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Citation: Olguín-Hernández, A.L.;
Arévalo-Galarza, M.d.L.;
Cadena-Iñiguez, J.; Jaén-Contreras,
D.; Peña-Valdivia, C.B. Plant Height
and Stem Diameter of Solanum
quitoense Lamarck Improved with
Applications of AMF and
Biostimulants. Agriculture 2023,13,
1420. https://doi.org/10.3390/
agriculture13071420
Academic Editor: Nadia Massa
Received: 7 June 2023
Revised: 11 July 2023
Accepted: 13 July 2023
Published: 18 July 2023
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
agriculture
Article
Plant Height and Stem Diameter of Solanum quitoense Lamarck
Improved with Applications of AMF and Biostimulants
Ana Laura Olguín-Hernández 1, Ma. de Lourdes Arévalo-Galarza 1, Jorge Cadena-Iñiguez 2 ,* ,
David Jaén-Contreras 1and Cecilia B. Peña-Valdivia 1
1Colegio de Postgraduados, Campus Montecillo, Fisiología Vegetal. Km. 36.5 Carretera México,
Texcoco 56264, Estado de México, Mexico; olguin.ana@colpos.mx (A.L.O.-H.);
larevalo@colpos.mx (M.d.L.A.-G.); djaen@colpos.mx (D.J.-C.); cecilia@colpos.mx (C.B.P.-V.)
2Colegio de Postgraduados, Campus San Luis Potosí, Salinas de Hidalgo 78600, San Luis Potosí, Mexico
*Correspondence: jocadena@colpos.mx
Abstract:
The lulo plant (Solanum quitoense Lamarck) is native to South America. In Mexico, this
species shows potential for the conversion of agroecosystems. It is used as food and pharmaceutical
sources for metabolites. However, there are few papers related to how this species can grow under
conditions outside of the Andean countries (Bolivia, Colombia, Ecuador, and Peru). The objective
of this research was to evaluate the development of lulo under cloud forest conditions and the
effect of inoculating the plant with mycorrhizae (Funneliformis mosseae (T. H. Nicolson and Gerd.)
C. Walker
and A. Schüssler, and Entrophospora colombiana Spain and N. C. Schenck) and diammonium
phosphate (DAP: NPK 18-46-00) fertilization. The plant growth, leaf area, mycorrhizal colonization,
and leaf mineral content were evaluated from transplant to fruit formation. The experiment was
conducted under field conditions in volcanic soils (clayey Vertisol) in a cloud forest. The inoculation
of
E. colombiana
was 86.19% of the colonization, and the content of N, K, Ca, Mg, Mn, Cu, Zn, and Fe in
the leaves was the higher in these plants. The highest P content was obtained from the DAP treatment
and the height of the plant was 11.8% and 12.5% in the treatments using DAP and
E. colombiana,
respectively. The plant growth was significantly higher in the plants inoculated with E. colombiana
followed by DAP. The plants inoculated with F. mosseae registered lower values than the control. Lulo
plants grow in the climate and soils of volcanic origin of the cloud forest. The results showed that
AMF colonization was beneficial and outperformed the native strains. The results are new for the
introduced lulo plants in Mexico and can help reduce the learning path for commercial cultivation.
Keywords: naranjilla; symbiotic mycorrhizae; growth variable; field crop
1. Introduction
The use of arbuscular mycorrhizal fungi (AMF) in agriculture has shown that it sub-
stantially improves various components of crop growth and yields. Researchers such as [
1
]
demonstrated these benefits using soybeans against drought stress when inoculating them
with AMF and Bradyrhizobium japonicum. Other authors such as (2022) [
2
] mentioned that
the agroecological approach favors the maintenance and balance of microorganisms in
the rhizosphere that interact with the host plants [
3
], in addition to inducing root protec-
tion schemes against various pathogens [
4
]. The interactions between plants and AMF
contribute to agricultural sustainability [
5
], and as a result, benefits are derived and plant
survival increases, especially in limiting agroecological conditions [
6
,
7
]. Endomycorrhizal
fungi are obligate symbionts found in approximately 80% of terrestrial plant roots [
8
]
and embody essential mutualism in the distribution and interaction of both plants and
fungi [
9
,
10
]. Ref. [
11
] evaluated the biofertilizers produced from Bradyrhizobium sp., Bacillus
subtilis, and AMF in guar plants, noting that the combined inoculation increased the physi-
ological and yield components. Due to the benefits that AMF represents for agriculture
Agriculture 2023,13, 1420. https://doi.org/10.3390/agriculture13071420 https://www.mdpi.com/journal/agriculture
Agriculture 2023,13, 1420 2 of 14
and the adaptation of plants to new agroclimatic environments, it is opportune to evaluate
their ability to associate with introduced agricultural species, such as lulo.
Lulo or naranjilla (Solanum quitoense Lamarck) (Solanaceae) is a crop of commercial
importance in South America, specifically for Ecuador, Colombia, and Peru, with yields of
7 to 15 t ha
−1
[
12
], although its economic importance has also increased in Guatemala and
Costa Rica [
13
]. The lulo plant is an herbaceous perennial (up to 3 years) with a 1 to 3 m
height (Figure 1A) and broad and densely pubescent leaves [
14
] (Figure 1B). The stem is
thick and lignescent with purple trichomes [
15
,
16
] (Figure 1C). Solanum quitoense grows
under a humid mountain forest climate between an altitude of 1000 and 2500 m, featuring
temperatures from 15 to 24
◦
C and precipitation from 2000–3000 mm per year. It prefers
acidic (pH 5.5–6.0) and well drained soils [17,18].
Agriculture 2023, 13, x FOR PEER REVIEW 2 of 15
physiological and yield components. Due to the benefits that AMF represents for agricul-
ture and the adaptation of plants to new agroclimatic environments, it is opportune to
evaluate their ability to associate with introduced agricultural species, such as lulo.
Lulo or naranjilla (Solanum quitoense Lamarck) (Solanaceae) is a crop of commercial
importance in South America, specifically for Ecuador, Colombia, and Peru, with yields
of 7 to 15 t ha−1 [12], although its economic importance has also increased in Guatemala
and Costa Rica [13]. The lulo plant is an herbaceous perennial (up to 3 years) with a 1 to 3
m height (Figure 1A) and broad and densely pubescent leaves [14] (Figure 1B). The stem
is thick and lignescent with purple trichomes [15,16] (Figure 1C). Solanum quitoense grows
under a humid mountain forest climate between an altitude of 1000 and 2500 m, featuring
temperatures from 15 to 24 °C and precipitation from 2000–3000 mm per year. It prefers
acidic (pH 5.5–6.0) and well drained soils [17,18].
