Article
Productivity and Oil Content in Relation to Jatropha
Fruit Ripening under Tropical Dry-Forest Conditions
Álvaro Cañadas-López 1,2,* , Diana Yasbhet Rade-Loor 3, Marianna Siegmund-Schultze 4,
Marys Iriarte-Vera 3, Juan Manuel Domínguez-Andrade 5, Jesús Vargas-Hernández 6and
Christian Wehenkel 7
1Universidad Laica Eloy Alfaro de Manabí, Facultad de Ingeniería Agropecuaria, Carrera Ingeniería
Agropecuaria, Campus ULEAM-Extensión Chone, Av. Eloy Alfaro, Chone C.P. 130301,
Provincia de Manabí, Ecuador
2Instituto Nacional de Investigaciones Agropecuarias (INIAP), Estación Experimental Tropical Pichilingue,
Programa de Forestaría, Km 5 vía Quevedo—El Empalme, Cantón Mocache C.P. 120501,
Provincia Los Ríos, Ecuador
3Escuela Superior Politécnica de Manabí(ESPAM-MFL), Centro de Investigación de las Carreras de la
ESPAM-MFL (CICEM), Campus Politécnico Calceta, Sitio El Limón, Calceta, Cantón Bolívar C.P. 130250,
[email protected] (M.I.-V.)
4Technische Universität Berlin, Environmental Assessment and Planning Research Group, Straße des 17,
5Escuela Superior Politécnica del Litoral (ESPOL), ESPAE Graduate School of Management, Campus Las
6Colegio de Postgraduados, Posgrado en Ciencias Forestales, Montecillo, Texcoco, Mexico;
7Instituto de Silvicultura e Industria de la Madera, Universidad Juárez del Estado de Durango,
Boulevard Guadiana #501, Ciudad Universitaria, Torre de Investigación, Durango C.P. 34120, Mexico;
*Correspondence: alvar[email protected]; Tel.: +593-93-906-8644
Received: 27 August 2018; Accepted: 1 October 2018; Published: 4 October 2018
Abstract:
Jatropha is promoted as a pro-poor bioenergy plant, while basic information about its
productivity, age of maximum production, and oil content are missing. This study aims to determine
the seed yield (dry weight) for three INIAP elite jatropha accessions, and to evaluate the changes
in physical and chemical seed traits at the different fruit ripening stage in a split-plot design.
Maximum seed production occurred four years after planting for the accessions CP041 and CP052,
while for accession CP054, it occurred after the first year. CP041 was the most productive, with a
mean of 316.46 g tree
−1
year
−1
(
±
76.50) over the 8-year study period. No significant differences
in oil content were found among accessions, fruit ripening stage, and their respective interactions.
Seed moisture content decreased drastically as the fruit ripening stage increased, from 40.5%
±
1.0% at
fruit ripening stage 1 (greenish-yellow) down to 13.8%
±
0.4% at fruit ripening stage 4 (black-brown).
No significant differences in seed weight were found among accessions, but it decreased as maturation
progressed. Yellow fruits (stage 2) were the heaviest (62.4 g
±
1.5 g) and the black-brown fruits the
lightest (44.3 g
±
1.9 g). The oil content (%) increased with seed weight up to the point of 58.3 g,
but then decreased for heavier seeds.
Keywords: harvesting point; jatropha accessions; seed productivity; seed humidity; seed oil content
Forests 2018,9, 611; doi:10.3390/f9100611 www.mdpi.com/journal/forests
Forests 2018,9, 611 2 of 13
1. Introduction
Jatropha curcas L. (in the following: jatropha) is a shrub or small tree belonging to the tribe
Joannesieae of the family Euphorbiaceae, adapted to arid zones, with potential use for biofuel production.
Jatropha is commonly used in the Manabíprovince, Ecuador, as living fence for pasture division [
1
].
Jatropha had often been classified as an ideal “pro-poor” crop, due to its potential value for seed oil
production in marginal and degraded areas. Consequently, substantial public and private investment
has been made available for jatropha plantations in marginal lands [
2
]. Nonetheless, it has become
clear that the requirements to obtain economically viable seed yields have been underestimated,
and therefore, many investments have been withdrawn [
3
–
5
]. Despite this reversal, production derived
from jatropha under favorable growing conditions continues to be a concept receiving considerable
political and commercial interest [
6
,
7
], and efforts are being made to estimate the biomass production
so that small jatropha producers could sell the carbon sequestration in the trees under the emissions
trading scheme of the Clean Development Mechanism (CDM) of the Kyoto Protocol [
8
]. For example,
in Ecuador, the Ministry of Electricity and Renewable Energy (Ministerio de Electricidad y Energía
Renovable, MEER), with the support of private investors, implemented the “Jatropha for Galápagos”
Project in 2011. The main objective of this project is to replace petro diesel by jatropha oil through
the agro industrial development of jatropha in the continent [
1
]. The selected province is Manabí,
which belongs to the tropical, dry forest zone [9], and focusing on smallholders.
Determination of seed productivity using long-term field data is crucial for the management of
jatropha plantations [
10
]. When regional or local data on seed productivity is missing, information
from the literature is commonly used to evaluate the economic and financial feasibility of jatropha
plantations [
10
]. However, estimates of jatropha production used in several economic studies range
between 3000–7000 kg ha
−1
year
−1
[
10
]. In Ecuador, Rade et al. [
2
] observed a huge seed production
variation during seven years’ data collection of the INIAP accession CP041 planted in jatropha live
fences in Manabí, Ecuador (average of 243.32 g tree
−1
year
−1
). In a jatropha pure plantation under
tropical dry forest conditions, Cañadas et al. [
1
] reported an average jatropha dry seed productivity
of 283.20 g tree
−1
year
−1
with 1677 trees per hectare for the INIAP accession CP041, but also
with a broad variation in productivity from one year to the next. In addition to year-to-year
variation in environmental factors, plantation age influences seed production. According to GTZ [
11
],
jatropha plantations reach maturity at about eight years of age. Van Eijck et al. [
10
] highlighted that
the jatropha production horizon is too short (10 years or less) to be able to reliably assess medium and
long-term economic viability of jatropha plantations. However, a perspective on jatropha productivity
in Ecuador was presented by Rade et al. [
2
], who found a negative covariance between jatropha dry
seed production and time in a live fence for the INIAP accession CP041 (
−
991.35) and for traditional
jatropha (−715.00) during seven years’ field observations.
