Nativa, Sinop, v. 10, n. 1, p. 90-94, 2022.

Pesquisas Agrárias e Ambientais

DOI: https://doi.org/10.31413/nativa.v10i1.13217 ISSN: 2318-7670

Morphology of tomato plants under nematode attack

and salicylic acid application

Francisco Romário Andrade FIGUEIREDO1*, João Everthon da Silva RIBEIRO2,

Toshik Iarley da SILVA3, Jackson Silva NÓBREGA2, Marlenildo Ferreira MELO1,

Manoel Bandeira de ALBUQUERQUE2, Guilherme Silva de PODESTÁ2

1Postgraduate Program in Fitotechnics, Federal Rural University of the Semi-Arid, Mossoró, RN, Brazil.

2Postgraduate Program in Agronomy, Federal University of Paraíba, Areia, PB, Brazil.

3Postgraduate Program in Fitotechnics, Federal University of Viçosa, Viçosa, MG, Brazil.

*E-mail: romarioagroecologia@yahoo.com.br

(ORCID: 0000-0002-4506-7247; 0000-0002-1937-0066; 0000-0003-0704-2046; 0000-0002-9538-163X;

0000-0001-7449-6916; 0000-0003-1871-0046; 0000-0003-1613-7178)

Recebido em 03/12/2021; Aceito em 04/03/2022; Publicado em 14/03/2022.

ABSTRACT: Root-knot nematodes are the main soil-dwelling phytopathogens that cause severe damages to

plants, especially tomato plants. Exogenous application of salicylic acid (SA) can mitigate such pathogenicity.

This work aimed to evaluate the growth of tomato plants submitted to Meloidogyne javanica population densities

(PD) and application of SA. The experiment was a randomized block design, in an incomplete factorial scheme

(central composite design), with five PD (0, 5815, 20000, 34184, and 40,000 eggs per pot) and five SA doses

(0.0, 0.29, 1.0, 1.71, and 2.0 mM), with four replicates containing two plants each. Number of leaves, plant

height, stem diameter, shoot dry mass, root dry mass and total dry mass, Dickson's quality index, leaf area,

specific leaf area, specific leaf weight, root volume, absolute and relative growth rates for plant height, number

of eggs, number of galls, and nematode reproduction factor were evaluated at 50 days after soil inoculation

(DAI). Results showed the application of 0.97, 2.0, and 0.88 mM SA increased, respectively, the RGR, SLA and

SLW. On the other hand, 0.91 and 0.93 mM SA decreased, respectively, the number of eggs and reproduction

factor of nematodes. Also, M. javanica did not affect the growth of tomato plants until 50 DAI.

Keywords: Meloidogyne javanica; phytohormone; Solanum lycopersicum.

Morfologia do tomateiro sob ataque de nematoides e aplicação de ácido salicílico

RESUMO: Nematoides das galhas são uns dos principais patógenos de solo que causam danos severos nas

plantas, especialmente em plantas de tomate. A aplicação exógena de ácido salicílico (AS) pode minimizar os

efeitos desses patógenos. O objetivo deste trabalho foi avaliar o crescimento de plantas de tomate submetidas

à densidades populacionais de Meloidogyne javanica (DP) e aplicação de AS. O delineamento em blocos

casualizados em esquema fatorial incompleto (Composto Central de Box) com cinco DP (0, 5815, 20000, 34184

e 40000 ovos por planta) e cinco doses de AS (0.0, 0.29, 1.0, 1.71 e 2.0 mM), com quatro repetições e duas

plantas por repetição foi utilizado. O número de folhas, altura de planta, diâmetro do caule, massa seca da parte

aérea, raiz e total, índice de qualidade de Dickson, área foliar, área foliar específica, peso específico de folha,

volume de raiz, taxas de crescimento absoluto e relativo para altura, número de ovos, número de galhas e fator

de reprodução dos nematoides foram avaliados aos 50 dias após a inoculação do solo (DAI). A aplicação de

0.97, 2.0 e 0.88 mM de AS aumentam a taxa de crescimento relativo de altura, área foliar específica e peso

específico de folhas, respectivamente. A aplicação de 0.91 e 0.93 mM de AS diminuem o número de ovos por

grama de raiz e fator de reprodução, respectivamente. M. javanica não influenciou o crescimento de plantas de

tomate até 50 DAI.