Figure 1. Lulo plant (Solanum quitoense). (A) Structure of the plant. (B) Inflorescences. (C) Fruits in
physiological maturity.
One of the factors with the greatest influence on growth is fertilization. Lulo plants
require high amounts of nutrients. An inadequate supply of nitrogen (N) causes chlorosis
in adult leaves, while a phosphorus deficiency (P) causes downward growth, giving the
impression of wilting. Potassium (K) generates yellow moling, affecting the vegetative
growth and causing gas exchange problems [19].
In plant nutrition schemes, the inoculation using arbuscular mycorrhizal fungi
(AMF) has shown an efficiency in bioprotection, biofertilization, and bioregulation [20,21].
The plants of the Solanaceae family respond favorably to inoculation using AMF [22,23].
The main morphological characteristic of these is the typical structure of the colonization
that the fungus develops inside the cells of the root bark [24]. This facilitates water and
nutrient absorption, especially for low mobility nutrients such as P, which occurs through
a network of extra radical hyphae that extend from the colonized roots to the surrounding
soil and function as a supplementary absorbent system [25].
In Mexico, 143 known AMF species [26] are evaluated in order to improve the pro-
duction of various tropical crops [27–29], from nursery conditions, phytosanitary quality,
transplant resistance, height, vigor, as well as fruit quantity and postharvest quality.
Based on the above, the growth and development of lulo plants inoculated with mycor-
rhizal fungi (Funneliformis mosseae and Entrophospora colombiana) accompanied by fertili-
zation using diammonium phosphate (18N-46P-00K) in cloud forest soils was evaluated
under the hypothesis that inoculation using AMF contributes to the adaptation and estab-
lishment of S. quitoense as an alternative crop in Mexico.
Figure 1.
Lulo plant (Solanum quitoense). (
A
) Structure of the plant. (
B
) Inflorescences. (
C
) Fruits in
physiological maturity.
One of the factors with the greatest influence on growth is fertilization. Lulo plants
require high amounts of nutrients. An inadequate supply of nitrogen (N) causes chlorosis
in adult leaves, while a phosphorus deficiency (P) causes downward growth, giving the
impression of wilting. Potassium (K) generates yellow mottling, affecting the vegetative
growth and causing gas exchange problems [19].
In plant nutrition schemes, the inoculation using arbuscular mycorrhizal fungi (AMF)
has shown an efficiency in bioprotection, biofertilization, and bioregulation [
20
,
21
]. The
plants of the Solanaceae family respond favorably to inoculation using AMF [
22
,
23
]. The
main morphological characteristic of these is the typical structure of the colonization that
the fungus develops inside the cells of the root bark [
24
]. This facilitates water and nutrient
absorption, especially for low mobility nutrients such as P, which occurs through a network
of extra radical hyphae that extend from the colonized roots to the surrounding soil and
function as a supplementary absorbent system [25].
In Mexico, 143 known AMF species [
26
] are evaluated in order to improve the pro-
duction of various tropical crops [
27
–
29
], from nursery conditions, phytosanitary quality,
transplant resistance, height, vigor, as well as fruit quantity and postharvest quality. Based
on the above, the growth and development of lulo plants inoculated with mycorrhizal
fungi (Funneliformis mosseae and Entrophospora colombiana) accompanied by fertilization
using diammonium phosphate (18N-46P-00K) in cloud forest soils was evaluated under
the hypothesis that inoculation using AMF contributes to the adaptation and establishment
of S. quitoense as an alternative crop in Mexico.
Agriculture 2023,13, 1420 3 of 14
2. Materials and Methods
2.1. Study Site
The study was conducted in Huatusco, Veracruz, Mexico (19
◦
08
0
56
00
N, 96
◦
57
0
58
00
W)
at an altitude of 1344 m. The climate was temperate humid with rain in the summer and an
average temperature of 19.4
◦
C (a maximum of 26.3
◦
C and a minimum of 12.4
◦
C) [
30
]. The
vegetation was a mountain mesophilic forest with an 85% relative humidity and 2250 mm
of annual precipitation. The soils were rich in nutrients with a moderate fertility, coarse
texture and fragments of volcanic glass, slightly acidic pH (4.3–6.5), rich organic matter,
low Ca contents, and high Fe, Mn, and Zn contents [31].
2.2. Biological Material Used
Lulo seeds were taken from ripe fruits, washed, and dried in the shade. The seeds were sown
in trays with 240 cavities (one seed per cavity) using a peat moss
®
(
Baie Sainte-Anne, NB, Canada
)
and vermiculite
®
(Mexico City, Mexico) substrate (4:1). After 30 days, the seedlings were trans-
planted into polyethylene bags with 90 L of soil from the town of Huatusco,
Veracruz, Mexico
.
2.3. Physicochemical Analysis of Soil
The physicochemical analysis of the soil was obtained from three composite samples
of the first 40 cm from random locations. The soil was air dried and sieved through a mesh
net (5 mm pore). In the soil samples, the pH, electrical conductivity, and organic matter
content were determined using the Walkley and Black method [
32
], N was determined
using the Kjeldahl method [
33
], and P was determined using the Bray–Kurtz method [
34
].
The micronutrients were extracted and quantified using wet digestion [
35
]. The K content
was determined using a flame emission spectrophotometer. The Ca and Mg contents were
determined using atomic absorption (SavantAA GBC
®
Scientific Equipment, Keysborough,
VIC, Australia). The texture of the soil was determined using the hydrometric method [
36
].
2.4. Isolation of Mycorrhizal Fungal Spores
The AMF F. mosseae and E. colombiana were isolated from the soil rhizosphere of a
mango orchard (Mangifera indica L.) in Manlio Fabio Altamirano, Veracruz, Mexico. The
spores were extracted using the methods of wet sieving (sieve numbers: 44, 325, and
400
µ
m) and decantation [
37
]. Morphological grouping was performed considering the
shape, color, and size [
38
]. Morphotypes were inoculated in the seedlings of wheat (Triticum
aestivum L.; one spore per plant and ten replicates). The monosporic culture was established
in pots with a 1.0 L capacity and sterile sand as a substrate. The plants were maintained
in a greenhouse at 40
◦
C. A Steiner nutrient solution [
39
] modified in P (20%, pH 7.5)
was applied using daily irrigation. Through monthly soil sampling, the propagation of
the inoculated morphotypes was assessed. In order to multiply the spores and set the
symbiosis in the fourth month, one wheat seed was placed per pot for a second crop cycle.