Moreover, jatropha oil content in seeds is known to vary between 40% to 60%, with protein
content varying from 10% to 30% (although it is not usable due to the presence of phrobol ester and
curcin contents) [
12
]. Jatropha fruits show different maturity degrees within the same tree as a result
of a continuous fructification process [
13
]. Since physiological changes occur during the maturation
stages [
14
], harvesting the fruits at an adequate maturation stage is an important factor determining seed
quality and oil content. This information is essential for planning harvesting and processing, with the
aim of optimizing oil extraction [
15
]. In addition, genetic variation of the lipid content of jatropha seeds
has been found among genotypes [
16
]. Oil content and moisture change with time, and affect the seed
quality and behavior in response to environmental changes, especially relative humidity [
17
]. Thus, it is
important to evaluate changes in physical and chemical properties, including oil and moisture content,
and dry weight of jatropha seed along the maturation process. These data are not only essential for
harvest timing and equipment, but also for seed processing and storage [18].
The productivity of mature jatropha stands is poorly described under tropical dry forest conditions.
Moreover, determination of optimum seed quality in relation to oil content during the jatropha fruit
ripening process is of utmost importance to establish the optimum time for fruit harvesting in jatropha.
Forests 2018,9, 611 3 of 13
The objective of this study was to evaluate the productivity and physical changes at four fruit ripening
stages for three INIAP elite jatropha accessions.
2. Materials and Methods
2.1. Study Area
The study was conducted at the Portoviejo Experimental Station (EEP) of the National
Institute of Agricultural Research (INIAP) during the period from August 2009 to December 2017.
The geographical coordinates are 0
◦
01
0
S and 80
◦
23
0
W, sector Lodana, canton Portoviejo, province of
Manabí. The EEP is located at 47 m.a.s.l, with an annual mean temperature of 26.4
◦
C and average
annual rainfall of 798 mm, with a large year-to-year rainfall variability, 78% average relative humidity,
and a total sun-light sum of 1159 h year
−1
. Figure 1shows the monthly precipitation along with
potential evapotranspiration, averaged over the experiment’s period. A surplus of water generally
occurs in the course of January to March, while there is a water deficit the rest of the year.
Forests 2018, 9, x FOR PEER REVIEW 3 of 13
harvesting in jatropha. The objective of this study was to evaluate the productivity and physical
changes at four fruit ripening stages for three INIAP elite jatropha accessions.
2. Materials and Methods
2.1. Study Area
The study was conducted at the Portoviejo Experimental Station (EEP) of the National Institute
of Agricultural Research (INIAP) during the period from August 2009 to December 2017. The
geographical coordinates are 0°01′ S and 80°23′ W, sector Lodana, canton Portoviejo, province of
Manabí. The EEP is located at 47 m.a.s.l, with an annual mean temperature of 26.4 °C and average
annual rainfall of 798 mm, with a large year-to-year rainfall variability, 78% average relative
humidity, and a total sun-light sum of 1159 h year−1. Figure 1 shows the monthly precipitation along
with potential evapotranspiration, averaged over the experiment’s period. A surplus of water
generally occurs in the course of January to March, while there is a water deficit the rest of the year.
Figure 1. Water balance in the INIAP-EEP, 2009–2017. The solid line represents the monthly average
of precipitation and the dashed line the potential evapotranspiration.
2.2. Soil Conditions
A soil analysis for the study area was carried out in the INIAP-EEP (Table 1). The soil has a
neutral pH, with low levels of Nitrogen, Zinc, and Iron, medium levels of Boron, and high levels of
Phosphorus, Potassium, Calcium, Magnesium, Copper, and Manganese.
Table 1. Soil chemical properties in the study area, INIAP-EEP, 2009.
pH
NH4
P
Zn
Cu
Fe
Mn
Zn
B
K
Ca
Mg
(in ppm)
(in meq 100 mL−1)
7.3
17.12
23.01
1.82
7.14
12.11
23.75
1.82
0.92
2.07
20.90
4.02
2.3. Preparation of Experimental Site
The land was prepared by mechanized clearing, ploughing, and harrowing. Jatropha curcas L.
cuttings were collected from the mother trees. Three INIAP jatropha accessions (CP041, CP052 and
CP054) were used in the present study. Diammonium phosphate fertilizer (18-46-0) was applied at a
dose of 50 g per planting hole before cuttings were transplanted. The plantlets were planted in
August 2009 as 70-day-old bare root transplants. Potassium chloride was subsequently applied, at a
dose of 4 g per tree, 30, 90, and 120 days after transplanting. Weeds were cut manually, once a month
with a machete, and Igran® liquid herbicide (Nufarm Australia Limited: Melboume, VIC, Australia)
was applied by spraying every 4 months, at a dose of 200 mL per 20 L of water. After jatropha
establishment, no fertilization, or pest or mite controls were provided.
0
50
100
150
200
250
0
50
100
150
200
250
E F M A M J Jl A S O N D
Evapotranspiration mm month-1
Precipitation mm month-1
Months
Precipitation
Evapotranspiration
Figure 1.
Water balance in the INIAP-EEP, 2009–2017. The solid line represents the monthly average of
precipitation and the dashed line the potential evapotranspiration.
2.2. Soil Conditions
A soil analysis for the study area was carried out in the INIAP-EEP (Table 1). The soil has a
neutral pH, with low levels of Nitrogen, Zinc, and Iron, medium levels of Boron, and high levels of
Phosphorus, Potassium, Calcium, Magnesium, Copper, and Manganese.
Table 1. Soil chemical properties in the study area, INIAP-EEP, 2009.