Palavras-chave: Meloidogyne javanica; fitohormônio; Solanum lycopersicum.

1. INTRODUCTION

Nematodes, especially those from the Meloidogyne genus,

are the main soil-dwelling phytopathogens. They form galls

on the roots of parasitized plants (VIGGIANO et al., 2014),

causing stunted growth, wilting, leaf discoloration, and root

deformation. M. incognita and M. javanica are the most harmful

nematode species, depending on population density, crop

susceptibility, soil type, and environmental conditions

(SAUCET et al., 2016).

These phytoparasites cause severe damages in tomato

plants (Solanum lycopersicum L.), one of the main vegetables

consumed in Brazil, as a source of vitamins and minerals

(PERVEEN et al., 2015). However, high nematode

infestation at planting can cause up to 100% fruit production

losses, in addition to reducing fruit quality (OLIVEIRA;

ROSA, 2014). Chemical nematicides have been used to

control these pathogens. However, frequent use of these

chemicals may cause toxicity and contaminate the

environment in addition to being ineffective and rising

production costs (ESCUDERO et al., 2016). Thus, it

becomes necessary to find effective products and techniques

that minimize such effects.

Salicylic acid (SA), a phytohormone of phenolic origin

that acts as a resistance inducer against biotic and abiotic

Figueiredo et al.

Nativa, Sinop, v. 10, n. 1, p. 90-94, 2022.

stresses, is a promising alternative against nematode attack on

plants (BORSATTI et al., 2015). SA was demonstrated as a

resistance inducer in soybean under Pratylenchus brachyurus

attack (LOPES et al., 2017) and as a resistance gene inducer

in Gynura aurantiaca L. (CAMPUS et al., 2014).

Studying the effect of SA on the growth of tomato plants

grown in soil infested by M. javanica is relevant due to the

effectiveness of this phytohormone in inducing resistance

(MOSTAFANEZHAD et al., 2014a). Thus, this work aimed

to evaluate the growth of tomato plants submitted to M.

javanica densities and application of salicylic acid.

2. 2. MATERIALS AND METHODS

2.1. Inoculum Preparation

Tomato plants (Solanum lycopersicum L. cv. Santa Clara)

were grown in pots (2 dm3 capacity) filled with soil and sand

(2: 1 v / v) for 70 days to multiply and obtain the pathogen

inoculum (Meloidogyne javanica). Tomato roots infected by

nematodes were washed and crushed in a blender in 0.5%

sodium hypochlorite solution (NaClO), under low rotation

for 20 seconds. Then, the solution was filtered through 200

and 500 mesh sieves, respectively. The content of the 500

mesh sieve was washed in running water to eliminate NaClO

then placed in a beaker to quantify the number of eggs under

an optical microscope (HUSSEY; BARKER, 1973). The soil

infestation was carried out at the time of transplanting

according to the treatments.

2.2. Preparation of Salicylic Acid

Distilled water was used to prepare the salicylic acid (SA)

doses. Three applications were performed at 15-day intervals:

the first one immediately after transplanting and soil

infestation, and the last one the day before the initial

evaluation.

2.3. Conditions and Experimental Design

The experiment was carried out in a greenhouse at the

Department of Crop and Environmental Sciences, Federal

University of Paraíba (UFPB), Areia city, Paraíba State,

Brazil.

