Population dynamics of Meloidogyne incognita on cucumber grafted onto the Cucurbita hybrid RS841 or ungrafted and yield losses under protected cultivation Ariadna Giné & Cristina González & Lydia Serrano & Francisco Javier Sorribas Accepted: 28 December 2016 # Koninklijke Nederlandse Planteziektenkundige Vereniging 2017 Abstract The influence of the squash hybrid RS841 rootstock (Cucurbita maxima x C. moschata) on popu- lation dynamics of Meloidogyne incognita and yield of cucumber cv. Dasher II was assessed during 2013 and 2014 in a plastic greenhouse. In addition, the relation- ship between ecophysiological parameters (plant water status, gas exchange, and leaf reflectance) and Pi and cucumber yield were also estimated in 2013. Nematode densities were determined at the beginning (Pi) and at the end (Pf) of each crop, and the relationship between these parameters was used to estimate the maximum multiplication rate (a), the maximum population density (M) and the equilibrium density (E) per grafted and ungrafted cucumber and cropping season. Moreover, the relationship between the multiplication rate (Pf/Pi) and Pi was compared between grafted and ungrafted cucumber per cropping season. Finally, the relative yield of grafted or ungrafted cucumber was plotted against Pi to determine the tolerance limit (T) and the minimum relative yield (m) by the Seinhorst damage function model. Values of a, M and E in grafted cucumber were higher than in ungrafted one irrespective of the cropping season. These results were supported by comparing the relationship between Pf/Pi and Pi between grafted and ungrafted cucumber. The relationship between Pi and yield fitted the Seinhorst damage function. The values of T and m did not differ between grafted and ungrafted each year. Predawn water potential, net photosynthetic rate, and leaf chlorophyll index decreased with increas- ing Pi. In addition, relative yield was related to variation in net photosynthetic rate and the leaf chlorophyll index. Under the conditions of this study, RS841 rootstock was neither resistant nor tolerant to M. incognita. Keywords Cucumis sativus . Cucurbita maxima X Cucurbita moschata . Equilibrium density . Multiplication rate . Root-knot nematode . Tolerance limit Introduction Cucumber (Cucumis sativus L.) is one of the most impor- tant vegetable crops worldwide, producing 65 million tons per year (FAOSTAT 2016). Spain produces 748,500 tons of cucumbers per year in 8811 ha, of which, 88% are under protected cultivation (MAGRAMA 2013). Cucum- ber is susceptible-intolerant to the most common root- knot nematodes (RKN) species, which can cause yield losses up to 88% under protected cultivation (Giné et al. 2014). Despite the chemical control is the most used control method (Talavera et al. 2012), non-chemical alter- natives are needed in order to implement the European Directive 2009/128/EC. Grafting is one of the most promising horticultural techniques, which involves the union of the aerial part (scion) of a susceptible plant with a root system (rootstock) of a resistant one. The main purpose of this Eur J Plant Pathol DOI 10.1007/s10658-016-1135-z A. Giné : C. González : L. Serrano : F. J. Sorribas (*) Departament d’Enginyeria Agroalimentària i Biotecnologia, Universitat Politècnica de Catalunya, Esteve Terradas 8, 08860 Castelldefels, Barcelona, Spain e-mail: francesc.xavier.sorribas@upc.edu