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The gray leaf spots caused by Cercospora spp. severely affect the yield and quality of maize. However, the evolutionary relation and pathogenicity variation between species of the Cercospora genus is largely unknown. In this study, we constructed high-quality reference genomes by nanopore sequencing two Cercospora species, namely, C. zeae-maydis and C. zeina, with differing pathogenicity, collected from northeast (Liaoning [LN]) and southeast (Yunnan [YN]) China, respectively. The genome size of C. zeae-maydis-LN is 45.08 Mb, containing 10,839 annotated genes, whereas that of Cercospora zeina-YN is 42.18 Mb, containing 10,867 annotated genes, of which approximately 86.58% are common in the two species. The difference in their genome size is largely attributed to increased long terminal repeat retrotransposons of 3.8 Mb in total length in C. zeae-maydis-LN. There are 41 and 30 carbohydrate-binding gene subfamilies identified in C. zeae-maydis-LN and C. zeina-YN, respectively. A higher number of carbohydrate-binding families found in C. zeae-maydis-LN, and its unique CBM4, CBM37, and CBM66, in particular, may contribute to variation in pathogenicity between the two species, as the carbohydrate-binding genes are known to encode cell wall–degrading enzymes. Moreover, there are 114 and 107 effectors predicted, with 47 and 46 having unique potential pathogenicity in C. zeae-maydis-LN and C. zeina-YN, respectively. Of eight effectors randomly selected for pathogenic testing, five were found to inhibit cell apoptosis induced by Bcl-2-associated X. Taken together, our results provide genomic insights into variation in pathogenicity between C. zeae-maydis and C. zeina. [Graphic: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Resistance of maize inbred lines to major leaf diseases should be characterized for the development of new hybrids in breeding programs. Thus, this study aimed to assess the severity of leaf diseases in maize inbredlines with different kernel hardnessand two sowingseasons. We assessed four inbred lines and one check hybrid with dent kernels and four inbred lines and a check hybrid with flint kernels. Treatments were conducted in two sowing seasons, one in October, and another in December 2013. The symptoms of gray leaf spot (Cercospora zeae-maydis), northern leaf blight (Exserohilum turcicum), and white leaf spot (a complex of Phaeosphaeria maydis and Pantoea ananatis) were assessed every 10 days from flowering. The area under the disease progress curve was also calculated. Severity level of the diseases was higher in inbred lines when compared to the check hybrds (AG8041 PRO and P30R50YH), regardless of kernel hardness. Dent-kernel inbred lines showed a higher severity of northern leaf blight symptoms when compared to flint-kernelones. It is worth mentioning that disease severity increased as sowing was delayed.

Os objetivos desse trabalho foram avaliar a eficiência de The aim of this study was evaluate efficacy fungicides to control cercospora leaf spot (Cercospora zeae-maydis) and helminthosporium leaf blight (Exserohilumturcicum), productivity, economic returns and quality of grain of corn culture of second crop in Farm Bandeirantes at Feliz Natal/MT. The treatments evaluated were: pyraclostrobina+epoxiconazol (0,7 L ha-1), trifloxistrobina+protioconazol (0,3L ha-1), azoxistrobina+cyproconazol(0,3 L ha-1), azoxystrobina (0,25 L ha-1), trifloxistrobina+ciproconazol (0,2 L ha-1) and control. Theapplicationof products occurred when corn was with 55 days, with a high propelled sprayer. The experimental design was a randomized block, with 6 treatments and 3 replications. The severity of each disease was visually determined through periodic analyses and ten plants were marked in each repetition, which were evaluated during the entire crop cycle. The data of severity obtained were used to calculate the area under disease progress curve (AUDPC). It was also obtained the production per ha, the economic return (R$ ha-1) and physiological quality of grain was evaluated by germination tests and accelerated aging of the grains. All treatments had significant difference compared to the control sample in controlling cercospora leaf spot about the control of helminthosporiumleat blight, the fungicides trifloxystrobin+prothioconazol and trifloxystrobin+cyproconazol were not efficient, and the fungicides pyraclostrobina+epoxiconazol, azoxystrobina, azoxistrobina+cyproconazol were efficient. The treatments that had major production are from the group of triazoles+strobilurine and the fungicide pyraclostrobin+epoxyconazol showed greater economic viability. Not were differences among fungicides, and neither of the treatments compared to control, in germination and accelerated aging tests, showing that the grains have good quality characteristics