In the last two months the plants were maintained with water stress in order to accelerate
the symbiosis, and subsequently, the spores of the AMF were extracted following the wet
sieving and decantation methods [37].
The identification of F. mosseae and E. colombiana was conducted based on the descrip-
tion of the spore wall groups in semi-permanent preparations using polyvinyl alcohol,
lactic acid, and glycerol with and without Melzer’s reagent [
40
]. For the AMF production,
the spores were disinfected on the wall surface with a solution of chloramine T (20 g L
−1
)
and streptomycin (200 mg L
−1
) and subsequently inoculated into sorghum plants (Sorghum
vulgare L.) developed in sterile river sand (120
◦
C for 3 h for three consecutive days) accord-
ing to the host plant method [
41
]. After four months, harvesting and root staining were
performed following the method of Phillips and Hayman [
42
] and the percentage of the
mycorrhizal colonization was measured using the quadrant intersection method [43].
Agriculture 2023,13, 1420 4 of 14
2.5. Treatments and Inoculation of Symbiotic Microorganisms
In order to evaluate the growth and development of the lulo plant, four treatments
were established: Entrophospora colombiana (350 spores: 10 g plant
−1
), Funneliformis mosseae
(350 spores: 10 g plant−1), DAP fertilization (18-46-00) 5 g plant−1, and a control.
The plants were inoculated with F. mosseae and E. colombiana on the day of transplan-
tation into the bags. A total of 350 spores of each AMF were added per plant in 10 g
of substrate–inoculum. The spores were placed over the root system to ensure contact.
For the treatment using diammonium phosphate (DAP; NPK 18-46-00 Phosagro
®
France
SAS, PhosAgro Group of Companies, Moscow, Russia), 5 g was applied to each plant.
Additionally, and for all the treatments, 5.0 g of a biostimulant (PHC Humex WS
®
Plant
health care de Mexico, Mexico city, México) based on natural humates was applied to each
plant, and 25 mL of PHC
®
YUCCAH
®
(Plant health care de Mexico, Mexico city, México)
as a soil improver and decompactor were applied to the lulo plants.
2.6. Variables
2.6.1. Plant Growth
The plant height was measured monthly up to the fifth month, considering the base of
the root neck to the apex of the youngest leaf. The diameter of the stem was recorded using
a digital vernier, starting 90 days after germination (dag) and always at the average height
of the plant.
2.6.2. Leaf Area Growth
The number of leaves was counted and the leaf area from transplantation (30 dag)
to fruit formation was measured monthly. For this evaluation, the equatorial length and
width were considered without considering the petiole.
2.6.3. Mycorrhizal Colonization in the Roots
Twelve months after transplantation, the roots of each treatment were sampled. The
samples were washed with domestic water, rinsed with KOH (10%), stained with trypan
blue (0.05%), and 10 segments of 1.0 cm in length were obtained, which represented a
replicate. The segments were placed (randomly) parallel on a slide to determine the
mycorrhizal colonization (hyphae, vesicles, and arbuscules) using a microscope at 45
×
.
Three visual fields were examined in each root segment to observe the colonization of F.
mosseae and E. colombiana, plus the native mycorrhizae. The percentage of the colonization
was calculated as the ratio of the colonized root sections by the observed sections per 100.
2.6.4. Foliar Analysis
The leaves were sampled 12 months after transplantation, and in each treatment the
mineral content was quantified. The total N was determined using the Microkjeldahl
method [
44
], P was determined using a spectrophotometer (20D, Milton Roy Co., San
Diego, CA, USA), the elements Ca, Mg, Mn, Cu, Zn, and Fe were analyzed using an
atomic absorption spectrophotometer, and K was analyzed using flame emission (IL 551,
Instrumentation Laboratories, Barcelona, Spain) [
44
]). Three repetitions per treatment were
analyzed.
2.7. Experimental Design and Statistical Analysis
The experiment was conducted in random blocks with four treatments, three repeti-
tions, and five plants for each experimental unit (n = 60 plants). The results were analyzed
using an ANOVA and multiple comparisons of a means by Tukey test (
α
= 0.05) using the
RStudio free version and MiniTab version 18 programs.
Agriculture 2023,13, 1420 5 of 14
3. Results
3.1. Soil Analysis
The soil where the lulo plants were established was a clayey Vertisol type, charac-
terized by plastic and moist compaction in the wet season. In the dry season, it formed
wide and deep cracks that are typical of tropical climates with defined periods of rain and
drought. The soil was slightly acidic (pH 6.39), rich in organic matter, high in Ca and Mg,
very high in Fe, Mn, and Cu, but low in N, P, K, and Zn, with a low cation exchange ca-
pacity (CEC). Although there was no technical guide for the values of the physicochemical
analysis of the soil for the cultivation of lulo, it was conducted based on the standard guide
(Table 1).
Table 1.
Physicochemical characteristics of the soil of the experimental location for twelve-month-old
plants in a reproductive stage.
Variable Content (mg kg−1) Interpretation
N 14.3 Low
P 11.3 Low
K 63.0 Low
Ca 3010 High
Mg 570 High
Fe 52.12 Very high
Zn 1.45 Low
Mn 57.30 Very high
Cu 3.04 Very high
CEC 14.64 cmol kg−1Low
Texture
Organic matter 4.02 (%) Rich
Arena 17.16 (%)
Clay soil
Limo 13.08 (%)
Clay 69.76 (%)
pH 6.39 Slightly acidic
3.2. Plant Height and Stem Diameter
The growth of lulo plants was recorded monthly (August to December) showing the
differences (
α
= 0.05) between the treatments. The plants inoculated with E. colombiana and
those fertilized with DAP (Figure 2A) stood out. During the first month after transplantation
(30 dag), the height of the plants inoculated with E. colombiana was 3.54
±
1.4, F. mosseae was
3.08
±
0.7, DAP was 2.50
±
1.0, and the control was 4.18
±
1.40 cm. At the second month
of evaluation, the plants inoculated with E. colombiana and fertilized with DAP achieved
the greatest heights with 11.06
±
2.91 and 9.81
±
3.3 cm, respectively. At 90 dag, there was
a significant increase in plant growth since all the treatments on average increased by 50%,
registering the greatest heights for the treatments fertilized with DAP and inoculated with
E. colombiana. In the fourth month of evaluation, the plants inoculated with E. colombiana
presented the largest increases, with 53.46
±
6.12 cm in height. After 150 dag, the plants
showed heights of 62.40
±
1.0 for those inoculated with E. colombiana and 61.40
±
1.0 cm
for those fertilized with DAP, which began fruiting and fruit growth.
