Carrot
seeds vigor on plant performance and crop yield
Vigor
de sementes de cenoura sobre o desempenho das plantas e rendimento da cultura
Vigor de semillas de zanahoria
sobre el desempeño de las plantas y rendimiento del cultivo
Gisela Hélnia Nunes Chipenete
1,
Denise Cunha Fernandes dos Santos Dias2,
Daniel Teixeira Pinheiro3*,
Laércio Junio da Silva2, Dalcionei Pazzin3,
Aparecida Leonir da Silva3
1Master in Crop Science at Agronomy
Department, Universidade Federal de Viçosa. Av. PH Rolfs,
s/n, Viçosa, Minas Gerais, Brazil. ghnchipenete@gmail.com. 2Professor at Agronomy Department, Universidade
Federal de Viçosa. Av. PH Rolfs, s/n, Viçosa, Minas Gerais, Brazil.
dcdias@ufv.br. ; laercio.silva@ufv.br. 3PhD in Crop Science at Agronomy
Department, Universidade Federal de Viçosa. Av. PH Rolfs,
s/n, Viçosa, Minas Gerais, Brazil. pinheiroagroufv@gmail.com*; dalcionei@hotmail.com ; aparecidaleonir@gmail.com
Recebido:
17/07/2020; Aprovado: 26/12/2020
Abstract: Rapid emergence
and uniform seedling growth are essential attributes in the production of
vegetables such as carrots, whose sowing is direct in the field. The experiment
was conducted to evaluate the effect of carrot seed vigor on seedling
emergence, plant development, and yield. Four seed lots of carrot, cv. Brasília
were characterized for their physiological potential by germination and vigor
tests. A field experiment was conducted, where the seeds of each lot were sown
in in the field to evaluate seedling emergence at 10 and 14 days, the length of
the shoot and root at 30, 45 and 60 days after sowing, the crop growth rate,
commercial, non-commercial and commercial roots yield.
Seed vigor significantly affected the seedling emergence and development of
carrot plants in the field. The less vigorous lot showed lower final emergence
than the most vigorous lots and these negative vigor effects extended to the
most advanced stages of plant development. Carrot seed vigor affects seedling
emergence and plant growth in the field. Vigorous seeds causes
greater emergence, plant height and plant dry matter during the vegetative
phase. The use of less vigorous seeds causes yield losses of up to 27%.
Key
words: Daucus carota L.; Germination;
Productivity; Quality.
Resumo: A rápida emergência e o crescimento
uniforme de plântulas são atributos essenciais na produção de culturas como a
cenoura, cuja semeadura é direta no campo. O experimento foi conduzido para avaliar
o efeito do vigor de sementes de cenoura na emergência de plântulas, no
desenvolvimento e no rendimento da cultura. Quatro lotes de sementes de
cenoura, cv. Brasília foram caracterizados por seu potencial fisiológico por
testes de germinação e vigor. Foi realizado um experimento de campo, no qual as
sementes de cada lote foram semeadas no campo para avaliar a emergência de
plântulas aos 10 e 14 dias, o comprimento da parte aérea e da raiz aos 30, 45 e
60 dias após a semeadura, a taxa de crescimento da cultura, raízes comerciais,
não comerciais e comerciais. O vigor das sementes afetou significativamente a
emergência e o desenvolvimento de mudas de cenoura no campo. O lote menos
vigoroso apresentou menor emergência final do que os lotes mais vigorosos e
esses efeitos negativos do vigor se estenderam aos estágios mais avançados do
desenvolvimento da planta. O vigor das sementes de cenoura afeta a emergência
de plântulas e o crescimento das plantas no campo. Sementes vigorosas ocasionam
maior emergência, altura de planta e matéria seca das plantas durante a fase
vegetativa. O uso de sementes menos vigorosas acarreta perdas de rendimento de
até 27%.
Palavras-chave: Daucus carota L.; Germinação;
Produtividade; Qualidade.
Resumen: La rápida
aparición y el crecimiento uniforme de las plántulas son atributos esenciales
en la producción de cultivos como la zanahoria, cuya siembra es directa en el
campo. El experimento se realizó para evaluar el efecto del vigor de semillas
de zanahoria en la aparición de las plántulas, en el desarrollo y rendimiento
del cultivo. Cuatro lotes de semillas de zanahoria, cv.