Forests 2018, 9, x FOR PEER REVIEW 3 of 13
harvesting in jatropha. The objective of this study was to evaluate the productivity and physical
changes at four fruit ripening stages for three INIAP elite jatropha accessions.
2. Materials and Methods
2.1. Study Area
The study was conducted at the Portoviejo Experimental Station (EEP) of the National Institute
of Agricultural Research (INIAP) during the period from August 2009 to December 2017. The
geographical coordinates are 0°01′ S and 80°23′ W, sector Lodana, canton Portoviejo, province of
Manabí. The EEP is located at 47 m.a.s.l, with an annual mean temperature of 26.4 °C and average
annual rainfall of 798 mm, with a large year-to-year rainfall variability, 78% average relative
humidity, and a total sun-light sum of 1159 h year−1. Figure 1 shows the monthly precipitation along
with potential evapotranspiration, averaged over the experiment’s period. A surplus of water
generally occurs in the course of January to March, while there is a water deficit the rest of the year.
Figure 1. Water balance in the INIAP-EEP, 2009–2017. The solid line represents the monthly average
of precipitation and the dashed line the potential evapotranspiration.
2.2. Soil Conditions
A soil analysis for the study area was carried out in the INIAP-EEP (Table 1). The soil has a
neutral pH, with low levels of Nitrogen, Zinc, and Iron, medium levels of Boron, and high levels of
Phosphorus, Potassium, Calcium, Magnesium, Copper, and Manganese.
Table 1. Soil chemical properties in the study area, INIAP-EEP, 2009.
pH
NH
4
P
Zn
Cu
Fe
Mn
Zn
B
K
Ca
Mg
(in ppm)
(in meq 100 mL
−1
)
7.3
17.12
23.01
1.82
7.14
12.11
23.75
1.82
0.92
2.07
20.90
4.02
2.3. Preparation of Experimental Site
The land was prepared by mechanized clearing, ploughing, and harrowing. Jatropha curcas L.
cuttings were collected from the mother trees. Three INIAP jatropha accessions (CP041, CP052 and
CP054) were used in the present study. Diammonium phosphate fertilizer (18-46-0) was applied at a
dose of 50 g per planting hole before cuttings were transplanted. The plantlets were planted in
August 2009 as 70-day-old bare root transplants. Potassium chloride was subsequently applied, at a
dose of 4 g per tree, 30, 90, and 120 days after transplanting. Weeds were cut manually, once a month
with a machete, and Igran® liquid herbicide (Nufarm Australia Limited: Melboume, VIC, Australia)
was applied by spraying every 4 months, at a dose of 200 mL per 20 L of water. After jatropha
establishment, no fertilization, or pest or mite controls were provided.
0
50
100
150
200
250
0
50
100
150
200
250
E F M A M J Jl AS O N D
Evapotranspiration mm month
-1
Precipitation mm month
-1
Months
Precipitation
Evapotranspiration
2.3. Preparation of Experimental Site
The land was prepared by mechanized clearing, ploughing, and harrowing. Jatropha curcas L.
cuttings were collected from the mother trees. Three INIAP jatropha accessions (CP041, CP052 and
CP054) were used in the present study. Diammonium phosphate fertilizer (18-46-0) was applied at a
dose of 50 g per planting hole before cuttings were transplanted. The plantlets were planted in August
2009 as 70-day-old bare root transplants. Potassium chloride was subsequently applied, at a dose of
4 g per tree, 30, 90, and 120 days after transplanting. Weeds were cut manually, once a month with
a machete, and Igran
®
liquid herbicide (Nufarm Australia Limited: Melboume, VIC, Australia) was
applied by spraying every 4 months, at a dose of 200 mL per 20 L of water. After jatropha establishment,
no fertilization, or pest or mite controls were provided.
Forests 2018,9, 611 4 of 13
2.4. Plot Sizes and Determination of Jatropha Productivity
A split-plot design with three replications was used. The experiment covered a total of 2304 m
2
(48 m
×
48 m). The three INIAP jatropha accessions (INIAP CP041, INIAP CP052, INIAP CP054) were
assigned to the main plots (768 m
2
), and the fruit ripening stage was considered as four sub-plots
(64 m
2
) which were located in each of the main plots. The experimental unit (each sub-plot) included
a total of 16 trees at a spacing of 2
×
2 m. From October 2009 to December 2017, jatropha fruits were
harvested monthly from four trees in each sub-plot. Seed weight was measured with a precision
balance after removing the pulp from the yellow fruits, extracting the seeds and drying them in a
convection oven at 60 ◦C until constant weight.
2.5. Determination of Seed Weight, Moisture, and Oil Content at Different Fruit Ripening Stages
In April 2012, when jatropha stands were three years old, fruits at several fruit ripening stages were
harvested in order to determine the relationship between fruit ripening and seed characteristics, such as
seed weight, moisture, and oil content. Once collected from the research plots, fruits were taken to the
laboratory, where they were separated visually according to their ripening stage. Four fruit ripening
stages were distinguished in the analysis: (a) early maturity (greenish-yellow fruits); (b) physiological
maturity (yellow fruits); (c) over maturity (mottled-yellow fruits); and (d) senescent (black-brown
fruits). After fruit separation, the fresh weight of 100 seeds per fruit ripening stage and replication
were weighed with a precision balance.
To determine seed moisture, a sample of 100 seeds from each replication was sun-dried for 30 days
and then dehydrated by the standard hot air oven method at 105
◦
C
±
10
◦
C for 24 h to obtain the
dry weight [
19
]. The moisture content was estimated as the weight loss (fresh weight - dry weight) of
the sample, divided by the dry weight, expressed in percent. The oil content was determined for each
seed sample by the solvent extraction method. The seeds were ground and placed in an extraction
thimble. The oil was extracted using a Soxhlet apparatus with hexane for 6 h. The solvent material
was evaporated with a rotary vacuum evaporator, and the remaining jatropha oil was weighed. The oil
content of the seed was expressed as percent of dry matter mass. All the analyses were done in the
seed laboratory of INIAP-EEP.
