Thermal time requirements of root

Thermal time requirements of rootknot nematodes on zucchini-squash and
population dynamics with associated yield
losses on spring and autumn cropping
cycles
María Dolores Vela, Ariadna Giné,
Manuel López-Gómez, Francisco Javier
Sorribas, Cesar Ornat, Soledad VerdejoLucas, et al.
European Journal of Plant Pathology
Published in cooperation with the
European Foundation for Plant
Pathology
ISSN 0929-1873
Eur J Plant Pathol
DOI 10.1007/s10658-014-0482-x
1 23
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Author's personal copy
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DOI 10.1007/s10658-014-0482-x
Thermal time requirements of root-knot nematodes
on zucchini-squash and population dynamics with associated
yield losses on spring and autumn cropping cycles
María Dolores Vela & Ariadna Giné & Manuel López-Gómez &
Francisco Javier Sorribas & Cesar Ornat &
Soledad Verdejo-Lucas & Miguel Talavera
Accepted: 7 July 2014
# Koninklijke Nederlandse Planteziektenkundige Vereniging 2014
Abstract The present research was undertaken to evaluate the effects of soil temperature on the life cycle of
root-knot nematodes (RKN) on zucchini-squash in
growth chambers and to assess the relationship between
Meloidogyne incognita soil population densities at
planting (Pi), its multiplication rate, and crop losses of
zucchini in field conditions. Thermal requirements for
M. incognita and M. javanica were determined by cultivating zucchini plants in pots inoculated with 200 second
stage juveniles (J2) of each Meloidogyne species at
constant temperatures of 17, 21, 25, and 28 °C.
Number of days from nematode inoculation until appearance of egg laying females and until egg hatching
were separately recorded. For life cycle completion,
base temperatures (Tb) of 12ºC and 10.8ºC and
M. D. Vela
IFAPA Chipiona,
Camino de Esparragosa, Chipiona Cádiz, Spain
A. Giné : F. J. Sorribas : C. Ornat
DEAB-UPC,
Castelldefels, Barcelona, Spain
M. López-Gómez : S. Verdejo-Lucas
IRTA Sustainable Plant Protection,
Cabrils, Barcelona, Spain
S. Verdejo-Lucas
IFAPA La Mojonera,
La Mojonera, Almería, Spain
M. Talavera (*)
IFAPA Camino de Purchil,
Apdo. 2027, 18004 Granada, Spain
e-mail: [email protected]
accumulated degree-days above Tb (S) of 456 and
526, were estimated for M. incognita and M. javanica,
respectively. The relationship between fruit weight and
M. incognita Pi fits the Seinhorst damage function, but
differed accordingly to the cropping season, spring or
autumn. Tolerance limits for M. incognita on zucchini
were 8.1 J2 per 250 cm3 of soil in spring and 1.5 in
autumn cropping cycles, and the minimum relative
yields were 0.61 in spring and 0.69 in autumn.
Zucchini-squash was a poorer host for M. incognita in
spring than in autumn, since maximum multiplication
rates (a) and equilibrium densities (E) were lower in
spring (a=16–96; E=274–484) than in autumn (a=
270–2307; E=787–1227).
Keywords Cucurbita pepo . Damage functions .
Meloidogyne incognita . M. javanica . Tolerance
Introduction
The family Cucurbitaceae consists of approximately
125 genera and 960 species, including important crops
cultivated worldwide such as cucumber, luffa, melon,
watermelon and squashes (gourds, pumpkins and zucchinis). Most cucurbits are susceptible to root-knot nematodes (RKN) (Fassuliotis 1971) causing yield losses in
many growing areas (Edelstein et al. 2010; Wesemael
et al. 2011; Talavera et al. 2012).
Although plant species and cultivars differ in their
tolerance to Meloidogyne species, it is assumed that for
any RKN-host plant combination the damage caused by
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nematodes depends on the soil population densities at
planting (Pi) as well as its reproductive potential in the
host plant (Greco and Di Vito 2009). There is a direct
positive correlation between Pi and yield loss and an
inverse correlation between Pi and the nematode multiplication rate on the host plant (Pf/Pi), being Pf the
nematode densities in soil at harvest (Seinhorst 1965,
1998). Moreover, the nematode reproductive rate is
strongly influenced by temperature and directly related
to the accumulated degree-days (DD) over a base temperature (Tb) during the cropping cycle (Trudgill 1995).
Therefore, it has been suggested that damage thresholds
for annual vegetable crops are also related to the planting time and the duration of the crop cycle (Ehwaeti
et al. 1998).