Brasilia, fueron caracterizados por su potencial fisiológico por pruebas de
germinación y vigor. Fue realizado un experimento de campo, en el cual las
semillas de cada lote fueron sembradas en el campo para evaluar la aparición de
plántulas a los 10 y 14 días, la longitud de la parte aérea y la raíz a los 30,
45 y 60 días después de la siembra, a tasa de crecimiento del cultivo, raíces
comerciales, no comerciales y comerciales totales. El vigor de las semillas
afectó significativamente la aparición y el desarrollo de plántulas de
zanahoria en el campo. El lote menos vigoroso mostró menos emergencia final que
los lotes más vigorosos y estos efectos negativos del vigor se extendieron a
las etapas más avanzadas del desarrollo de la planta. El vigor de las semillas
de zanahoria afecta la emergencia de plántulas y el crecimiento de plantas en
el campo. Las semillas vigorosas provocan mayor emergencia, altura de la planta
y materia seca de la planta durante la fase vegetativa. El uso de semillas
menos vigorosas conduce a pérdidas de rendimiento de hasta un 27%.
Palabras Clave: Daucus carota L.; Germinación; Productividad; Calidad.
INTRODUCTION
Successful crop
production depends on adequate seedling establishment in the field, which is
directly related to seed germination and vigor. Seed vigor comprises the sum of
seed properties that determine the potential for rapid and uniform seedling
emergence under environmental conditions, determining the development, yield,
and quality of the harvested product (FINCH-SAVAGE; BASSEL, 2016). Under field
conditions, vigorous seeds tend to produce seedlings with higher growth rates,
uniform emergence, and greater competition and survival. However, low-quality
seeds tend to lead to irregular stands, with emergence failures that compromise
the quality and yield (NASCIMENTO et al., 2011; LING et al., 2015).
The direct relation
between vigorous seeds and satisfactory yield has been reported in crops such
as wheat (ABATI et al., 2018), soybean (CAVERZAN et al., 2018) and others. In
vegetables, these characteristics are also related (RODO et al., 2003;
NASCIMENTO et al., 2011). In squash seeds at different maturity stages, which was
observed that seedling vigor is an effective parameter for composing quality
control in this species (SILVA et al., 2017). In cucumber, the seed vigor index
is directly related to yield (SHARMA et al., 2018). However, in some cases, the
effect of seed vigor on plant growth and final yield when there is no reduction
in field plant population can be controversial (MONDO et al., 2012).
Carrot (Daucus carota L.) is a vegetable of
great importance, with a global production that exceeds 40 million tons per
year (SHARMA, 2018). In Brazil, carrot production is around 700,000 tons per
year, being a very important activity for the family farm (EMBRAPA, 2020). In
this way, it is an extremely important vegetable, since has a good source of
nutritional substances such as vitamins, minerals, and dietary fibers (QUE et
al., 2019). Moreover, recent studies have shown other benefits of carrots, such
as pectin production (JAFARI et al., 2017), carotenoids production (ELLISON et
al., 2018), antioxidant properties (DONG et al., 2021), and others. Carrot
seeds are small, with few reserves, and are sown directly in the field.
According to Nascimento et al. (2011), the vigor in vegetable seeds is
important especially for species with these characteristics (small and few
reserves), once they are very sensitive to adverse environmental conditions,
affecting the uniform seedling establishment and compromising yield and final
product quality.
There is not much information about the
relation between seed vigor and carrot yield. Therefore, the experiment was
conducted to evaluate the effect of carrot seed vigor on seedling emergence,
plant development, and final crop yield.
MATERIAL AND METHODS
The research was conducted in the Agronomy Department at the Universidade Federal de Viçosa, Brazil.
Four commercial seed lots of carrot, cultivar “Brasília”, were used. Initially,
the seeds were evaluated by the following tests to characterize their initial
quality:
Moisture content (MC)
It was determined
by the oven method at 105 ± 3 °C for 24 hours (BRASIL, 2009). Two replications
of 5 g of seeds were used and the results were expressed as a percentage (%).
