In the summers of 1989 and 1990, researchers in Va. and Md. began to observe lateseason reductions in com vigor in areas treated with nicosulfuron or primisulfuron for postemergence johnsongrass control. Symptoms observed included chlorosis, reddening of the leaves and shortening of the internodes. The nature and time of symptom expression were consistent with those caused by maize chlorotic dwarfvirus (MCDV) and maize dwarf mosaic virus (MDMV) infection of com. It was hypothesized that postemergence johnsongrass control increased the incidence and severity of MCDV and MDMV in virus-susceptible corn hybrids due to increased feeding by vectors of these viruses on treated corn. Field experiments were conducted in 1991 and 1992 to evaluate the effect of postemergence johnsongrass control with broad casted nicosulfuron, postemergence directed imazethapyr, mechanical control and no control on virus disease incidence and severity in a virus-susceptible ('Southern States 565') and a virus-tolerant ('Southern States 844) corn hybrid. Visual injury evaluations taken 10 weeks after treatment showed that the virus-susceptible com hybrid sustained significantly more injury, averaged across johnsongrass control methods, than did the virus-tolerant corn hybrid. Within the virus-susceptible com hybrid, where johnsongrass was controlled, regardless of method, significantly more injury was observed relative to the nontreated check. Further, averaged across johnsongrass control treatments, the virus-tolerant corn hybrid yielded significantly higher compared to the virus-susceptible com hybrid. Experiments conducted in 1993 and 1994 utilized cages as a means of preventing insect movement from the infected johnsongrass to the crop. Blackfaced leafhopper evaluations suggested that the cages significantly reduced leafhopper movement from the infected johnsongrass to the corn, however complete exclusion was not achieved. Results of corn tissue assays showed that MCDV and MDMV were being transmitted, however no treatment differences were detected. Two experiments were conducted in 1994 to analytically test the hypothesis and to determine the time course of MCDV and MDMV double infection of corn tissue. Johnsongrass control treatments evaluated included broadcast nicosulfuron and no treatment. Postemergence johnsongrass control increased MCDV and MDMV incidence 9 to 21 days after treatment. Further, significantly more double infections of MCDV and MDMV were observed 14 to 21 days after treatment in experimental units receiving the nicosulfuron application. / Ph. D.

学位プログラム名: 京都大学大学院思修館 / 京都大学 / 新制・課程博士 / 博士(総合学術) / 甲第25517号 / 総総博第39号 / 新制||総総||7(附属図書館) / 京都大学大学院総合生存学館総合生存学専攻 / (主査)准教授 趙 亮, 教授 長山 浩章, 教授 関山 健 / 学位規則第4条第1項該当 / Doctor of Philosophy / Kyoto University / DGAM

Insect damage in stored maize is one of the major post-harvest losses occurring in developing countries, especially in sub-Saharan Africa. To reduce economic losses, separation of infested grains from clean ones is critical and requires detection of infestation in stored grains. This study aimed at developing a rapid non-destructive detection system with three goals; - the first goal was to investigate the acoustic behavior of internally feeding S. zeamais (Coleoptera: Curculionidae) in maize. The pests were monitored for peak activity and signal amplitudes. The study was performed in the morning, afternoon and night times for three consecutive days with an ultrasonic probe attached to acoustic emission detector. The average number of peaks above threshold in the morning, afternoon and night was significantly different and were 60, 2 and 31 counts/s, respectively (P-value < 0.01). The average maximum amplitude was also different: 2.5, 1 and 1.8V for morning, afternoon and night sessions, respectively. The signal frequencies ranged between 1 and 15 kHz with a peak around 7 kHz. The second goal was to design and develop an inexpensive acoustic device for the detection of S. zeamais in the stored maize. This device included a microphone, signal conditioning circuit and a microcontroller. The third goal was to test the prototype in both clean and infested maize. The device could be manufactured for $55 or less. The device has a noise level below 0.2V in clean maize, infestation amplitude up to 1V and about 93.3% correct detection performance in infected maize. / Master of Science

