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| Author(s): |
Evandro Henrique Schinor
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2001-10-15 |
| Advisor: | Francisco de Assis Alves Mourao Filho |
| Abstract | |
Citrus Black Spot (CBS), caused by Guignardia citricarpa, has prompted serious economic damages to the citrus industry in the last 20 years. The present work was developed at the Centro de Citricultura 'Sylvio Moreira' (CCSM) of the Instituto Agronômico de Campinas, in Cordeirópolis-SP. Evaluations were conducted to detect differences among ten 'Pêra' sweet orange Citrus sinensis (L.) Osbeck clones and five related varieties in regard to their susceptibility to CBS. The 'Pêra' sweet orange clones evaluated were: Vimusa, EEL, GS 2000 (IAC 2000), Olímpia 15161, Bianchi, R Gul10 1569/244, Dibbern c.v., Premunizada 1743/82; and the related varieties were: Corsa Tardia, Lamb's Summer, Ovale 968, Ovale San Lio 969, and Redonda C.N. Trees were budded on Rangpur lime are planted in 1980, at the CCSM. Studies investigated the evaluation severity of symptoms and distribution on the plants; induction of structures in vitro in leaves previously autoclaved; induction of fungus reproductive structures in mature leaves; and quantified density of colonization of G. citricarpa by means of isolation. The comparison among different clones was also accomplished by determining correlations between the severity of disease symptoms and the variables: leaf drop, vegetative growth, and light penetration insíde the plants. In regard to fruit, the severity was correlated with: color; fruit shape; base and apex shape; angle and flattening; epicarp, mesocarp and peeI thickness; and with juice quaIity (soluble solids and soluble solids to acidity ratio). The relationship for quantification of severity of CBS incidence in the field and the density of natural leaves colonization (isolates/cm2 was not significant. The incidence and the severity of the disease symptoms are greater in the low part of the plants, up to 1 meter height, and smaller above 2 meters, probably because of the influence of fruit infection by ascospores (sexual) and pícnidiospores (asexual) through water splash. Differentiation among the varieties was detected based on the reproductive capacíty of G. citricarpa on dead leaves in vitro and also based on the induction of fungus structures, as evaluated by the percentage of area of the leaves occupied by them. There was not a significant correlation for fruit externaI characteristics, such as peeI color, fruit shape, base and apex shape, basaI area angle and flattening, and peeI thickness of either mesocarp and epicarp with the severity of disease. Similarly there was not a correlation for fruit internal characteristics such as soluble solids, total acidity, and soluble solids to acidity (ratio), with the severity of disease. Therefore, the CBS of the fruit does not interfere on the fluit organoleptic quality. However, visual aspect of fruit ís severeIy depressed (AU) | |