Germination (G)
The seeds were arranged
on two sheets of paper towel, moistened with distilled water (2.5 times the
weight of dry paper), in “gerbox” boxes. The boxes
were kept in a germinator at 20 °C and the evaluation was performed at 14 days
after sowing (BRASIL, 2009). Four replicates of 50 seeds from each lot were
used and the results were expressed as a percentage (%) of normal seedlings.
It was performed together with the germination test,
with the evaluation of normal seedlings performed seven days after sowing (BRASIL,
2009).
Seedling emergence (SE) and seedling emergence speed
index (ESI)
It was carried out in a greenhouse with four
replications of 50 seeds sowed in polystyrene trays containing moistened sand
up to 2/3 of the retention capacity. Daily evaluations were made of the number
of emerged seedlings with a size equal to or greater than 1.0 cm until the counts stabilization. The results were expressed as a
percentage (%) of normal seedlings. For the emergence speed index (ESI), the Equation
1 proposed by Maguire (1962) was used:
(1)
Where: ESI = Emergence speed
index (seedlings.day-1); E1, E2, En = Number of normal seedlings computed in the
first count, in the second count and last count; N1, N2, Nn = Number of days after sowing from the first
count to the second count and the last count.
Controlled
Deterioration (CD)
Initially, the
moisture content of the seeds was adjusted to 24% by the moist atmosphere
method at 20 oC. The moisture content of
the seeds was monitored by successive weighing at one-hour intervals until the
desired values were obtained. The seeds were placed in aluminized paper bags,
which were hermetically sealed and kept in a refrigerator at 10 ºC for 24 h.
After this period, they were kept in a water bath at 45 oC for
24 h (KRZYZANOWSKI; MARCOS-FILHO, 2020). Then the seeds were placed to
germinate as described for the germination test (BRASIL, 2009). Four replicates
of 50 seeds from each lot were used and the results were expressed as the
percentage of normal seedlings obtained seven days after sowing.
Germination
at sub (G15o) and supra optimum (G30o) temperatures
Four replications
of 50 seeds were placed to germinate according to the germination test, but at
temperatures of 30 °C (supra-optimum) and 15 °C (sub-optimal) in a BOD
incubator. The results were expressed as a percentage (%) of normal seedlings
obtained at seven days after sowing for supra-optimal temperature and at 10
days for sub-optimal temperature.
After the initial
characterization of the lots, a field experiment was conducted. Two rows of 20
m long and 1 m wide each were prepared, with four blocks of 5 m each. Four
replicates of 100 seeds from each lot were sown in longitudinal grooves 1 m
long and 2 cm deep, 0.20 m apart. The lateral grooves were considered as
borders and the useful area only the two central grooves (MATOS et al., 2011).
The soil chemical analysis was performed (Table 1). Before sowing, fertilization
with 40, 180, and 60 kg ha-1 of N, P2O5, and K2O
respectively was performed, defined on the basis of
soil analysis results and fertilizer recommendations for carrot cultivation (AQUINO
et al., 2016).
Table
1.
Chemcical analysis of the soil.
|
pH |
P |
K |
Ca2+ |
Mg2+ |
Al3+ |
|||||
|
H2O |
mg.dm3-1 |
cmol.dm3-1 |
||||||||
|
6.3 |
58.3 |
220 |
2.7 |
1.0 |
0 |
|||||
|
H + AL |
SB |
CTC (t) |
CTC (T) |
V |
m |
|||||
|
cmol.dm3-1 |
% |
|||||||||
|
3.0 |
4.2 |
4.2 |
7.2 |
59 |
0 |
|
||||
pH in water, KCl and CaCl - Relation 1:2,5. P
- K – Mehlich exctrator 1. Ca
- Mg - Al - Extractor: KCl - 1 mol/L. H + Al –
Calcium acetate extractor 0.5 mol/L - pH 7,0. SB = Sum of exchangeable bases CTC
(t) - Effective cation exchange capacity. CTC (T) - Cation exchange capacity. pH
7,0. V = Base saturation index. m = Aluminum saturation index.
