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Master's Dissertation
DOI
Document
Author
Full name
Nuria Pereira Calvet
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Piracicaba, 2001
Supervisor
Title in Portuguese
Lesão virtual causada pela mancha de Alternaria helianthi em diferentes genótipos de girassol (Helianthus annuus L.), e sua relação com a fotossíntese
Keywords in Portuguese
FOTOSSÍNTESE
FUNGOS FITOPATOGÊNICOS
GENÓTIPOS
GIRASSOL
MANCHA DE ALTERNARIA
Abstract in Portuguese
A mancha de Alternaria causada pelo fungo Alternaria helianthi, é uma das doenças com maior potencial de dano na cultura do girassol no Brasil, uma vez que as condições climáticas favoráveis ao seu desenvolvimento coincidem com as principais épocas de plantio desta cultura. Considerando-se a importância da fotossíntese para as plantas, os patógenos podem interferir, inicialmente causando clorose, até atingir grandes áreas foliares com lesões necróticas, levando à perda de tecido e à desfolha. Para quantificar os efeitos da doença em folhas de girassol, foi medida a taxa de fotossíntese líquida (A) de folhas sadias e de folhas doentes durante o ciclo de crescimento da cultura, em duas épocas distintas de plantio. Através de uma equação matemática, a severidade da doença foi relacionada à fotossíntese ('β'). Analisou-se, para o patossistema Girassol x Alternaria, a influência do patógeno nas áreas verdes remanescentes do tecido foliar. Foi observada redução das taxas fotossintéticas dos tecidos verdes remanescentes das folhas doentes, comprovando-se que existe lesão virtual para o patossistema Girassol x Alternaria. Os valores de 'β' encontrados variaram de 1,4 a 4,7, indicando que as épocas de plantio têm influência sobre a severidade da doença. Observou-se que folhas ainda sem lesões de plantas doentes apresentaram comprometimento fotossintético
Title in English
Virtual lesion caused by Alternaria helianthi blights in different sunflower (Helianthus annuus L.) genotypes, and its relation with the photosynthesis
Abstract in English
The Alternaria blights in sunflower caused by the fungus Alternaria helianthi is one of the major diseases that affects sunflower in Brazil. The effects of them upon net photosynthetic rate of four different sunflower genotypes leaves were measured in the field. Alternaria blights reduced photosynthesis not only through a reduction in green leaf area, but also through an effect on photosynthesis of the remaining green leaf tissue. A mathematics approach was derived to relate the infected leaf area with net photosynthetic rate (β). This relationship was used to analyse the pathosystem Sunflower x Alternaria. For all genotypes studied, a decrease in the photosynthetic rates of infected leaves was observed when compared to healthy leaves. ln addition, reduction in photosynthesis was observed in the remaining green leaf tissue of infected plants proving the existence of virtual lesions in sunflower leaves when infected by Alternaria helianthi. Values of β ranged from 1,4 to 4,7, showing that season of planting has a strong influence upon severity of the disease.
 
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Publishing Date
2019-08-22
 
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