Drechslera Maydis Research Articles

Quarantine pathogen interceptions on crop germplasm in India during 1986 - 2010 and their possible economic impact

The National Bureau of Plant Genetic Resources Regional Station, Hyderabad has facilitated safe introduction of 356 521 (1986–2010) germplasm accessions of various crops into India. About 60 seed-borne pathogens of quarantine importance were intercepted on crop germplasm during seed examination in the laboratory and post-entry quarantine observations in the field. Of these, the quarantine pathogens, viz. Ralstonia solanacearum and peanut stripe virus in groundnut (Arachis hypogaea L.), Peronospora manshurica (Naum.) Syd. and peanut stripe virus in soybean [Glycine max (L.) Merr.], tobacco streak virus in sunflower (Helianthus annuus L.), Xanthomonas campestris pv holcicola (Elliot) Dye, Burkholderia andropogonis (Smith) Gillis et al. on sorghum [Sorghum bicolor (L.) Moench], Drechslera maydis (Nisik.) Subram. & Jain on maize (Zea mays L.) and Pseudomonas syringae pv tomato (Okabe) Young et al. on tomato (Lycopersicon esculentum Mill.) were intercepted from different countries. Yield losses that could have occurred were estimated had these pathogens of groundnut, soybean, sunflower, maize, sorghum and tomato not been intercepted.

Antifungal Potential of Dill (Anethum graveolens L.) Seed Essential Oil, its Extracts and Components Against Phytopathogenic Maize Fungi

Dill (Anethum graveolens L.) is an aromatic herb that is mainly used as a flavoring agent in the food industry. It has been also used to treat various ailments. Many reports are available in the literature regarding its biological activities. So, the present study reports the fungitoxic impact of dill (Anethum graveolens L.) seed extracts, essential oil, isolated and derivatized compounds using the poisoned food technique against phytopathogenic maize fungi (Fusarium verticillioides and Drechslera maydis). GC/MS analysis of hydro distilled essential oil (yield 1.5%) revealed carvone (42.2%) and limonene (30.0%) to be the major compounds that were further isolated using column chromatography and were chemically modified. Dill seed extracts were prepared by different extraction methods (maceration, sonication, and soxhlet) using methanol and hexane solvents and maximum yield was observed for soxhlet extraction (5.7%). The antifungal activity of all the components (essential oil, extracts, isolated compounds and derivatives) was evaluated at different concentrations (125-1000 μg/mL) using Carbendazim 50 WP and Mancozeb 75 WP as the positive control. Overall, the isolated compounds and their derivatives were more effective in comparison to the extracts and essential oil. Further, the activity was increased with increasing the concentration as well as the polarity of the molecule.

Bio-efficacy of different fungicides against Drechslera maydis causing maydis leaf blight of maize

Bio-efficacy of different fungicides against Drechslera maydis causing maydis leaf blight of maize

Unraveling the metabolite signatures of maize genotypes showing differential response towards southern corn leaf blight by 1H-NMR and FTIR spectroscopy

Southern corn leaf blight, caused by Drechslera maydis, is the most prevalent fungal disease in maize growing regions of India. This is the first study that identified genotypic variability among maize genotypes, LM 13, CM 140 and LM 15 (highly resistant, moderately resistant and highly susceptible towards infection, respectively) on the basis of metabolite profiling, using 1H-NMR and FTIR techniques. High intensity peaks of quercetin, ascorbic acid, glycine betaine and flavonoids were observed in the inoculated leaves of LM 13 by 1H-NMR spectroscopy. LM 15 showed intense peaks of alanine, γ- amino butyric acid (GABA), fatty acids and threonine in their leaves. FTIR spectral analysis of the inoculated leaves of LM 13 and CM 140 genotypes showed O–H stretching vibrations of carbohydrates and glycoconjugates and the C–O–C bending vibrations of cellulose and hemicelluloses in their cells. These vibrations were absent in the infected leaves of LM 15. Principal component analysis showed that the primary and secondary metabolites contributed significantly towards genotypic variability. It may thus be concluded that the presence of polyphenols, flavonoids and lignin might be responsible for inducing resistance against infection. Threonine, GABA, malic acid, fatty acids and the unassigned metabolite could be regarded as potential biochemical markers for disease susceptibility.

