Pasture Science
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Study of morphoagronomic indicators of Cenchrus purpureus clones for biomass production
[*] Email:rherrera@ica.co.cu
ABSTRACT
Using a randomized block design with four replications, clones of Cenchrus purpureus (CT-6, CT-9, CT-13, CT-15, CT-24 and CT-28) obtained by in vitro
tissue culture were evaluated and compared with their progenitor
(CT-115) in typical red Ferralitic soil, for two years without
irrigation and fertilization. In both evaluation years during the
seasonal periods the height differed (P<0.001) between the clones and
the CT-28 surpassed the CT-115 was highlighted. There were differences
(P <0.001) in the percent of DM and their values varied in narrow
range (17-23 % and 19-21 % in the dry and rainy season, respectively).
With the exception of CT-24, the rest of clones showed leaves contents
higher than 50 % and differed among them, but the highest value (64.88
%, P <0.001) was showed by CT-28 during the rainy season. The leaves
length varied (P <0.0001) between clones and CT-9 was highlighted in
both years (73.73 and 84.23 cm for the dry and rainy season,
respectively for the first year and 68.6 and 76.7 cm for similar stages
of the second year). Similar response pattern was obtained in the leaf
width. The leaf area also differed between clones and the highest values
were recorded in the rainy season of both years. There were significant
differences between the clones in the seasonal and annual DM yield and
the clones CT-9, CT-15, CT-24 and CT-28 were highlighted. There were
also significant differences in the population of the clones at the
beginning and end of the experiment, but when comparing these two stages
there were not variation and the values ranged between 5.43 and 9.49
bunches/5m. In general terms, the studied indicators varied when
comparing the studied years. There is a group of clones with favorable
characteristics for forage production, where CT-9 and CT-28 were
highlighted. Future studies using strategic fertilization and irrigation
of promising clones are suggested.
Key words:
height; yield; leaves; population; leaf area.
The
cattle feeding in Cuba is based on the use of grasses and forages due
to different reasons, among which can be mentioned: it is possible to
grow them all year, when they are properly managed produce a high amount
of biomass with appropriate quality, protect to the soil of erosion,
they replace a certain amount of high-cost imported food and do not
compete as a source of food with other animal species and even with man.
One of the species widely used as animal food in Cuba is Cenchrus purpureus
determined by its ecological plasticity and high yields, due to its C4
photosynthetic path which efficiently converts light energy into biomass
(Sage 2016).
On the other hand, in the Instituto de Ciencia Animal it has been worked on the improvement of C. purpureus through biotechnology applying in vitro
tissue culture and physical mutagenesis. From this program, a group of
clones with promising characteristics for forage, grazing, drought and
salinity conditions were obtained (Herrera 2015, Herrera and Martínez 2015).
Therefore, the objective of this study was to evaluate some agronomic indicators of Cenchrus purpureus new clones, obtained by in vitro tissue culture at the Instituto de Ciencia Animal, with probable characteristics for biomass production.
Location, type of soil and climate.
The experiment was carried out at the "Miguel Sistachs Naya"
experimental station belonging to the Instituto de Ciencia Animal,
located at 22º 53 NL and 82º 02 WL at 80 m o. s. l. The soil was typical
red Ferralitic (Hernández et al. 2015).The
rainfall during the experimental stage was 1234 mm and 80 % occurs
during the rainy period, while the average annual mean temperature is 26
ºC, although in the dry season the value is lower (Herrera et al. 2018).
Treatment and design.
A randomized block design, with four replications was used. As an
experimental unit, the plot of 25 m2 was used. Six clones of Cenchrus purpureus obtained by in vitro tissue culture (CT-6, CT-9, CT-13, CT-15, CT-24 and CT-28) were evaluated and compared with their progenitor (C. purpureus vc Cuba CT-115).
Experimental procedure.