2.6. Statistical Analyses
Analysis of variance (ANOVA) for seed dry weight, seed moisture, and oil content was performed
with the MIXED procedure, using SAS software (V 9.4, SAS Institute Inc., Cary, NC, USA), and mean
values were compared by a post-hoc Tukey’s multiple comparison test. A significance level of 0.05 was
assumed. The following linear model for the split-plot design was used:
Yijk =µ+ Bi+ Aj+ Bi×Aj + Rk+ Aj×Rk+εijk
where Y
ijk
is the value of the seed sample in the kth sub-plot of the jth main-plot in the ith block;
µ
is
the population mean; B
i
is the random effect of the ith block; A
j
is the fixed effect of the jth accession;
B
i×
A
j
is the random effect of the main-plot error; R
k
is the fixed effect of the kth ripening stage; A
j×
R
k
is the fixed effect of the interaction between the jth accession and the kth ripening stage; and
εijk
is
the experimental error.
To determine the relationship between oil content (%) and seed weight for the seed samples
harvested in April 2012 (n = 36), linear, quadratic and two-segment piecewise linear regression models
were evaluated with the GLM procedure of SAS software, considering their respective coefficient of
determination (R
2
) and mean square error (MSE). For piecewise linear regression, the optimal break
point model (with the lowest MSE) was found before comparisons were made with the linear and
quadratic regression models.
Forests 2018,9, 611 5 of 13
3. Results
3.1. Jatropha Seed Productivity
The dry seed production per tree from October 2009 to December 2017 is shown in Figure 2.
Three months after the jatropha plantation, the fruit production began. The maximum jatropha dried
seeds production occurred at four-year-old plantations for the accessions CP041 and CP052, while for
accession CP054 it occurred after the first year.
Jatropha accession CP041 was the most productive, with 316.46
±
76.50 g tree
−1
year
−1
(here and
in the following: mean followed by its standard error), taking into account all harvests from the early
fruits in the first year up to the harvest at 8 years of age. The jatropha accession CP052 obtained an
average of 314.02 ±63.19 g tree−1year−1and CP054 308.74 ±59.07 g tree−1year−1.
Forests 2018, 9, x FOR PEER REVIEW 5 of 13
3. Results
3.1. Jatropha Seed Productivity
The dry seed production per tree from October 2009 to December 2017 is shown in Figure 2.
Three months after the jatropha plantation, the fruit production began. The maximum jatropha dried
seeds production occurred at four-year-old plantations for the accessions CP041 and CP052, while
for accession CP054 it occurred after the first year.
Jatropha accession CP041 was the most productive, with 316.46 ± 76.50 g tree−1 year−1 (here and
in the following: mean followed by its standard error), taking into account all harvests from the early
fruits in the first year up to the harvest at 8 years of age. The jatropha accession CP052 obtained an
average of 314.02 ± 63.19 g tree−1 year−1 and CP054 308.74 ± 59.07 g tree−1 year−1.
Figure 2. Dry seed production per tree for three jatropha INIAP accessions during the years 2009–2017
at INIAP Portoviejo Research Station, Ecuador. Vertical bars indicate the standard error.
3.2. Seed Dry Weight and Fruit Ripening Stage
There were no significant differences in seed weight among jatropha accessions or for the
interaction accessions × fruit ripening stage, but seed weight was significantly affected (p < 0.001) by
fruit ripening stage (Table 2). Tukey’s (alpha value of 0.05) multiple test showed two distinctive
group ranges of seed ripening. The first was the yellow fruits, being the heaviest, with 62.4 g ± 1.5 g
(for 100 seeds), and the black-brown fruits the lightest, with 44.3 g ± 1.9 g (Figure 3).
Figure 3. Dry seed weight (100 seeds) at four jatropha fruit ripening stages. Vertical bars indicate the
standard error. Different letters indicate a significant difference.
0
100
200
300
400
500
600
700
800
900
1000
2009 2010 2011 2012 2013 2014 2015 2016 2017
Dry Seed Production in g tree-1
Year
CP041
CP052
CP054
0
10
20
30
40
50
60
70
Greenish-yellow Yellow Mottled-yellow Black-brown
Seed weight (g)
a
aa
b
Figure 2.
Dry seed production per tree for three jatropha INIAP accessions during the years 2009–2017
at INIAP Portoviejo Research Station, Ecuador. Vertical bars indicate the standard error.
3.2. Seed Dry Weight and Fruit Ripening Stage
There were no significant differences in seed weight among jatropha accessions or for the
interaction accessions
×
fruit ripening stage, but seed weight was significantly affected (p< 0.001)
by fruit ripening stage (Table 2). Tukey’s (alpha value of 0.05) multiple test showed two distinctive
group ranges of seed ripening. The first was the yellow fruits, being the heaviest, with 62.4 g
±
1.5 g
(for 100 seeds), and the black-brown fruits the lightest, with 44.3 g ±1.9 g (Figure 3).
Forests 2018, 9, x FOR PEER REVIEW 5 of 13
3. Results
3.1. Jatropha Seed Productivity
The dry seed production per tree from October 2009 to December 2017 is shown in Figure 2.
Three months after the jatropha plantation, the fruit production began. The maximum jatropha dried
seeds production occurred at four-year-old plantations for the accessions CP041 and CP052, while
for accession CP054 it occurred after the first year.
Jatropha accession CP041 was the most productive, with 316.46 ± 76.50 g tree−1 year−1 (here and
in the following: mean followed by its standard error), taking into account all harvests from the early
fruits in the first year up to the harvest at 8 years of age. The jatropha accession CP052 obtained an
average of 314.02 ± 63.19 g tree−1 year−1 and CP054 308.74 ± 59.07 g tree−1 year−1.
Figure 2. Dry seed production per tree for three jatropha INIAP accessions during the years 2009–2017
at INIAP Portoviejo Research Station, Ecuador. Vertical bars indicate the standard error.