Effect of harvest stage and drying methods on germination and seed-borne fungi of maize (Zeamays L.) in South West Nigeria

Germination of seed and infection by seed-borne fungi of two maize varieties DMRLSR-W and DMRLSR-Y as affected by stage of harvest and method of drying were studied in the growing seasons of year 2002 and 2003 at the Institute of Agricultural Research and Training, Moor Plantation, Ibadan, Nigeria. The experiment was a split-plot arranged in a randomized complete block design with four replications. Ears were harvested at 30, 35, 40, and 45 days after tasselling (DAT). Extracted seeds were dried to 13-14% moisture content (i) in shade, (ii) in sun, and (iii) artificially at 45oC in a Thermax batch type seed drier. “Initial” and “final” germination tests were conducted immediately after harvest and drying, respectively. Significant higher percentage germination was associated with seeds from cobs harvested 35 DAT which were sun dried. The highest 100-seed weight was recorded in seeds from cobs harvested 45 DAT irrespective of drying method. Associated fungi were isolated by plating seeds on potato dextrose agar. Results indicated seeds from ears harvested at 30 and 35 DAT irrespective of drying method were not infected with Fusarium moniliforme, Fusarium graminearium, Botryodiplodia theobromae and Drechslera maydis. However, seed germination was significantly lower for seeds from ears harvested at 30 DAT. Aspergillus sp. were isolated from all the seeds irrespective of stage of harvest and drying method. Penicillium sp. was not isolated from any of the seeds dried artificially. Significant higher percentage germination was associated with seeds from cobs harvested 35 DAT which were sun dried. Maximum 100-seed weight was recorded in seeds from ears harvested 45 DAT irrespective of drying method. Key words: Seed-borne, fungi, harvest, stage, drying, germination, Zea mays.

Effect of harvest stage and drying methods on germination and seed-borne fungi of maize ( Zea mays L.) in South West Nigeria

Germination of seed and infection by seed-borne fungi of two maize varieties DMRLSR-W and DMRLSRY as affected by stage of harvest and method of drying were studied in the growing seasons of year 2002 and 2003 at the Institute of Agricultural Research and Training, Moor Plantation, Ibadan, Nigeria. The experiment was a split-plot arranged in a randomized complete block design with four replications. Ears were harvested at 30, 35, 40, and 45 days after tasselling (DAT). Extracted seeds were dried to 13- 14% moisture content (i) in shade, (ii) in sun, and (iii) artificially at 45oC in a Thermax batch type seed drier. “Initial” and “final” germination tests were conducted immediately after harvest and drying, respectively. Significant higher percentage germination was associated with seeds from cobs harvested 35 DAT which were sun dried. The highest 100-seed weight was recorded in seeds from cobs harvested 45 DAT irrespective of drying method. Associated fungi were isolated by plating seeds on potato dextrose agar. Results indicated seeds from ears harvested at 30 and 35 DAT irrespective of drying method were not infected with Fusarium moniliforme, Fusarium graminearium, Botryodiplodia theobromae and Drechslera maydis. However, seed germination was significantly lower for seeds from ears harvested at 30 DAT. Aspergillus sp. were isolated from all the seeds irrespective of stage of harvest and drying method. Penicillium sp. was not isolated from any of the seeds dried artificially. Significant higher percentage germination was associated with seeds from cobs harvested 35 DAT which were sun dried. Maximum 100-seed weight was recorded in seeds from ears harvested 45 DAT irrespective of drying method.

Durable resistance to two leaf blights in two maize inbred lines

It has been determined that the occurrence of 'durable resistance' as defined by Johnson and Kranz operates in maize inbred lines CM104 and CM105 against the leaf blight pathogens Setosphaeria turcica (= Exserohilum turcicum) and Drechslera maydis (=Cochliobolus heterostrophus), by analyzing data for 16 and 14 years, respectively. Essentially the methodology estimated the longevity of cultivar resistance by determining whether the regression coefficient of linear regression with years of testing and mean disease intensity is zero or not significantly different from zero. The values for both Turcicum Leaf Blight and Maydis Leaf Blight were not significantly different from zero. The resistant inbred lines have been used in hybrid combinations and have the potential to transmit this resistance to progenies in hybrid combinations that are governed by additive gene action.