As shown in Figure 2A, the inoculation using E. colombiana helped increase the height.
In contrast, F. mosseae did not promote plant elongation. The stem diameter in all the
treatments was evaluated from 90 dag. In this period, the treatments using E. colombiana
and DAP exhibited the highest circumference (1.82
±
0.43 and 1.88
±
0.50 cm, respectively)
(Figure 2B). At the fourth month, there were significant differences in all the treatments,
where the plants inoculated with E.colombiana registered 2.39
±
0.40, F. mosseae registered
1.97
±
0.39, DAP registered 2.21
±
0.40, and the control registered 2.12
±
0.32 cm. However,
at the fifth month, all the treatments became similar.
Agriculture 2023,13, 1420 6 of 14
Agriculture 2023, 13, x FOR PEER REVIEW 6 of 15
1 2 3 4 5
0
20
40
60
80
A
Months
Pl ant he ig ht (c m)
3 4 5
0
1
2
3
E.colomb iana
F. mosseae
DAP (18-46-00)
Control
a
b
a
ab
a
b
ab ab
aaaa
B
Months
Stem diameter (cm)
Figure 2. (A) Total height (± S.D.) of lulo plants (Solanum quitoense) from transplantation to fruiting.
(B) Stem diameter (± S.D.) in lulo plants at the third, fourth, and fifth months (fruited) after trans-
plantation. The different leers on the bars indicate a significant difference at each evaluation date
(n = 60).
As shown in Figure 2A, the inoculation using E. colombiana helped increase the
height. In contrast, F. mosseae did not promote plant elongation. The stem diameter in all
the treatments was evaluated from 90 dag. In this period, the treatments using E. colombi-
ana and DAP exhibited the highest circumference (1.82 ± 0.43 and 1.88 ± 0.50 cm, respec-
tively) (Figure 2B). At the fourth month, there were significant differences in all the treat-
ments, where the plants inoculated with E. colombiana registered 2.39 ± 0.40, F. mosseae
registered 1.97 ± 0.39, DAP registered 2.21 ± 0.40, and the control registered 2.12 ± 0.32 cm.
However, at the fifth month, all the treatments became similar.
3.3. Number of Leaves and the Leaf Area
The number of leaves per plant during the first month of evaluation ranged from 6.3
± 1.9 to 8.7 ± 1.1, where the lowest number of leaves was recorded with the inoculation of
F. mosseae, while the control had significantly more leaves. In the second and third months
of evaluation, all the treatments behaved statistically the same in terms of the number of
sheets. However, in the fourth month, the number of leaves per plant showed significant
differences since it decreased due to pruning. From the fifth month onwards, new sheets
were exposed (Figure 3A). In this case, E. colombiana generated the highest number of
leaves (10.33 ± 2.69), and the plants inoculated with F. mosseae had the lowest number (7.66
± 2.02).
1 2 3 4 5
0
5
10
15
ab
bb
aa
aaaaaaaabb
a
a
b
ab ab
Months
Number of leaves
1 2 3 4 5
0
500
1000
1500
2000
E. colombiana
F. mosseae
DAP (18-46-00)
Control
aaaa abaab
ab
c
a
bc
a
b
abab
a
a
aa
Months
Leaf area (cm
2
)
AB
Figure 3. (A) Number of leaves (± S.D.) in lulo plants (Solanum quitoense) from transplant to fruiting.
The different leers on the bars indicate a significant difference at each evaluation date (n = 60). (B)
Leaf area (± S.D.). The different leers on the bar indicate a significant difference at each evaluation
date (n = 60).
In relation to leaf development (Figure 3B) in the first month, the leaves in all the
treatments began to grow while still presenting an oval shape with an average area of 6.5
Figure 2.
(
A
) Total height (
±
S.D.) of lulo plants (Solanum quitoense) from transplantation to fruiting.
(
B
) Stem diameter (
±
S.D.) in lulo plants at the third, fourth, and fifth months (fruited) after trans-
plantation. The different letters on the bars indicate a significant difference at each evaluation date
(n = 60).
3.3. Number of Leaves and the Leaf Area
The number of leaves per plant during the first month of evaluation ranged from
6.3 ±1.9
to 8.7
±
1.1, where the lowest number of leaves was recorded with the inoculation
of F. mosseae, while the control had significantly more leaves. In the second and third
months of evaluation, all the treatments behaved statistically the same in terms of the
number of sheets. However, in the fourth month, the number of leaves per plant showed
significant differences since it decreased due to pruning. From the fifth month onwards,
new sheets were exposed (Figure 3A). In this case, E. colombiana generated the highest
number of leaves (10.33
±
2.69), and the plants inoculated with F. mosseae had the lowest
number (7.66 ±2.02).
Agriculture 2023, 13, x FOR PEER REVIEW 6 of 15
1 2 3 4 5
0
20
40
60
80
A
Months
Pl ant he ig ht (c m)
3 4 5
0
1
2
3
E.colomb iana
F. mosseae
DAP (18-46-00)
Control
a
b
a
ab
a
b
ab ab
aaaa
B
Months
Stem diameter (cm)
Figure 2. (A) Total height (± S.D.) of lulo plants (Solanum quitoense) from transplantation to fruiting.
(B) Stem diameter (± S.D.) in lulo plants at the third, fourth, and fifth months (fruited) after trans-
plantation. The different leers on the bars indicate a significant difference at each evaluation date
(n = 60).
As shown in Figure 2A, the inoculation using E. colombiana helped increase the
height. In contrast, F. mosseae did not promote plant elongation. The stem diameter in all
the treatments was evaluated from 90 dag. In this period, the treatments using E. colombi-
ana and DAP exhibited the highest circumference (1.82 ± 0.43 and 1.88 ± 0.50 cm, respec-
tively) (Figure 2B). At the fourth month, there were significant differences in all the treat-
ments, where the plants inoculated with E. colombiana registered 2.39 ± 0.40, F. mosseae
registered 1.97 ± 0.39, DAP registered 2.21 ± 0.40, and the control registered 2.12 ± 0.32 cm.
However, at the fifth month, all the treatments became similar.