The PROTEOLYSIS 6 (PRT6) branch of the N-end rule pathway is a well-characterized negative regulator of flooding and low oxygen tolerance in plants. This study investigated the role of this pathway in adaptation to salinity stress in Arabidopsis and maize via physiological and molecular characterization of Arabidopsis prt6-1 and maize prt6 MU insertion mutants, respectively. Our study demonstrated that the loss of function mutation of prt6 in Arabidopsis activated hormonal and transcriptional responses associated with adaptation to salinity stress, enhancing high salt tolerance at seed germination, seedling, and adult plant stages. Our data also indicated that salinity tolerance conferred by the prt6 mutation is attributed to increased mRNA abundance of key transcriptional factors in ABA-dependent (AREB/ABFs) and independent (DREBs) pathways, together with the dominant expression of downstream dehydrins. Furthermore, this study revealed that the prt6 mutation enhances ethylene and brassinosteroid responses, resulting in restricted Na+ accumulation in roots and shoots as well as increased expression of dehydrin genes such as RD29A and RD29B. Maize prt6 mutant plants, contrary to our observation in Arabidopsis, showed lower seed germination, primary root elongation, and shoot biomass growth along with increased malondialdehyde (MDA) accumulation under high salt. Moreover, maize prt6 mutants exhibited reduced grain yield and yield-related components under high salt. These results indicate that PRT6 functions as a negative regulator for salinity tolerance in Arabidopsis, whereas this gene plays a positive role in salinity tolerance in maize. In wheat, we compared two genotypes with contrasting nitrogen-use-efficiency (NUE), VA08MAS-369 and VA07W-415, to dissect physiological and molecular mechanisms underlying NUE regulation. Our agronomic data revealed that line 369 maintained yield and yield-related parameters and exhibited greater NUE indexes relative to line 415 under N deficient conditions. Furthermore, our analyses suggested that the significantly higher nitrogen use efficiency (NUE) in line 369 could be attributed to the greater N uptake efficiency in this genotype. In fact, line 369 was able to maintain the development of root systems under N limitation. Consistently, genes encoding high-affinity nitrate transporters such as TaNRT2.1 and TaNRT2.2 were expressed more abundantly in the roots of line 369 than line 415 at limited N. Overall, the results of this study characterized physiological and molecular phenotypes associated with high N uptake efficiency in line 369. This is useful information for the development of new wheat accessions with improved NUE. / Doctor of Philosophy / In coastal areas, sea-level rise increases the chances of saltwater intrusion into cultivable lands, making a hostile environment for crop growth and production by imposing flooding and salinity stresses simultaneously. Identification of central regulators that regulate the adaptation to both flooding and salinity is a critical step for the development of new crop genotypes with enhanced tolerance to these stresses. Previous studies have characterized the function of the PROTEOLYSIS 6 (PRT6) gene in adaptation to flooding stress in plants. This study assessed whether this gene is involved in adaptation to salinity stress in Arabidopsis and maize by evaluating the growth and survival of their respective prt6 mutants under high salt. Consistent with the flooding tolerance data, our study showed that the PRT6 gene also functions as a negative regulator of salinity stress tolerance in Arabidopsis. The prt6 mutation in Arabidopsis activated the key transcriptional and hormone response pathways associated with adaptation to both salinity/osmotic stress and sodium toxicity, expressed as enhanced tolerance to excess salt at seed germination, seedling, and adult plant stages. In maize, disruption of the PRT6 gene decreased seed germination, primary root elongation, and shoot biomass growth under high salt, which is opposite to our observations in Arabidopsis. Additionally, the maize mutant plants encountered more oxidative stress, as demonstrated by the higher accumulation of malondialdehyde (MDA) under high salt. Moreover, maize prt6 mutants exhibited reduced grain yield under high salt. Overall, these results indicate that disruption of the PRT6 gene confers increased tolerance to high salt in Arabidopsis, whereas it conversely reduced salinity tolerance in maize. In wheat, we compared two genotypes with distinct nitrogen use efficiency (NUE), VA08MAS-369 and VA07W-415, to determine critical traits involved in NUE regulation. Our study showed that grain yield and yield-related parameters were significantly higher in line 369 than line 415 under low N. Moreover, high NUE in line 369 was attributed to efficient N uptake in this genotype under limited N. Our root architecture analysis demonstrated that line 369 was able to maintain root depth, volume, and thickness even under N limitation. Consistently, line 369 highly induced expression of genes associated with nitrogen transport at low N. Altogether, this study identified key traits involved in high NUE in wheat, facilitating the breeding of new wheat genotypes with enhanced NUE.