Drechslerol-C, a phytotoxin produced by Drechslera maydis, the causal organism of leaf blight of Costus speciosus

Drechslerol-C, a phytotoxin, has been isolated from culture filtrates and mycelial homogenate of Drechslera maydis, the organism which causes severe leaf blight disease of Costus speciosus (Koen.) Sm., was characterized as 3-hydroxy-eicos-11( Z)-enylheptacos-11( Z)-enoate on the basis of spectral analysis. Drechslerol-C has been isolated from tissues infected with D. maydis implicating it in the disease process. The toxin produced characteristic necrotic and chlorotic lesions on the leaves of C. speciosus with concentrations from 2.85 × 10 −5 to 2.28 × 10 −4 M.

Drechslerol-B, A host-selective phytotoxin produced by Drechslera maydis

A new host-selective phytotoxin, drechslerol-B, isolated from the culture filtrate of Drechslera maydis, the organism which causes leaf blight of Costus speciosus, was characterized as 3-hydroxy-eicos-11( Z)-enyl eicos-4( Z)-enoate on the basis of spectral analysis.

Ascospore abortion in crosses of Cochliobolus heterostrophus heterozygous for the virulence locus Tox1

Crosses heterozygous for the virulence locus Tox1 show a high frequency of nonrandom ascospore abortion, in addition to a high frequency of random abortion seen in homozygous crosses. In crosses among closely related laboratory strains, the frequency of asci with eight mature, viable spores dropped from 35–47% of asci with mature spores in crosses homozygous for Tox1 to 3–17% in heterozygous crosses. Segregation for alternate alleles of Tox1 was 2:2 in 98% of asci with four viable spores. Patterns of abortion in crosses involving field isolates were similar to the patterns in crosses among laboratory strains. No recombinants between Tox1 and the abortion-inducing factor were detected among 112 progeny of laboratory strains. The results suggest that race T (TOX1) and race O (tox1) strains of C. heterostrophus differ by a chromosome rearrangement, possibly a reciprocal translocation, with a breakpoint at or near Tox1.Key words: fertility, T-toxin, Cochliobolus heterostrophus, Helminthosporium maydis, Bipolaris maydis, Drechslera maydis, chromosome rearrangement, reciprocal translocation.

6-Epiophiobolin A and 3-anhydro-6-epiophiobolin A—host specific phytotoxins of Drechslera maydis (race T)

6-Epiophiobolin A and 3-anhydro-6-epiophiobolin A were isolated from Drechslera maydis race T, the causal agent of Southern corn leaf blight in Tex

Phytotoxins from the pathogenic fungi Drechslera maydis and Drechslera sorghicola

Drechslera maydis, the causal agent of Southern corn leaf blight, and Drechslera sorghicola, the causal agent of leaf spot on Johnson grass, produce a series of phytotoxic sesterterpenoids. These sesterterpenoids belong to the ophiobolin family. One of them, ophiobolin I, was characterized by x-ray diffraction and served as a crucial reference compound for characterizing four other ophiobolins. All of the ophiobolins studied produce characteristic lesions on host plants at concentrations of 1 mM to 1 muM. The ophiobolin characterized as 6-epiophiobolin A is selectively toxic to corn bearing Texas-male-sterile (Tms) cytoplasm when assayed in a dark CO(2) fixation assay. It is plausible that these ophiobolins had a role in the 1970 corn-blight epidemic in North America.

Influence of Various Factors on Toxicity of Culture Filtrate of a Drechslera maydis Strain from Costus speciosus

Abstract Drechslera maydis causing severe leaf blight of Costus speciosus, produced toxic matabolites in vitro. Maximum toxin was produced in modified Fries’ medium if its carbon source was substituted with glucose and nitrogen source with asparagine. Highest toxin accumulation was found at 21 days of incubation and with the initial pH 5.0. The toxin was stable in acidic condition (pH 3.5—7.0) but unstable under alkaline conditions.