The preparation of the soil was conventional (plowing, crossing and
harrow). The experiment was sowing in the rainy season of 2015 and the
plots were kept free of weeds until their establishment without the use
of herbicides. Five-month-old seeds were planted in plots of 5 x 5 m,
with sowing distance between furrows of 1 m and all the plots had equal
number of buds.
After 120 days of establishment
the establishment cut was made and the population was counted (number of
bunches/5m). From then on, the samplings were made during the dry
season every 90 days of regrowth and in the rainy period every 60 days
for two years, under dry conditions and without fertilization. The cut
was made with a machete at 10 cm above the soil level. The plot was cut
leaving border effect of the external furrows, as well as 50 cm at the
ends. All the cut material was homogenized, weighed and a random sample
of 500 g was taken per plot. The sample was manually separated into
leaves and stems which were introduced in an air circulation oven at 60
ºC to constant weight. The height, percent of DM of the whole plant,
length of the fourth leaf completely open from the apex, width of the
previous leaf in its middle part, leaf area of the referred leaf, leaves
percent, DM yields and population according to Herrera (2006) methodology.
Statistical analysis. Analysis of variance (Visauta 2007)
was performed according to the experimental design and the values
represent the mean per cut in each seasonal period, except the total
yield and the population. For the normal distribution of the data the
Kolmogorov-Smirnov (Massey 1951) test was used and for the variances the Bartlett (1937) test, so that the population was transformed by square root of the observation. The mean values were compared according to Duncan (1955) test.
In
all seasonal periods there were significant differences between the
clones heights and there is a general tendency to decrease the height in
the second year (table 1). Vieira da Cunha (2006) when evaluating clones and hybrids of Pennisetum sp.
found variation in the height of each of them and attributed it to the
specific characteristics of each plant and its response to climate, soil
and management conditions. This performance was also reported by Herrera et al. (2012) when evaluating clones of Cenchrus purpureus
which showed better agronomic indicators than their progenitor and
attributed it to the recent preparation of the soil, the seed quality
and the competition with weeds.
Table 1.
Height of clones during the experimental period
abcd Values with dissimilar letters per column differ at P<0.05 (Duncan 1955)
In both seasonal periods of the first year
the DM percentage of the whole plant differed between clones and CT-24
highlighted, while, in the second year despite differing among clones,
the values were in a narrower range with average value of 20 % (figure 1).
This indicator is useful if the harvested biomass is used for the
silage production, since it is a science that, in order to obtain
quality silages, it is necessary that the material to be silage must
have not less than 25 % of DM. Taking into account the above and
considering the management conditions of this experiment, it is not
advisable to directly ensile the biomass of these clones and it is
necessary to pre-dry the green mass to increase the DM content.
Fig. 1.
DM percent of the clones in both seasonal periods for two years
The leaves content significantly varied between clones (table 2)
and it was important to find values higher than 50 %, a quality that
seems to beinhered from its progenitor (CT-115), which is characterized
by its leafy character. This feature, join to its non-high height, makes
it promising for the biomass production and had been previously
obtained in clones that were obtained with better quality indicators and
tolerant to drought and salinity (Díaz 2007 and Álvarez 2009).
Table 2.
Leaf content of the clones during the experimental period
abc Values with dissimilar letters per column differ at P<0.05 (Duncan 1955)
The length of the fourth fully open leaf
significantly differed between clones in both seasonal periods in the
two experimental years where CT-9 highlighted. However, the values of
the second year were, in general, lower than those of the first year (table 3). Similar response pattern showed the leaf width (figure 2).
In
both seasonal periods and during the two evaluation years, the leaf
area of the fourth completely open leaf significantly differed between
clones and CT-9 highlighted, the values of the rainy season were higher
than the dry season and there was a certain tendency to decrease, in
general, the values of the second year (table 4).
Table 3.
Length of the fourth completely open leaf of the clones
abcde Values with dissimilar letters per column differ at P<0.05 (Duncan 1955)
Fig. 2.