Mid-Atlantic crop producers are increasingly transitioning to soil conservation methods that include reducing or eliminating tillage and planting high residue cover crops. These practices are associated with an increase in moderate to severe damage to field crops by slugs. Conserving, and even enhancing, natural enemy populations is a desirable way to manage slug infestations because remedial control measures are limited. To better understand how cover crop usage and tillage practices affect slug and natural enemy populations, 43 Virginia fields with different combinations of tillage practices and cover crop use were intensively sampled in 2018 and 2019. Fields were sampled over a six-week period during the early planting season when slugs are most problematic. Shingle traps and pitfall traps were used to sample slugs and natural enemies, respectively. To determine how multiple farming practices, soil composition, landscape features, and field history affect slug feeding injury to seedling plants, over 1,000 hectares of commercial production fields in the Shenandoah Region of Virginia were scouted for slug feeding injury to seedling plants. Corresponding crop producers were then surveyed on management methods. Our goal was to determine if slug feeding risk could be predicted by a single factor and or a combination of factors. Behavioral assays were performed with a common slug pest, Deroceras laeve, to determine if this species prefers feeding on maize, soybean, daikon radish, crimson clover, rye, or hairy vetch leaf tissue. Our sampling study found that cover crop use and conservation tillage type did not affect slug presence and damage, but that these factors affected various slug predators in different ways. We also observed that fields with more Phalangiidae and total predators overall had fewer slugs. Average slug feeding injury in both years was low and no factor or interaction of factors in our broader survey affected slug feeding injury ratings in fields. Behavioral assays indicated that slugs fed more on soybean tissue compared with maize, slugs consumed less maize when it was offered with hairy vetch or crimson clover, and slugs consumed less soybean when it was offered with hairy vetch or daikon radish. / Master of Science in Life Sciences / Invasive slug species the gray field slug, Deroceras reticulatum (Muller), and the marsh slug, Deroceras laeve, are major pests of maize and soybean grown in Virginia no-till systems. Slug feeding causes injury to young plants that, when severe, can reduce crop yield and necessitate replanting a field. Chemical control options are limited, and farmers may not be willing to use tillage as a control measure. Conserving arthropod slug predators may suppress pest populations below economic levels. Research is needed to understand how farming methods such as tillage type (e.g., no-till, strip tillage, vertical tillage) and cover crop use affect slugs and their predators. Our study investigated 1) how tillage type and cover crop use affected slug and slug predators, 2) if certain farming practices and field characteristics can be used to predict slug injury, and 3) if slugs preferred feeding on commonly-used cover crop species when offered with maize or soybean seedlings. Commercial production fields with different combinations of no tillage or reduced tillage, and planted with or without cover crops, were sampled to evaluate how these farming practices affect slugs and slug predators. Shingle traps and frames were used before planting and during early plant growth stages to collect and identify slug species; pitfall traps were used throughout the growing season to collect and identify slug predator species. To determine if slug feeding risk could be predicted, a survey of commercial production fields in the Shenandoah area was conducted and used to identify factors, if any, that influence slug feeding. Laboratory assays were used to determine feeding preference by offering slugs opportunity to feed on leaf tissue from a maize or soybean seedling or a mature cover crop species. We found that tillage type and use of cover crops did not affect the abundance of slugs, but that they did influence predator populations. The highest number of total predators were found in fields with reduced tillage, cover crops, and no insecticide use prior to crop emergence. Harvestmen were potentially the most impactful slug predator in the region. Field surveys suggested that no tested factor or interaction of factors affected slug injury to plants in commercial fields. Finally, we observed that slugs fed differently on soybean and maize tissue depending on cover crop species present.