Inhibition of growth of some plant pathogens by antagonistic microorganisms

AbstractFour known antagonistic microorganisms, namely, Bacillus cereus, Bacillus subtilis, Aspergillus ochraceus and Penicillium cyclopium were paired against four pathogens of maize, namely, Curvularia pallescens, Drechslera maydis, Fusarium moniliforme and Macrophomina phaseoli and a pathogen of cassava, Colletotrichum gloeosporioides f. sp. manihotis on potato dextrose agar. The main aim was to test the ability of the antagonists to inhibit the growth of the pathogens. Whereas B. cereus and B. subtilis inhibited the growth of C. pallescens, D. maydis, M. phaseoli and C. gloeosporioides f. sp. manihotis, they did not inhibit the growth of F. moniliforme. A. ochraceus and P. cyclopium were effective only against M. phaseoli. Inhibitory activity on the target organisms are thought to be due to some toxic substances produced by the antagonists.

Drechslerol-A, a new phytotoxic metabolite produced by Drechslera maydis, a strain from costus speciosus

Drechslera maydis causes severe leaf blight disease of Costus speciosus. One compound, drechslerol-A, isolated from the culture filtrate of this fungus was elucidated as ( cis) hentetracont-10-ene-12-hydroxymethyl-4-ol on the basis of spectral analysis. The production of necrotic lesion was observed on the leaves of Costus speciosus with 1.6 × 10 −4 M concentration. In the most sensitive reaction drechslerol-A shows complete killing effect on the root growth of wheat seedlings at the concentration of 3.2 × 10 −5 M.

Effect of Nitrogen Source and Vitamins on Ethanol and Pyruvate Production byBipolaris MaydisRace T

The dry weight of Bipolaris maydis race T incubated three da in a glucose-mineral salts liquid medium containing asparagine as the nitrogen source was approximately twice that obtained with either glutamate or NH4C1. Thiamine at 0.1 or 1 Mg/rnl was inhibitory to growth at pH 5 in asparagine medium, was stimulatory at pH 6.5 in glutamate medium, and had no effect in NH4C1 medium at any pH tested. The concentration of ethanol in the culture medium was greatest with glutamate as the nitrogen source and least with NH4C1. When asparagine was the nitrogen source, caused an increase in extracellular ethanol levels and a decrease in the levels of both intra- and extracellular pyruvate. This appeared to be due to a thiamine-mediated increase in pyruvate decarboxylase but not alcohol dehydrogenase activity. No similar trends were evident in either NH4C1 or glutamate media. The intracellular pyruvate level appeared to be a more important regulator of ethanol production than the activities of pyruvate decarboxylase and alcohol dehydrogenase. Of six other vitamins tested on glucose-asparagine pH 5 medium, only folic acid stimulated growth; biotin was inhibitory and the others had no effect. The inhibitory effect of biotin could be nullified by the presence of thiamine. Although each vitamin could stimulate ethanol production, only folic acid and pantothenate were as effective as thiamine. Thiamine inhibits sporulation in Bipolaris maydis (Nisikado) Shoemaker [Drechslera maydis (Nisikado) Subram. & Jain; Helminthosporium maydis Ni? sikado] race T, the southern corn leaf blight pathogen, when it is incubated on an agar medium containing L-asparagine, ammonium citrate, or sodium nitrate as the nitrogen source (Garraway, 1973; Garraway and Evans, 1977). Although B. maydis does not sporulate in liquid media, we have used tissue grown in this manner as a model system to investigate biochemical effects of under defined nutritional conditions (Evans and Garraway, 1976). When B. maydis is incubated in shake culture in asparagine medium, inhibits growth and stimulates ethanol production. We have previously shown that this latter event is due to a thiamine-mediated increase in the synthesis of pyruvate decarboxylase (PD), an enzyme in the alcoholic fermentation pathway that requires pyrophosphate as a cofactor. In the absence of added thiamine, PD activity is low, and pyruvate accumulates intracellularly. Apparently a portion of the intracellular pyruvate pool leaks into the medium where it can be detected in relatively high concentrations. As the concentration of the medium is increased, PD activity also increases and the pyruvate level drops as it is converted to acetaldehyde. Acetaldehyde is then converted to ethanol via alcohol dehydrogenase (ADH), an enzyme whose activity is not affected by thia? mine (Evans and Garraway, 1976). Because ethanol production may be a mechanism by which inhibits growth and sporulation in B. maydis, we wished to determine if the thiamine

