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The anthracnose stalk rot of corn (ASR), caused by Colletotrichum graminicola, is a major disease of this crop and occurs in most Brazilian regions where corn is grown. Despite its widespread occurrence, there are no estimates of the effect of ASR on the yield of corn under the Brazilian conditions. In this study, we evaluated the effect of ASR on corn hybrids yield. Two experiments were conducted (first crop 2007/2008 and second crop, 2009) in areas with a history of occurrence of leaf anthracnose and ASR. Five hybrids were evaluated in the first and second crops: AG1051, BRS 1001, BRS 1010, BRS 1035, P30F80 and BRS 1010, 2B710, P30F80, DKB390, BRS 1035, respectively. At harvest, we evaluated the incidence of plants with anthracnose stalk rot (IPASR), and we selected pairs of healthy and diseased plants to quantify the effect of ASR in the ear weight (EW), grain weight (GW) and the weight of a sample containing 100 kernels (W100). The IPASR was higher in the hybrid BRS 1010 (21.87 and 45.28%, first and second crops, respectively). The EW, GW and W100 were lower in diseased plants in all hybrids. The mean weight loss in the first season was EW 29.03%, GW 27.83% and W100 17.08%, and the second season was EW 27.75%, GW 25.60% and W100 16.99%. The most affected hybrids with weight loss in the first crop were AG1051 (EW 34.31%, GW 33.05%, W100 19.96%) and BRS 1035 (EW 34.74%, GW 34.65%, W100 22.31%). In the second crop, were P30F80 (EW 30.72%, GW 30.92%, W100 19.24%), DKB390 (EW 30.61%, GW 29.81%) and 2B710 (W100 19.27%). Corn yield was strongly affected by ASR.

A study was carried out to investigate the inheritance of resistance to anthracnose, caused by Colletotrichum sublineolum, in sorghum. Crosses between resistant and susceptible parents and backcrosses between F 1 plants and the susceptible parents were carried out under field conditions. The F 1 generations and the segregant populations were evaluated under artificial inoculation conditions in the greenhouse. In the F 1 generation of all crosses with the respective isolates, all of the plants presented a resistance reaction except for the F 1 plants resulting from the BR009 · SC283 cross. In the F 2 generation, the frequencies of resistant and susceptible plants conformed to the hypothesis that one gene with two alleles controls host resistance, except in one cross. Out of the eight backcrosses, six presented segregation that corresponded to the hypothesis formulated. For most crosses, resistance was dominant, and the proportions of resistant and susceptible plants in the segregant populations conformed to the frequencies expected under the hypothesis of gene-for-gene resistance and dominant gene action.

RESUMO Objetivou-se propor e validar uma escala diagramática para quantificar a antracnose do colmo em milho. A severidade da antracnose foi estimada por dez avaliadores sem o uso de escala em 139 entrenós, e os mesmos avaliadores avaliaram os entrenós usando uma escala publicada anteriormente na literatura (primeira escala) e uma nova escala proposta. Com o uso da escala proposta, todas as variáveis foram significativamentediferentes em relação à primeira escala, e os valores foram mais próximos de uma medição acurada (r=0,97, C b =0.98, u=0.09, υ=1.06, ρ c =0.96 INTRODUÇÃOA antracnose do colmo Colletotrichum graminicola (Ces.) Wils é uma das doenças mais importantes na cultura do milho em vários países, causando acamamento das plantas, redução na produção e qualidade dos grãos (BERGSTROM & NICHOLSON, 1999;COTA et al., 2012;MATIELLO et al., 2013). Os sintomas da antracnose do colmo são mais visíveis após o florescimento das plantas de milho, porém o processo infeccioso inicia-se pelos propágulos provenientes das lesões foliares ou daqueles presentes em restos culturais. Na casca, surgem lesões estreitras, longitudinais e com aspecto encharcado, que são inicialmente de coloração pardo-avermelhada, posteriormente tornando-se marromescuras a negras. Nos tecidos internos do colmo, ocorre uma coloração marrom-escura, que entra em processo de desintegração, afetando o fluxo de água e nutrientes do colmo para a parte superior, podendo ocasionar a morte prematura e o acamamento das plantas (KELLER &

RESUMONos últimos anos, grande ênfase tem sido dada ao uso de fungicidas para o manejo de doenças foliares na cultura do milho no Brasil. Esse trabalho teve como objetivo a realização de uma análise da viabilidade técnica e econômica da aplicação de fungicidas no rendimento de cultivares de milho em diferentes regiões produtoras. Foram conduzidos experimentos para avaliação do efeito da aplicação de fungicidas no rendimento de diferentes cultivares de milho, em três localidades: Sete Lagoas (MG), Londrina (PR) e Rio Verde (GO). Foram consideradas a não aplicação, uma e duas aplicações de fungicidas em cada cultivar. Foram avaliadas a severidade das doenças foliares e o rendimento de cada cultivar. Os resultados de rendimento das cultivares tratadas com fungicidas apresentaram elevada inconsistência em condições de baixa severidade de doenças. Maior frequência de rendimentos positivos e benefício econômico ocorreu quando as aplicações de fungicida foram realizadas em condição de elevada pressão de doença. Mais estudos são necessários para o melhor entendimento do efeito dos fungicidas do grupo das estrobilurinas na fisiologia e na produção de plantas de milho. Palavras-chave: Zea mays, azoxistrobina, efeito fisiológico, piraclostrobina. ABSTRACT Technical and economic feasibility of strobilurin fungicides application on maizeIn recent years, great emphasis has been given to the use of fungicides for managing foliar diseases in corn in Brazil. This study aimed to conduct an analysis of technical and economic feasibility of application of fungicides on maize in different growing regions. Trials were conducted to evaluate the effect of fungicides on the yield of different maize cultivars at three locations: Sete Lagoas (state of Minas Gerais), Londrina (state of Paraná) and Rio Verde (state of Goiás). The effect of one and two fungicide applications on each cultivar was evaluated. For each trial, the difference in mean yield and disease severities between treated and untreated plots for each cultivars was compared. For all trials, yield response of cultivars treated with fungicides was highly inconsistent under low disease severity. A higher frequency of positive yields and economic benefit occurred when fungicide applications were made under conditions of high disease pressure. More studies are needed to better clarify the effect of strobilurin fungicides on the physiology and production of corn plants.

The hemibiotrophic fungus Colletotrichum graminicola may cause severe damage to maize, affecting normal development of the plant and decreasing grain yield. In this context, understanding plant defense pathways at the inoculation site and systemically in uninoculated tissues can help in the development of genetic engineering of resistance against this pathogen. Previous work has discussed the molecular basis of maize -C. graminicola interaction. However, many genes involved in defense have not yet been exploited for lack of annotation in public databases. Here, changes in global gene expression were studied in root, male and female inflorescences of maize under local and systemic fungal infection treatments, respectively. RNA-Seq with qPCR was used to indicate genes involved in plant defense. We found that systemic acquired resistance induction in female inflorescences mainly involves accumulation of salicylic acid (SA)-inducible defense genes (ZmNAC, ZmHSF, ZmWRKY, ZmbZIP and PR1) and potential genes involved in chromatin modification. Furthermore, transcripts involved in jasmonic acid (JA) and ethylene (ET) signaling pathways were also accumulated and may participate in plant immunity. Moreover, several genes were functionally re-annotated based on domain signature, indicating novel candidates to be tested in strategies involving gene knockout and overexpression in plants.