For sustainable management of RKN, it is fundamental to develop accurate information on the nematode
population densities that cause yield losses and quantify
them into plant damage functions. These damage functions allow the estimation of: i) the tolerance limit (t),
defined as the nematode Pi up to which no measurable
yield loss occurs; and ii) the minimum yield (m), when
at high values of Pi, increasing numbers of nematodes
may not further reduce crop yield or plant productivity
(Seinhorst 1965). Estimation of these critical levels is
basic for the design of integrated nematode management
programs (Ferris et al. 1986).
Damage functions for various Meloidogyne species
have been described on some vegetable crops including
common bean, pepper, tomato, artichoke, cabbage, eggplant, spinach and tomato as summarized in Greco and
Di Vito (2009). In cucurbits, several studies have also
established tolerance limits for RKN and estimated yield
losses on cucumber (Cucumis sativus) (Giné et al.
2014), melon (Cucumis melo) (Di Vito et al. 1983;
Ploeg and Phillips 2001; Kim and Ferris 2002) and
watermelon (Citrillus lanatus) (Xing and Westphal
2012). However, for other cucurbit crops, such as
squashes (Cucurbita pepo), these relationships have
not been accurately determined and the quantitative
yield response of squashes to RKN infection is poorly
understood.
Zucchini-squash is an important crop in Southern
Spain, where it is cultivated either as a spring or autumn
crop in growing periods of three to five months. Most of the
production is concentrated in the provinces of Almería,
Cádiz and Granada, which account for one third of the
total zucchini production in Spain (MAGRAMA 2011).
In 2010, 7,618 ha were dedicated to zucchini cultivation
in Spain with a production of 366498 Tm. Losses caused
by RKN on zucchini under protected cultivation were
estimated at € 649504 in south-eastern Spain (Talavera
et al. 2012).
The present study was undertaken to determine the
thermal requirements of M. incognita and M. javanica
on zucchini-squash in growth chamber pot trials, and to
evaluate the relationships of M. incognita Pi vs. crop
yield and Pi vs. multiplication rate (Pf/Pi) in spring and
autumn plantings of zucchini-squash under field
conditions.
Materials and methods
Thermal requirements
Development of two RKN isolates of Meloidogyne incognita and M. javanica on zucchini-squash (Cucurbita
pepo L.) cv. Amalthee HF1 was determined at four
constant temperatures in separate climatic growth chambers set at 17, 21, 25, and 28 °C with a 16/8 h light/dark
photoperiod. Nematode isolates were maintained on
susceptible tomato cv. Durinta and eggs were extracted
by blender maceration of infected roots in a 0.5 %
NaOCl solution for 5 min accordingly to the Hussey
and Barker (1973) procedure. The egg suspension was
then passed through a 74-μm aperture sieve to remove
root debris, and the dispersed eggs were collected on a
25-μm sieve, and placed on Whitehead trays at 25 °C to
obtain second-stage juveniles (J2) (Whitehead and
Hemming 1965). Juveniles were collected daily on a
25-μm sieve. The J2 emerging during the first 24 h were
discarded, and those emerging from day 2 to 5 were
used as inoculum. They were stored at 9 °C until 8 h
before inoculation, when they were placed inside the
respective growth chambers for acclimatization.
Zucchini seeds were germinated in trays containing
vermiculite. Two-week-old seedlings were transplanted
singly into 250-cm3 pots containing steam-sterilized
sand. Sixty replicated plants were prepared per RKN
species temperature combination. Plants were allowed
to grow and acclimatize, in each growth chamber for
one-week, prior inoculation with 200 J2 per pot. The
inoculum was added into opposite holes 1 cm apart from
the stem and 3 cm deep. Plants were irrigated as needed
with water at the same temperature of the growth chambers to prevent dramatic changes in soil temperature.
Plants were fertilized with a slow release fertilizer
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(Osmocote Plus ®: NPK 15–10-12+2 % MgO+microelements) by adding approximately 1 g onto the soil
surface at the time of transplanting. Soil temperatures
were recorded daily at 30 min intervals with probes
(PT100, Campbell Scientific Ltd. ®) placed 4 cm deep
into the potted soil, one probe per growth chamber.
Three developmental processes were separately
assessed because different processes may have different
thermal requirements (Madulu and Trudgill 1994). The
processes considered were: i) development, from J2
inoculation until the first observation of female laying
eggs, (ELF); ii) egg production, from ELF stage to first
egg hatch of J2 (EH) as indicated by the presence of
empty egg shells; and iii) life cycle completion, from J2
inoculation to EH. Three plants per incubation temperature were removed daily until infection had occurred.
Thereafter, plants were removed periodically to follow
the process.
Nematodes inside roots were stained with 0.05 %
acid fuchsine (Bridge and Page 1982) cleared and observed the same day under a stereoscopic microscope.