Gray leaf spot, caused by Cercospora zeae-maydis, can be a yield-limiting factor in maize where continuous minimum tillage practices are followed. Commercial corn hybrids were evaluated for response to gray leaf spot for seven years at two Virginia locations (Shenandoah and Wythe Counties) and one year at a third location in Virginia (Montgomery County). Yield losses, when comparing resistant to susceptible classes, were approximately 2,000 kg ha⁻¹ at Wythe County in 1982, 750 kg ha⁻¹ at Shenandoah County in 1984, and 2,150 kg ha⁻¹ at Montgomery County in 1988. The inheritance of reaction to gray leaf spot was studied using a 14 inbred diallel in Montgomery and Wythe Counties, Virginia in 1987 and 1988 planted in randomized complete block designs. Resistance was found to be highly heritable and controlled by additive gene action. Inbreds producing high yielding, resistant, and agronomically superior hybrids were identified (B68, NC250, Pa875, Va14, Va17, and Va85); and several hybrids between these lines had high levels of resistance, high yield, and good general agronomic characters (B68 x KB1250, KB1250 x Pa875, and NC250 x Pa875). Currently available inbreds could be used to produce hybrids with higher levels of resistance than hybrids currently available to growers, and these could serve as a basis for gray leaf spot breeding programs. Lesion size measurements were not correlated with disease scores. Late-season photosynthesis rates were associated positively with resistance. The hybrids of some inbreds were found to produce high levels of pigment (believed to be anthocyanins) around the gray leaf spot lesions. These did not limit the size of the individual lesion later in the season. Some pigment(s)-producing genotypes were found to be resistant when the pigment character was expressed. This type of resistance must prevent or inhibit infection of the leaf but not later colonization, once established. Maize dwarf mosaic virus (MDMV) also limits maize production in some areas where johnsongrass (Sorghum halepense L.) is a problem. Resistance to MDMV was found to be mainly additive and highly heritable. However, a strong specific combining ability component was found, indicating that the background of the material receiving resistance genes may have a strong effect on the expression of resistance. Inbreds capable of producing high-yielding, resistant, and agronomically acceptable hybrids are available (B68, NC250, A632, Pa875, Va17, and Va85); and several hybrids between these lines have high levels of resistance, high yield, and good general agronomic characters (B68 x KB1250, KB1250 x Pa875, and NC250 x Pa875). / Ph. D.

Thesis (MScAgric (Soil Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Acidic soils are a major limitation to agriculture worldwide. The Highveld in South Africa has many acidic soils and several coal burning power stations. These coal burning power stations generate alkaline fly ash as a waste material and it can thus serve as an ameliorant to the surrounding acidic soils. A two year field trial was undertaken to compare fly ash and other calcium ameliorants to alleviate the effects of subsoil acidity on maize root development. The field trail was established on Beestepan Farm in Middelburg, Mpumalanga. It consisted of 24 treatments, each done in triplicate, rendering a total of 72 plots. The materials used were unweathered fly ash (CCE 10%), calcitic lime (CCE 77%) and Calmasil (a calcium silicate slag, CCE 99%). Calmasil and lime were applied at rates of 0-, 1-, 2-, and 4t/ha, while fly ash was applied at 0-, 7-, 14- and 28t/ha. These treatments were applied to an acidic sandy loam soils in the presence or absence of 4t/ha gypsum. Beans were harvested after the first season following the application of amendments and maize was harvested in the second season. Yield, root length, leaf and soil analysis was undertaken to evaluate the effectiveness of the different liming materials. The effect of the treatments on fertility indicators such as pH, exchangeable acidity, Ca and Mg was investigated. Results indicated that all liming materials increased topsoil pH, soil nutrient and base status and crop yield in both seasons. Calmasil was the superior liming material in all respects. Fly ash increased pH minimally but reduced exchangeable acidity by 12% and 24% in the first and second seasons, respectively. Fly ash increased topsoil Ca levels from 74 