Tomato seedlings (Santa Cruz Kada cultivar (Paulista),

Isla®, Porto Alegre, Brazil) were produced in polyethylene

trays with a commercial substrate (Basaplant®, Artur

Nogueira, Brazil). When they reached 10 to 15 cm in height,

the seedlings were transplanted into pots (5 dm3 capacity)

filled with a substrate composed of soil, sand, and cattle

manure (3: 1: 1 v / v). The substrate was previously sterilized

in an autoclave at 120ºC and 1 atm of steam pressure for two

hours. The plants were daily irrigated to keeping substrate at

field capacity. A substrate sample was taken for for

physicochemical analysis (Embrapa, 2018): 7.8 pH; 85.55 and

693.60 mg kg-3 P and K, respectively; 0.23, 0.00, 2.91, 1.59,

6.50, and 6.50 cmolc dm-3 Na+, H++Al3+, Ca2+, Mg2+, sum

of bases (SB), and cation exchange capacity (CEC),

respectively; and 22.21 g kg-1 organic matter (OM).

The experimental design was a randomized block, in an

incomplete factorial scheme (central composite design), with

five nematode population densities (0, 5815, 20000, 34184,

and 40,000 eggs per pot) and five doses of salicylic acid (0.0,

0.29, 1.0, 1.71, and 2.0 mM), with four replicates containing

two plants each, totalling nine combinations (MATEUS et al.,

2001).

2.4. Analyzed Variables

The evaluations were carried out at 50 days after

transplanting and soil inoculation (DAI), being measured the

variables: number of leaves, plant height, stem diameter,

shoot dry weight, root dry weight and total dry mass,

Dickson's quality index (DICKSON et al. 1960) (Equation

1):

DQI = /(

)

/

(01)

where: DQI = Dickson’s quality index, TDM = total dry mass, PL

= plant length, SD = stem diameter, SDM = shoot dry mass and

RDM = root dry mass.

Leaf area (BLANCO; FOLEGATTI, 2003) (Equation 2):

LA = 0.347(LxW)− 10.7 (02)

where: LA = leaf area (cm2), L = length (cm) and W = width (cm).

Specific leaf area and specific leaf weight (BENICASA,

2003) (Equation 3 and 4):

SLA = LA/LDM (03)

SLW = LDM/LA (04)

where: LDM = leaves dry mass.

Root volume (RV): determined with the support of a

beaker, where the roots were submerged in a known volume

of water.

Relative (RGRph) and absolute growth rates (AGRph)

were determined according to Benicasa (2003) (Equation 5

and 6):

RGRph = ()

 (05)

AGRph = ( )

 (06)

The evaluations were carried out every 15 days, in that: Ph1

= plant height (cm) at time t1, Ph2 = plant height (cm) at

time t2 and ln = natural logarithm.

The number of eggs per gram of root (NE g-1) was

determined by counting, under an optical microscope, the

total number of eggs in Petri dishes then divided by root fresh

weight; the number of galls per gram of root (NG g-1) was

determined by counting the number of galls present in the

root system; and the reproduction factor (RF) was obtained

by the ratio between the final and initial population density.

2.5. Statistical analysis

Data were submitted to analysis of variance by the F test

(p < 0.05) followed by polynomial regression analysis. All

statistical analyses were performed in R software (R CORE

TEAM, 2019).

3. RESULTS

Interaction between M. javanica population densities and

SA doses was not significant. Also, the population densities

did not affect the studied variables. On the other hand, SA

doses affected specific leaf area, specific leaf weight and

relative growth rate (p<0.05).

Morphology of tomato plants under nematode attack and salicylic acid application

Nativa, Sinop, v. 10, n. 1, p. 90-94, 2022.

SA stimulated RGRPH, SLW and SLA in the tomato

plants (Figure 1). RGRPH and SLW increased under up to

0.97 and 0.88 mM SA concentrations, reaching 0.100 cm cm-

1 day-1 and 0.020 g cm2 on average, respectively.

Figure 1. Relative growth rate for plant height (A), specific leaf

weight (B), and specific leaf area (C) in tomato plants under salicylic

acid application.

Figura 1. Taxa de crescimento relativo para altura de plantas (A),

peso específico de folhas (B) e área foliar específica (C) em plantas

de tomate sob aplicação de ácido salicílico.

Nematode population densities positively influenced the

number of eggs (NE), number of galls (NG), and

reproduction factor (RF). In turn, SA positively influenced

NE and RF (p<0.05).