To assess both egg production and egg hatching, the
entire root system was submerged in a 0.1 g l -1
erioglaucine solution for 2 h to stain in blue the gelatinous matrix and facilitate counting of the egg masses
(Omwega et al. 1988). For assessing the begining of egg
hatching, egg masses were handpicked and dispersed in
0.5 % NaOCl solution to estimate the number of days
until egg production started and the first empty eggs
were observed.
Rates of development and egg production for each
temperature were calculated as the reciprocal of the
number of days (days−1) required to reach a certain
biological stage. Rates were related to temperature of
incubation by regression analysis to calculate the base
temperature (Tb) for each biological stage, which is the
temperate below which the given rate is equal to zero,
and the thermal constant (S), which is the accumulated
DD over Tb, calculated as the reciprocal of the slope of
the regression equation (Trudgill 1995).
Field trials
Four field trials were carried out from 2011 to 2013 in an
experimental unheated plastic greenhouse (1040 m2) at
IFAPA Chipiona, Cádiz, Spain (36°44’56”N 6°24’06”W). Two trials were carried out in spring from
23/02 to 08/06/2011 and from 01/03 to 14/06 2012, and
the other two in autumn from 10/10/2011 to 24/01/2012
and from 04/10/2012 to 17/01/2013. All trials lasted
105 days.
Ground beds containing sandy soil (90 % sand: 8 %
silt: 2 % clay), with pH 8.1, electric conductivity 0.5 dS/
m and 1.0 % organic matter, were naturally infested with
a population of M. incognita. The field was divided into
36 individual plots of 24.5 m2 (7×3.5 m). Ten plants of
zucchini cv. Amalthee HF1 were planted per plot, in two
rows with five plants each. Plants were spaced 100 cm
within the row and 100 cm between rows with these in
different plots being at least 200 cm apart. The soil was
prepared by hand-hoeing plots individually to prevent
cross contamination between them. Plants were irrigated
as needed through a drip irrigation system and were
fertilized weekly with a solution consisting of NPK
(15-5-30) at 31 kg per ha and iron chelate and
micronutrients at 0.9 kg per ha. Zucchini plants were
vertically trellised and plant growth regulators (ANA
0.45 %+ANA-AMIDA 1.2 % w/v at 0.06 %) were
applied at the start of flowering by foliar spraying.
Weeds were removed manually during and between
cropping cycles. Soil temperatures were recorded daily
at 30 min intervals with probes (Tinytag plus 2, Gemini
Data Loggers Ltd. ®) placed at 15 cm deep. At the end
of each cropping cycle, plants were cut at ground level
and the root systems removed from the plastic house. To
determine zucchini yield, fruits produced by the ten
plants of each plot were harvested once a fortnight.
Fruit yields were expressed as kilograms of fruit per
plant (mean±standard error).
Composite soil samples were collected from each
plot at the beginning and at the end of each cropping
cycle to estimate Pi and Pf values, respectively.
Individual samples, consisting of ten soil cores, were
taken from the rhizosphere of each plant to a depth of
30 cm with a sampling tube (2.5 cm diameter). Samples
were mixed thoroughly and nematodes extracted from
250 cm3 soil subsamples using the Whitehead tray
method (Whitehead and Hemming 1965). After 1 week
of incubation in the trays, J2 were concentrated on a
25-μm aperture sieve and counted. Nematode counts
were expressed per 250 cm3 of soil (mean±standard
error).
At the end of each cropping cycle, root systems of all
the plants per plot were dug from the soil and the gall
index rated according to a 0–10 scale to assess the
disease severity. In this scale, 0=a well-developed and
healthy root system and 10=plants and roots dead
(Bridge and Page 1980). To determine egg production,
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the 10 root systems were bulked, chopped in 1 cm long
segments, mixed and two 30 g sub-samples were used to
extract eggs by maceration for 10 min in a blender
containing a 0.5 % NaOCl solution (Hussey and
Barker 1973). Eggs and J2s were counted and expressed
per g of root.
The relationship between Pi vs. fruit weight were
determined by fitting the data to the Seinhorst model
(Seinhorst 1998):
Pi=t−1
y ¼ m þ ð1–mÞ0:95
when Pi > t
y ¼ 1 when Pi < t
where y=relative value of the plant growth parameter
(fruit yield); m=minimum y value (y at a very large Pi)
and t=tolerance limit (Pi at which plant growth is not
impaired).
Statistical analyses
Statistical analyses were performed using Statistix 9.0
software © (Analytical Software, Tallahassee, FL) and
the general linear model procedure of the SAS software
version 8 © (SAS institute Inc. Cary, NC).
For the thermal requirements, regression analyses
were carried out to determine linear equations between
the reciprocal of time elapsed between biological stages
and the soil temperature recorded along the experiments.