Length of the fourth completely open leaf of the clones
Table 4.
Leaf area of the fourth completely open leaf of the clones
abcd Values with dissimilar letters per column differ at P<0.05 (Duncan 1955)
Viera da Cunha (2006) when evaluating varieties of Pennisetum sp.
showed that the height and density of the leaf blade were key
indicators to describe and explain the variability between these plants,
while Romalo Faca (2008), when studying 14
clones of this genus, reported the importance of the height and length
of leaves, among other indicators, to establish the differences between
them.
Fortes (2012) determined that the length and width of the leaf, leaf area and height of Pennisetum purpureum
vc. Cuba CT-115 increased with the regrowth age, but these values
decreased in the second year of exploitation in grazing and attributed
it to the variations found in the content of chlorophylls and
carotenoids in addition to the effect of climatic factors. Uvidia et al. (2014) reported that the characteristics of leaves, leaf area and height varied with the distance and sowing dose in Pennisetum purpureum, while Castañeda et al. (2015), Ray et al. (2016) and Olivera et al. (2017)
when evaluating different varieties of this genus by means of
multivariate analysis they found that the leafiness, length and width of
the leaf and height were outstanding indicators to explain the
variability between plants.
The DM yield differed between clones (table 5)
and the highest values were recorded in the rainy season. It was noted
that during the dry season of the first year the clones CT-9, CT-24 and
CT-28 exceeded the yield of the progenitor, while, in the second year,
in the same period all clones were higher than CT-115. This
characteristic makes them promising for the biomass production in the
period of low rainfalls and is an indicator of its possible drought
tolerance, an aspect that should be studied in future researches.
Table 5.
DM yields of the clones during the experimental period
abcd Values with dissimilar letters per column differ at P<0.05 (Duncan 1955)
The performance of the measurements made in
the fourth completely open leaf and its leaf area in relation to the DM
yield attracted attention, since it was expected that its decrease in
the second experimental year would lead to lower yield and this did not
happen in a number of clones and agrees with that explained by Herrera (2018) who when studying the Pennisetum purpureum
performance and climatic factors in a period of 40 years found that
this plant increased its height but decreased its yield over the years.
However, it would be important to study this performance related to
photosynthetic pigments, since everything seems to show that there is a
process which is related to the transformation efficiency of light
energy in biomass through the photosynthetic pigments that must be
studied.
Table 6 shows the performance of the
population (bunches/5m) at the beginning and end of the experimental
stage. In both cases there were significant differences between clones,
but at the beginning of the experiment the CT-15 and CT-24 surpassed the
CT-115, while at the end both clones and the CT-28 also did.
Table 6.
Population (bunches/5m) at the beginning and end of the study
abcd Values with dissimilar letters per column differ at P<0.05 (Duncan 1955).
( ) Real value
The results showed that there is a group of
clones with appropriate characteristics for the production of forage
biomass and of them the CT-9 and CT-28 were promising for their yields,
especially in the dry season. In addition, its leaf content was high and
it was notorious that these clones were not depopulated by the cut
frequency used in the two studied years without irrigation or
fertilization. However, it is necessary to performed future researches
related to their possible drought tolerance, to know their quality
indicators, apply fertilization and strategic irrigation, as well as to
determine their performance in the performance of the animal that intake
them.
La
alimentación del ganado vacuno en Cuba se fundamenta en el empleo de
los pastos y forrajes debido a distintas razones, entre las cuales se
pueden señalar: es posible cultivarlos todo el año, cuando se manejan
adecuadamente producen elevada cantidad de biomasa con apropiada
calidad, protegen al suelo de la erosión, sustituyen cierta cantidad de
alimentos importados de altos costos y no compiten como fuente de
alimentos con otras especies de animales e incluso con el hombre.