3.3. Number of Leaves and the Leaf Area
The number of leaves per plant during the first month of evaluation ranged from 6.3
± 1.9 to 8.7 ± 1.1, where the lowest number of leaves was recorded with the inoculation of
F. mosseae, while the control had significantly more leaves. In the second and third months
of evaluation, all the treatments behaved statistically the same in terms of the number of
sheets. However, in the fourth month, the number of leaves per plant showed significant
differences since it decreased due to pruning. From the fifth month onwards, new sheets
were exposed (Figure 3A). In this case, E. colombiana generated the highest number of
leaves (10.33 ± 2.69), and the plants inoculated with F. mosseae had the lowest number (7.66
± 2.02).
1 2 3 4 5
0
5
10
15
ab
bb
aa
aaaaaaaabb
a
a
b
ab ab
Months
Number of leaves
1 2 3 4 5
0
500
1000
1500
2000
E. colombiana
F. mosseae
DAP (18-46-00)
Control
aaaa abaab
ab
c
a
bc
a
b
abab
a
a
aa
Months
Leaf area (cm
2
)
AB
Figure 3. (A) Number of leaves (± S.D.) in lulo plants (Solanum quitoense) from transplant to fruiting.
The different leers on the bars indicate a significant difference at each evaluation date (n = 60). (B)
Leaf area (± S.D.). The different leers on the bar indicate a significant difference at each evaluation
date (n = 60).
In relation to leaf development (Figure 3B) in the first month, the leaves in all the
treatments began to grow while still presenting an oval shape with an average area of 6.5
Figure 3.
(
A
) Number of leaves (
±
S.D.) in lulo plants (Solanum quitoense) from transplant to fruiting.
The different letters on the bars indicate a significant difference at each evaluation date (n = 60).
(
B
) Leaf area (
±
S.D.). The different letters on the bar indicate a significant difference at each evaluation
date (n = 60).
In relation to leaf development (Figure 3B) in the first month, the leaves in all the
treatments began to grow while still presenting an oval shape with an average area of
6.5 cm
2
. In the second month, the leaves showed changes in their shape and color (green on
the beam and purple on the underside with densely pubescent surfaces). At this stage, the
plants inoculated with F. mosseae registered a smaller leaf area, while the other treatments
did not show significant differences. In the third month, the leaf area increased by 90%.
The plants inoculated with E. colombiana and DAP exhibited the largest leaf area and
maintained this behavior until the fifth month of evaluation, generating areas of 1758.53
and 1666.67 cm2, respectively.
Agriculture 2023,13, 1420 7 of 14
3.4. Mycorrhizal Colonization
The analysis of the mycorrhizal colonization after 12 months of transplantation showed
the presence of hyphae, vesicles, and arbuscules. The highest values of these structures
in the roots were obtained with the inoculation of E. colombiana, achieving a 70.5% total
colonization, while the treatment using diammonium phosphate (DAP) had a 63.4% native
mycorrhizal colonization. In this case, the addition of the DAP fertilization favored the
available content of P, and F.mosseae showed a 59.30% colonization. Since this study aimed
to evaluate the adaptability of lulo to soils different from those of its original habitat, the
soil was not sterilized to determine the level of colonization, both native and induced by
Funneliformis mosseae and Entrophospora colombiana. Table 2indicates the values of this
variable, highlighting the induced colonization with respect to the native colonization.
The above suggests that inoculation using these AMF can contribute to the successful
establishment of lulo as an agricultural crop in the study region, applying this activity from
the nursery.
Table 2.
Mycorrhizal colonization in the roots of lulo plants (Solanum quitoense). The different letters
indicate a significant difference at each evaluation date (n = 60).
Treatment Hyphae (%) Vesicles (%) Arbuscules
(%)
Colonization
Total (%)
Entrophospora colombiana 63.20 a 32.10 a 36.50 a 70.50 a
Funneliformis mosseae 53.12 b 10.70 b 24.78 b 59.30 b
Diammonium phosphate (DAP), native colonization 59.70 a 14.70 b 28.70 b 63.40 a
Control (native colonization) 21.36 c 1.47 c 0.98 c 9.74 c
3.5. Foliar Analysis
Twelve months after transplantation, the leaves inoculated with E. colombiana and
F. mosseae showed the highest N contents with values of 3.85
±
0.21 and 3.54
±
0.08%,
respectively, while the control showed the lowest value (1.85
±
0.07%) (Figure 4A). The
highest content of P was obtained from DAP fertilization, with a value of 0.17
±
0.0%, which
was equivalent to 58.83% more than the control (Figure 4B). The highest concentration of K
was recorded in the plants inoculated with E. colombiana (3.57
±
0.02%), with F. mosseae and
DAP (69.54 and 58.94%) achieving higher concentrations than the control (Figure 4C).
Agriculture 2023, 13, x FOR PEER REVIEW 7 of 15
cm2. In the second month, the leaves showed changes in their shape and color (green on
the beam and purple on the underside with densely pubescent surfaces). At this stage, the
plants inoculated with F. mosseae registered a smaller leaf area, while the other treatments
did not show significant differences. In the third month, the leaf area increased by 90%.
The plants inoculated with E. colombiana and DAP exhibited the largest leaf area and main-
tained this behavior until the fifth month of evaluation, generating areas of 1758.53 and
1666.67 cm2, respectively.
3.4. Mycorrhizal Colonization
The analysis of the mycorrhizal colonization after 12 months of transplantation
showed the presence of hyphae, vesicles, and arbuscules. The highest values of these
structures in the roots were obtained with the inoculation of E. colombiana, achieving a
70.5% total colonization, while the treatment using diammonium phosphate (DAP) had a
63.4% native mycorrhizal colonization. In this case, the addition of the DAP fertilization
favored the available content of P, and F. mosseae showed a 59.30% colonization. Since this
study aimed to evaluate the adaptability of lulo to soils different from those of its original
habitat, the soil was not sterilized to determine the level of colonization, both native and
induced by Funneliformis mosseae and Entrophospora colombiana. Table 2 indicates the
values of this variable, highlighting the induced colonization with respect to the native
colonization. The above suggests that inoculation using these AMF can contribute to the
successful establishment of lulo as an agricultural crop in the study region, applying this
activity from the nursery.
Table 2. Mycorrhizal colonization in the roots of lulo plants (Solanum quitoense). The different leers
indicate a significant difference at each evaluation date (n = 60).