The slopes of the regression lines for the two RKN
species were compared by the SAS GLM procedure.
For field trials, data on soil nematode densities at
harvest (Pf), multiplication rates (Pf/Pi), gall rating, eggs
per g of roots and fruit yield were submitted to analysis
of variance, using Pi as covariate, to compare data from
Table 1 Number of days, base temperature (Tb) and accumulated
degree-days (DD) above Tb (S) from inoculation of 200 secondstage juveniles until completion of several developmental stages in
the four cropping cycles, and from the two cropping
seasons (spring vs. autumn). Shapiro-Wilk and Levene’s
tests were performed to check for normality and homoscedasticity of discrete variables. Where significant,
numerical data were log (x+1) transformed before analysis. When the overall F test was significant (P<0.05),
means were separated by the least significant difference
(LSD) method.
Regression analyses were used to determine the relationship between log (Pi+1) and log (Pf/Pi) and compare them between cropping cycles. When no differences were found, data were pooled to construct a single
general model. The adjustment between Pi and the
relative yield of zucchini to the Seinhorst function damage model was determined by the ‘nlin’ procedure of
SAS version 8 ©. This is an iterative process starting
with values of the parameters provided by the user, as
well as the bounds between which they can vary. The
values of m and t used to start the iteration were estimated from plotting experimental values of squash yield
against log10 (Pi+1). The goodness of fit was estimated
by the coefficient of determination.
Results
Thermal requirements
Thermal requirements and values of Tb and S for the
different biological processes and the whole life cycle of
M. incognita and M. javanica on zucchini are shown in
Table 1. The rates of development, egg production and
life cycle completion did not differ (P>0.05) between
these two RKN species (Figs. 1a, b and c).
the life cycle of Meloidogyne incognita or M. javanica on zucchini
cv. Amalthee HF1 in growth chambers
M. incognita
M. javanica
Soil temperature (ºC)
ELF
EH
LCC
Soil temperature (ºC)
ELF
EH
LCC
16.8
57
28
85
17.0
56
24
80
21.6
30
20
50
21.4
32
17
49
24.3
21
14
35
24.4
23
14
37
27.8
17
11
28
27.6
19
12
31
Tb (°C)
12.0
10.6
12.0
Tb (°C)
11.9
6.4
10.8
S (DD)
250.0
196.1
454.5
S (DD)
303.0
250.0
526.3
ELF: Egg laying females, EH: Egg hatching, and LCC: Life cycle completion
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Development rate
(days-1)
0.12
MJ
y = 0.0038x - 0.0447
R² = 0.9926
MI
y = 0.0040x - 0.0480
R² = 0.9903
0.10
0.08
0.06
0.04
0.02
a
0.00
0
5
10
15
20
25
30
25
30
25
30
Egg production rate
(days-1)
0.12
MJ
0.10
MI
0.08
y = 0.0040x - 0.0255
R² = 0.9996
y = 0.0051x - 0.0539
R² = 0.9633
0.06
0.04
0.02
b
0.00
0
5
10
15
20
Life cycle completion rate
(days-1)
0.12
0.10
0.08
MJ
y = 0.0019x - 0.0197
R² = 0.9976
MI
y = 0.0022x - 0.0263
R² = 0.9869
0.06
0.04
0.02
c
0.00
0
5
10
15
20
Soil Temperature (°C)
Fig. 1 Relationship between soil temperature and rates of development a, egg production b, and life cycle completion c, of
Meloidogyne incognita (MI, continuous line) and M. javanica
(MJ, dashed line) on zucchini-squash cv. Amalthee HF1 in growth
chambers
Field trials
The daily mean, maximum and minimum soil temperatures recorded during the four trials are presented in
Fig. 2. In the spring cycles, mean daily temperatures at
planting were in the range of 15.9–18.6ºC, and they
gradually increased to 24.6–26.9ºC, close to the last
harvest. In contrast, in the autumn cycles, mean daily
temperatures at planting were 25.7–25.9ºC and gradually decreased to 14.7–16.7ºC at the last harvest. The
sum of Celsius degrees, recorded during the trials, were
2409 and 2218 in the spring cycles and 1974 and 2085
in the autumn cycles.
Nematode initial (Pi) and final densities (Pf), multiplication rates (Pf/Pi), gall rating and egg per g of roots
at harvest per cropping cycle are shown in Table 2.