A caracterização de linhagens de milho quanto à resistência às principais doenças é fundamental para o desenvolvimento de novos híbridos em programas de melhoramento. Assim, o objetivo deste trabalho foi avaliar a severidade de doenças foliares em linhagens de milho com diferentes texturas de grãos em duas épocas de semeadura. Foram avaliadas quatro linhagens e um híbrido testemunha com grãos dentados e quatro linhagens e um híbrido testemunha com grãos duros. Os tratamentos foram conduzidos em duas épocas de semeadura, em outubro e em dezembro de 2013. A partir do florescimento, a cada 10 dias, foram avaliadas as doenças foliares cercosporiose (Cercospora zeae-maydis), helmintosporiose (Exserohilum turcicum) e mancha branca (complexo Phaeosphaeria maydis/Pantoea ananatis). Foi calculada a área abaixo da curva do progresso das doenças (AACPD). A severidade das doenças foi maior nas linhagens, comparativamente aos híbridos testemunhas AG8041 PRO e P30R50YH, independentemente da textura dos grãos. As linhagens de textura dentada apresentaram maior severidade de sintomas da helmintosporiose, quando comparada às linhagens de grãos duros. Houve aumento da severidade das doenças avaliadas com o atraso da semeadura.

Seven commercial maize hybrids (AS1575, 2B688, Penta, GNZ2004, AG8021, Sprint e P30F53) were intercrossed in a complete diallel, excluded reciprocal, obtaining 21 crosses. The 28 treatments were evaluated in two environments characterized by different densities (62,500 and 90,000 plants ha-1), with the aim of selecting the most promising parents for generating base population to obtain lines. Two experiments were carried out in Guarapuava-PR, at randomized block design with three replications. We estimated the general (GCA) and specific (SCA) combining abilities for yield and disease severity assessed by the area under the common rust (Puccinia sorghi) progress curve (AURPC) and the area under the leaf spot (Cercospora zeae-maydis) progress curve (AULPC). The effects of GCA and SCA were significant for grain yield and diseases severity in both densities, revealing the importance of both additive and non-additive effects. There GCA x densities interaction was significant only for grain yield. Crossings P30F53 x AG8021 and P30F53 x Penta had negative estimates of SCA for AURPC and AULPC on the environments average. Hybrids GNZ 2004 and P30F53 stood out showing positive GCA for grain yield and negative for AURPC and AULPC in both densities and therefore are recommended for generating base populations for obtaining lines adapted for both densities, conventional and denser plantings, given the current trends in management of maize.

Ten elite maize inbred lines were selected based on all over per se performance and gray leaf spot disease reaction. Crosses were made in a 10 × 10 half-diallel mating design to produce 45 F 1 single cross hybrids. The experiment was conducted at Bako national maize research center in 2015 and evaluation of the crosses were made at Bako and Jimma research centers in 2016 by using alpha lattice design with three replications including three commercial checks. All the necessary yield, agronomic and GLS disease data were recorded. In all the studied traits highly significant genotypic differences were observed indicating the existence of genetic variability among the crosses. Analysis of variance for the combining ability indicated GCA and SCA mean squares were significant at ( P  < 0.001) for all traits except for anthesis-silking interval, ear per plant, ear diameter, lesion length and width. The ratios of GCA/SCA variances for agronomic parameters and all disease parameters were greater than unity except for that of first disease appearance implying the predominance of additive gene actions. Among all inbred lines, P1, P4, P7, P8 and P9 were identified as desirable sources of resistant genes for GLS disease resistance with positive days of first disease appearance and negative disease incidence, severity and AUDPC values for GCA effects. From the analysis of epidemiological data and disease progress curves the Logistic model (R 2  = 96.5) better described the disease progress curves than the Gompertz model (R 2  = 92.5) indicating the presence of delayance in epidemics and the inflection point of the GLS. P1, P7 and P8 were identified as a good general combiners for yield, yield related traits and GLS disease parameters. Thus, these parents were recommended to be used in breeding programs with a purpose of developing high yielder and GLS resistant single cross hybrids. In conclusion this study identified potential high yielding and GLS resistant single cross hybrids (CML-395/CML-383, CML-395/Sc-22, CML-395/CML-197 and CML-383/CML-197). Therefore, it is recommended that these hybrids can be used for direct production where this disease is the most prevalent and/or for further breeding programs in generating novel hybrids for future use. [ABSTRACT FROM AUTHOR]