Treatment Hyphae (%) Vesicles (%) Arbuscules (%) Colonization
Total (%)
Entrophospora colombiana 63.20 a 32.10 a 36.50 a 70.50 a
Funneliformis mosseae 53.12 b 10.70 b 24.78 b 59.30 b
Diammonium phosphate (DAP), native colonization 59.70 a 14.70 b 28.70 b 63.40 a
Control (native colonization) 21.36 c 1.47 c 0.98 c 9.74 c
3.5. Foliar Analysis
Twelve months after transplantation, the leaves inoculated with E. colombiana and F.
mosseae showed the highest N contents with values of 3.85 ± 0.21 and 3.54 ± 0.08%, respec-
tively, while the control showed the lowest value (1.85 ± 0.07%) (Figure 4A). The highest
content of P was obtained from DAP fertilization, with a value of 0.17 ± 0.0%, which was
equivalent to 58.83% more than the control (Figure 4B). The highest concentration of K
was recorded in the plants inoculated with E. colombiana (3.57 ± 0.02%), with F. mosseae
and DAP (69.54 and 58.94%) achieving higher concentrations than the control (Figure 4C).
0
1
2
3
4
5
aab
c
Treatments
N(%)
0.00
0.05
0.10
0.15
0.20
b
c
a
d
Tre at me nts
P (%)
0
1
2
3
4
Entrophospora colombiana
Funneliformis mosseae
DAP (18-46-00)
Contr ol
a
b
c
d
Treat m en ts
K (% )
ABC
Figure 4.
Percentages (
±
S.D.) of N (
A
), P (
B
), and K (
C
) in the leaf tissue of lulo plants (Solanum
quitoense) twelve months after transplantation. The different letters on the bars indicate a significant
difference in the concentration of each element between the treatments (n = 12).
The highest content of Ca (3.07
±
0.04%) in the leaf tissue was observed in the treat-
ment with E. colombiana (Figure 5A), while the lowest content was obtained in the con-
trol (
1.10 ±0.03%
). The highest Mg content was observed in the plants inoculated with
E. colombiana
and F.mosseae (0.31
±
0.01 and 0.28
±
0.01%), and these concentrations were
46.43 and 53.57% higher than the control (Figure 5B).
Agriculture 2023,13, 1420 8 of 14
Agriculture 2023, 13, x FOR PEER REVIEW 8 of 15
Figure 4. Percentages (± S.D.) of N (A), P (B), and K (C) in the leaf tissue of lulo plants (Solanum
quitoense) twelve months after transplantation. The different leers on the bars indicate a significant
difference in the concentration of each element between the treatments (n = 12).
The highest content of Ca (3.07 ± 0.04%) in the leaf tissue was observed in the treat-
ment with E. colombiana (Figure 5A), while the lowest content was obtained in the control
(1.10 ± 0.03%). The highest Mg content was observed in the plants inoculated with E. co-
lombiana and F. mosseae (0.31 ± 0.01 and 0.28 ± 0.01%), and these concentrations were 46.43
and 53.57% higher than the control (Figure 5B).
0
1
2
3
4
a
b
c
d
Treatments
Ca (%)
0.0
0.1
0.2
0.3
0.4
Entrophospora colombiana
Funneliformis mosseae
DAP (18-46-00)
Contro l
aa
b
c
Treatments
Mg (%)
AB
Figure 5. Concentrations (± S.D.) of Ca (A) and Mg (B) in the leaf tissue of lulo plants (Solanum
quitoense) twelve months after transplantation. The different leers on the bars indicate a significant
difference in the concentration of each element between the treatments (n = 12).
The foliar analysis of the micronutrient content showed significant differences be-
tween the treatments. The highest content of Mn (40.69%) was observed in the plants in-
oculated with E. colombiana, and the treatments with F. mosseae and DAP presented 33.6
and 37.1% higher concentrations than the control (Figure 6A).
0
5
10
15
20
25
a
bb
c
Treatments
Mn (%)
0.00
0.05
0.10
0.15
0.20
0.25
Entrophospora colombiana
Funneliformis mosseae
DAP (18-46-00)
Contr ol
a
b
c
d
Tr ea t m en t s
Cu (%)
0
20
40
60
80
a
b
c
d
Treatments
Fe (%)
0
1
2
3
4
a
bb
c
Treatments
Zn ( %)
AB
C
D
Figure 6. Concentrations of Mn (A), Cu (B), Fe (C), and Zn (D) in the leaf tissue of lulo plants (Sola-
num quitoense) twelve months after transplantation. The different leers on the bars indicate a sig-
nificant difference in the concentration of each element between the treatments (n = 12).
The Cu concentration of 0.21 ± 0.02 mg kg−1 was the highest and corresponded to the
plants inoculated with E. colombiana. The lowest value (0.050 mg kg−1) corresponded to the
Figure 5.
Concentrations (
±
S.D.) of Ca (
A
) and Mg (
B
) in the leaf tissue of lulo plants (Solanum
quitoense) twelve months after transplantation. The different letters on the bars indicate a significant
difference in the concentration of each element between the treatments (n = 12).
The foliar analysis of the micronutrient content showed significant differences between
the treatments. The highest content of Mn (40.69%) was observed in the plants inoculated
with E. colombiana, and the treatments with F.mosseae and DAP presented 33.6 and 37.1%
higher concentrations than the control (Figure 6A).
Agriculture 2023, 13, x FOR PEER REVIEW 8 of 15
Figure 4. Percentages (± S.D.) of N (A), P (B), and K (C) in the leaf tissue of lulo plants (Solanum
quitoense) twelve months after transplantation. The different leers on the bars indicate a significant
difference in the concentration of each element between the treatments (n = 12).
The highest content of Ca (3.07 ± 0.04%) in the leaf tissue was observed in the treat-
ment with E. colombiana (Figure 5A), while the lowest content was obtained in the control
(1.10 ± 0.03%). The highest Mg content was observed in the plants inoculated with E. co-
lombiana and F. mosseae (0.31 ± 0.01 and 0.28 ± 0.01%), and these concentrations were 46.43
and 53.57% higher than the control (Figure 5B).
0
1
2
3
4
a
b
c
d
Treatments
Ca (%)
0.0
0.1
0.2
0.3
0.4
Entrophospora colombiana
Funneliformis mosseae
DAP (18-46-00)
Contro l
aa
b
c
Treatments
Mg (%)
AB
Figure 5. Concentrations (± S.D.) of Ca (A) and Mg (B) in the leaf tissue of lulo plants (Solanum
quitoense) twelve months after transplantation. The different leers on the bars indicate a significant
difference in the concentration of each element between the treatments (n = 12).
The foliar analysis of the micronutrient content showed significant differences be-
tween the treatments. The highest content of Mn (40.69%) was observed in the plants in-
oculated with E. colombiana, and the treatments with F. mosseae and DAP presented 33.6
and 37.1% higher concentrations than the control (Figure 6A).