Initial nematode densities were similar among cropping
cycles, with the exception of the spring 2012, and averaged 408±38 J2 per 250 cm3 of soil in the spring crops
and 221±18 in the autumn crops. Final population
densities (Pf) and multiplication rates (Pf/Pi) were lower
in the spring (422±33 J2 per 250 cm3 of soil and 2.4±
0.5, respectively) than autumn cropping cycles (1059±
71 per 250 cm3 and 15.5±2.9) (P<0.001), and there
were no significant differences in Pf/Pi within the trials
conducted in spring or autumn. There was no clear
effect of cropping cycles on disease severity but the gall
rating after four consecutive cropping cycles was lower
than after the first cycle (P<0.05). Planting date did not
affect the M. incognita population within the roots, since
similar number of eggs per g of roots were produced on
zucchini in each cropping cycle, except for autumn
2011.
The relationship log10 (Pf/Pi) vs. log10 (Pi+1) differed among the four field trials (P<0.05) and a stronger
correlation between the Pi and Pf/Pi was found in the
autumn than spring cycles as indicated by the R2 values
(Fig. 3). Maximum multiplication rates were 16 and 96
in spring cycles, and 270 and 2307 in autumn cycles.
Equilibrium densities were 274 and 484 J2 per 250 cm3
of soil in spring cycles, and 787 and 1227 in autumn
cycles.
Yield, as fresh fruit weight per plant, was higher in
spring (2.7±0.1 kg per plant) than in autumn cycles (2.1±
0.1) (P<0.001). Average yield in nematode-free plants
was estimated in 3.4±0.7 kg per plant for spring and
autumn cycles. The relationship between Pi and fruit yield
fits the Seinhorst damage function equation (P<0.001),
but differed between cropping seasons. The minimum
relative yields were 0.61±0.05 and 0.69±0.04, for the
spring and autumn cycles, respectively. The tolerance
limits were 8.1±1.8 J2 per 250 cm3 of soil for the spring
cycles and 1.5±0.3 for the autumn ones (Fig. 4).
Discussion
The epidemiological characterization of RKN-induced
diseases is an important tool for decision-making in
nematode management. It should include information
on the geographical distribution of the nematode, the
occurrence and relative abundance, the thermal
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Fig. 2 Maximum, minimum and
mean daily soil temperatures
during four cropping cycles of
zucchini-squash cv. Amalthee
HF1 in field trials conducted in a
plastic greenhouse infested with
Meloidogyne incognita
35 °C
30 °C
25 °C
20 °C
15 °C
2011 Spring daily temperatures
10 °C
35 °C
˚
— Average ··· Minimum --- Maximum
Soil Temperature ( C)
30 °C
25 °C
20 °C
15 °C
2011 Autumn daily temperatures
10 °C
35 °C
30 °C
25 °C
20 °C
15 °C
10 °C
2012 Spring daily temperatures
35 °C
30 °C
25 °C
20 °C
15 °C
10 °C
2012 Autumn daily temperatures
Dates
requirements of RKN species, the relationship between
Pi and Pf/Pi on key crops cultivated in a certain area, and
the nematode survival rate between crops. In addition,
information on the relationship between Pi and crop
yield is needed to determine the damage thresholds
and maximum yield losses.
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Table 2 Average values of soil nematode densities at planting (Pi)
and harvest (Pf), multiplication rates (Pf/Pi), gall rating, eggs per
gram of roots of Meloidogyne incognita and fresh fruit yield from
Year and season
Pi x
2011
Spring
222±24 a
430±55 a
Autumn
269±28 a
916±96 b
Spring
594±58 b
415±38 a
Autumn
174±22 a
1202±102 c
2012
x
Pf x
36 plots cultivated with zucchini squash cv. Amalthee HF1 in a
nematode infested plastic house in spring and autumn
Gall rating
Eggs y
Fruit yield z
3.8±0.9 a
5.1±0.2 c
4961±306 a
2.7±0.1 b
12.9±3.7 b
1.7±0.2 a
6630±842 b
3.1±0.1 c
0.9±0.1 a
2.6±0.3 a
4089±770 a
2.7±0.1 b
18.1±4.4 b
3.0±0.1 b
4099±164 a
1.1±0.1 a
Pf/Pi
Juveniles per 250 cm3 of soil; y eggs per g of roots; z Kg per plant
Values are the average±standard error of 36 plots. Values within the same column followed by the same letter do not differ significantly
(P<0.05) according to the LSD test
Information on thermal requirements can be useful to
establish the most suitable planting dates for vegetables
with the aim of reducing root infection or the number of
generations per cropping cycle and thus preventing
yield losses. In this study, thermal requirements of
M. incognita and M. javanica on zucchini were determined by splitting the entire life cycle from J2 to J2 into
two epidemiological key processes: i) development,
which includes J2 penetration into the roots, infection
and development until egg laying females; and ii) egg
production until hatching.
