Incidência e severidade do mofo-cinzento-da-mamoneira sob diferentes temperaturas, períodos de molhamento e concentração de conídios

Abstract

The effect of temperature (15, 20, 25 and 28 °C), wetness period (0, 6, 12, 24, 48 and 72 hours) and conidia concentration (0, 1x10 2 , 1x10 3 , 1x10 4 , 1x10 5 and 1x10 6 conidia/mL -1 ) on the incidence and severity of gray mold caused by Amphobotrys ricini in castor bean (Ric inus communi s) b unch es were evaluated. The c onid ia concentration effect was evaluated fixing the temperature at 25°C and the wetness duration at 48 hour. The temperature and wetness duration were evaluated fixing the conidial concentration at 1x10 5 conidia mL -1 . The plants were evaluated as to the incidence of fruit wiht symptons and severity in each bunch. progress curve (AUIPC) and under severity progress curve (AUSPC) was calculated, and the results submitted to variance and regression an alys is. There wa s a signifi cant difference for the different concentrations of conidia, for the temperatures and for the wetness period. There was significant interaction between temperature and the wetness period. With the increased concentrations of conidia, both the incidence and the severity of the gray mold showed increases until the 10 5 conidia mL -1 concentration. There was an increase of AUIPC and AUS PC for the wetn ess period inc reas e a nd t he temperature. There were no symptoms in the absence of wetness.(AACPI) e da severidade (AACPS) e os dados submetidos à análise de variância e regressão. Houve diferença significativa quanto à influência de diferentes concentrações de conídios, temperaturas e períodos de molhamento no progresso do mofo-cinzento-da-mamoneira, além de ocorrer interação significativa entre a temperatura e o período de molhamento. A incidência e a severidade do mofo-cinzento-damamoneira apresentaram acréscimos com a elevação da concentração de conídios até 10 5 conídios mL -1 . A AACPI e a AACPS aumentaram com o incremento do perí odo de molh amento e eleva ção da temperatura. Não houve manifestação de sintomas na ausência do molhamento foliar.O cultivo da mamoneira (Ricinus communis L.) expandiu-se impulsionado pelo programa nacional de biocombustíveis. Contudo, em algumas regiões onde o período de chuvas prolongadas e temperaturas amenas coincidem com a época de florescimento da mamona e o início da frutificação, foram constatadas perdas severas causadas pelo mofo-cinzento (Amphobotrys ricini [Buchw.] Hennebert) (17). Esse patógeno infecta o racemo em qualquer fase de seu desenvolvimento, encobrindo-o totalmente com micélio e esporos, conferindo-lhe um aspecto pulverulento cinza.Inicialmente, o fungo foi descrito como Botrytis ricini Godfrey e seu teleomorfo foi denominado de Sclerotinia ricini Godfrey (10). O gênero foi modificado por Whetzel para Botryotinia e Hennebert estabeleceu o novo gênero Amphobotrys para acomodar a forma conidial semelhante à Botrytis de B. ricini (11). O gênero Amphobotrys possui uma única espécie típica, A. ricini (Buchw.) Hennebert.A doença caracteriza-se pelo apodrecimento dos frutos nos cachos da mamoneira, principalmente sob alta umidade relativa. Em patossistemas q...

Influence of the limitation of axillary bud growth on grain and oil yield of castor bean hybrids

“…Considering that the final stage of grain development may coincide with occurrence of water scarcity or low temperatures, depending on the growth location, growth pattern and plant cycle shortening are crucial for maintaining crop yield (Severino et al, 2012). Additionally, other risk factors for castor bean crop can be minimized, such as gray mold (Amphobotrys ricini), as the removal of secondary stems results in higher incidence of direct light and airflow on the plant, promoting a microclimate less beneficial to fungal growth (Sussel et al, 2011).…”

Fatores epidemiológicos de Phytophthora palmivora afetando a severidade da podridão-dos-frutos do mamoeiro na pós-colheita

“…Em vários patossistemas a ocorrência de epidemias em um curto espaço de tempo está diretamente ligada ao número de propágulos do patógeno dentro ou próximo dos campos com plantas hospedeiras (33).…”

Gray Mold of Castor: A Review

“…At temperatures below 20ºC, the disease is little expressed and highly dependent on long periods of high relative humidity (Sussel, 2008). According to Sussel et al (2011), there is a high correlation between the temperature and duration of leaf wetness with the disease incidence and severity. The same authors also concluded that the disease was more intense with a temperature of 28ºC and 72 hours of leaf wetness, and that for temperatures below 15º the fungus needs more than 6 hours of leaf wetness, otherwise the disease does not occur (Sussel et al, 2011).…”

“…According to Sussel et al (2011), there is a high correlation between the temperature and duration of leaf wetness with the disease incidence and severity. The same authors also concluded that the disease was more intense with a temperature of 28ºC and 72 hours of leaf wetness, and that for temperatures below 15º the fungus needs more than 6 hours of leaf wetness, otherwise the disease does not occur (Sussel et al, 2011). Even when under optimal temperatures (near 25ºC), the fungus appears to be highly dependent on periods of high humidity, since in a study developed by Esuruoso (1966) with 39 castor varieties in two distinct places, Ibadan and Ilora (West Nigeria), that share similar temperatures (24.4 to 27.9 and 24.2 to 27.2°C, respectively), but that rainfall was twofold higher in Ibadan than Ilora, the disease level in Ibadan was 1.5 fold higher than in Ilora.…”