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CHAPTER 3 - MATURATION PERIOD AND RESISTANCE IN RELATION TO
Guignardia citricarpa
ABSTRACT
The objectives of this work were determined the maturation period and the
behavior of Orange genotypes in relation to
Guignardia citricarpa. Assays were
conducted in two experimental fields in Rincão and Tambaú districts, São Paulo
State. The nursery trees were provided by the Banco Ativo de Germoplasma de
Citros, from Estação Experimental de Citricultura of Bebedouro (EECB), São Paulo
State. The maturation period was evaluated through the characters: Brix, acidity
and " ratio ", in 4 evaluations between the months of April and August of 2008 and
Disease severity was evaluated by a value scale ranging from 0 (absence/lack of
symptoms) to 6 (severe symptoms). Disease index (DI) was also calculated,
corresponding to the sum of each fruit multiplied to the correspondent disease
severity value and divided by the total evaluated fruits. In relation to the maturation
period they were divided in three groups, they are them: Group I (late) - Berry
Valência, Castellana, Dom João, Finike, Folha Murcha, Natal, Natal Murcha, Natal
PI-587, Vacaro Blood, Valência 74, Valência 77, Valência Campbell, Valência
Temprana, Vera 97, Werly Valência; Group II (precocious) - Casa Grande, Hamlin,
João Nunes, Oliverlands, Sweet, Valência 457, Verde de Espanha, Westin; Group
III (stocking-station) - Bedewells Bar, Biondo Corigliano, Boukhobza, Cara Cara,
China SRA 547, China, Commune, Doblefina, Fukuraha, Fullameuda, Levels,
Kawatta, Lue Gin Gong, Maçã, Mayorca, Murtera, Newhall Navel, Orange Clanor,
Ovale Mut, Ovale, Pera, Prata, Premier, São Miguel, Telde, Torregrossa,
Torregrosso, Tua Mamede, Tua. For the behavior to G. citricarpa, for the crop
2007, in the rehearsal of Rincão among the 65 acess/variety evaluated 59 they
only produced fruits, and the absence of symptoms of the disease was verified in
the Genótipos Castellana, Maçã and Oliverlands. Us other genotypes the severity
levels verified they varied of 0,35 for Grada and 3,0 for China SRA-547. For
Tambaú, the severity values varied from 0,40 to Cadenera and 2,46 for ' Pêra'. the
year of 2008, in Rincão, all the genotypes exhibited symptoms of the disease. The
severity levels verified they varied from 0,18 to Belladona and 3,92 for Vera 97. In
Tambaú, just the variety Navelina didn't present symptoms of the black stain of the
citros. It was observed that among the plants that fructified, and except for that
whose fruits didn't exhibit symptoms, the severity values varied from 0,11 to Tua
Mamede and 3,57 for Amares. All the appraised genotypes in the experimental
fields were shown susceptible, in varied levels of severity of symptoms in the fruits.
However, the genotype Maçã presented low levels of severity of MPC in the crop
2007 in both experimental fields and in the crop 2008 in Tambaú, demonstrating
potential in relation to the resistance to
G. citricarpa, needing future studies.
Key words: Citrus sinensis, genotypes, fruit.