Gray leaf spot (GLS), caused by Cercospora zeae-maydis, is an important foliar disease of maize (Zea mays L.) worldwide, resistance to which is controlled by multiple quantitative trait loci (QTL). To gain insights into the genetic architecture underlying the resistance to this disease, an association mapping population consisting of 161 inbred lines was evaluated for resistance to GLS in a plant pathology nursery at Shenyang in 2010 and 2011. Subsequently, a genome-wide association study, using 41,101 single-nucleotide polymorphisms (SNPs), identified 51 SNPs significantly (P < 0.001) associated with GLS resistance, which could be converted into 31 QTL. In addition, three candidate genes related to plant defense were identified, including nucleotide-binding-site/leucine-rich repeat, receptor-like kinase genes similar to those involved in basal defense. Two genic SNPs, PZE-103142893 and PZE-109119001, associated with GLS resistance in chromosome bins 3.07 and 9.07, can be used for marker-assisted selection (MAS) of GLS resistance. These results provide an important resource for developing molecular markers closely linked with the target trait, enhancing breeding efficiency.

An efficient Agrobacterium tumefaciens -mediated transformation (ATMT) approach was developed for the plant pathogenic fungus, Cercospora zeae-maydis , which is the causative agent of gray leaf spot in maize. The transformation was evaluated with five parameters to test the efficiencies of transformation. Results showed that spore germination time, co-cultivation temperature and time were the significant influencing factors in all parameters. Randomly selected transformants were confirmed and the transformants were found to be mitotically stable, with single-copy T-DNA integration in the genome. T-DNA flanking sequences were cloned by thermal asymmetric interlaced PCR. Thus, the ATMT approach is an efficient tool for insertional mutagenesis of C. zeae-maydis. [ABSTRACT FROM AUTHOR]

Among the diseases that affect the corn crop and can reduce the yield, there is cercospora gray leaf, caused by Cercospora spp. This disease is very important in the second season crop or ‘safrinha’. The objective of this study was to evaluate the severity of cercospora leaf spot in transgenic corn hybrids Agroceres Yieldgard AG 9010 YG and Advance NK Agrisure TL (Bt11), using two plant densities: 78,000 and 100,000 plants per hectare. The results showed that the higher density of plants increased the severity of the disease and provided a lower yield. There was no significant interaction between hybrids and severity of the disease. Entre as doenças que incidem na cultura do milho e podem reduzir seu rendimento, há a mancha de cercospora, causada por Cercospora spp., especialmente importante em milho de segunda época, ou ‘safrinha’. O objetivo deste trabalho foi avaliar a severidade da cercosporiose em nos híbridos transgênicos de milho Agroceres Yieldgard AG 9010 YG e Advance NK Agrisure TL (Bt11), em duas densidades de cultivo: 78.000 e 100.000 plantas por hectare. Os resultados permitiram constatar que a menor densidade de plantas favoreceu o incremento da severidade da doença e proporcionou menor rendimento de grãos. Não houve interação significativa entre os híbridos e a severidade da doença.

The main goal of this study was to assess the nature and magnitude of gene effects for resistance to Cercospora leaf spot. A randomized block design with three replications was used. The data were obtained at the plant level by assessing the disease severity. The data were analyzed per experiment, using the average data per plot. A dominant-additive genetic model without epistasis was considered, with estimation of the components of means and variance. The genetic control of resistance to gray leaf spot is polygenic with predominance of the additive effects. Dominance was observed in a few small-effect loci and high heritability values.

Gray leaf spot is an important maize disease in São Paulo State. Due to its relevance, the effect of this disease on maize grain yield was studied during the 2004 to 2008 autumn-winter seasons. Experiments were carried out to evaluate corn cultivars, comprising 44 to 60 simple and triple hybrids, being 19 trials in 2004, 15 in 2005, 16 in 2006, 16 in 2007 and 15 in 2008. The evaluations of disease severity were done at the kernel dough stage, ascribing notes 1 to 9 (for 0%; 1%; 2.5%; 5%; 10%; 25%; 50%; 75% and more than 75% affected leaf area, respectively). Significant negative correlation between gray leaf spot severity and grain yield was detected in 16 of the 35 trials where the disease occurred. In order to quantify the effect of gray leaf spot on yield of these 16 trials, attempting to minimize the dispersion caused by differences of yield potential, cultivars tolerance to the disease and other factors, cultivars were grouped into categories of disease intensity based on the Scott-Knott test at 5%, and means for severity and yield were calculated for each category. The adjustment of linear equations to these data allowed to estimate the yield reduction as a function of disease severity, for the intervals studied in each trial, that was on average 238 kg ha-1 (4%) with note 2, 634 kg ha-1 (11%) with note 3, 1006 kg ha-1 (17%) with note 4 and 1574 kg ha-1 with note 5, in relation to the groups with greatest gray leaf spot resistance which showed mean note 1.4 and mean grain yield 5655 kg ha-1. These results indicate that even with low disease severity a significant maize yield loss can be observed, demonstrating the importance of the use of genetic resistance in the control of gray leaf spot and to reduce losses in maize grain yield.

