Transmissão e controle de Didymella bryoniae em meloeiro nobre

• Autor(a) principal: Gasparotto, Francielli
• Data de Publicação: 2010
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Estadual de Maringá (RI-UEM)
• Texto Completo: http://repositorio.uem.br:8080/jspui/handle/1/1166
• topic: Melão; Doenças e pragas; Cultivo protegido, Sementes; Manejo integrado; Enxertia; Cucumis melo var; reticulatus; Podridão gomosa; Patologia de sementes; Brasil.; Cucumis melo var; Reticulatus; Gummy stem blight; Seed pathology; Integrated pest management; Brazil.; Ciências Agrárias; Agronomia

The melon belongs to the Cucurbitaceae family, genus and species Cucumis melo L. This vegetable is much appreciated and your consumption is rising in Brazil. In Parana, aromatic melons are grown mainly at environment protected, in plastic greenhouse, this mode was introduced in the 80s as a new activity to diversify the farm. Among the major diseases of melon, the gummy stem blight stands out, caused by the fungus Didymella bryoniae (anamorph: Ascochyta cucumis). Damages of up to 100% in melon plants have been reported under high inoculum and favorable environmental conditions. The most frequent symptoms are "damping off" with cancer and gum exudation on stem. D. bryoniae survives in weeds and cultivated cucurbits, crop residues, infested soil and seeds. The seeds are the main way of introducing the pathogen into new areas. The control can be done through crop rotation, elimination of wild cucurbits, sterilization of soils and adequate irrigation. Although there are reports of resistance in cucurbits, none hybrid melon is highly resistant to disease. It is also recommended seed treatment and control with fungicides registered for culture, this being the most widely used form of control. Despite the importance of culture of muskmelon in greenhouse and gummy stem blight, a major disease of culture, this is a little studied pathosystem in the world and especially in Brazil. Given the scarcity of data, this study had the objective to investigate the transmission of D. bryoniae to seed, the biology and control of gummy stem blight on muskmelon. The work was composed of six chapters: In Chapter I, was studied the physiological and sanitary quality seeds of four hybrids of muskmelon (Sunrise, Bonus II, Royal Suite and Prince Hakucho) through the test germination, first germination count, controlled deterioration, accelerated aging, germination at low temperature and sanity. The accelerated aging tests and cool germination were sensitive enough to evaluate the physiological potential of seeds, seeds of hybrid Bonus II had higher vigor and seeds of hybrid Prince Hakucho had smaller vigor. The seeds lots with the highest association of pathogens showed less physiological quality. In Chapter II, was studied the transmission routes of D. bryoniae of the mother plant to seed of muskmelon culture and transmission of disease from produced seed to plant. Five treatments were used to evaluate routes of transmission of disease from the mother plant to seeds (T1, T2, T3, T4, T5). To evaluate the association of the pathogen with seeds were used sanity tests on filter paper and on potato dextrose agar (PDA) using whole seeds and divided. The transmission of disease to plants was evaluated through tests of symptoms in plants at commercial substrate, sand and soil and sandy in greenhouse, and water-agar substrate and vermiculite in incubation chamber. It was not possible to evaluate the seeds of the T3, because occurred fruit rot after inoculation. The pathogen D. bryoniae was not detected associated with the seeds of the four treatments via the sanity test on filter paper, in BDA, the pathogen was detected in seeds from the T1, T2, T4 and T5. In all three tests symptoms on plants in greenhouse was possible to detect the transmission of D. bryoniae seeds for the plants from the T1, T2, T4 and T5. In tests in the incubation chamber also showed the pathogen transmission from seeds to plants in the two substrates for T1, T2, T4 and T5. Infection of melon seeds by D. bryoniae can occur for more than one route, systemically through the plant's parent or through the female flower. Same pathogen causing no damage to fruit and seeds, it is transmitted from seeds, causing damage to the field. In Chapter III, was studied the detection of D. bryoniae in muskmelon seeds by multiplex PCR. For this, it was evaluated three methods of DNA extraction (SDS, CTAB and Guanidine) and three sample sizes of seeds (50, 100 and 200) for developing a method of detecting D. bryoniae in muskmelon seeds by multiplex PCR using specific primers previously designed to detect the pathogen in symptomatic stems of cucurbits. The protocols based on the detergent SDS and the detergent CTAB worked successfully in the extraction of DNA from seed lots. It was possible to detect D. bryoniae in muskmelon seeds by multiplex PCR in seed lots with a rate of association of 4 to 46%. In chapter IV, was studied the occurrence of latent infection and systemic D. bryoniae muskmelon plants by detecting the pathogen by multiplex PCR using specific primers previously developed. The presence of D. bryoniae was proved in stem and cotyledons of asymptomatic plants by multiplex PCR proving the occurrence of latent infection of the pathogen. Was found the incidence of systemic infection of D. bryoniae by detecting the pathogen in asymptomatic fragments located 5, 15 and 30 cm from distance of symptomatic tissue. In Chapter V, was studied the chemical control of gummy stem blight in the culture of muskmelon in plastic greenhouse, using seed treatment with carbendazim (150 g/L) + thiram (350 g/L) with dose of 0,3 + 0,7g i.a./kg seed and foliar spraying every ten days with fungicide epoxiconazol (50 g/L) + pyraclostrobin (133 g/L) at concentration of 0,1 + 0,3g i.a./L and quality of produced fruits. Was used the following treatments: TP - treated seed and sprayed plants; NPT - treated seeds and plants without spraying; NTP - untreated seeds and plants sprayed; NTNP - untreated seeds and plants not sprayed (control). Seed treatment with carbendazim + thiram associated with spraying the crop with fungicide pyraclostrobin + epoxiconazole constituted an efficient strategy for the control of gummy stem blight on muskmelon Sunrise grown in plastic greenhouse and in improving fruit quality. In Chapter VI, studied the effect of grafting on the control of gummy stem blight in muskmelon plants grafted onto immune pumpkin to D. bryoniae. The grafting on rootstock immune caused a reduction in disease severity in plants of muskmelon Sunrise over ungrafted plants of the same hybrid, both grown in condition green-house and in plastic greenhouses.