Occurrence of Meloidogyne arenaria in black pepper (Piper nigrum L.) in the extreme south of the State of Bahia, Brazil

For this study formal consent is not required.

Black pepper plants parasitized by gall nematodes generally become chlorotic, with severe leaf yellowing, defoliation and reduction in chlorophyll content, which affects vegetative development, resulting in significant reduction in yield and even death (Freire & Monteiro, 1978; Ferraz & Lordello, 1989; Mohandas & Ramana, 1991). Some of these symptoms, such as yellowing, defoliation and roots with numerous galls were observed in the plants analyzed in our study.

Studying the anterior region of the males and analyzing the perineal configuration of the females, the presence of Meloidogyne arenaria was confirmed (Figs. 2A and 2B).

Fig. 2

We observed females with perineal pattern rounded to ovoid, with thin to thick streaks. Low dorsal arch, flattened, with smooth or slightly wavy streaks, slightly bent towards the tail tip on the lateral line; usually forming shoulders on the lateral portion of the arch. The dorsal and ventral striations are usually at an angle on the lateral lines; distinct lateral field, slightly irregular. In males, the labial region was continuous with the rest of the body, smooth, labial disc more or less rounded, slightly elevated above the level of the medial lips. Long distance from the orifice of the dorsal esophageal gland to the base of the stylet.

The analysis of polyacrylamide gel electrophoresis also revealed a characteristic profile of M. arenaria (Fig. 3).

Fig. 3

The numbers of second stage juveniles (J2) + eggs extracted from black pepper roots are shown in Table 1. Both cultivars showed a high number of M. arenaria demonstrating the susceptibility of these cultivars to this species.

The first study that showed the presence of Meloidogyne spp. in black pepper plantations was carried out in 1901 by Zimmerman cited by Winoto (1972).

In Brazil, reports involving the black pepper pathosystem x Meloidogyne spp. are rare and mostly related to M. incognita in the State of Pará (Lordello & Silva, 1974; Ichinohe, 1976; Freire & Monteiro 1978).

In Brazil, the only report of M. arenaria in black pepper is from 1965, made by Dr. Jair C. Carvalho, based on the analysis of soil and roots from Caraguatatuba, SP (Carvalho, 1965). It is important to highlight that before the development of the isoenzyme electrophoresis technique, the identification of Meloidogyne species was performed exclusively by examining the perineal configuration (Chitwood, 1949). It is known, however, that this technique is extremely subjective, and it is of fundamental importance also to characterize these pathogens by biochemical means, through the technique of isoenzyme electrophoresis (Carneiro & Almeida, 2001; Oliveira et al. 2012), and by observation of the region of the males, as performed in the present study. The use of these last two techniques associated with the analysis of the perineal configuration brings certainty regarding the correct diagnosis of Meloidogyne spp. (Cunha et al, 2018).

Considering that the success of any nematode management strategy depends, initially, on the knowledge of the species present in the areas where it is desired to reduce the population of these pathogens, the information obtained in the present work may be useful in the development and adoption of appropriate techniques for the management of parasitic nematodes of black pepper.

The species of gall nematode associated with black pepper cultivation in the extreme south of the State of Bahia is Meloidogyne arenaria. It is the first report of this pathosystem in the State, and therefore expands its geographical scope.