Isolates of Cercospora species from leaves displaying symptoms of grey leaf spot were collected in maize-producing areas of south-central Brazil in 2001 and 2002. Restriction digests of the internal transcribed spacer region of rDNA detected the presence of the same two Cercospora species described on maize in the United States, namely C. zeae-maydis and the recently described species, C. zeina . Genetic variability among isolates was assessed by analysing 104 amplified fragment length polymorphism loci. Cluster analysis confirmed the genetic separation of isolates into two species with a mean similarity of 35%. Similarity levels within species were high, averaging 93% and 92% among isolates of C. zeae-maydis and C. zeina , respectively. The mean genetic similarity between C. zeae-maydis and C. zeina and two isolates of C. sorghi f. sp. maydis was 45% and 35%, respectively. Results of this study showed that populations of the grey leaf spot pathogens in Brazil are similar to those in the United States regarding species composition and that C. zeina is also present in Brazil.

A adaptabilidade e a estabilidade da produção de grãos de milho e às variações ambientais são características importantes no processo de recomendação de genótipos para a semeadura em determinado ambiente. Três ensaios em diferentes locais (Água Doce, SC, Iraí de Minas, MG e Chapadão do Céu, GO) foram instalados objetivando estimar os parâmetros adaptabilidade e estabilidade fenotípica em genótipos de milho. Para tanto, foram estimados os parâmetros supracitados para os caracteres rendimento de grãos e severidade de cercosporiose a partir de 20 híbridos de milho obtidos pelo cruzamento de cinco genitores (S7) denominados A, B, C, D e E da empresa Agroeste Sementes S.A. O delineamento experimental utilizado em todos os ensaios foi o de blocos completamente ao acaso, com três repetições por tratamento. Para a característica rendimento de grãos foi realizada a colheita das espigas da área útil de cada parcela. Já para doença foi utilizada a escala diagramática de severidade. A avaliação foi realizada no estádio fenológico R5. Os parâmetros adaptabilidade e estabilidade fenotípica foram estimados pelo método de regressão linear proposto por Eberhart e Russel (1966). Os resultados revelaram diferenças significativas entre os fatores de tratamento (ambientes, híbridos e interação de híbridos e ambientes). A maioria dos híbridos testados revelou adaptabilidade ampla e alta estabilidade fenotípica para os caracteres rendimento de grãos e severidade de cercosporiose. A utilização dos genótipos 5, 6 e 10 (BxA, BxC e CxB, respectivamente) dentro do programa de melhoramento da empresa deve ser continuada, em função da necessidade de novos ensaios em ambientes com índices favoráveis.

The gray leaf spots caused by Cercospora spp. severely affect the yield and quality of maize. However, the evolutionary relation and pathogenicity variation between species of the Cercospora genus is largely unknown. In this study, we constructed high-quality reference genomes by nanopore sequencing two Cercospora species, namely, C. zeae-maydis and C. zeina , with differing pathogenicity, collected from northeast (Liaoning [LN]) and southeast (Yunnan [YN]) China, respectively. The genome size of C. zeae-maydis -LN is 45.08 Mb, containing 10,839 annotated genes, whereas that of Cercospora zeina -YN is 42.18 Mb, containing 10,867 annotated genes, of which approximately 86.58% are common in the two species. The difference in their genome size is largely attributed to increased long terminal repeat retrotransposons of 3.8 Mb in total length in C. zeae-maydis -LN. There are 41 and 30 carbohydrate-binding gene subfamilies identified in C. zeae-maydis -LN and C. zeina -YN, respectively. A higher number of carbohydrate-binding families found in C. zeae-maydis -LN, and its unique CBM4, CBM37, and CBM66, in particular, may contribute to variation in pathogenicity between the two species, as the carbohydrate-binding genes are known to encode cell wall-degrading enzymes. Moreover, there are 114 and 107 effectors predicted, with 47 and 46 having unique potential pathogenicity in C. zeae-maydis -LN and C. zeina -YN, respectively. Of eight effectors randomly selected for pathogenic testing, five were found to inhibit cell apoptosis induced by Bcl-2-associated X. Taken together, our results provide genomic insights into variation in pathogenicity between C. zeae-maydis and C. zeina . [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

