influence of quince rootstocks on entomosporium leaf spot (Entomosporium mesplii) susceptibility in European pear cv Abate Fetel

The incidence and severity of disease was quantified weekly from the appearance of first symptoms in 100 randomly leaves distributed in four medium-height branches per plant with eight replications. The ELS incidence was evaluated by the percentage of leaves with at least one lesion per leaf in relation of the total leaves evaluated and the severity by an infection score system. Disease progress curves of ELS were constructed and the epidemics compared according to: a) the beginning of symptoms appearance (BSA); b) the time to reach the maximum disease incidence and severity (TRMDI and TRMDS); c) area under the incidence and severity disease progress curve (AUIDPC and AUSDPC). The incidence and severity data were analyzed by linear regression and adjusted for three empirical models: Logistic, Monomolecular and Gompertz. The Abate Fetel cultivar under all rootstocks evaluated was susceptible to E. mespili. However, there were significant differences in ELS intensity among rootstocks evaluated. The highest ELS intensities were observed in combinations with EMA and Adams quince rootstock. Abate Fetel cultivar grafted on EMC quince rootstock showed significantly different results to that seen on EMA quince rootstock. EMC quince rootstock induced late resistance compared with the others considerated rootstocks. The Logistic epidemiological model was the most appropriates to describe the ELS progress of Abate Fetel cultivar under quince Adams, EMA and EMC rootstocks in the edafoclimatic conditions of Southern Brazil, during the growing season of 2009/10, 2010/11 and 2011/12.

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