Plant-parasitic Nematodes Associated with Commercial Orchards of Passion Fruit and Adjacent Cerrado Vegetation in the Brazilian Federal District

Abstract

Empresa Brasileira de Pesquisa Agropecuaria, Embrapa Cerrados, BR 020, Km 18, 73310-970, Planaltina, DF, Brazil(Received on January 18, 2012; Revised on July 6, 2012; Accepted on July 7, 2012)Populations of plant-parasitic nematodes were evaluat-ed in soil and root samples from areas planted withpassion fruit, or covered with adjacent native cerradovegetation, in five different cropping regions of theBrazilian Federal District. From July 2007 to January2008, twenty samples had been collected in five RuralCenters (Nucleo Rural–NR) planted with passion fruit.In five sites, samples were also collected in native cerradovegetation. Specimens of nine genera of plant-parasiticnematodes ( Meloidogyne , Helicotylenchus , Rotylenchulus ,Scutellonema, Pratylenchus, Paratylenchus, Hemicyclio-phora, Xiphinema and Criconemoides ) were found in thepresent survey. Important nematode pathogens, such asRotylenchulus reniformis and Meloidogyne spp. wereobserved in the passion fruit plantations throughoutfive major producing regions of the Brazilian FederalDistrict. Keywords : field survey, Meloyogyne, Passiflora spp, root-knot nematodes, Rotylenchulus reniformisPassiflora edulis Simmonds f. flavicarpa Degener is aplant species of a high economic importance in America,whereas Brazil and Ecuador are important world producersand consumers of passion fruit (Souza et al., 2008). Theeconomic importance of P. edulis and other Passifloraspecies relies on the quality of the fruits for consumptionand on its medicinal properties (Crochemore et al., 2003).Due to favorable climatic and soil conditions, extensiveproduction of sour passion fruit occurs in commercialorchards in the Brazilian Cerrado. Despite the advantages mentioned above, sour passionfruit is susceptible to pests and diseases. Soil pathogens areof main concern among passion fruit growers, especiallyplant-parasitic nematodes. Nematodes belonging to severalgenera have been reported in association with Passifloraroot systems in Brazil (Sharma et al., 1999; Soares et al.,2003; Dias-Arieira et al., 2008), however, for the majorityof them their role as pathogens remains unknown forthis crop. On the other side, the root-knot nematodes(Meloidogyne javanica, M. incognita, and M. arenaria),and the reniform nematode (Rotylenchulus reniformis) areamong the most destructive soil pathogens for passion fruit.These sedentary nematodes lead to root damage, poor plantdevelopment, and consequently to decreased yield andplant longevity.In addition to preventive measures, such as planting insoil free of harmful nematodes, crop rotation is the mostappropriate control measure available to lower populationlevels of nematodes in passion fruit plantations underBrazilian conditions. At the present time there is no nemati-cide registered for this crop. Despite richness of geneticvariability among Passiflora germplasm, and efforts tobreed nematode resistant varieties (Castro et al., 2011; El-Moor et al., 2009; Sharma et al., 2002), commercial vari-eties are not yet available to growers. Thus, knowledge ofthe distribution and population levels of nematodes isrequired for implementation of management practices.Direct field seeding, instead of planting seedlings fromnurseries is a common practice among passion fruit growersin the Brazilian Federal District (DF). This practice contri-butes to avoid dissemination of nematodes and otherpathogens from the nurseries through planting materials.Under these conditions, the sources of soil contamination ofplant-parasitic nematodes in the commercial orchards arepossibly from previous crops, weeds, or accidental intro-duction of infested soil from other locations. Susceptibleplants from the native vegetation may also be the source ofplant-parasitic nematodes when the area is claimed foragricultural purposes. For instance, Souza et al. (1994)reported the association of Meloidogyne spp. with severalnative plants of cerrado vegetation in Brazilian FederalDistrict (DF). The fact that the same plant-parasitic nema-todes appear associated with crops and plants in theassociated native vegetation is an indication that these