to 102mg/kg and subsoil Ca from 61 to 114mg/kg. Topsoil Mg levels were increased from 7.3 to 16mg/kg and subsoil Mg was increased from 9.4 to 13mg/kg. The consequence of these increased nutrients was the subsequent increased foliar uptake of Ca and Mg. The substantial increase in bean yield from 958 to 1724kg/ha and maize yield from 5569 to 7553kg/ha following ash application compared well with results obtained from lime and Calmasil application. This may partly be due to the presence of additional plant nutrients such as P and K in the fly ash. Dissolution behaviour of fly ash indicates that upon exposure to acidity the release of micronutrients like B, Co, Cu, Fe, Mo, Mn and Zn occurs, and preliminary data shows that there is comparatively little concern regarding heavy metal accumulation in crops. The application of 4t/ha gypsum had no effect on pH and decreased subsoil acidity only minimally however, subsoil Ca status and acid saturation levels were considerably improved which would possibly account for the overall beneficial effect on maize yield, increasing by an average of 1071kg/ha. It was not possible to make any conclusions relating treatment application and maize root length. This field trial has confirmed that fly ash can be used as an efficient liming material and that it compares well with traditional liming materials. / AFRIKAANSE OPSOMMING: Suurgronde is ‘n groot beperking tot landbou wêreldwyd. Die Suid Afrikaanse Hoëveld het menigte suurgronde en verskeie steenkool-aangedrewe kragstasies. Hiedie kragstasies produseer alkaliese vliegas as ‘n afvalproduk. Hierdie vliegas kan dus dien as ‘n grondverbeteringsmiddel vir die aangrensende suurgronde. ‘n Tweejarige veldproef was onderneem om vliegas met ander kalsium-bevattende grondverbetereringsmiddels te vergelyk om die effek van ondergrondse suurheid op mielies op te hef. Hierdie veldproef was opgeset te Beestepan plaas in Middelburg, Mpumalanga. Dit het bestaan uit 24 behandelings wat drie keer herhaal was en lewer dus ‘n totaal van 72 persele. Die kalkmateriale wat gebruik was, is onverweerde vliegas (KKE 10%), kalsitiese kalk (KKE 77%) en Calmasil (‘n kalsium silikaat slak, KKE 99%). Calmasil en kalk was toegedien teen 0-, 1-, 2-, en 4t/ha, en vliegas teen 0-, 7-, 14- en 28t/ha. Hierdie behandelinge was toegedien tot ‘n suur leemsand met of sonder gips. Gips was toegedien teen 4t/ha. Een jaar nadat behandelinge toegedien was, is boontjies geoes en mieles was die daaropvolgende jaar geoes. Opbrengs, wortel lengte blaar- en grondontledings was uitgevoer om effektiwiteit te evalueer. Die effek van die behandelinge op indikatore van grondvrugbaarheid soos pH, uitruilbare suurheid, Ca en Mg was ondersoek. Resultate dui daarop dat alle kalkmateriale die grond se voedingstof- en basisstatus, bogrond pH asook gewasopbreng verhoog het. Calmasil was die beste kalkmateriaal in alle opsigte. Vliegas het die pH minimaal verhoog, terwyl dit die uitruilbare suurheid verminder het met 12% en 24% in die eerste en tweede jaar onderskeidelik. Vliegas het bogrond Ca vlakke vanaf 74 tot 102mg/kg vermeer, sowel as ondergrond Ca vanaf 61 tot 114mg/kg. Bogrond Mg was vermeer vanaf 7.3 tot 16mg/kg, asook ondergrond Mg vanaf 9.4 tot 13 mg/kg. Die gevolg van hierdie verhoogde voedingstowwe was die toename van Ca en Mg in die blare van die gewasse. Die beduidende toename in opbrengste van boontjies vanaf 958 tot 1724mg/kg en mielies vanaf 5569 tot 7553kg/ha na die toediening van vliegas vergelyk goed met die resultate van kalk en Calmasil. Dit is gedeeltelik toe te skryf aan die teenwoordigheid van addisionele plantvoedingstowwe soos P en K in vliegas. Oplossingstudies van vliegas dui op die teenwoordigheid van mikrovoedingstowwe soos B, Co, Cu, Fe, Mo, Mn en Zn. Aanvanklike data wys dat daar relatief min kommer oor swaarmetaal akkumulasie in gewasse is. Alhoewel 4t/ha gips geen effek op pH gehad het nie, en ondergondrondse suurheid minimaal verminder het, het ondergrondse Ca en gevolglik suurversadiging heelwat verbeter. Dit mag moontlik as verduideliking dien vir die oorhoofse voordelige effek van gips op mielie opbrengste, wat verhoog het met ‘n gemiddelde 1071kg/ha. Oorvleuende omstandighede het daartoe gelei dat geen konkrete afleidings gemaak kon word oor die wortel lengte van die mielies nie. Hierdie veldproef bevestig dat vliegas as ‘n effektiewe kalkmateriaal gebruik kan word en goed vergelyk met tradisionele kalkmateriale.