3.2. Seed Dry Weight and Fruit Ripening Stage
There were no significant differences in seed weight among jatropha accessions or for the
interaction accessions × fruit ripening stage, but seed weight was significantly affected (p < 0.001) by
fruit ripening stage (Table 2). Tukey’s (alpha value of 0.05) multiple test showed two distinctive
group ranges of seed ripening. The first was the yellow fruits, being the heaviest, with 62.4 g ± 1.5 g
(for 100 seeds), and the black-brown fruits the lightest, with 44.3 g ± 1.9 g (Figure 3).
Figure 3. Dry seed weight (100 seeds) at four jatropha fruit ripening stages. Vertical bars indicate the
standard error. Different letters indicate a significant difference.
0
100
200
300
400
500
600
700
800
900
1000
2009 2010 2011 2012 2013 2014 2015 2016 2017
Dry Seed Production in g tree-1
Year
CP041
CP052
CP054
0
10
20
30
40
50
60
70
Greenish-yellow Yellow Mottled-yellow Black-brown
Seed weight (g)
a
aa
b
Figure 3.
Dry seed weight (100 seeds) at four jatropha fruit ripening stages. Vertical bars indicate the
standard error. Different letters indicate a significant difference.
Forests 2018,9, 611 6 of 13
Table 2.
Significance (p-value) of effects from jatropha accessions and fruit ripening stage on seed dry
weight, moisture content, and oil content in a jatropha plantation at Portoviejo, Ecuador.
Effects Source of Variation (p-Value)
Seed Weight Seed Moisture Oil Content
Accession 0.9688 <0.0001 0.1497
Fruit ripening stage 0.0002 <0.0001 0.3239
Accession ×fruit ripening stage 0.9206 <0.0001 0.2575
3.3. Seed Moisture Content and Fruit Ripening Stage
Highly significant differences (p< 0.001) in seed moisture content were found among jatropha
accessions, fruit ripening stage, and the interaction of these factors (Table 2). A Tukey’s multiple
comparison test showed three ranges of fruit moisture content among accessions. Accession CP052
had the highest average moisture content with 37.2%
±
4.1%, followed by CP041 with 31.3%
±
3.3%,
and CP054 with 25.8% ±3.0%.
As expected, fruit moisture content decreased as fruit ripening advanced, from an average value
of 40.53%
±
1.0% at the initial stage (greenish-yellow fruits), down to 13.81%
±
0.4% at the senescent
stage (black-brown fruits). Physiologically mature and over-mature fruits still have moisture contents
over 30%, on average (Figure 4).
Forests 2018, 9, x FOR PEER REVIEW 6 of 13
Table 2. Significance (p-value) of effects from jatropha accessions and fruit ripening stage on seed dry
weight, moisture content, and oil content in a jatropha plantation at Portoviejo, Ecuador.
Effects
Source of Variation (p-Value)
Seed Weight
Seed Moisture
Oil Content
Accession
0.9688
<0.0001
0.1497
Fruit ripening stage
0.0002
<0.0001
0.3239
Accession × fruit ripening stage
0.9206
<0.0001
0.2575
3.3. Seed Moisture Content and Fruit Ripening Stage
Highly significant differences (p < 0.001) in seed moisture content were found among jatropha
accessions, fruit ripening stage, and the interaction of these factors (Table 2). A Tukey’s multiple
comparison test showed three ranges of fruit moisture content among accessions. Accession CP052
had the highest average moisture content with 37.2% ± 4.1%, followed by CP041 with 31.3% ± 3.3%,
and CP054 with 25.8% ± 3.0%.
As expected, fruit moisture content decreased as fruit ripening advanced, from an average value
of 40.53% ± 1.0% at the initial stage (greenish-yellow fruits), down to 13.81% ± 0.4% at the senescent
stage (black-brown fruits). Physiologically mature and over-mature fruits still have moisture contents
over 30%, on average (Figure 4).
Figure 4. Jatropha seed moisture variation between jatropha INIAP accessions along the fruit ripening
stages. INIAP Portoviejo Research Station, Ecuador. Vertical bars indicate the standard error.
Different letters indicate a significant difference.
3.4. Oil Content and Fruit Ripening Stage
No significant differences in oil content were found among accessions, fruit ripening stage, or
the interaction of these factors (Table 2). Mean oil content varied from 36.54% ± 1.45% (accession
CP041) to 33.48% ± 1.08% (accession CP052). Among fruit ripening stage, it varied from 36.01% ±
1.60% (yellow stage) to 33.31% ± 1.10% (black brown stage). The coefficients of variation (a measure
of the experiment’s validity) for main plots (9.92%) and subplots (8.64%) are acceptable for field
experiments. One component that explains the variation in seed oil content in jatropha is seed weight
(Figure 5). However, the relationship was not as simple as expected; the linear regression model
based on seed weight explains only about 13.5% of the variation in seed oil content expressed as
percentage of seed mass (Table 3). The quadratic regression model showed a somewhat better fit,
with an R2 = 0.275, indicating that seed oil content (%) has a maximum value around 58 g of seed
mass, decreasing at both sides of this point. The optimal two-segment piecewise linear regression
model, however, showed the best fit, with an R2 = 0.317 and the lowest MSE (2.72).
10
15
20
25
30
35
40
45
50
Greenish-yellow Yellow Mottled-yellow Black-brown
Seed moisture (%)
CP041
CP052
CP054
aa
c
ba
a
b
a
a
b
Figure 4.
Jatropha seed moisture variation between jatropha INIAP accessions along the fruit ripening
stages. INIAP Portoviejo Research Station, Ecuador. Vertical bars indicate the standard error.
Different letters indicate a significant difference.
3.4. Oil Content and Fruit Ripening Stage
No significant differences in oil content were found among accessions, fruit ripening stage, or the
interaction of these factors (Table 2). Mean oil content varied from 36.54% ±1.45% (accession CP041)
to 33.48%
±
1.08% (accession CP052). Among fruit ripening stage, it varied from 36.01%
±
1.60%
(yellow stage) to 33.31%
±
1.10% (black brown stage). The coefficients of variation (a measure of the
experiment’s validity) for main plots (9.92%) and subplots (8.64%) are acceptable for field experiments.
