Fungos associados às sementes (Cariopses) de cana-de-açúcar: métodos para detecção, incidência e relação entre incidência fúngica e ambiente de produção das sementes

Abstract

T his study had as objectives: to determine the most adequate method for detection and identification of sugarcane seedborne fungi; to characterize the associated fungi; to verify the incidences and to relate the fungical incidence in these seeds with the conditions where they were produced. To know the most adequate method of detection, two substrates were compared in Petri dishes: filter paper on agarwater culture medium and only filter paper. Glass and plastic Petri plates were utilized, to verify the recipient influence. It was also compared two light regimens (12h alternating cycles of light and darkness and continuous darkness). The seeds were kept during seven days under constant temperature of 28 ± 2ºC, when the evaluations were proceeded. The requirements for comparison of the methods were sensitivity, economicity and practicity. After the determination of the most adequate method, were done health tests of 29 crosses of the years 2002, 2003 and 2004, to characterize the seedborne fungi and verify their incidences. Later, these incidences were compared to the conditions of temperature and relative humidity from where the seeds were produced at the breeding program. The method considered Martins, T.D.; Menten, J.O.M.; Sanguino, A.. Sugarcane seedborne (Caryopses) fungi: detection methods, incidence and relation between fungical incidence and seed production conditions. Summa Phytopathologica, v.35, n.3, p.173-178, 2009 Keywords: Substract; Light regimen; Petri dishes; Fungical incidence most appropriated, in agreement with the analyzed parameters, was the filter paper in plastic Petri plate and the incubation under light regimen (12h alternating cycles of light and darkness). The detected fungi were: Alternaria alternata; Aspergillus sp.; Bipolaris sacchari; three distinct morphologic groups (GM) of the Bipolaris genera; two morphological groups of the Cladosporium; Colletotrichum sp.; three morphological groups of Curvularia; Epicoccum sp.; Fusarium verticillioides; Fusarium semitectum; Leptosphaerulina sp.; Nigrospora sp.; Penicillium sp.; Periconia sp.; Phoma herbarum; Rhizopus sp. and Trichoderma sp. The most frequently found were: Bipolaris sacchari; Bipolaris spp.; Cladosporium spp.; Curvularia spp.; Fusarium verticillioides; Fusarium semitectum and Phoma herbarum. When the incidence percentage of the diverse fungi was compared with the seed production conditions, the relation of temperature and relative hu midity with fu ngical incidence was not noticed. It was considered that the incidence's variations can be related to different sources of inoculum where the plants were crossed or to genetic characteristics of the seeds. Palavras

Fungi associated with Paspalum guenoarum seeds: their impact on physiology and control

“…In addition to Epicoccum, Fludioxonil; Metalaxil-M effectively controlled Bipolaris and Curvularia. MARTINS et al (2009) also reported Fludioxonil; Metalaxil-M inhibiting 50% of mycelial growth of isolates of Bipolaris, Curvularia and Phoma at concentrations below 1 µg/mL. Despite the fact that we only investigated the chemical treatment of Paspalum seeds, our results provide useful information for controlling these pathogens, with possible application to other forage crops.…”

“…In a study of grasses such as sugarcane, E. sorghinum was among the most common fungal species associated with seeds (MARTINS et al, 2009). These authors advocated investigations to establish chemical treatments aiming to reduce this pathogen in sugarcane and limiting seedling mortality rates.…”

Fertilidade de cruzamentos, potencial fisiológico e armazenamento de sementes de cana-de-açúcar

“…Além disso, a deficiência na polinização é um dos principais fatores envolvidos na redução da produção de sementes, em gramíneas até 40% dos floretes podem não ser polinizados adequadamente (FAIREY, 1993). Ainda segundo MARTINS et al (2009), a incidência de patógenos associados a determinados cruzamentos pode limitar a produção de sementes de cana-de-açúcar, por estes serem beneficiados pelas condições ambientais (altas umidades e temperaturas) em que as sementes são produzidas, diminuindo portanto, o potencial de produção.…”

“…Germinação (%) de sementes (espiguetas) de cana-de-açúcar sob condições controladas (A) e não controladas (B), provenientes de diferentes cruzamentos e anos de colheita. Este fato pode ter ocorrido em razão da incidência de fungos nos locais de cruzamentos (MARTINS et al, 2009), os quais podem afetar significativamente a sanidade das sementes e trazer sérios prejuízos à germinação.…”