In the first two
weeks, two irrigations were performed per day, lasting two hours each, keeping
the surface of the bed always moist. From then on, only daily irrigation
lasting 2 h was performed. The crop treatments were performed whenever
necessary. Topdressing fertilization was performed at 28 and 45 days after
sowing, using 60 kg ha-1 of N and K, respectively. At 28 days after
sowing, thinning was done leaving a spacing of about 5 cm between plants. One
of the rows was used to evaluate seedling emergence in the field and the other
to evaluate vegetative development and final crop production. In this, the
harvest was performed at 90 days after sowing.
The maximum, average and
minimum temperatures and relative humidity recorded during the experimental
period, as well as monthly cumulative rainfall are shown in Figure 1.
Figure
1. Minimum
(Min.), average (Aver.), and maximum (Max.) temperatures (oC);
relative air humidity (%) (A) and cumulative rainfall (B) during carrot development
in the field
Field seedling emergence was represented by percentage
of normal seedlings emerged (at least 1.0 cm height) at 10 and 14 days after
sowing.
Plant height and
root length
The height
of each plant was measured from the base to the top and the length of the root
was measured with the aid of a ruler. The results were expressed in cm plant-1 (KRZYNANOWSKI et al., 2020).
Shoot and root dry matter
Plants were
separated into root and shoots, placed separately in paper bags and kept in a oven with regulated air
circulation at 70 °C until they reached constant weight. The dried material was
weighed on a precision scale and the results were expressed in g plant-1 (KRZYNANOWSKI
et al., 2020).
Shoot
and root growth rate
With shoot and root
dry matter values, shoot and root growth rate (GR) (Equation 2) were
determined, according to Kolchinski et al.
(2006).
(2)
Where: DM1: Value
of dry mass obtained on the first day of the period to be considered (T1);
DM2: Value of dry mass obtained on the last day of the period to be
considered (T2); GR values are given in g.plant-1.day-1.
Evaluation of crop production and yield
Harvesting was performed by collecting plants from all
useful areas (25 m2 per block). The roots were separated from the
shoots and weighed to determine the total roots yield in kg. Then they were
classified into: commercial (length greater than 12
cm) and non-commercial (length less than 12 cm and / or roots with defects such
as purple / green shoulder, bifurcation and crack) (CEAGESP, 2015).
Statistical
analysis and experimental design
The seed quality
tests were conducted in a completely randomized design with four replications.
The data were submitted to analysis of variance and the means obtained for each
lot were compared by Tukey test at 5% probability.
The field
experiment was conducted in a completely randomized block design with four
replications. The data obtained for each variable were submitted to analysis of
variance. The means obtained for each lot were compared by the Tukey test at 5%
probability. Pearson correlation analysis was performed at 1 and 5%
probability. The R software
was used in all statistical analyses (R Core Team, 2020).
RESULTS AND DISCUSSION
The
seed moisture content was similar for all analyzed lots, being around 7%. This
value is adequate for the packaging of vegetable seeds stored in hermetically
sealed aluminum containers. The germination of the lot 3 was inferior to the
others, which did not differ significantly from each other. Similar results
were obtained in the seedling emergence, emergence speed index, controlled
deterioration, and germination at supra-optimal temperature (Table 2).
|
Table
2.
Seed moisture content (MC), germination (G), first germination count (FGC),
seedling emergence (SE), emergence speed index (ESI), controlled
deterioration (CD), temperature germination sub (G15 °) and supra-optimal
(G30 º) obtained for the four seed lots of carrot. |
||||||||
|
Lots |
MC |
G |
FGC |
SE |
ESI |
CD |
G15º |
G30º |
|
(%) |
|
(%) |
||||||
|
1 |
7.2 |
83.5 a |
77.0 a |
69 a |
18 a |
51 a |
77.0 a |
76.5 a |
|
2 |
7.7 |
81.5 a |
72.5 ab |
67 a |
20 a |
51 a |
79.5 ab |
71.0 a |
|
3 |
7.2 |
68.7 b |
62.5 b |
47 b |
12 b |
39 b |
64.0 b |
53.0 b |
|
4 |
7.3 |
82.5 a |
74.0 ab |
68 a |
20 a |
53 a |
75.5 ab |
72.0 a |
|
CV (%) |
- |
6.24 |
8.01 |
9.97 |
13.34 |
10.91 |
8.64 |
7.23 |
Means followed by
the same letter in the column do not differ from each other by the Tukey test
at 5% probability. CV: Coefficient of variation
In
general, all of these tests are important for
assessing seed performance under adverse conditions, defining seed vigor
(FINCH-SAVAGE; BASSEL, 2016). In this context, the first germination count and
sub-optimal temperature germination tests allowed to classify the seed lots
into three vigor levels, being lot 1 as the most vigorous, lot 3 the less
vigorous, and lots 2 and 4 as intermediate. In all tests performed, we found
worse performance for seed lot 3 compared to the others (Table 2).