One component that explains the variation in seed oil content in jatropha is seed weight (Figure 5).
However, the relationship was not as simple as expected; the linear regression model based on seed
weight explains only about 13.5% of the variation in seed oil content expressed as percentage of seed
mass (Table 3). The quadratic regression model showed a somewhat better fit, with an R
2
= 0.275,
indicating that seed oil content (%) has a maximum value around 58 g of seed mass, decreasing at both
sides of this point. The optimal two-segment piecewise linear regression model, however, showed the
best fit, with an R2= 0.317 and the lowest MSE (2.72).
Forests 2018,9, 611 7 of 13
Forests 2018, 9, x FOR PEER REVIEW 7 of 13
Figure 5. Linear, quadratic, and two-segment piecewise linear regression models for oil content on
seed weight of jatropha seed from three elite accessions. INIAP Portoviejo Research Station, Ecuador.
Table 3. Parameter estimates for linear, quadratic, and two-segment piecewise linear regression
equations of oil content (y) on seed weight (x) of jatropha seed samples from three elite accessions.
INIAP Portoviejo Research Station, Ecuador.
Model
Equation
R2
CV (%)
MSE
p-Value
b0 ± (se)
b1 ± (se)
b2 ± (se)
Linear
y = b0 + b1x
0.135
8.695
3.012
0.02
27.441 (3.164)
0.129 (0.056)
n.a.
Quadratic
y = b0 + b1x + b2x2
0.275
8.082
2.800
0.01
−8.218 (14.444)
1.499 (0.546)
−0.013 (0.005)
Piecewise §
y = b0 + b1x + b2(x − t)(x2)
0.317
7.845
2.718
0.001
18.797 (4.082)
0.309 (0.079)
−0.617 (0.208)
§ For piecewise regression model, t = 58.8, is the optimal break point and x2 is an indicator variable
(x2 = 0 when x ≤ t; x2 = 1 when x > t).
The optimal piecewise linear regression model had a break point at 58.8 g of seed mass. Below
this point, seed oil content is positively related to seed mass, but beyond the break point, the
relationship becomes negative, so seed oil content decreases as seed mass increases (Figure 5).
4. Discussion
4.1. Jatropha Maturity and Productivity
The early study undertaken by Jongschaap et al. [20] established that the maturity of jatropha as
a crop depends on its geographical location, i.e., radiation and temperature levels, resulting in higher
net primary production potential in some in comparison to other latitudes. In general, these
plantations can reach their maturity and maximum production 3–4 years after planting. This
information on jatropha stand maturity is comparable to our results in this study. Under dry forest
conditions in the province of Manabí-Ecuador, seed production of jatropha declined after four years
for INIAP jatropha accessions CP041 and CP052. Nevertheless, INIAP jatropha accession CP054
reached maximum production 1.4 years after planting. Such jatropha behaviour was observed in rain
fed marginal lands of Uttar Pradesch (India), where the best dry seeds production was in the first
year, with a yield between 3.2 to 4.1 t seeds ha−1 [21].
These results do not agree with data provided by Euler and Gorriz [22], and Achten et al. [23],
who observed that jatropha plantations show considerably lower dry seeds production at younger
ages due to the inefficient interception of radiation, and therefore, the distribution of dry matter to
permanent biomass instead of harvestable parts such as fruits and seeds. Our results also differ from
R² = 0.1352
R² = 0.275
26
28
30
32
34
36
38
40
42
44
46
30 35 40 45 50 55 60 65 70
Oild content (%)
Seed weight (g)
R
2
= 0.317
R
2
=0.951
Figure 5.
Linear, quadratic, and two-segment piecewise linear regression models for oil content on
seed weight of jatropha seed from three elite accessions. INIAP Portoviejo Research Station, Ecuador.
Table 3.
Parameter estimates for linear, quadratic, and two-segment piecewise linear regression
equations of oil content (y) on seed weight (x) of jatropha seed samples from three elite accessions.
INIAP Portoviejo Research Station, Ecuador.
Model Equation R2CV (%) MSE p-Value b0±(se) b1±(se) b2±(se)
Linear y = b0+ b1x
0.135
8.695
3.012
0.02 27.441 (3.164)
0.129 (0.056)
n.a.
Quadratic y=b0+ b1x+b2x2
0.275
8.082
2.800
0.01 −8.218 (14.444)
1.499 (0.546)
−0.013 (0.005)
Piecewise
§
y=b
0
+ b
1
x+b
2
(x
−
t)(x
2
)
0.317
7.845
2.718
0.001 18.797 (4.082)
0.309 (0.079)
−0.617 (0.208)
§
For piecewise regression model, t = 58.8, is the optimal break point and x
2
is an indicator variable (x
2
= 0 when
x≤t; x2= 1 when x > t).
The optimal piecewise linear regression model had a break point at 58.8 g of seed mass. Below this
point, seed oil content is positively related to seed mass, but beyond the break point, the relationship
becomes negative, so seed oil content decreases as seed mass increases (Figure 5).
4. Discussion
4.1. Jatropha Maturity and Productivity
The early study undertaken by Jongschaap et al. [
20
] established that the maturity of jatropha as a
crop depends on its geographical location, i.e., radiation and temperature levels, resulting in higher net
primary production potential in some in comparison to other latitudes. In general, these plantations
can reach their maturity and maximum production 3–4 years after planting. This information on
jatropha stand maturity is comparable to our results in this study. Under dry forest conditions in
the province of Manabí-Ecuador, seed production of jatropha declined after four years for INIAP
jatropha accessions CP041 and CP052. Nevertheless, INIAP jatropha accession CP054 reached maximum
production 1.4 years after planting. Such jatropha behaviour was observed in rain fed marginal lands of
Uttar Pradesch (India), where the best dry seeds production was in the first year, with a yield between
3.2 to 4.1 t seeds ha−1[21].
