Título :	Modelling propagule effects in bean white mould epidemics
Otros títulos :	Modelagem do efeito dos propágulos em epidemias de mofo-branco do feijoeiro
Autor :	Geraldine, Alaerson Maia
Orientador(es)::	Café Filho, Adalberto Corrêa
Coorientador(es)::	Savary, Serge
Assunto::	Feijão - doenças e pragas Mofo (Botânica) Plantas - doenças e pragas Infecção - fungos
Fecha de publicación :	5-feb-2016
Data de defesa::	6-nov-2015
Citación :	GERALDINE, Alaerson Maia. Modelling propagule effects in bean white mould epidemics. 2015. xviii, 160 f., il. Tese (Doutorado em Fitopatologia)—Universidade de Brasília, Brasília, 2015.
Abstract:	Despite the large number of studies on Sclerotiniadiseases on several hosts, the processes composing disease cycles are almost always studied separately.The cycle of Sclerotiniadiseases is complex, and can be divided in four broad phases, corresponding to typical structures of the pathogen life cycle. These phases correspond to the formation and the biological functions of four different types of propagules: (1) sclerotia, (2) apothecia and ascospores, (3) infected petals, and (4) infectious hyphae. An ethograph graphically synthesizes knowledge relevant to epidemiology of a disease. In the first chapter, successive versions of an ethograph are used to discuss the phenomenology of the bean white mould cycle and to highlight relationships among S. sclerotiorum propagules, successive stages of the disease and bean developmental stages. The ethograph describe the phenomenology of bean white mould through the examination of the several stages of the disease cycle in more detail than it is usually attempted and taking into account the concatenation of events. The method is useful to identify key stages and to explicit the relationships among disease stages of the disease cycle, the four types of propagules, and the factors that affect their respective processes of infection. It constitutes an initial step to for the development of a quantitative, simulation model. In Chapter 2 we analysed these successive stage (phases), as well as their regulating processes and factors. Sets of experimental epidemics were created in bean fields under natural environmental conditions prevailing in the winter season in Central Brazil. The sets of experimental epidemics aimed to promote a range of white mould epidemics. Fifty-seven epidemics, representing a wide variation in severity levels and in disease progress shapes, were monitored, with specific attention paid to the four considered propagule types. Epidemics were analysed by different statistical techniques and three groups (A, B, or C) of epidemics were distinguished. Group A includes epidemics which were slow to establish, developed at a low rate, and led to very low terminal incidence and severity. Epidemics in Group C had an earlier onset, progressed very rapidly with an initially high rate of increase, followed by stabilization. Epidemics in Group B displayed an intermediate behaviour, with an initially low rate of disease increase, followed by a strong increase of the rate of foliage infection at later stages. It is assumed that plant-to-plant spread (secondary infection) occurs rarely in Group A epidemics because of the lower frequency of effective contacts, resulting into a small number of lesions on the foliage and low incidence of diseased plants (average 0.12% of incidence). By contrast, it is assumed that, in epidemics of Group C, plant-to-plant spread occurs frequently, because of the higher frequency of effective contacts, leading to a much higher number of lesions and higher incidence of diseased plants (average 0.81% of incidence). Therefore, even if the primary inoculum in the form of sclerotia and the subsequent formation of apothecia are, in part, relevant, the role of subsequent infections by other propagules on white mould epidemics must be taken into account. In chapter 3 we described the structure of a model for bean white mould epidemics that emphasizes on the successive types of pathogen propagules and their interaction with host plants. An ethograph describing the infection cycle in bean white mould was developed using symbols and concepts developed for system analysis and a simplified model was built using the STELLA® 10.6 programme (Isee systems, USA). Next, eight model parameters were set to vary in four levels for model evaluation. Sensitivity analyses and statistical methods were then conducted in order to identify gaps, which inputs contribute most to output variability and which parameters are most highly correlated with the outputs. Sensitivity analysis of the sclerotia germination sub-model showed that changes in the relative rate of germinated sclerotia (RRGSC) caused variation in the area under disease progress curve (AUDPC) that were smaller than those caused by variation in the parameter initial number of sclerotia (SC). Sensitivity analysis of the flower infection sub-model showed that changes in values of the relative rate of flower senescence (RRFS) caused narrower AUDPC variation than changes in the relative rate of flower infection, RRFI. In the third sub-model simulating infection of bean foliage, the relative rate of primary infection on foliage, RRP, had the strongest effect on AUDPC values. Different analyses (analyses of variance and principal component analysis) indicate that SC, RRGS, RRFI, RRP and RRS were the most important parameters of the white mould epidemic simulation model. Three epidemics groups were established using the outputs of the model (AUDPC values) as a criterion for group formation. As a result three epidemic groups were defined by discriminant analysis involving a combination of parameters of the white mould simulation model. Clearly, the bean (Phaseolus vulgaris) - Sclerotiniasclerotiorumpathosystem is much more complex than the theoretical general “simple interest” diseases model, even if the amount of initial inoculum (in the form of propagule 1, sclerotia) remains as one of the most important parameters, as shown by sensitivity analysis.
metadata.dc.description.unidade:	Instituto de Ciências Biológicas (IB) Departamento de Fitopatologia (IB FIT)
Descripción :	Tese (doutorado)—Universidade de Brasília, Instituto de Ciências Biológicas, Departamento de Fitopatologia, Programa de Pós-Graduação em Fitopatologia, 2015.
metadata.dc.description.ppg:	Programa de Pós-Graduação em Fitopatologia
Licença::	A concessão da licença deste item refere-se ao termo de autorização impresso assinado pelo autor com as seguintes condições: Na qualidade de titular dos direitos de autor da publicação, autorizo a Universidade de Brasília e o IBICT a disponibilizar por meio dos sites www.bce.unb.br, www.ibict.br, http://hercules.vtls.com/cgi-bin/ndltd/chameleon?lng=pt&skin=ndltd sem ressarcimento dos direitos autorais, de acordo com a Lei nº 9610/98, o texto integral da obra disponibilizada, conforme permissões assinaladas, para fins de leitura, impressão e/ou download, a título de divulgação da produção científica brasileira, a partir desta data.
DOI:	http://dx.doi.org/10.26512/2015.11.T.19456
Aparece en las colecciones:	Teses, dissertações e produtos pós-doutorado

Los ítems de DSpace están protegidos por copyright, con todos los derechos reservados, a menos que se indique lo contrario.