O experimento avaliou os efeitos da ensilagem, da maturidade e do genótipo na matriz amido-protéica e no valor nutritivo de silagens de grão de milho com alta umidade. O delineamento experimental foi blocos ao acaso, com esquema fatorial 2×3×5: dois genótipos (duro ou dentado), três pontos de maturação (ponto de ensilagem de planta inteira, ponto de grão úmido e ponto de grão seco) e cinco tempos de armazenamento (0, 7, 21, 60 e 120 dias), com 4 repetições. Os tratamentos foram constituídos por híbridos de milho AG 1051 (dentado) e IAC 8390 (duro). Os dados foram submetidos à análise de variância e as suas médias comparadas pelo Teste Tukey (5%). Foram avaliadas as características físicas dos grãos ao longo da maturidade, características físico-químicas, composição química e perfil fermentativo das silagens, extração e quantificação de proteínas prolaminas (zeínas) e degradabilidade ruminal in situ da matéria seca e de amido das silagens. Nos grãos, as concentrações de proteínas prolaminas foram maiores para o híbrido duro (P < 0,01) e aumentaram conforme a maturidade, sendo que a vitreosidade teve alta correlação com a concentração dessas proteínas. Já na silagem, os teores de proteínas prolaminas foram similares para grão úmido e grão seco reconstituído ao longo do período de armazenamento, independentemente do híbrido ensilado. O teor de nitrogênio amoniacal e proteína solúvel das silagens aumentaram (P < 0,01) ao longo do período de armazenamento. Silagens de grão seco reconstituído apresentaram maiores valores de pH, maiores teores de ácido butírico, etanol, acetona e 2,3-butanodiol. A maior degradabilidade ruminal de amido foi correlacionada negativamente (P < 0,01) com a concentração de proteínas prolaminas e positivamente relacionada (P < 0,01) aos teores de proteína solúvel e nitrogênio amoniacal. O efeito de genótipo e maturidade foram superados por tempos de armazenamento superiores a 60 dias, no tocante à degradabilidade ruminal das silagens. Silagens de grão seco reconstituído apresentaram maiores perdas de matéria seca e qualidade higiênica inferior às silagens de grão úmido. / The experiment evaluated the effects of silage maturity and genotype on starch-protein matrix and nutritive values of corn grain silage with high moisture. The experiment design was randomized blocks with 2 × 3 × 5 factorial: two genotypes (flint or dent), three maturity stages (whole plant silage stage, moisture grain stage and dry grain stage) and five lengths of storage (0, 7, 21, 60 and 120 days), with four replications. The treatments were composed by two corn hybrids - AG 1051 (dent) and IAC 8390 (flint). The data were subjected to analysis of variance and the averages were compared by Tukey test (5%). Corn grains physical characteristics along the maturity, physicochemical characteristics, chemical composition and fermentation characteristics of silages, extraction and quantitation of prolamin protein (zein) and dry matter and starch in situ silage degradability were evaluated. In corn grains, the concentration of prolamin protein was higher for hybrid flint (P < 0.01) and also increased with maturity, and the vitreousness had higher correlation with the concentration of these proteins. Furthermore in silages, prolamin proteins were similar to high moisture grain and dry grain reconstituted, along with storage, regardless of the hybrid. In silage, the ammonia nitrogen and soluble crude protein contents increased (P < 0.01) during the length of storage. Reconstituted dry grain silages had higher pH, higher concentrations of butyric acid, ethanol, acetone and 2,3 - butanediol. The highest ruminal starch degradability was negatively correlated (P < 0.01) with the prolamin protein concentration and positively (P < 0.01) related to soluble crude protein and ammonia nitrogen protein levels. The effect of genotype and maturity were overcome by 60 days length of storage, according to ruminal degradability of silages. Reconstituted dry grain silages had higher DM losses and the hygienic quality was lower compared with high moisture corn silages.

