniques. Mice raised on the maize-based (gluten-free) diet responded well to parenteral immunization with each of six gluten-derived protein preparations (whole gliadin, two omega-gliadin fractions, wheat salt-soluble proteins, a peptic-tryptic digest and a subtilisin digest of gluten), as serum antibody levels increased at least 300-fold in each case. In contrast, mice raised on the wheat-based diet responded poorly to immunization with either whole gliadin or omega-gliadin and were virtually non-responsive to enzymic digest of gluten. Diet had little effect on the magnitude of the antibody response to wheat salt-soluble proteins, with both groups showing a 300-fold increase in titre. Similarly, tolerance to alpha-zeins, the alcohol-soluble proteins of maize, did not occur on either diet. However, some oral tolerance was observed to maize glutelin. The specificity of the various antibody responses was then analysed by immunoblotting. Following immunization with gluten proteins or digests, antibodies from the maize-fed mice bound more or less equally to each of the main gliadin bands and to the glutenins while the mice on the wheat-based diet had antibody specific for omega-gliadin proteins. Serum antibodies from the maize-fed mice, immunized with either alpha-zein or maize glutelin, showed even labelling of the major maize endosperm proteins while antibodies from mice on the wheat diet showed strong labelling of the Mr 27,000 and 58,000 bands. These results show that diet influenced the specificity, as well as the magnitude of serum antibody responses to cereal proteins. In addition, oral tolerance appeared to affect the humoral response to some cereal proteins more than others. Both of these findings have important implications for our understanding of coeliac disease.

Animals↗

PubMed1991

Antimicrobial effect of fermented Ghanaian maize dough.

Unhygienic conditions of a typical rural community in a developing country were simulated in the laboratory by inoculating fermented maize dough porridge with Shigella flexneri and enterotoxigenic Escherichia coli (ETEC). The antimicrobial effects of the different processes involved in the preparation of fermented maize dough porridge were assessed. The soaking process reduced the pH but no antimicrobial effect against shigella and ETEC was noted. Unfermented maize dough did not inhibit any of the test strains. When the fermentation process had become established, half of the strains tested were inhibited by the fermented maize dough when examined 8 h after inoculation. Cooking the fermented maize dough into porridge reduced the antimicrobial effect but there was still significant inhibition of pathogens. This suggests that the antimicrobial effect of fermented maize dough is not due to pH per se. Fermentation of maize dough appears to be a useful strategy for reducing contamination of weaning foods by Sh. flexneri and ETEC. The possible nature of the antimicrobial agent(s) produced during the fermentation of maize dough is discussed.

Escherichia coli↗

PubMed2004

New in silico insight into the synteny between rice (Oryza sativa L.) and maize (Zea mays L.) highlights reshuffling and identifies new duplications in the rice genome.

A unigene set of 1411 contigs was constructed from 2629 redundant maize expressed sequence tags (ESTs) mapped on the maizeDB genetic map. Rice orthologous sequences were identified by blast alignment against the rice genomic sequence. A total of 1046 (74%) maize contigs were associated with their corresponding homologues in the rice genome and 656 (47%) defined as potential orthologous relationships. One hundred and seventeen (8%) maize EST contigs mapped to two distinct loci on the maize genetic map, reflecting the tetraploid nature of the maize genome. Among 492 mono-locus contigs, 344 (484 redundant ESTs) identify collinear blocks between maize chromosomes 2 and 4 and a single rice chromosome, defining six new collinear regions. Fine-scale analysis of collinearity between rice chromosomes 1 and 5 with maize chromosomes 3, 6 and 8 shows the presence of internal rearrangements within collinear regions. Mapping of maize contigs to two distinct loci on the rice sequence identifies five new duplication events in rice. Detailed analysis of a duplication between rice chromosomes 1 and 5 shows that 11% of the annotated genes from the chromosome 1 locus are found duplicated on the chromosome 5 paralogous counterpart, indicating a high degree of re-organisations. The implications of these findings for map-based cloning in collinear regions are discussed.

Chromosome Mapping↗

PubMed1999

Incidence of Fusarium spp. and levels of fumonisin B1 in maize in western Kenya.

Maize kernel samples were collected in 1996 from smallholder farm storages in the districts of Bomet, Bungoma, Kakamega, Kericho, Kisii, Nandi, Siaya, Trans Nzoia, and Vihiga in the tropical highlands of western Kenya. Two-thirds of the samples were good-quality maize, and one-third were poor-quality maize with a high incidence of visibly diseased kernels. One hundred fifty-three maize samples were assessed for Fusarium infection by culturing kernels on a selective medium. The isolates obtained were identified to the species level based on morphology and on formation of the sexual stage in Gibberella fujikuroi mating population tests. Fusarium moniliforme (G. fujikuroi mating population A) was isolated most frequently, but F. subglutinans (G. fujikuroi mating population E), F. graminearum, F. oxysporum, F. solani, and other Fusarium species were also isolated. The high incidence of kernel infection with the fumonisin-producing species F. moniliforme indicated a potential for fumonisin contamination of Kenyan maize. However, analysis of 197 maize kernel samples by high-performance liquid chromatography found little fumonisin B1 in most of the samples. Forty-seven percent of the samples contained fumonisin B1 at levels above the detection limit (100 ng/g), but only 5% were above 1,000 ng/g, a proposed level of concern for human consumption. The four most-contaminated samples, with fumonisin B1 levels ranging from 3, 600 to 11,600 ng/g, were from poor-quality maize collected in the Kisii district. Many samples with a high incidence of visibly diseased kernels contained little or no fumonisin B1, despite the presence of F. moniliforme. This result may be attributable to the inability of F. moniliforme isolates present in Kenyan maize to produce fumonisins, to the presence of other ear rot fungi, and/or to environmental conditions unfavorable for fumonisin production.

Animals↗