NG linearly increased with increasing inoculum

concentration (Figure 2A). On the other hand, NE was

higher at 23903 eggs per plant, decreasing afterwards (Figure

2B), while RF (20.01) was higher in 20079 eggs per plant

(Figure 2C).

NE decreased by 67.5% while RF decreased by 46.4%

under application of up to 0.91 and 0.93 mM SA, respectively,

but increased after that (Figures 3A and 3B).

Figure 2. Number of galls (A) and eggs (B) per gram of root and

reproduction factor (C) in tomato plants under population densities

of Meloidogyne javanica.

Figure 2. Número de galhas (A) e ovos (B) por grama de raiz e fator

de reprodução (C) em plantas de tomate sob densidades

populacionais de Meloidogyne javanica.

4. DISCUSSION

PDs did not affect plant growth because the time (50

days) between the soil infestation and plant evaluation was

not enough for the nematodes to reproduce and increase the

infestation (ABRÃO; MAZZAFERA, 2001). However,

different results were observed in cherry tomato (S.

lycopersicum var. Cerasiforme) infested by nematodes.

Regardless of population density, the parasitized site worked

as a sink for photoassimilates resulting in reduced leaf

expansion (BELAN et al., 2011).

In turn, SLA was higher at 2.0 mM dose, with a 13.5%

increase compared to control. Results support that SA effects

on plant growth vary according to the application form and

plant species studied (EL-ESAWI et al., 2017). It has been

shown that SA favors cell extension but limit cell division,

denoting a reason for the effectiveness of this phytohormone

(JAYAKANNAN et al., 2015).

Figueiredo et al.

Nativa, Sinop, v. 10, n. 1, p. 90-94, 2022.

Figure 2. Number of eggs (A) and reproduction fator (B) in tomato

plants under population densities of Meloidogyne javanica.

Figure 2. Número de ovos (A) e fator de reprodução (C) em plantas

de tomate sob densidades populacionais de Meloidogyne javanica.

Similar results were observed in tomato plants treated

with 0.75 mM SA, which increased the number of leaves, leaf

area, and leaf dry weight (ARFAN et al., 2007). Such benefits

on tomato growth occurred because SA significantly affects

the plant physiological processes, like photosynthesis that can

be induced or inhibited respectively by low and high SA

concentrations used (KHAN et al., 2015). Also, the duration

of exposure, plant species, age, and treated organ may

influence the SA effects on plants (MIURA; TADA, 2014).

The linear increase in NG occurred because the inoculum

amount directly affects the number and size of galls, thus

increasing according to population density (KAYANI et al.,

2017). In a short time, in plants under low infestation levels,

the nematode population growth is exponential. However, as

the population increases, competition for space and nutrients

also increases among nematodes, which thus reduces their

growth rate (CARNEIRO et al., 1999). It may explain why

NE and RF reduced under higher population densities.

The beneficial effect of SA is due to this hormone induce

defense mechanisms in plants, such as increasing production

of resistance-related enzymes like phenylalanine ammonium

lyase (PAL), peroxidase (POX) and polyphenol oxidase

(PPO), and stimulating the accumulation of phenolic

compounds (MOSTAFANEZHAD et al., 2014b). However,

SA causes hormonal imbalance at high levels, becoming

plants susceptible to pathogen attack. In tomato plants, the

beneficial effect of this hormone is associated with the

activation of SAR-related genes (MOSLEMI et al., 2016).

5. CONCLUSIONS

Salicylic acid applied at 0.97, 2.0 and 0.88 mM

concentrations increases respectively the relative growth rate

for plant height, specific leaf area, and specific leaf weight in

tomato plants.

At 0.91 and 0.93 mM concentrations, SA reduces the

number of eggs per gram of root and reproduction factor of

nematodes, respectively.

Meloidogyne javanica does not influence tomato growth

until 50 days after soil infestation under these experimental

conditions.

6. ACKNOWLEDGMENTS

The authors thank the Coordenação de Aperfeiçoamento

de Pessoal de Nível Superior (CAPES) and the Conselho

National de Desenvolvimento Científico e Tecnológico

(CNPq), Brazil, for granting the scholarships.

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