O histórico agronômico da cultura, em geral, explica a comunidade microbiana presente na massa ensilada, entretanto, a diversidade e o grau de contaminação da população microbiana epifítica pode auxiliar na compreensão do padrão de fermentação da silagem e da estabilidade desse produto quando em exposição ao ambiente aeróbio. No presente trabalho, foram avaliados a influência do genótipo, maturidade e período de estocagem na composição da comunidade bacteriana em silagens de grãos de milho. Para isso, dois cultivares de milho AG 1051 (\"dent\") e IAC 8390 (\"flint\") foram colhidos em três estágios de maturidade (ponto de silagem de planta inteira, ponto de silagem de grão úmido e ponto de grão seco), moídos e ensilados por 0, 7 e 120 dias. Atualmente, a aplicação de técnicas de microbiologia molecular permite acessar alterações causadas nestas comunidades de maneira independente do cultivo bacteriano, por esse motivo, a comunidade bacteriana foi avaliada por meio da técnica de Eletroforese em Gel de Gradiente Desnaturante (DGGE) e sequenciamento dos produtos de PCR via sistema MiSeqTM Illumina. Foi demonstrado que em silagens de grãos de milho contendo alta umidade, os diferentes estágios de desenvolvimento da cultura, e por conseguinte, do grão, são os principais determinantes da composição da comunidade bacteriana deste, sendo menos importantes o genótipo das plantas e os tempos de estocagem das silagens. Aos 120 dias de estocagem nas amostras de grão seco reconstituído, as sequências afiliadas ao gênero Clostridium representaram total de aproximadamente 40% das sequências afiliadas aos gêneros encontrados, enquanto o gênero Lactobacillus representou menos de 7% das sequências afiliadas a este gênero. Provavelmente, grãos secos sofrem mais estresse a campo, o que consequentemente, pode interferir na qualidade higiênico sanitária das silagens desses grãos. Com base nestes resultados fica evidenciada a possibilidade de realização de recomendações potenciais de aditivos específicos para ensilagem de grãos de milho, direcionados para cada ponto de maturidade da cultura. / The agronomic background of crops in general, explains the microbial community present in silage, however, diversity and contamination status may help on understanding the silage fermentation profile and aerobic stability. In the present work, the influence of factors such as different genotypes, different stages of plants development and storage time in the composition of bacterial communities were evaluated. On this way, maize cultivars AG 1051 (\"dent\") and IAC 8390 (\"flint\") were harvested in three physiological stages (whole plant silage, wet grain silage and dry grain), the grain were grounded and ensiled for 0, 7 and 120 days. Nowadays, the applications of techniques of molecular microbiology allow assessing the shifts caused on these communities by a culture independent approach, therefore, bacterial community were evaluated by Denaturing Gradient Gel Electrophoresis technique (DGGE), and PCR products were sequenced by Illumina MiSeqTM System. It was demonstrated that in high moisture corn silage, different stages of plants development are main determinants of bacterial community composition rather than the plants genotypes and storage time. In addition in the samples of reconstituted dry grain, it was demonstrated that after 120 days of storage, sequences affiliated to the gender Clostridium accounted for a total of approximately 40% of total sequences affiliated to genera found, while the genus Lactobacillus represented less than 7% of sequences affiliated to this gender. Probably dried grains suffer more stress at field conditions, which in turn can interfere with the sanitary hygienic quality of silages obtained from these grains. At least, based on these results it is clear the possibility of performing potential specific additives recommendations, unique at each stage of maize plants development.