The photosynthetic bacterium Rhodobacter sphaeroides and plant pathogenic fungus Cercospora nicotianae have been used as models for understanding resistance to singlet oxygen (¹O2), a highly toxic reactive oxygen species. In Rhodobacter and Cercospora, ¹O2 is derived, respectively, from photosynthesis and from the ¹O2-generating toxin cercosporin which the fungus produces to parasitize plants. We identified common genes recovered in transcriptome studies of putative ¹O2-resistance genes in these two systems, suggesting common ¹O2-resistance mechanisms. To determine if the Cercospora homologs of R. sphaeroides ¹O2-resistance genes are involved in resistance to cercosporin, we expressed the genes in the cercosporin-sensitive fungus Neurospora crassa and assayed for increases in cercosporin resistance. Neurospora crassa transformants expressing genes encoding aldo/keto reductase, succinyl-CoA ligase, O-acetylhomoserine (thiol) lyase, peptide methionine sulphoxide reductase and glutathione S-transferase did not have elevated levels of cercosporin resistance. Several transformants expressing aldehyde dehydrogenase were significantly more resistant to cercosporin. Expression of the transgene and enzyme activity did not correlate with resistance, however. We conclude that although the genes tested in this study are important in ¹O2 resistance in R. sphaeroides, their Cercospora homologs are not involved in resistance to ¹O2 generated from cercosporin. [ABSTRACT FROM AUTHOR]

Stability of pathogen populations characterised by slow temporal variation is important for durability of disease management systems in any agroecology. Temporal variation in population structure is attributed to factors related to ecology, biology and life history, and varies among organisms and ecosystems. The objective of this study was to investigate genetic variability of Cercospora zeina (previously called Cercospora zeae-maydis Type II) populations in maize (Zea mays) producing areas under Uganda conditions. Populations of the fungus were analysed for genetic variability using a fluorescent amplified fragment length polymorphism (AFLP) technique. Little or no genetic differentiation (ϕFST 0.05) was detected for populations sampled within the same year, within an agroecology. However, a weak to moderate population structure was detected between populations from different locations, within the same (ϕFST = 0.08) or different agroecologies (ϕFST = 0.09). Pair-wise comparisons using ϕFST gene diversity and genetic distance, showed a reduction in genetic diversity in younger populations, suggestive of minor effects of selection and genetic drift. Overall, the data suggest that during the 3 years of study the impact of selection and genetic drift on C. zeina populations in the two Ugandan agroecologies is slow, but progressive leading to homogenetity with agroecologies and differences between agroecologies. [ABSTRACT FROM AUTHOR]

The infection process of Cercospora zeae-maydis type II (syn. Cercospora zeina Meisel and Korsman) in resistant, moderately resistant and susceptible maize genotypes was studied in the greenhouse under artificial inoculation. The percent spore germination, germ tube growth and formation of mature appressorium on leaves at 24, 36, 48, and 72 h after inoculation did not differ between resistant, moderately resistant, and susceptible maize genotypes (P ⩽ 0.05). More germlings were established after penetration on susceptible than resistant and moderately resistant maize genotypes at 72, 96, 120, and 144 h after inoculation. The hyphal wefts in cells of resistant and moderately resistant genotypes were shorter than in susceptible genotypes (P ⩽ 0.05). The slow pathogen growth was associated with a reduced number of conidiophores per stroma, spores per unit area and smaller lesions. The reduced pathogen growth after penetration suggests possible involvement of pathogen growth inhibitory substances in maize resistance to C. zeae-maydis type II. [ABSTRACT FROM AUTHOR]

