Meloidogyne and Pratylenchus species in sugarcane fields in the state of Alagoas, Brazil

Espécies de Meloidogyne e de Pratylenchus em áreas cultivadas com cana-de-açúcar no estado de Alagoas

ABSTRACT:

The objective of this study was to accomplish a survey on populations of Meloidogyne andPratylenchus species in sugarcane farming areas in the state of Alagoas, Brazil. Twenty samples of soil and roots were processed to extract and quantify nematodes; however, the identification ofMeloidogyne species was performed using only 12 samples.Pratylenchus spp. were reported at moderate population levels of 68-1556 specimens 50g^-1 of roots and 2-298 specimens 100cm^-3 of soil in twenty analyzed samples. ForMeloidogyne spp., these values were of 12-487 specimens 50g^-1 of roots and 0-140 specimens 100cm^-3 of soil. Based on electrophoresis of esterase isozymes,M. incognita was reported to be the most frequent species, followed by M. javanica and M. arenaria. Pratylenchus species identified through morphometrical and morphological characteristics were P. zeae andP. brachyurus , with predominance for the first species. No significant correlation (P≤0.05) were reported between nematode populations and sugarcane cropping systems.

Key words:
field survey; plant-parasitic nematodes; Saccharum spp

RESUMO:

O objetivo deste trabalho foi realizar um levantamento de espécies deMeloidogyne e dePratylenchus existentes em áreas de cultivo de cana-de-açúcar, no estado de Alagoas. Vinte amostras de solo e raízes foram processadas para a extração e quantificação, sendo a identificação das espécies deMeloidogyne realizada em 12 amostras. Detectou-se a presença dePratylenchus spp. em níveis populacionais médios de 68-1556 espécimes 50g^-1 de raízes e 2-298 100cm^-3 de solo, em todas as amostras. ParaMeloidogyne spp., esses valores foram de 12-487 50g^-1 de raízes e 0-140 100cm^-3 de solo. Com base na eletroforese da isoenzima esterase,M. incognita foi a espécie mais frequente, seguida por M. javanica eM. arenaria . As espécies dePratylenchus identificadas pelas características morfológicas e morfométricas, foram P. zeae eP. brachyurus , com predomínio da primeira espécie. Não houve correlações significativas (P≤0,05) entre as populações de nematoides e as características dos sistemas de cultivo de cana-de-açúcar.

Palavras-chave:
levantamento; fitonematoides; Saccharum spp

Among the plant-parasitic nematodes in sugarcane fields throughout the world, the most economically significant should be considered the genus Meloidogyne Goeldi, particularly M .javanica (Treub) Chitwood and M. incognita (Kofoid & White) Chitwood, as well as Pratylenchus zeae Graham (BARBOSA et al., 2013; STEVEN et al., 2014). Yield losses range from 20 to 30% in the first cut in susceptible sugarcane cultivars, due to the presence of M. javanica and P. zeae . Additionally, M. incognita can cause higher losses, of around 40% (DINARDO-MIRANDA, 2005).

In Alagoas State, the genera Pratylenchus and Meloidogyne have been previously detected; however, the nematodes' species were not identified (CRUZ et al., 1986). Thus, the objective of this study was to update this information identifying and quantifying Meloidogyne and Pratylenchus species in the major sugarcane producing areas from Alagoas State.

During 2012, soil and root samples were collected from 20 sugarcane farms located in 16 municipalities, which represented the major sugarcane growing areas in the state of Alagoas (SINDAÇÚCAR, 2012). Four samples were collected from each field, with approximately 1.0kg of soil and 100g of sugarcane roots. Soil samples were homogenized, and 100cm³ of each sample were processed as described by JENKINS (1964); whereas, 50g of root was used for nematode extraction according to COOLEN & D´HERDE (1972). Pearson and Spearman correlation analyses (P≤0.05) were performed between nematode populations and sugarcane crop stage, application of nematicide and vinasse, irrigation, and the harvest method.

Pratylenchus spp. were identified to the species level by morphological characters and morphometric measurements according to CASTILLO & VOVLAS (2007). For isozyme characterization, young egg-laying females of Meloidogyne spp. were removed from tomato galls [(Solanum lycopersicum Mill.) Santa Cruz cv. Kada Gigante] and macerated in extraction buffer (KUNIEDA DE ALONSO & ALFENAS, 1998). Females of M. javanica were used as reference phenotype. Electrophoresis was performed in a vertical slab in polyacrylamide gels (ESBENSHADE & TRIANTAPHYLLOU, 1985; ALFENAS et al., 1991).

The genera Pratylenchus and Meloidogyne were observed in roots and/or soil from all sampled areas (Table 1) and it is in accordance to other studies in Brazil (CHAVES et al., 2009; BELLÉ et al., 2014). Pratylenchus spp. had the highest mean population densities in roots from a sugarcane farm located in the county of Teotônio Vilela (1,556 specimens 50g^-1 roots) while in the soil the highest value was observed in the county of Maceió (298 specimens 100cm^-3 of soil). According to STIRLING & BLAIR (2000), P . zeae population densities higher than 250 specimens per 200g of soil, detected six months after planting, can expressively reduce sugarcane yield.

Table 1
Pratylenchus and Meloidogyne species on sugarcane growing areas in Alagoas State, Brazil.

• ^*Each value is a mean of four samples. Ma = Meloidogyne arenaria ; Mi = M. incognita ; Mj = M. javanica ; Pb = Pratylenchus brachyurus ; Pz = P. zeae .

When considering the sugarcane cultivar, the highest Pratylenchus spp. populations occurred in 'RB 92579' (Table 1). For Meloidogyne spp., the highest population densities (487 juveniles 50g^-1 roots) were observed in 'SP 813250', followed by 'SP 753046' (389 juveniles 50g^-1 roots) and 'RB 92579' (262 juveniles 50g^-1 roots) (Table 1). The susceptibility of the RB 92579 cultivar to M. incognita has been previously reported under greenhouse condition (SILVA et al., 2012), representing 50% of all cultivars evaluated in this study.

Electrophoresis separation of esterases revealed four distinctive phenotypes: phenotype I1 with one band (Rm 1.00), phenotype I2 with two bands (Rm 1.00 and 1.09) specific toM. incognita , phenotype J3 with three bands (Rm 1.00, 1.07, and 1.17) characteristic of M. javanica , and phenotype A2 with two bands (Rm 1.17 and 1.28) specific to M. arenaria . Of these three species, M. incognita was the most recurrent, either alone or in association with M. arenaria or M. javanica (Table 1). These observations are not in accordance with previous reports (SEVERINO et al., 2008) where M. javanica was reported as being the predominant species in several sugarcane fields in Brazil.

Regarding the genus Pratylenchus the predominant species was P. zeae , either alone or in mixed population; whereas, P. brachyurus occurred in only two areas (Table 1). In survey conducted by BELLÉ et al. (2014), within this genus, P. zeae was the most common species associated with sugarcane crop.

Pratylenchus zeae, P. brachyurus, M. javanica , M. incognita and M. arenaria prevailed in sugarcane fields in Alagoas State. Out of the five species, P. zeae and M. incognita were the most frequently observed. No significant correlations (P≤0.05) were reported between nematode populations and sugarcane cropping systems.

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• 1
  CR-2015-1402.R1

Publication Dates

• Publication in this collection
  08 Dec 2016
• Date of issue
  2017

History

• Received
  08 Oct 2015
• Accepted
  15 Sept 2016
• Reviewed
  14 Nov 2016