Thermal requirements of both RKN species from soil
inoculation to ELF on zucchini (Tb=11.9–12.0; S=
250–303) were quite similar to those reported for egg
mass formation of M. arenaria, M. incognita and
M. javanica on squash under black polythene mulch
(Davila et al. 2005) or M. arenaria on oriental melon
(Tb = 12.2; S = 313) (Yeon et al. 2003), and for
M. incognita and M. javanica on cucumber (Tb=12.1;
S=294) (Giné et al. 2014). This result also agree with
those reported by López-Gómez and Verdejo-Lucas
(2014), who observed the presence of the same biological stages of these RKN species from 4–11 days post
inoculation in zucchini.
Thermal requirements for life cycle completion of
M. incognita (Tb=12.0; S=454.5 DD) on zucchini were
slightly different from those of M. javanica (Tb=10.8; S
=526.3 DD), which could reflect a differential host
status of zucchini squash cv. Amalthee to M. incognita
than M. javanica as suggested by López-Gomez and
Verdejo-Lucas (2014). However, both RKN species
showed similar thermal requirements on cucumber (Tb
=11.4; S=500 DD) (Giné et al. 2014) and these were
similar to those on tomato (Tb=10.1, S=400 DD)
(Ploeg and Maris 1999) or clover (Tb=10.1, S=410
DD) (Vrain et al. 1978). Our results support the suggestion that any factor delaying nematode development,
such as host status, may affect thermal requirements
(Tb and S) (Madulu and Trudgill 1994; Trudgill 1995).
This hypothesis is further supported by the fact that
development of M. konaensis on coffee was slower than
on tomato (Zhang and Schmitt 1995), or that of
M. hispanica on resistant than susceptible tomato
(Maleita et al. 2012).
Estimations based on thermal requirements of
M. incognita on zucchini for life cycle completion
and the accumulated degree-days over the base
temperature in the field trials, indicated that the
nematode has completed two generations during
the spring cropping cycles but only one in the
autumn cycles in the agro-environmental conditions of the field experiments.
Maximum multiplication rates and equilibrium densities were higher in the autumn than spring cycles as it
has been reported on tomato cropped in plastic house in
the same growing area (Talavera et al. 2009), and on
chickpea cropped in spring or winter (Di Vito and Greco
1988). These results sustain the concept that environmental conditions have a strong impact on population
dynamics of RKN. Ferris et al. (1986) reported a maximum multiplication rate of 495 for M. incognita on
zucchini cv. Fordhook in field experiments, which is
within the range obtained in the autumn cycles (270–
2307). The maximum multiplication rate (a) and the
equilibrium density (E) are indicators of the host status
for a given set of agro-environmental conditions
(Seinhorst 1967). Accordingly, zucchini was a better
host of M. incognita in autumn than in spring cycles
because the higher values of “a” and “E”, but it was
more sensitive to RKN infection, as shown by a lower
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Eur J Plant Pathol
2.0
1
1.5
1.0
0.5
0.0
Spring 2011
-0.5
0
1
2
2.0
3
4
y = -0.7869x + 2.4306
R² = 0.835
1.5
Relative yield (Fresh Fruit Weight)
y = -0.7434x + 1.982
R² = 0.6332
0.9
0.8
0.7
0.6
y = 0.61+(1-0.61)·0.95 (Pi / 8.1-1); R2 = 0.9626
Spring
0.5
Autumn y = 0.69+(1-0.69)·0.95 (Pi / 1.5-1); R2 = 0.9462
0.4
1.0
0
2
3
4
Log10(Pi+1)
0.5
Autumn 2011
Log10(Pf/Pi)
1
0.0
0
1
2
0.4
3
y = -0.4976x + 1.2128
R² = 0.5051
0.2
0.0
-0.2
-0.4
-0.6
Spring 2012
-0.8
0
1
2
2.5
3
4
y = -1.1613x + 3.3631
R² = 0.8254
2.0
1.5
1.0
0.5
Autumn 2012
0.0
0
1
2
3
Log10(Pi+1)
Fig. 3 Relationship between log10 (Pi+1) and log10 (Pf/Pi) of
Meloidogyne incognita on zucchini-squash cv. Amalthee HF1 in
field trials conducted in spring and autumn
tolerance limit in the autumn cycles. The higher temperatures observed at planting in autumn (25ºC), could
favour J2 movement, root penetration, infection, and
subsequent development, in comparison to the lower
temperatures observed at planting in spring (16ºC), with
the result of higher multiplication rates and stronger
negative effects on plants in the autumn than spring
cycles. The reduced inoculum effectiveness due to lower soil temperatures (reduced movement to penetrate
and infect roots) could be the cause of a major
Fig. 4 Relationship between log (Pi+1) of Meloidogyne incognita
and relative yield (fruit fresh weight) of zucchini-squash cv.