0
5
10
15
20
25
a
bb
c
Treatments
Mn (%)
0.00
0.05
0.10
0.15
0.20
0.25
Entrophospora colombiana
Funneliformis mosseae
DAP (18-46-00)
Contr ol
a
b
c
d
Tr ea t m en t s
Cu (%)
0
20
40
60
80
a
b
c
d
Treatments
Fe (%)
0
1
2
3
4
a
bb
c
Treatments
Zn ( %)
AB
C
D
Figure 6. Concentrations of Mn (A), Cu (B), Fe (C), and Zn (D) in the leaf tissue of lulo plants (Sola-
num quitoense) twelve months after transplantation. The different leers on the bars indicate a sig-
nificant difference in the concentration of each element between the treatments (n = 12).
The Cu concentration of 0.21 ± 0.02 mg kg−1 was the highest and corresponded to the
plants inoculated with E. colombiana. The lowest value (0.050 mg kg−1) corresponded to the
Figure 6.
Concentrations of Mn (
A
), Cu (
B
), Fe (
C
), and Zn (
D
) in the leaf tissue of lulo plants
(Solanum quitoense) twelve months after transplantation. The different letters on the bars indicate a
significant difference in the concentration of each element between the treatments (n = 12).
The Cu concentration of 0.21
±
0.02 mg kg
−1
was the highest and corresponded to
the plants inoculated with E. colombiana. The lowest value (0.050 mg kg
−1
) corresponded
to the control (Figure 6B). Regarding Fe, the maximum content was presented by the
plants inoculated with E. colombiana and represented a 48.78% higher concentration than
in the control (Figure 6C). The highest Zn content (3.0 mg kg
−1
) was identified from the
treatment with E. colombiana. The plants inoculated with F.mosseae and fertilized with DAP
showed a content of 2.5 mg kg
−1
and the control plants presented a content of 1.0 mg kg
−1
(Figure 6D).
Agriculture 2023,13, 1420 9 of 14
4. Discussion
4.1. Soil Analysis
Lulo thrives in slightly acidic soils (pH 6.0–6.4) that are moist, deep, and have good
drainage. Interacting with native mycorrhizal fungi improves its development [
45
]. Despite
the “rustic” appearance of the lulo plant, its development depends directly on the nutrition
and characteristics of the soil. Generally, the type of soil where it develops best is loam
with a good content of organic matter and a clayey–sandy composition [
46
,
47
]. Solanum
quitoense is used as a colonizer for land from clearings on hillsides, so it is common for it to
be planted in virgin soils.
The lulo plant can be adapted to humid mountain forests and can grow in in areas
with coffee cultivation (Coffea arabica L.), as was the case for the cloud forest of Huatusco,
Veracruz [48,49].
Researchers such as [
50
] evaluated three bocashi-type organic sources, a treatment
using a chemical fertilizer (10 N-30 P-10 K), and a control in a soil derived from volcanic ash
that was well drained, soft, or friable, and slightly plastic with a high fertility and loamy
texture in order to obtain a better performance in the cultivation of the lulo ‘La Selva’. The
researchers recorded that organic matter applications improved the soil characteristics, and
with organic matter contents between 172 and 180 g kg
−1
, chemical fertilization produced
contents of 0.5 to 1.54 cmol kg
−1
of K, 4.2 to 10.5 cmol kg
−1
of Ca, 1.1 to 2.4 cmol kg
−1
of Mg, and 990 mg kg
−1
of P, which stabilized at a pH of 5.6. With the above, Ref. [
50
]
concluded that the best performance was obtained using a bocashi of poultry manure,
which saw a 38.3% increase in fruit productivity that was equivalent to the highest yield of
4.7 t ha−1.
4.2. Plant Height and Stem Diameter
AMF inoculations in S. quitoense var. Septentrionale resulted in an increased in the
plant height of 54.7% with Glomus sp. and S. heterogama compared to those that were not
inoculated. In addition, shade increased growth by 11.6% compared to the plants exposed
to the sun [51].
The biomass in gooseberry plants (Physalis peruviana L.) increased from an inoculation
of 200 g of mycorrhiza Glomus sp., Acaulospora sp., and Entrophospora sp. and fertilization
using 15-15-15 (N-P-K of 200 g plant
−1
). AMF increased the landfill capacity of the root
system, thereby increasing the photosynthetic rate and growth of the plant [52].
Other researchers evaluated the inoculation of E. colombiana plus the addition of
100N-30P-150K (Heliconia L. f psittacorum
×
H. spathocircinata) in a reported stimulus or
vegetative growth, increase or plant height, stem diameter, number of shoots, leaf area, or
chlorophyll content [
53
]. Additionally, F. mosseae favored the development of the rootstocks
of avocados (Persea americana) in nursery conditions, improving the quality and constituting
a nutritional alternative for this crop [54].
Fertilization in soil and the foliar applications using biostimulant derivatives of the
seaweed extract Ascophyllum nodosum in lulo plants increased the diameter of the stem with
respect to the control, registering at 150 days after transplantation with a soil fertilization
diameter of 1787 cm. In contrast, the diameter of the foliar fertilization registered as
1.630 cm, the mixture of fertilizers (soil and foliar) registered as 1.877 cm, the control
registered as 1.48 cm [55].
In our study, from the application of arbuscular mycorrhizae and DAP, the diameter of
the stem was 27.25% greater than the control plants. Similar values were reported by [
56
]
in tomato seedlings (S. lycopersicum L.) whose increased stem diameters ranged between
5.55 and 6.13 cm while the control showed a value of 4.88 cm.
4.3. Number of Leaves and the Leaf Area
The results of the present study coincided with those reported by [
56
] in tomato plants
(S. lycopersicum L.) from inoculation with Rhizophagus irregularis, which generated between
7.10 and 7.70 sheets unlike the control, which generated 6.50 sheets. In relation to leaf
Agriculture 2023,13, 1420 10 of 14
development, the length of the leaves were up to 60 cm [
57
], while Ref. [
58
] reported
lengths between 25 and 30 cm. The evaluations of lulo to determine the effect of NaCl
(30 and 60 mM) applied via foliar fertilization in different substrates showed that the
highest values of the leaf area corresponded to the control plants grown in peat without
NaCl (2900 cm
2
) [
59
]. The effect of the fertilization with N (10 and 110 mg N L H
2
O
−1
) in
greenhouse conditions, treating a group of plants with a foliar urea (250 mg de N L
−1
),
resulted in plants with 110 mg N L
−1
and the best performance in waterlogging conditions.
The leaf area was 62% greater in the plants with a high N content than in the plants with
the lowest concentration [60].
