Genome-wide association analysis of ear rot resistance caused by Fusarium verticillioides in maize.

The identification of causal regions associated with resistance to Fusarium verticillioides can be useful to understand resistance mechanisms and further be used in breeding programs. In this study, a genome-wide association study (GWAS) was conducted to identify candidate markers associated with resistance to the ear rot caused by the fungus F. verticillioides. A total of 242 maize inbred lines were genotyped with 23,153 DArT-seq markers. A total of 12 DArTs were associated with ear rot resistance. Some DArTs were localized close to genes with functions directly related to ear rot resistance, such as a gene responsible for the innate immune response that belongs to the class of NBS-LRR receptors. Some markers were also found to be closely associated with genes that synthesize transcription factors (nactf11 and nactf61), genes responsible for the oxidation-reduction process and peroxidase activity. These results are encouraging since some candidate markers can present functional relationship with ear rot resistance in maize.

Genetic control and combining ability of agronomic attributes and northern leaf blight-related attributes in popcorn.

The present study was conducted to investigate the genetic control and to estimate the general and specific combining abilities of popcorn for agronomic attributes and attributes related to resistance to northern leaf blight (NLB). The 56 hybrids (F1 and reciprocals), together with the eight parent lines and six controls, were evaluated in two harvests, in a randomized-block design with four replications. Dominance components were more expressive than the additive components for grain yield and expression of resistance, and hybridization was the most suitable option for obtaining resistant and productive genotypes. For grain yield, popping expansion, and resistance to NLB, there was no significance for reciprocal effects, which indicates that the direction in which the cross is performed does not interfere with the hybrid's performance. Then, the superior hybrids recommended for more profitable growth were P8 x L61, L61 x L76, and L61 x L77.

Selection of maize inbred lines and gene expression for resistance to ear rot.

In recent years, there has been a large incidence of fungi causing "ear rot" in maize in Brazil, the main fungus being Fusarium verticillioides. The most efficient and competitive alternative for control of this disease consists of using maize hybrids resistant to this pathogen. Thus, the aims of this study were to analyze the genetic variability of maize inbred lines in regard to resistance to ear rot to observe if there is a maternal effect to resistance to ear rot, to study genetic control of the traits evaluated in hybrids originating from inbred lines of the maize breeding program at the Agriculture Department of Universidade Federal de Lavras (Lavras, MG, Brazil), and characterize the gene expression pattern related to the plant defense mechanism against F. verticillioides. High genetic availability was observed for resistance to this disease among the inbred lines evaluated. Considering combined diallel analysis, it was observed that the mean square of general combining ability (GCA) was not significant for the characteristic under study. However, specific combining ability (SCA) was significant, which indicates the predominance of non-additive effects involved in control of the characteristic for the population evaluated. A maternal effect was not observed for the characteristic of ear rot resistance in this study. Inbred lines 22, 58, and 91 showed potential for use in breeding programs aiming at resistance to F. verticillioides. Only two genes, LOX8 and Hsp82, had a satisfactory result that was able to be related to a plant defense mechanism when there is ear rot infection, though expression of these genes was observed in only one susceptible genotype. Thus, the genes LOX8 and Hsp82 are potential molecular markers for selection of maize inbred lines resistant to F. verticillioides.

Genetic variability among elite popcorn lines based on molecular and morphoagronomic characteristics.

Knowledge of genetic diversity among genotypes and relationships among elite lines is of great importance for the development of breeding programs. Therefore, the objective of this study was to evaluate genetic variability based on the morphoagronomic and molecular characterization of 18 elite popcorn (Zea mays var. everta) lines to be used by Universidade Estadual de Maringá breeding programs. We used 31 microsatellite primers (widely distributed in the genome), and 16 morphological descriptors (including the resistance to maize white spot, common rust, polysora rust of maize, cercospora and leaf blights). The molecular data revealed variability among the lines, which were divided into four groups that were partially concordant with unweighted pair group method with arithmetic mean (UPMGA) and Bayesian clusters. The lines G3, G4, G11, and G13 exhibited favorable morphological characters and low disease incidence rates. The four groups were confirmed using the Gower distance in the UPGMA cluster; however, there was no association with the dissimilarity patterns obtained using the molecular data. The absence of a correlation suggests that both characterizations (morphoagronomic and molecular) are important for discriminating among elite popcorn lines.

Corn-based vaccines: current status and prospects.