Amalthee HF1 in field trials conducted in spring and autumn
dispersion of data in spring than in autumn, which
results in a stronger correlation between Pi and PF/Pi
in autumn than in spring cycles. Yield losses in squash
due to pests and nematodes also differed between spring
and autumn cycles in Florida, USA (McSorley and
Waddill 1982) and Australia (Vawdrey and Stirling
1996). In addition, root injury in carrot was reduced at
late planting dates in Southern California, when soil
temperatures were reduced and fluctuated near or under
the M. incognita activity threshold of 18 °C (Roberts
1987).
Although Cucurbita species have been suggested as
the most susceptible cucurbits to RKN (Edelstein et al.
2010), Pi values below 125 nematodes per 250 cm3 of
soil had little impact on squash yield in Australia
(Stirling 2000). Continuous cropping of zucchini did
not increase progressively egg production (Table 2),
which is in agreement with the poorer status of zucchini
to M. incognita, compared to other cucurbit crops
(López-Gómez and Verdejo-Lucas 2014). In this study,
tolerance limits for M. incognita in zucchini were between 1.5 J2 per 250 cm3 of soil in autumn cycles and
8.1 J2 in spring cycles, within the range of to those
reported for melon and cucumber (Kim and Ferris
2002; Giné et al. 2014).
This study shows that there is a range of
susceptibility-tolerance to RKN in zucchini-squash depending on the agro-environmental conditions it is cultivated in, since differences in crop tolerance were observed between spring and autumn cycles. These results
suggest that modification of planting time and a careful
selection of the cultivars to be planted could reduce the
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Eur J Plant Pathol
economic impact of RKN on production of zucchini and
other vegetables.
Acknowledgments This work was funded by INIA project
RTA2010-00017-C02 and FEDER support from European Union.
Authors are thankful to Juan José Pertíñez and Maria Rubio for
technical assistance in the field and laboratory. Manuel LópezGómez received support from INIA through a pre-doctoral grant.
References
Bridge, J., & Page, S. L. J. (1980). Estimation of root knot
nematode infestation levels on roots using a rating chart.
Tropical Budapest Management, 26, 296–298.
Bridge, J., & Page, S. L. J. (1982). The rice root-knot nematode,
Meloidogyne graminicola on deep water rice (Oryza sativa
subsp. indica). Revue de Nematologie, 5, 225–232.
Davila, M., Allen, L. H., & Dickson, D. W. (2005). Influence of
soil temperatures under polyethylene mulch and bare soil on
root-knot nematode egg laying. Journal of Nematology, 37,
364–365.
Di Vito, M., Greco, N., & Carella, A. (1983). The effect of
population densities of Meloidogyne incognita on the yield
of cantaloupe and tobacco. Nematologia Mediterranea, 11,
169–174.
Di Vito, M., & Greco, N. (1988). The relationship between initial
population densities of Meloidogyne artiellia and yield of
winter and spring chickpea. Nematologia Mediterranea, 16,
163–166.
Ehwaeti, M. E., Phillips, M. S., & Trudgill, D. L. (1998).
Dynamics of damage to tomato by Meloidogyne incognita.
Fundamental and Applied Nematology, 21, 627–635.
Edelstein, M., Oka, Y., Burger, Y., Eizenberg, H., & Cohen, R.
(2010). Variation in the response of cucurbits to Meloidogyne
incognita and M. javanica. Israel Journal of Plant Sciences,
58, 77-84.
Fassuliotis, G. (1971). Susceptibility of Cucurbita spp. to the rootknot nematode, Meloidogyne incognita. Plant Disease
Reporter, 55, 666.
Ferris, H., Ball, D., Beem, L. W., & Gudmundson, L. A. (1986).
Using nematode count data in crop management decisions.
California Agriculture, 40, 12–14.
Giné, A., López-Gómez, M., Vela, M. D., Ornat, C., Talavera, M.,
Verdejo-Lucas, S., & Sorribas, F. (2014). Thermal requirements and population dynamics of root-knot nematodes on
cucumber and yield losses under protected cultivation. Plant
Pathology (In press).
Greco, N., & Di Vito, M. (2009). Population dynamics and damage levels. In R. N. Perry, M. Moens, & J. L. Starr (Eds.),
Root-Knot Nematodes (pp. 246–274). Wallingford: CABI.
Hussey, R. A., & Barker, K. R. (1973). A comparison of methods
of collecting inocula of Meloidogyne spp. including a new
technique. Plant Disease Reporter, 57, 1025–1028.
Kim, D. G., & Ferris, H. (2002). Relationship between crop losses
and initial population densities of Meloidogyne arenaria in
winter-grown oriental melon in Korea. Journal of
Nematology, 34, 43–49.