Gray leaf spot (GLS), caused by the causal fungal pathogen Cercospora zeae- maydis, is one of the most serious foliar diseases of maize worldwide. In the current study, a highly resistant inbred line Y32 and a susceptible line Q11 were used to produce segregating populations for both genetic analysis and QTL mapping. The broad-sense heritability ( H) for GLS resistance was estimated to be as high as 0.85, indicating that genetic factors played key roles in phenotypic variation. In initial QTL analysis, four QTL, located on chromosomes 1, 2, 5, and 8, were detected to confer GLS resistance. Each QTL could explain 2.53-23.90 % of the total phenotypic variation, predominantly due to additive genetic effects. Two major QTL, qRgls1 and qRgls2 on chromosomes 8 and 5, were consistently detected across different locations and replicates. Compared to the previous results, qRgls2 is located in a 'hotspot' for GLS resistance; while, qRgls1 does not overlap with any other known resistance QTL. Furthermore, the major QTL- qRgls1 was fine-mapped into an interval of 1.4 Mb, flanked by the markers GZ204 and IDP5. The QTL- qRgls1 could enhance the resistance percentages by 19.70-61.28 %, suggesting its usefulness to improve maize resistance to GLS. [ABSTRACT FROM AUTHOR]

Abstract: Gray leaf spot is one of the most important yield-limiting diseases of maize (Zea mays L.) and it is more severe in reduced tillage cropping where over-seasoning soilborne inoculum from infected crop debris provides primary inoculum for infection of the newly planted maize. The objective of this study was to investigate the effects of intercropped beans on movement of soil surface inoculum and its overall impact on gray leaf spot severity and yield of maize. Conventional tillage with minimum soil surface inoculum was included for comparison. Trials were conducted in two cropping seasons using resistant (‘UH6303’), moderately resistant (‘Staha’) and susceptible (‘Pannar’) maize varieties. Pooled data for susceptible maize during two growing seasons indicated that the area under disease progress curve (AUDPC) in the inter-cropping treatments was reduced by 12%, 15% and 23% in no-till, minimum, and conventional tillage treatments, respectively, compared to non-intercropping (P ≤ 0.05). The rate of disease increase (r) and the number of spores trapped during the season had similar trends. A moderately resistant cultivar displayed results similar to the susceptible cultivar, whereas treatment effects on resistant genotype were not significant. Yield was 21% higher in the intercropped compared to non-intercropped maize. Spore counts of Cercospora zeae-maydis trapped in the inter-cropping treatment were lower than in non-intercropped maize (P ≤ 0.05). It is concluded that the bean canopy in maize/bean intercrops created a barrier to movement of soilborne spores into the maize canopy, thus minimizing the number of leaves infected by wind-borne, and rain splash. The concomitant use of multiple management options (conventional tillage + inter-cropping + resistant variety) provided superior reduction of gray leaf spot severity and increased yield of maize. [Copyright &y& Elsevier]

The main goal of this study was to assess the nature and magnitude of gene effects for resistance to Cercospora leaf spot. A randomized block design with three replications was used. The data were obtained at the plant level by assessing the disease severity. The data were analyzed per experiment, using the average data per plot. A dominant-additive genetic model without epistasis was considered, with estimation of the components of means and variance. The genetic control of resistance to gray leaf spot is polygenic with predominance of the additive effects. Dominance was observed in a few small-effect loci and high heritability values. [ABSTRACT FROM AUTHOR]