MAIN CONCLUSION: Corn is an attractive host for vaccine production and oral delivery. The present review provides the current outlook and perspectives for this field. Among seed-crops, corn represents a key source of biomass for food, fuel production, and other applications. Since the beginning of the development of plant-based vaccines, corn was explored for the production and delivery of vaccines. About a dozen of pathogens have been studied under this technology with distinct degrees of development. A vaccine prototype against enterotoxigenic Escherichia coli was evaluated in a phase I clinical trial and several candidates targeting bacterial and viral diseases are under preclinical evaluation. The present review provides an updated outlook on this topic highlighting the employed expression strategies; perspectives for the field are also provided.

Genomic selection to resistance to Stenocarpella maydis in maize lines using DArTseq markers.

BACKGROUND: The identification of lines resistant to ear diseases is of great importance in maize breeding because such diseases directly interfere with kernel quality and yield. Among these diseases, ear rot disease is widely relevant due to significant decrease in grain yield. Ear rot may be caused by the fungus Stenocarpella maydi; however, little information about genetic resistance to this pathogen is available in maize, mainly related to candidate genes in genome. In order to exploit this genome information we used 23.154 Dart-seq markers in 238 lines and apply genome-wide selection to select resistance genotypes. We divide the lines into clusters to identify groups related to resistance to Stenocarpella maydi and use Bayesian stochastic search variable approach and rr-BLUP methods to comparate their selection results. RESULTS: Through a principal component analysis (PCA) and hierarchical clustering, it was observed that the three main genetic groups (Stiff Stalk Synthetic, Non-Stiff Stalk Synthetic and Tropical) were clustered in a consistent manner, and information on the resistance sources could be obtained according to the line of origin where populations derived from genetic subgroup Suwan presenting higher levels of resistance. The ridge regression best linear unbiased prediction (rr-BLUP) and Bayesian stochastic search variable (BSSV) models presented equivalent abilities regarding predictive processes. CONCLUSION: Our work showed that is possible to select maize lines presenting a high resistance to Stenocarpella maydis. This claim is based on the acceptable level of predictive accuracy obtained by Genome-wide Selection (GWS) using different models. Furthermore, the lines related to background Suwan present a higher level of resistance than lines related to other groups.

[Prevalence of sensitization to allergens in school children with asthma residents from Guadalajara metropolitan area]. / Prevalencia de sensibilización a alergenos en niños escolares con asma que viven en la zona metropolitana de Guadalajara.

BACKGROUND: Allergic sensitization is dependent on the geographical and climatic conditions in each region; therefore, identify agents most commonly sensitized children with asthma is important for planning prevention measures. OBJECTIVE: To determine the prevalence of the sensitization to allergens in children with asthma. MATERIAL AND METHOD: This cross-sectional and prolective study includes children from ages 6 to 14, who have asthma, attended for the first time in an allergy service. The patients were recruited consecutively between the months of January 1st 2014 to December 31st 2014. The frequency of the allergen sensitization was estimated. RESULTS: This study included 186 children, the median age was 7 years olds, the male group was 104/186 (55.9%) The median of the positive results was 5 and monosensitized were 47/186 (2.2%). The most common category of allergens was the indoor (90.3%), then trees (71.0%), and finally the fungi (9.7%). Individually, the house dust mites were more common in between the interior allergens, followed by the epithelial; in the tree pollen were oaks (31.7%) and ashes (28.0%), in weeds was mugwort (21.5%), in grasses was Zea mays (18.3%) and in the fungi was Cladosporium spp. (6.5%). CONCLUSION: The high prevalence of the sensitization to house dust mites and epithelial in children with asthma, stimulates to implement methods of environmental control for contributing a better control of the disease.

Antecedentes: la prevalencia de rinosinusitis crónica en pacientes adultos con inmunodeficiencia común variable (IDCV) es de 52%. Los pacientes con esta enfermedad tienen mayor frecuencia de rinosinusitis crónica, enfermedad inflamatoria que afecta a la mucosa de uno o más senos paranasales y la cavidad nasal. Objetivo: identificar los microorganismos de secreción del meato medio obtenida por endoscopia asociados con rinosinusitis crónica en pacientes adultos con inmunodeficiencia común variable (IDCV). Material y método: estudio descriptivo, transversal, que incluyó a pacientes adultos con inmunodeficiencia común variable, de quienes se obtuvo una muestra vía endoscópica de secreción del meato medio de ambas fosas nasales, que se envió a cultivo para bacterias aerobias, anaerobias y hongos. Se obtuvo consentimiento informado de todos los pacientes. Resultados: se estudiaron 29 pacientes: 18 mujeres y 11 hombres, con edad promedio de 40±13 años. Los resultados obtenidos fueron: 2 muestras de pacientes no tuvieron desarrollo microbiano, 24 tuvieron desarrollo de bacterias aerobias, en 3 casos hubo crecimiento fúngico sin desarrollo de bacterias anaerobias. Conclusiones: nuestros resultados muestran que los microorganismos asociados con rinosinusitis crónica en pacientes adultos con inmunodeficiencia común variable más comunes son: Moraxella catarrhalis, Staphylococcus, Sphingomonas paucimobilis y Citrobacter koseri; los agentes micóticos asociados fueron: Candida albicans y Aspergillus fumigatus.

