Expanded geographic distribution of meloidogyne paranaensis confirmed on coffee in Brazil

Abstract

SUPPLEMENTAL TOOLS SHARE Meloidogyne paranaensis, the most destructive root-knot nematode (RKN) on coffee in Brazil (Campos and Villain 2005), was described in 1996 in the state of Paraná, Brazil (Carneiro et al. 1996). M. paranaensis-parasitized coffee plants have demonstrated symptoms of chlorosis, defoliation, reduced growth, and often plant death in extensive areas. It was first recorded in the mountainous coffee of Minas Gerais, in the southeastern region of Brazil, in 2008, and later in three other counties despite the quarantine regulations enforced by the state government (Castro et al. 2008; Salgado et al. 2015). The state of Minas Gerais produces 50% of the Brazilian coffee, which represents 15% of the world’s coffee production (Krishnan 2017). The Cerrado region of Minas Gerais produces 25% of the state’s coffee using the most modern, innovative, and technological coffee farming in Brazil. In response to the claim of coffee vigor decline and production by farmers of this region of Minas Gerais, a survey was undertaken. In this survey, 153 samples were collected from 105 farms in 11 counties. The RKN species found were characterized using esterase phenotypes (Carneiro and Almeida 2001) and confirmed by molecular identification using the sequence characterized amplified region technique as described by Randig et al. (2002). M. paranaensis was found in 11.4% of the sampled farms in seven coffee-producing counties. M. exigua, known as the most widespread but less aggressive RKN species in coffee plantations in Brazil (Castro et al. 2008), was detected in all counties in 54.2% of the sampled farms. Pathogenicity of the M. paranaensis to coffee was confirmed by infection of coffee seedlings. Coffee seedlings (Coffea arabica ‘Catuaí Vermelho IAC 144’) were transplanted into 5-liter pots filled with autoclaved soil. After 3 weeks, 1,500 s-stage juveniles (J2) of each M. paranaensis population collected from the field were inoculated into three coffee seedlings. A total of 36 pots were used for the experiment, consisting of 12 populations and three replicates. Five months after inoculation, 9,050 to 15,122 nematodes (eggs or J2) were recovered from each coffee seedling with 0.5% NaOCl according to the method of Hussey and Barker (1973), using a blender instead of manual shaking. The roots of the coffee plants parasitized by M. paranaensis showed cracking, peeling, and intense necrosis. No galls were observed in inoculated plants. To our knowledge, this is the first report of M. paranaensis in Araguari, Carmo do Paranaíba, Indianópolis, Monte Carmelo, and Rio Paranaíba, Brazil. Previously, M. paranaensis had been detected in only two other counties of the Cerrado region (Castro et al. 2003). The rapid spread M. paranaensis in the Cerrado region might be owing to the intensive use of harvesting machines. Although nematicides can be used to treat against M. exigua, infection of susceptible coffee with the more aggressive M. paranaensis requires their removal, followed by replanting, which is an expensive operation. The consequence of the M. paranaensis outbreak in Brazil is the discouragement of coffee farmers, who may sell the land or change to grain farming.