Heterokaryosis in Cochliobolus heterostrophus

Heterokaryons of Cochliobolus heterostrophus (= Bipolaris maydis = Helminthosporium maydis = Drechslera maydis) formed when complementing auxotrophs were paired on minimal medium. The growth rate of each heterokaryon was influenced by the nutritional requirement of each partner. Mycelium of complementary colonies was composed of a mixture of homokaryotic and heterokaryotic cells. On minimal agar medium hyphal tips of colonies were homokaryotic whereas cells behind the colony front were heterokaryotic; conidia formed by the heterokaryotic colonies were 99.2% homokaryotic (approximately 50% of the homokaryotic conidia were of each component type) and 0.8% heterokaryotic. All conidia from a single conidiophore had the same genotype. In minimal liquid culture 73% of the mycelial fragments (two to four cells per fragment), and 10% of the protoplasts isolated from mycelial cells were heterokaryotic. Proportions of component nuclei were approximately equal in all heterokaryotic cells. Heterokaryons were resolved on complete medium and in infected corn plants to yield nearly equal numbers of each component type. Neither diploids nor parasexual recombinants were found. Interspecific complementation did not occur between C. heterostrophus and either C. carbonum or C. sativus although both of the latter species complemented intraspecifically.

Mitochondrial DNA analyses of fertile and sterile maize plants derived from tissue culture with the texas male sterile cytoplasm

Maize plants carrying Texas (T) cytoplasm are male-sterile and sensitive to Drechslera maydis race T toxin, whereas plants carrying Normal (N) cytoplasm are male-fertile and resistant to the toxin. Some plants regenerated from T cytoplasm tissue cultures exhibit a N cytoplasm-like phenotype with respect to malefertility and toxin-resistance. Analysis of the high molecular weight mitochondrial DNA (mtDNA) of such regenerants has shown that the plants do not contain N cytoplasm mtDNA. However, their mtDNAs do show sequence differences from each other and from the mtDNA of plants possessing T cytoplasm. No single alteration detected correlates with the change to malefertility or toxin resistance. Sequence alterations were also evident in high molecular weight mtDNA isolated from a plant regenerated from N cytoplasm callus. No changes in low molecular weight mtDNA molecules were observed in regenerants from N or T cytoplasm callus.

Methods for Selection of Mutants and In Vitro Culture of Cochliobolus heterostrophus

Auxotrophic, morphological and drug-resistant mutants of Cochliobolus heterostrophus (= Bipolaris maydis = Helminthosporium maydis = Drechslera maydis) were isolated after mutagenesis with ethyl methanesulphonate. Exposure of the fungus to other mutagens (N-methyl-N′-nitro-N-nitrosoguanidine, nitrous acid, and UV light) resulted in recovery of morphological but not auxotrophic mutants. Antibiotic enrichment or filtration enrichment in medium containing high levels of sorbose increased the proportion of auxotrophs in the surviving population. All sexually fertile mutants were found to have single gene lesions; those with the same phenotype were allelic in some cases but not in others. Defined minimal and complete media, designed to facilitate genetic and molecular biological manipulations, supported maximal growth rate at 30 °C and maximal conidiation of the fungus at 23 °C with a 16 h long-wave UV light photoperiod. Under all in vitro growth conditions tested, near-isogenic lines of two known races of the fungus were essentially identical. Sexual fertility was improved by a programme of breeding and selection, but not by physical or chemical changes in the medium used for crossing. The fungus can be stored conveniently on silica gel.

Mitochondrial sensitivity to Drechslera maydis T-toxin and the synthesis of a variant mitochondrial polypeptide in plants derived from maize tissue cultures with texas male-sterile cytoplasm

Tissue cultures of maize carrying cms-T cytoplasm have been found to regenerate fertile, T-toxin resistant plants, with and without a selective treatment with T-toxin. Progeny of these plants were tested for mitochondrial sensitivity to T-toxin and the translation products synthesised by isolated mitochondria were analysed. The results confirm previous indications of a close correlation between susceptibility to T-toxin and the synthesis of a variant 13,000 Mr mitochondrial polypeptide. Interestingly, there appeared to be a critical level at about 33% maximum synthesis of the 13,000 Mr polypeptide above which male sterility and sensitivity to T-toxin are jointly expressed. The possibility that there is a causal link between synthesis of this additional mitochondrial polypeptide, pollen abortion and sensitivity to T-toxin is discussed.