Mapping of HtNB, a gene conferring non-lesion resistance before heading to Exserohilum turcicum (Pass.), in a maize inbred line derived from the Indonesian variety Bramadi.

The gene HtNB confers non-lesion resistance to the fungal pathogen Exserohilum turcicum in maize. To map this gene, we developed two F2 populations, P111 (resistant line) x HuangZao 4 (susceptible line) and P111 x B73 (susceptible). HtNB was located on chromosome 8.07 bin, flanked by MAC216826-4 and umc2218 at distances of 3.3 and 3.4 cM, respectively. HtNB appears to be a new gene responsible for resistance to northern corn leaf blight. Functions of the genes in the region between umc1384 and umc2218 were predicted. In addition, several genes were found to be related to disease resistance, such as the genes encoding Ser/Thr protein kinase and protein-like leaf senescence.

Induction of a protective immune response to rabies virus in sheep after oral immunization with transgenic maize, expressing the rabies virus glycoprotein.

The introduction of exogenous genes into plants permits the development of a new generation of biological products, i.e., edible vaccines. Cereals, especially maize, have been the systems of choice for the expression of antigenic proteins because the proteins can be expressed at high levels in the kernel and stored for prolonged periods without excessive deterioration. The utilization of plant-derived antigens for oral delivery provides an alternative strategy for the control of pathogens in animals compared to the current vaccine administration methods, such as injection. However, there is some doubt about the efficacy of these types of vaccines in polygastric animals due to the features of their digestive system. Here, we report the efficacy of an edible vaccine against rabies evaluated in sheep. Kernels containing different doses of G protein (0.5, 1, 1.5 and 2mg) were given in a single dose by the oral route. Cumulative survival was better in groups that received 2mg of G protein and for the positive control (inactivated rabies vaccine); this observation was supported by the presence of neutralizing antibodies. Animals in the control group died after challenge. The degree of protection achieved for 2mg of G protein was comparable to that conferred by a commercial vaccine. In conclusion, this is the first study in which an orally administered edible vaccine showed efficacy in a polygastric model.

Fumonisins: probable role as effectors in the complex interaction of susceptible and resistant maize hybrids and Fusarium verticillioides.

Fusarium verticillioides is best known for its worldwide occurrence on maize resulting in highly variable disease symptoms, ranging from asymptomatic to severe rotting and wilting and fumonisin production. The aim of this study was to investigate the influence of hybrid genotypes in the early stages of F. verticillioides infection, and the role of fumonisins as effectors in the outcome of this complex interaction. Disease symptoms, growth parameters, root morphology, and fungal colonization were evaluated at 7, 14, and 21 days after planting in seedlings from maize seeds of resistant (RH) and susceptible (SH) hybrids inoculated with F. verticillioides or watered with solutions of fumonisins. F. verticillioides induced growth enhancement or retardation depending on the plant genetic background and the fungal colonization rate, while fumonisins caused severe reduction in biomass and fitness. Seedlings watered with high fumonisin concentrations displayed lesions similar to those seen in F. verticillioides maize seedling disease, and also elicited inhibitory effects on root growth and morphology and on functional properties. In summary, these data strongly suggest a dual role for fumonisins in the F. verticillioides-maize interaction, acting as pathogenic factors at high concentrations, or triggering the plant detoxification mechanisms at low levels.

Fumonisin B1, a toxin produced by Fusarium verticillioides, modulates maize ß-1,3-glucanase activities involved in defense response.

Fusarium verticillioides is an important pathogen in maize that causes various diseases affecting all stages of plant development worldwide. The fungal pathogen could be seed borne or survive in soil and penetrate the germinating seed. Most F. verticillioides strains produce fumonisins, which are of concern because of their toxicity to animals and possibly humans, and because they enhance virulence against seedlings of some maize genotypes. In this work, we studied the action of fumonisin B1 (FB1) on the activity of maize ß-1,3-glucanases involved in plant defense response. In maize embryos, FB1 induced an acidic isoform while suppressing the activity of two basic isoforms. This acidic isoform was induced also with 2,6-dichloroisonicotinic acid, an analog of salicylic acid. Repression of the basic isoforms suggested a direct interaction of the enzymes with the mycotoxin as in vitro experiments showed that pure FB1 inhibited the basic ß-1,3-glucanases with an IC(50) of 53 µM. When germinating maize embryos were inoculated with F. verticillioides the same dual effect on ß-1,3-glucanase activities that we observed with the pure toxin was reproduced. Similar levels of FB1 were recovered at 24 h germination in maize tissue when they were treated with pure FB1 or inoculated with an FB1-producing strain. These results suggest that ß-1,3-glucanases are a relevant physiological target and their modulation by FB1 might contribute to F. verticillioides colonization.