Through
the correlation analysis between the physiological quality evaluation and the
emergence of the field, it is observed that the first germination count and
sub-optimal germination temperature were significantly correlated with the
seedling emergence at 10 and 14 days (Table 3).
|
Table
3.
Pearson correlation coefficients obtained between germination (G), first
germination count (FGC), seedling emergence (SE), controlled deterioration
(CD), emergence speed index (ESI), germination at optimum sub (G15º) and
supra (G30º) temperature and emergence results at 10 (EM10) and 14 (EM14)
days for four carrot lots. |
|||||||||
|
|
G |
FGC |
SE |
CD |
ESI |
G15 ° |
G30 ° |
EM10 |
EM14 |
|
G |
|
0.629** |
0.827** |
0.564* |
0.729** |
0.529* |
0.724** |
0.350 |
0.235 |
|
FGC |
|
|
0.602* |
0.712** |
0.577* |
0.777** |
0.628* |
0.644* |
0.748** |
|
SE |
|
|
|
0.509* |
0.895** |
0.689** |
0.776** |
0.457 |
0.284 |
|
CD |
|
|
|
|
0.528* |
0.569* |
0.659** |
0.250 |
0.578* |
|
ESI |
|
|
|
|
|
0.523* |
0.702** |
0.270 |
0.276 |
|
G15 ° |
|
|
|
|
|
|
0.598* |
0.637* |
0.606* |
|
G30 ° |
|
|
|
|
|
|
|
0.472 |
0.500* |
|
EM10 |
|
|
|
|
|
|
|
|
0.649* |
|
EM14 |
|
|
|
|
|
|
|
|
|
|
*;**: Significant
correlation at 5 and 1% probability, respectively. |
|||||||||
It was also
observed that there was a significant correlation among the data obtained from
controlled deterioration, germination at supra-optimal temperature, and
emergence at 14 days (Table 3). These results indicate an association between
laboratory vigor test results and the emergence of carrot seedlings in the
field. Thus, the first germination count, controlled deterioration, and
germination tests at the sub and supra-optimal temperatures provided an
estimate of field seed performance. Among these tests, the first germination
count test is recommended to evaluate the physiological quality of carrot seeds
due to its simplicity of conduction and efficiency in ranking lots.
The germination at
sub or supra-optimal temperatures has been successfully used to classify seed
lots of carrot (SINGH et al., 2014),
cucumber (BALABUSTA et al., 2016), and melon
(PINHEIRO et al., 2017). As observed, the
germination at sub-optimal temperature was directly related to the carrot
emergence. It’s also related that temperatures above
30 °C caused decreases in seed germination of both “Brasília” and “Alvorada” cultivars. Dias et al. (2015) observed that the
germination of cultivar “Brasília” was reduced by the temperature of
35 °C. In general, these effects can be related to many cellular
alterations such as hormonal imbalance, genetic alterations, and others, the
reduce seed germination and vigor (WANG et al., 2018).
Lots 1 and 3
presented higher and lower emergence in the field at 10 (Figure 2A) and 14 days
(Figure 2B) after sowing, respectively.
Figure 2. Field seedling emergence (%) of four carrot seed lots at 10 (A) and 14 (B) days after sowing
Means followed by the same letters do not differ among lots within each period by the Tukey test at 5% probability. CV: Coefficient of Variation