These results do not agree with data provided by Euler and Gorriz [
22
], and Achten et al. [
23
],
who observed that jatropha plantations show considerably lower dry seeds production at younger
ages due to the inefficient interception of radiation, and therefore, the distribution of dry matter
to permanent biomass instead of harvestable parts such as fruits and seeds. Our results also differ
from the eight years required by jatropha to reach maturity in Kenya, as observed by GTZ [
11
].
Forests 2018,9, 611 8 of 13
Jongschaap et al. [
20
] emphasized that a decrease in jatropha seed productivity has been reported for
aging plantations. What is still unclear is whether or not this is a general phenomenon. The study
conducted by Cañadas et al. [
1
] and Rade et al. [
2
] showed a decreasing production of seed for INIAP
jatropha mono-plantation and a local jatropha material in live fences, Manabí, Ecuador.
The seed production estimated in this study for jatropha is similar to that obtained for jatropha
stands under 6 years of age in other regions of the world (Table 4). Cañadas et al. [
1
] showed
that, after having reached a maximum, jatropha production decreases over time. These results were
accompanied by a high inter-annual variation in dry seed production, which was not related to the
mean annual precipitation. Rade et al. [
2
] calculated a 7-year average of 0.24 kg tree
−1
year
−1
(
±
0.06)
for jatropha INIAP CP041 accession in life fences, while the local jatropha varieties reached an average
production of 0.18 kg tree
−1
year
−1
(
±
0.03) with comparatively little variation in dry seed production.
Site-specific knowledge about the development of seed production of jatropha trees is fundamental for
estimating their economic viability. Projections of seed production in the literature for more mature
jatropha stands often lack sound scientific bases, or contain wrong assumptions [2].
Table 4. Published data for seed productivity of jatropha plantations from different countries.
Country, Region Age of Jatropha
Plantation in Years
Productivity
(in kg tree−1)References
Brazil 1 0.4 Saturnino et al. [24]
Guatemala 1 0.8 Ouwens et al. [25]
Indonesia 1 1.6–2.0 Ouwens et al. [25]
Indonesia 1 1.8 Manurung [26]
India, Pradesh 1 2.4 Lal et al. [21]
India 1.25 1.7 Achten et al. [27]
India 2 1.5 Ouwens et al. [25]
Mali, Digini 2 0.3 Achten et al. [27]
India 2.5 0.8 Ghosh et al. [28]
India, Rajasthan 2.5 0.1–0.5 Achten et al. [27]
Kenya 2–3 <1.0 Iiyama et al. [29]
Tanzania, Arusha 3 0.5–2.0 Messemaker [30]
Nicaragua 5 4.5 Heller [31]
Ecuador, CP052, 041, 054 6 0.2–0.3 Cañadas et al. [1]
Ecuador, CP041 7 0.2 Rade et al. [2]
Ecuador, CP041, 052, 054 8 0.1–0.3 Present study
Jatropha stands in the present study had received minimal care in relation to plantation
maintenance. This could significantly affect the productivity potential and sustainability of the
jatropha plantation. However, most small farmers do not have alternatives, and apply sub-optimal
management practices [
29
], so the productivity shown in this research would be a real scenario for
jatropha, when used in a pro-poor crop program.
4.2. Seed Dry Weight
No statistical significance was detected in relation to seed weight of the three INIAP jatropha
accessions investigated in the present study. This result contrasted with those reported by
Ginwal et al. [
32
], who found statistical differences (p< 0.05) in relation to seed weight and seed
size of diverse jatropha provenances of Central India. Similar results were obtained by Kaushik [
33
]
in Andhra Pradesh, India. In the present study, however, a high statistical difference in seed weight
was found across the various fruit ripening stages. This corresponds with the results obtained by
Kaushik [33].
Rondanini et al. [
34
] emphasized the need to determine how temperature during seed filling
could affect several characteristics of jatropha fruit. Not only the fruit ripening stage influences
seed weight; the environmental conditions throughout the various fruit ripening stages also do
Forests 2018,9, 611 9 of 13
so, and for this reason, a broad variation in seed weight (from 32.6 g to 75.2 g) was found in
Argentina [
13
]. Seed weights found in our study are similar to those obtained in the province of
Andhra Pradesh, India by Rao et al. [
16
] in accessions CRDJ1 (77.4 g), CRDJ20 (78.3 g) and CRDJ6
(79.1 g). While Subramanyam et al. [
35
] reported a seed weight between 49.3 g and 74.2 g and
Rathbauer et al. [
36
] between 49.3 g and 74.2 g and this broad variation was attributed to the diverse
agro-ecological growth conditions and genetics. Wani et al. [
37
] found that seed weight for 100 seeds
in Indian jatropha accessions varied between 44 g and 77 g. In Ecuador, Cañadas et al. [
1
] recorded
an average weight of 72.6 g
±
0.77 g for 100 seeds in seven jatropha elite accessions of INIAP in
Portoviejo-Manabí.
4.3. Seed Moisture Content
According to Silva et al. [
14
] seed moisture content is not a good indicator of physiological
ripening, since this parameter can vary among genotypes. In fact, seed moisture content varied
widely among the jatropha accessions tested, from 25.8% in INIAP CP054 to 37.2% in INIAP CP052.
Statistical differences were also identified in seed moisture contents among the fruit ripening stage,
which was negatively and significantly correlated. A clear gradient of moisture content as ripening
advanced was established. A similar seed moisture content decline was described by Dias et al. [
38
]
and Dias et al. [
39
]. The rapid humidity reduction is proportional to the reserve deposit compounds,
which to a large extent replace the space occupied by water. Finally, water reduction occurs by the
search for hygroscopic equilibrium between the seed water content and the environmental relative
humidity [
40
]. The moisture content varies in relation to the maturation and ripening of the jatropha
fruit with high water content in the physiological maturity stage and low moisture content in the
senescent stage [40].