López-Gómez, M., & Verdejo-Lucas, S. (2014). Penetration and
reproduction of root-knot nematodes on cucurbit species.
European Journal of Plant Pathology, 138, 863–871.
Maleita, C., Curtis, R., & Abrantes, I. (2012). Thermal requirements for the embryonic development and life cycle of
Meloidogyne hispanica. Plant Pathology, 61, 1002–1010.
Madulu, J. D., & Trudgill, D. L. (1994). Influence of temperature
on the development and survival of Meloidogyne javanica.
Nematologica, 40, 230–243.
MAGRAMA (2011). Anuario de estadística Ministerio de
Agricultura, Alimentación y Medio Ambiente 2011. Madrid:
Ministerio de Agricultura, Alimentación y Medio Ambiente.
1189 pp.
McSorley, R., & Waddill, V. H. (1982). Partitioning yield loss on
yellow squash into nematode and insect components. Journal
of Nematology, 14, 110–118.
Omwega, C., Thomason, I. J., & Roberts, P. A. (1988). A nondestructive technique for screening bean germplasm for resistance to Meloidogyne incognita. Plant Disease, 72, 970–
972.
Ploeg, A. T., & Maris, P. C. (1999). Effects of temperature on the
duration of the life cycle of a Meloidogyne incognita population. Nematology, 1, 389–393.
Ploeg, A. T., & Phillips, M. S. (2001). Damage to melon (Cucumis
melo L.) cv. Durango by Meloidogyne incognita in Southern
California. Nematology, 3, 151-157.
Roberts, P. A. (1987). The influence of planting date of carrot on
Meloidogyne incognita reproduction and injury to roots.
Nematologica, 33, 335–342.
Seinhorst, J. W. (1965). The relationship between nematode density and damage of plants. Nematologica, 11, 137–154.
Seinhorst, J. W. (1967). The relationship between population
increase and population density in plant parasitic nematodes.
III. Definition of terms host, host status and resistance. IV.
The influence of external conditions on the regulation of
population density. Nematologica, 13, 429–442.
Seinhorst, J. W. (1998). The common relation between population
density and plant weight in pot and microplot experiments
with various nematode plant combinations. Fundamental
and Applied Nematology, 21, 459–468.
Stirling, G. R. (2000). Nematode monitoring strategies for vegetable crops. RIRDC Publication 00/25, Kingston: Rural
Industries Research and Development Corporation. 47 pp
Talavera, M., Verdejo-Lucas, S., Ornat, C., Torres, J., Vela, M. D.,
Macias, F. J., Cortada, L., Arias, D. J., Valero, J., & Sorribas,
F. J. (2009). Crop rotations with Mi gene resistant and susceptible tomato cultivars for management of root-knot nematodes in plastic houses. Crop Protection, 28, 662–667.
Talavera, M., Sayadi, S., Chirosa-Ríos, M., Salmerón, T., FlorPeregrín, E., & Verdejo-Lucas, S. (2012). Perception of the
impact of root-knot nematode-induced diseases in horticultural protected crops of south-eastern Spain. Nematology, 14,
517–527.
Trudgill, D. L. (1995). An assessment of the relevance of thermal
time relationships to Nematology. Fundamental and Applied
Nematology, 18, 407–417.
Vawdrey, L. L., & Stirling, G. R. (1996). The use of tolerance and
modification of planting times to reduce damage caused by
root-knot nematodes (Meloidogyne spp.) in vegetable
cropping systems at Bundaberg, Queensland. Australasian
Plant Pathology, 25, 240–246.
Author's personal copy
Eur J Plant Pathol
Wesemael, W. M. L., Viaene, N., & Moens, M. (2011). Root-knot
nematodes (Meloidogyne spp.) in Europe. Nematology, 13, 3–
16.
Vrain, T. C., Barker, K. R., & Holtzman, G. I. (1978). Influence of
low temperature on rate of development of Meloidogyne
incognita and M. hapla larvae. Journal of Nematology, 10,
166–171.
Whitehead, A. G., & Hemming, J. R. (1965). A comparison of
some quantitative methods of extracting small vermiform
nematodes from soil. Annals of Applied Biology, 55, 25–38.
Xing, L., & Westphal, A. (2012). Predicting damage of
Meloidogyne incognita on watermelon. Journal of
Nematology, 44, 127–133.
Yeon, I. K., Kim, D. G., & Park, S. D. (2003). Soil
temperature and egg mass formation by Meloidogyne
arenaria on oriental melon (Cucumis melo L.). Nematology,
5, 721–25.
Zhang, F., & Schmitt, D. P. (1995). Embryogenesis and postinfection development of Meloidogyne konaensis. Journal of
Nematology, 27, 103–108.

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