4.4. Mycorrhizal Colonization
Solanaceae plants such as S. quitoense respond favorably to inoculation with arbuscular
mycorrhizal fungi (AMF) [
61
]. The fungi offer amino acids, nutrients, and water to the
host in exchange for photosynthates. Due to this, the photosynthesis and distribution of
carbohydrates in the host plant is altered [
53
]. The efficiency of mycorrhizae depends on the
conditions in which it is applied, including the culture and local microbiota in the soil [
62
].
Colonization with AMF promotes the availability of P in soils with poor concentrations of
this element and in clay soils, facilitates the release of this element, and transfers it to the
plants through a series of physicochemical and biological reactions, actively transforming P
through the processes of mineralization, solubilization, immobilization, and oxidation [
63
].
Glomus aggregatum was evaluated under greenhouse conditions to determine the
dependence of the lulo var. ‘La Selva’. Researchers classified the species as moderately
dependent on its association with mycorrhizae with 0.002 mg L
−1
de P, with a tendency to
decrease when there is an increase in the concentration of P in the soil solution [
64
]. Other
researchers such as [
65
] evaluated the colonization of the mycorrhizae of G. mosseae and
E. colombiana in the papaya (Carica papaya L.) var. Maradol and observed a colonization
of 91.5% by G. mosseae, 58.2% by E. colombiana, and 16.5% in the control plants, which
indicated that G. mosseae responded favorably to temperate climates and that E. colombiana
was effective in tropical climate zones.
4.5. Foliar Analysis
Ref. [
60
] determined the concentrations of N, P, K, Ca, and Mg in (S. quitoense var.
Quitoense), obtaining 3.49% N, which was considered as an adequate value. For P, they
reported 0.25%, which was considered a medium level. The average K was 2.9, 2.7, and
3.2% in the plants growing in a peat, sand, and substrate mix, respectively, which was
considered low. In Ca, the highest percentage was 2.63%, and for Mg they reported 0.19 to
0.47%. This mineral is relevant because its deficiency affects the structure and integrity of
chloroplasts, photosynthesis, sugar accumulation, and various metabolic activities [66].
The physiological response of the Solanum quitoense var. Septentrionale to foliar
concentrations of 125, 250 y 500 mg kg
−1
of N was evaluated. The results reported that the
control plants had a shorter length and a lower dry mass and chlorophyll content in the
lower leaves than the plants grown with fertilizer. In addition, they revealed that the lack
of nutrients caused more biomass in the roots. These results indicate that a poor nutritional
status may limit foliar absorption [67].
The relationship of macro and micronutrients influences the physiological processes
of plants, since they intervene in the activity of enzyme systems and participate in oxide
reduction reactions, such as nitrate reduction, photosynthesis, N fixation, and oxidations.
Cu participates in oxide reduction reactions as a constituent of the enzymes (oxidases,
cytochrome oxidase, and others) in photosynthesis, metabolism of the cell walls (synthesis
of lignins), nitrogen fixation, and degradation of proteins.
Fe deficiencies are usually induced by inadequate assimilation caused by elevated
soil pH, excess Ca ions, bicarbonates in the soil solution, and interactions with other
elements. [
68
]. The Mn concentrations in lulo were lower than those obtained by [
69
] in
pepper (Capsicum annuum L.) from 90 to 250 mg kg
−1
. However, [
70
] showed that the Mn
Agriculture 2023,13, 1420 11 of 14
content in plants varies widely and that deficiencies are generally observed as those with
leaf concentration below 20 mg kg
−1
. Ref. [
71
] recommend the application of 135, 86, 126,
9, 4, 4 y 5 g plant
−1
of N, P
2
O
5
, K
2
O, Fe, Zn, and B y S, respectively, distributed throughout
the year in six applications every two months. Likewise, Ref. [
72
] found that, by removing
Mg from the nutrient solution, the height of the lulo plants decreased significantly and
possibly lacked Mn, Mo y Cu.
Other researchers such as [
73
,
74
] identified that lulo was significantly susceptible
to deficiencies in B, Mg, and Mn, and that P was the cause of delays in growth and the
ripening of fruits since this element was considered to be responsible for malformations in
the seeds.
5. Conclusions
S. quitoense can grow favorably in and show an adaptability to Vertisol-type clay soils
in cloud forests. The composition of macro and microelements increased in K, Ca, Mn, Cu,
Zn, and Fe with the inoculation with E. colombiana, and to a lesser extent with F. mosseae,
which increased the concentration of N and Mg. The fertilization with DAP increased the
content of P. Therefore, the application of mycorrhizae, as well as the application of DAP
for seedlings, is a recommended practice for lulo. The results are encouraging to continue
with expanding the cultivation areas in the study region, since the components of growth
and adaptation in cloud forest soils were attributed to the association with AMF.
Author Contributions:
Conceptualization: J.C.-I., M.d.L.A.-G. and D.J.-C.; methodology, J.C.-I. and
D.J.-C.; software, A.L.O.-H.; validation, C.B.P.-V. and A.L.O.-H.; formal analysis, A.L.O.-H. and
C.B.P.-V.; investigation, A.L.O.-H.; resources, M.d.L.A.-G.; data curation, A.L.O.-H. and
D.J.-C.
;
writing—original
draft preparation, A.L.O.-H., J.C.-I.; writing—review and editing, A.L.O.-H.,
M.d.L.A.-G. and J.C.-I.; supervision, M.d.L.A.-G. All authors have read and agreed to the published
version of the manuscript.
Funding:
This research was funded by National Council for Science and Technology (CONACyT),
Mexico, for the scholarship awarded to Ana Laura Olguín Hernández, with the support num-
ber: 788985.
Institutional Review Board Statement: Not applicable.
Acknowledgments:
The authors wish to thank the Colegio de Postgraduados and the Interdisci-
plinary Research Group at Sechium edule in Mexico, A.C., for the support with the laboratories,
equipment, and biological materials from Lulo for the development of the research.
Conflicts of Interest: The authors declare no conflict of interest.
Abbreviations
Arbuscular mycorrhizal fungi (AMF), potassium hydroxide (KOH), analysis of variance (ANOVA),
liter (L), cation exchange capacity (CEC), diammonium phosphate (DAP), standard error (S.D.),
centimoles per kilogram (cmol kg
−1
), nitrogen (N), phosphorus P), potassium (K), calcium (Ca),
magnesium (Mg), copper (Cu), molybdenum (Mo), iron (Fe), boron (B), zinc (Zn), diphosphorus
pentaoxy (P2O5), potassium oxide (K2O).
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