Grey leaf spot is an important maize foliar disease caused by the fungal pathogens Cercospora zeae-maydis and Cercospora zeina. Although methods exist to detect these Cercospora species in maize, current techniques do not allow quantification of the fungi in planta. We developed a real-time SYBR® Green PCR assay for quantification of grey leaf spot disease in maize based on the amplification of a fragment of a cytochrome P450 reductase ( cpr1) gene. In planta fungal DNA content was normalised to a maize glutathione S-transferase III gene ( gst3) to yield values of ng Cercospora DNA/mg maize DNA. The assay was specific to the two Cercospora spp., and we observed no amplification of the cpr1 fragment in non-target maize leaf pathogens or saprophytes. The assay was employed to quantify C. zeina in glasshouse inoculated maize plants and grey leaf spot infected field plants of resistant and susceptible maize lines. In both instances, C. zeina DNA content correlated with symptomatic leaf lesion area, and the susceptible maize line contained significantly more C. zeina DNA than the resistant line. Sequence differences between the C. zeina and C. zeae-maydis cpr1 amplicons enabled us to perform melt curve analyses to identify the Cercospora species causing grey leaf spot at a particular location. This assay has application in the early detection and quantification of Cercospora spp., both of which are important tools in grey leaf spot disease management and maize breeding programmes. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess the aggressiveness and adaptation of Cercospora zeae-maydis the causal of grey leaf spot of maize in low-, mid- and high-altitude maize agro-ecologies. Field and laboratory studies were carried out to assess components of resistance, pathogen aggressiveness, sporulation, culture variations and morphological features of C. zeae-maydis isolates. Pathogen aggressiveness and morphological features differed among 30 isolates of C. zeae-maydis collected at different altitudes (p ≤ 0.05). Conidiophores per stroma between isolates ranged from 3.3 to 9.2 μ, conidiophore length 22.4–93.2 μ and colony growth rate ranged from 1.2 to 3.9 mm−1. High-altitude isolates grew 0.25 mm per day faster (9.3%), formed 1.1 cm longer lesions (25.9%), produced 1.1 × 104 more spores per cm2 of the lesion (13.6%) and formed symptoms 1 day earlier than low-altitude isolates. Prevalence of high numbers of aggressive isolates in low-altitude agro-ecologies indicates increased adaptation of C. zeae-maydis to warmer conditions. [ABSTRACT FROM PUBLISHER]

The molecular marker technology has been used on mapping of quantitative trait loci (QTLs) associated with plant resistance. The objectives of this research were to estimate genetic parameters and to map genomic regions involved in the resistance to gray leaf spot in maize. Ninety F3 families from the BS03 (susceptible) and BS04 (resistant) cross were used. Field trials were performed using a 10 × 10 square lattice design with three replications. Data from 62 SSR markers were used for linkage analysis. The locations of the QTLs on the linkage groups were determined by composite interval mapping method and the phenotypic variance explained by each marker was determined by regression analysis. Several QTLs associated to disease resistance were identified in the population BS03 × BS04. Some QTLs showed significant effects over the different environments studied. The existence of significant QTLs in common among different environments indicates these genomic regions as possible new tools for marker-assisted selection in maize breeding programs. [ABSTRACT FROM AUTHOR]

Gray leaf spot, caused by the fungus Cercospora zeae-maydis, is the most destructive foliar disease of maize in the United States. However, little is known about the biochemical and molecular events of pathogenesis. C. zeae-maydis produces cercosporin, a phytotoxin shown to be a virulence factor in diseases caused by other Cercospora species. To identify genes involved in cercosporin biosynthesis and ultimately determine the role of cercosporin in disease development, we constructed a cDNA subtraction library of C. zeae-maydis by suppression subtractive hybridization. Poly (A)+ RNA isolated from cultures grown in a cercosporin-suppressing medium was subtracted from poly (A)+ RNA isolated from cultures grown in a cercosporin-inducing medium, resulting in transcripts that are specific to the cercosporin-producing culture. Analyses of 768 sequences in this cDNA subtraction library revealed 197 cDNAs with high similarity to genes in the GenBank and Saccharomyces Genome Database, and these genes were grouped into nine categories based on predicted functions of the encoded proteins. Northern analysis of seven selected clones with predicted functions in fatty acid metabolism (fatty acid synthase, oleate Δ-12 desaturase, and linoleate diol synthase) and secondary metabolism [cytochrome P450 oxidoreductase, cytochrome P450 monooxygenase, dihydrogeodin (phenol) oxidase, and coproporphyrinogen oxidase] indicated that those genes were expressed in cercosporin-inducing conditions. Analysis of expression kinetics confirmed that those genes are expressed concomitantly with cercosporin accumulation. Published by Elsevier Science Ltd. [Copyright &y& Elsevier]

Grey leaf spot of maize, (Zea maydis L.) (Cercospora zeae-maydis) Tehon and Daniels, is one of the most destructive leaf diseases of maize. The distribution and severity of grey leaf spot has increased over the past 10 to 15 years. The United States and South Africa are main areas where research on the disease has been concentrated. The research results have provided valuable and significant insight into pathogen epidemiology and allowed an integrated management system to be developed. However, management options are a result of the agricultural system under which maize is produced. The pathogen survives only on maize, so crop rotation and stubble management are major factors in disease management, but resistant hybrids offer the best option for economic control. Many other factors, such as soil fertility, plant density, irrigation and chemical control, can significantly influence a grey leaf spot epidemic, although a single management practice will not control the pathogen effectively. [ABSTRACT FROM AUTHOR]