O histórico agronômico da cultura, em geral, explica a comunidade microbiana presente na massa ensilada, entretanto, a diversidade e o grau de contaminação da população microbiana epifítica pode auxiliar na compreensão do padrão de fermentação da silagem e da estabilidade desse produto quando em exposição ao ambiente aeróbio. No presente trabalho, foram avaliados a influência do genótipo, maturidade e período de estocagem na composição da comunidade bacteriana em silagens de grãos de milho. Para isso, dois cultivares de milho AG 1051 (\"dent\") e IAC 8390 (\"flint\") foram colhidos em três estágios de maturidade (ponto de silagem de planta inteira, ponto de silagem de grão úmido e ponto de grão seco), moídos e ensilados por 0, 7 e 120 dias. Atualmente, a aplicação de técnicas de microbiologia molecular permite acessar alterações causadas nestas comunidades de maneira independente do cultivo bacteriano, por esse motivo, a comunidade bacteriana foi avaliada por meio da técnica de Eletroforese em Gel de Gradiente Desnaturante (DGGE) e sequenciamento dos produtos de PCR via sistema MiSeqTM Illumina. Foi demonstrado que em silagens de grãos de milho contendo alta umidade, os diferentes estágios de desenvolvimento da cultura, e por conseguinte, do grão, são os principais determinantes da composição da comunidade bacteriana deste, sendo menos importantes o genótipo das plantas e os tempos de estocagem das silagens. Aos 120 dias de estocagem nas amostras de grão seco reconstituído, as sequências afiliadas ao gênero Clostridium representaram total de aproximadamente 40% das sequências afiliadas aos gêneros encontrados, enquanto o gênero Lactobacillus representou menos de 7% das sequências afiliadas a este gênero. Provavelmente, grãos secos sofrem mais estresse a campo, o que consequentemente, pode interferir na qualidade higiênico sanitária das silagens desses grãos. Com base nestes resultados fica evidenciada a possibilidade de realização de recomendações potenciais de aditivos específicos para ensilagem de grãos de milho, direcionados para cada ponto de maturidade da cultura. / The agronomic background of crops in general, explains the microbial community present in silage, however, diversity and contamination status may help on understanding the silage fermentation profile and aerobic stability. In the present work, the influence of factors such as different genotypes, different stages of plants development and storage time in the composition of bacterial communities were evaluated. On this way, maize cultivars AG 1051 (\"dent\") and IAC 8390 (\"flint\") were harvested in three physiological stages (whole plant silage, wet grain silage and dry grain), the grain were grounded and ensiled for 0, 7 and 120 days. Nowadays, the applications of techniques of molecular microbiology allow assessing the shifts caused on these communities by a culture independent approach, therefore, bacterial community were evaluated by Denaturing Gradient Gel Electrophoresis technique (DGGE), and PCR products were sequenced by Illumina MiSeqTM System. It was demonstrated that in high moisture corn silage, different stages of plants development are main determinants of bacterial community composition rather than the plants genotypes and storage time. In addition in the samples of reconstituted dry grain, it was demonstrated that after 120 days of storage, sequences affiliated to the gender Clostridium accounted for a total of approximately 40% of total sequences affiliated to genera found, while the genus Lactobacillus represented less than 7% of sequences affiliated to this gender. Probably dried grains suffer more stress at field conditions, which in turn can interfere with the sanitary hygienic quality of silages obtained from these grains. At least, based on these results it is clear the possibility of performing potential specific additives recommendations, unique at each stage of maize plants development.