Geographic variation in adaptation at the molecular level: a case study of plant immunity genes.

Natural selection imposed by interacting species frequently varies among geographic locations and can lead to local adaptation, where alternative phenotypes are found in different populations. Little is known, however, about whether geographically variable selection acting on traits that mediate species interactions is consistent or strong enough to influence patterns of nucleotide variation at individual loci. To investigate this question, we examined patterns of nucleotide diversity and population structure at 16 plant innate immunity genes, with putative functions in defending plants against pathogens or herbivores, from six populations of teosinte (Zea mays ssp. parviglumis). Specifically, we tested whether patterns of population structure and within-population diversity at immunity genes differed from patterns found at nonimmunity (reference) loci and from neutral expectations derived from coalescent simulations of structured populations. For the majority of genes, we detected no strong evidence of geographically variable selection. However, in the wound-induced serine protease inhibitor (wip1), which inhibits the hydrolysis of dietary proteins in insect herbivores, one population showed unusually high levels of genetic differentiation, very low levels of nucleotide polymorphism, and was fixed for a novel replacement substitution in the active site of the protein. Taken together, these data suggest that wip1 experienced a recent selective sweep in one geographic region; this pattern may reflect local adaptation or an ongoing species-wide sweep. Overall, our results indicate that a signature of local adaptation at the molecular level may be uncommon-particularly for traits that are under complex genetic control.

Maize (Zea mays): allergen or toleragen? Participation of the cereal in allergic disease and positivity incidence in cutaneous tests.

BACKGROUND: The maize (zea mays) is considered one of the fundamental nutrients in the diet of the Mexican population. It can cause allergic reactions, according to reports from countries other than Mexico. OBJECTIVE: To know the participation of maize in the etiology of allergic disease and the incidence of positivity to its antigens by cutaneous tests, in Mexican patients. METHODS: Six hundred sixty-one patients were studied. There were obtained a complete clinical history and samples for laboratory tests, as well as the results of cutaneous tests. RESULTS: Of 661 patients, 56 (8.5%) manifested allergic symptoms attributable to maize, which correlated (p < 0.0001) with a positive cutaneous response to its antigens. Fifty (88%) of them worked with maize and had a significant relative risk value (RR=102). The remaining six patients did not work with maize, four of them were included in the group who had a positive response for both allergens (n = 25), and two in that one with positive response for only one of these allergens (n = 100). CONCLUSIONS: The low frequency (8.5%) to which the allergic disease was attributed to maize, and the strong association (88%) with workers of maize induce us to consider the influence of some differences concerning to the cereal, such as physical characteristics, years and frequency to contact with, and specially to its entrance route. In fact, it plays an important role in the development of either toleragenic or immunogenic response to an antigen.

Functional characterization of a maize ribosomal S6 protein kinase (ZmS6K), a plant ortholog of metazoan p70(S6K).

Ribosomal protein S6 (S6rp) is phosphorylated by the p70S6K enzyme in mammals, under mitogen/IGF regulation. This event has been correlated with an increase in 5'TOP mRNA translation. In this research, a maize S6 kinase (ZmS6K) was isolated from maize (Zea mays L.) embryonic axes by human p70S6K antibody immunoprecipitation. This enzyme, a 62 kDa peptide, proved to be specific for S6rp phosphorylation, as revealed by in vivo and in vitro kinase activity using either the 40S ribosomal subunit or the RSK synthetic peptide as the substrates. ZmS6K activation was achieved by phosphorylation on serine/threonine residues. Specific phospho-Threo recognition by the p70S6K antibody directed to target phospho-Threo residue 389 correlated with ZmS6K activation. The ZmS6K protein content remained almost steady during maize seed germination, whereas the ZmS6K activity increased during this process, consistent with Zm6SK phosphorylation. Addition of insulin to germinating maize axes proved to increase ZmS6K activity and the extent of S6rp phosphorylation. These events were blocked by rapamycin, an inhibitor of the insulin signal transduction pathway in mammals, at the TOR (target of rapamycin) enzyme level. We conclude that ZmS6K is a kinase, structurally and functionally ortholog of the mammalian p70S6K, responsible for in vivo S6rp phosphorylation in maize. Its activation is induced by insulin in a TOR-dependent manner by phosphorylation on conserved serine/threonine residues.