4.4. Oil Content
The best jatropha INIAP accessions were collected from Manabíprovince (Ecuador) for further
testing [
1
]. Jatropha local accessions had adapted to a wide range of edaphic and ecological
conditions, suggesting that a considerable amount of genetic variability exists to be exploited for
potential oil production. Osorio et al. [
41
] found a higher genetic variability of jatropha in Central
American accessions compared to Asian, African, and South American accessions. Nevertheless,
a variation of oil seed concentration was reported by Rao et al. [
16
] ranging between 29.8%–37.1%,
by Subramanyam et al. [
35
] between 17.1%–38.8%, and by Kaushik et al. [
42
] 28.0%–38.8% from
different genotypes evaluated under the same environmental conditions. Among INIAP’s jatropha
accessions, no statistical differences were found in seed oil content; mean values varied by only 3%
among the evaluated accessions. The small variation in jatropha oil content found in the present
investigation is not sufficient as a viable selection option at a very early stage (germplasm collection)
form seed base material.
Singer et al. [
43
] mentioned that seed oil concentration does not only depend on the genotype,
but is also affected by the environmental conditions during grain filling, i.e., mainly temperature,
that modifies seed oil concentration and the fatty acid composition through changes in grain filling
dynamics and biosynthetic activity. Jatropha oil is accumulated during the last third of the seed
filling period [
44
], so a shortening of grain filling duration should lead to lower oil concentrations.
Furthermore, changes in seed weight generated by different temperatures can affect seed oil
concentration through changes in the seed coat-kernel relationship. Such seed weight variation
was detected, but only through the fruit ripening stage.
Fruit color has been associated as a visual indicator of the fruit ripening stage. In the current
research, no statistical differences were found in oil content between fruit ripening stages. This fact
has a practical application. The difference in price between a quintal (45 kg) jatropha fruit for US $10
and jatropha seed for US $12, as paid in Manabíprovince, is currently not a sufficient incentive to
invest more labor which is necessary for the sale of seeds, because this would increase production
Forests 2018,9, 611 10 of 13
costs excessively [
2
]. The harvest timing of small producers within the project “Jatropha for Galápagos”
would be the yellow fruit ripening stage, due to the greater weight.
The oil content fluctuated from 33.3% in the dry fruits (fruit ripening stage 4) to 36% in yellow
fruits (fruit ripening stage 2). Nevertheless, Silva et al. [
14
] had associated the jatropha fruit color with
the oil content and germination power of seeds. The oil contents from jatropha INIAP accessions is
comparable with the values reported by Wassner et al. [
13
] in Argentina, under subtropical conditions
and precipitation of 1005 mm year
−1
, with a maximum seed oil content of 38.7%
±
0.6% and a minimum
of 19.6%
±
1.8%. Wani et al. [
37
] for Jammu and Kashmir State in Northwest India obtained an oil
concentration from 27.8% to 37.9%. Kaushik et al. [
41
] found an oil content range from 28% to 39% in
the Haryana-India accession. Rao et al. [
16
] established between 30% to 37% of oil contained in Andhra
Pradesh, India accessions. Other referential data on oil content is reported by Srivastava et al. [
45
],
who observed values between 17.1% for accession IC5660864 to 34.5% for the accession IC558231 in
New Delhi and China, and between 34.1% for accession S1 and 55.5% for accession S2 [
46
]. Higher oil
content (61%–64%) was found in jatropha seeds coming from Malaysia, Indonesia, and Thailand [
47
].
In the Latin-American context, the jatropha oil content reported in Colombia with jatropha variety Brazil
tested in two areas, varied just slightly from 37% in Vichada to 38% in Santander [48].
5. Conclusions
Our study revealed that there are no differences in oil content among the three compared jatropha
accessions, nor do oil content changes occur during the fruit ripening process. This means that, for oil
content in the Ecuadorian jatropha accessions, the genotype and collection date of fruits under tropical
dry forest conditions are not relevant. Under subtropical conditions, the harvest timing is as relevant
as the jatropha genotypic selection [13].
Studies conducted by Rao et al. [
16
] and Karaj and Müller [
49
] pointed out that the significant
statistical correlation between seed weight and oil content can be considered as an important trait for
early selection of seed sources. A bilinear relationship for oil content and seed weight was observed
in the present study, even though the coefficient of determination was not high. Better adjustment
of the bilinear relationship between these variables was reported by Wassner et al. [
13
], where the
harvest time was at the mottled-yellow color stage, characteristic of ripe fruit. In both studies the
bilinear relationship showed similar trends, but the break point, where the linear relationship between
oil content and seed weight changes in slope, was 58.8 g in our study, while in the subtropical zones
of Argentina, the break point was at 62.5 g [
13
]. Additionally, the particular relationship between
seed weight and oil content limits the usefulness of a rapid selection for genotypes with high oil
concentration based on seed weight.
Finally, it is safe to state that site-specific data on jatropha is necessary when aiming at promoting
it, since reported variation is high. Basing management plans on literature data bears the risk of
overestimating potential returns to farmers. Some authors reported rather high yields, which might
be due to studies being undertaken under “optimal” conditions, which are different from usual farm
management, as simulated in our study, where caring for jatropha trees is just one duty among many
others. Our results provide important building blocks for a comprehensive cost-benefit analysis
essential for realistic planning of jatropha plantations at farm, regional energy, and national levels.
Author Contributions:
Á.C.-L., D.Y.R.-L. and M.I.-V. conceived, collected de data, designed the experiments and
wrote the first draft; J.V.-H. and M.S.-S. expanded the statistical analyses; M.S.-S., J.M.D.-A. and C.W. carried out a
detailed revision of the paper.
Funding: This research received no external funding.
Acknowledgments:
We are thankful to the Director of the Portoviejo Experimental Research Station (EEP) of
the National Institute of Agricultural Research (INIAP) period 2015–2016 and INIAP General Director for the
jatropha data release and the updating of the information. Thanks to two anonymous reviewers for their very
valuable comments.
Conflicts of Interest: The authors declare no conflict of interest.
Forests 2018,9, 611 11 of 13
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