Una de las especies ampliamente empleada como alimento animal en Cuba es Cenchrus purpureus
determinado por su plasticidad ecológica y altos rendimientos, debido a
su sendero fotosintético C4, que convierte eficientemente la energía
luminosa en biomasa (Sage 2016).
Por otro lado, en el Instituto de Ciencia Animal se ha trabajado en el mejoramiento de C. purpureus mediante la biotecnología aplicando el cultivo de tejidos in vitro
y la mutagénesis física. De este programa se obtuvieron un grupo de
clones con características promisorias para forraje, pastoreo,
condiciones de sequía y salinidad (Herrera 2015, Herrera y Martínez 2015).
Por ello, el objetivo del presente trabajo fue evaluar algunos indicadores agronómicos de nuevos clones de Cenchrus purpureus, obtenidos por cultivo de tejidos in vitro en el Instituto de Ciencia Animal, con probables características para la producción de biomasa.
Ubicación, tipo de suelo y clima.
El experimento se desarrolló en la estación experimental “Miguel
Sistachs Naya” perteneciente al Instituto de Ciencia Animal, ubicado en
los 22º 53 LN y los 82º 02 LO a 80 msnm. El suelo fue Ferralítico rojo
típico (Hernández et al. 2015). La
lluvia durante la etapa experimental fue de 1234 mm y el 80% de ellas
ocurre durante el período lluvioso, mientras que la temperatura media
promedio anual es de 26 ºC aunque en el período poco lluvioso el valor
es inferior (Herrera et al. 2018).
Tratamiento y diseño.
Se utilizó un diseño de bloques al azar, con cuatro réplicas. Como
unidad experimental se empleó la parcela de 25 m2. Se evaluaron seis
clones de Cenchrus purpureus obtenidas por cultivo de tejidos in vitro (CT-6, CT-9, CT-13, CT-15, CT-24 y CT-28) y se compararon con su progenitor (C. purpureus vc. Cuba CT-115).
Procedimiento experimental.
La preparación del suelo fue convencional (aradura, cruce y grada). El
experimento se sembró en el período lluvioso de 2015 y las parcelas se
mantuvieron libres de arvenses hasta su establecimiento sin el empleo de
herbicidas. Se plantaron semillas de cinco meses de edad en parcelas de
5 x 5 m, con distancia de siembra entre surcos de 1 m y todas las
parcelas tenían igual número de yemas.
Transcurridos
120 días de establecimiento se realizó el corte de establecimiento y se
contó la población (número de macollas/5m). A partir de ahí los
muestreos se realizaron durante el período poco lluvioso cada 90 días de
rebrote y en el lluvioso cada 60 días durante dos años, en condiciones
de secano y sin fertilización. El corte se realizó a machete a 10 cm
sobre el nivel del suelo. La parcela se cortó dejando efecto de borde de
los surcos externos, así como 50 cm por los extremos. Todo el material
cortado se homogenizó, se pesó y se tomó una muestra aleatoria de 500 g
por parcela. La muestra se separó manualmente en hojas y tallos las que
se introdujeron en estufa de circulación de aire a 60 ºC hasta peso
constante. Se evaluaron la altura, por ciento de MS de la planta
íntegra, longitud de la cuarta hoja completamente abierta a partir del
ápice, ancho de la hoja anterior en su parte media, área foliar de la
referida hoja, por ciento de hojas, rendimientos de MS y población según
la metodología de Herrera (2006).
Análisis estadístico. Se realizó análisis de varianza (Visauta 2007)
de acuerdo con el diseño experimental y los valores representan la
media por corte en cada período estacional, excepto el rendimiento total
y la población. Para la distribución normal de los datos se utilizó la
prueba de Kolmogorov-Smirnov (Massey 1951) y para las varianzas la prueba de Bartlett (1937),
por lo que la población se transformó mediante raíz cuadrada de la
observación. Los valores medios se compararon de acuerdo con Duncan (1955).
En
todos los períodos estacionales hubo diferencias significativas entre
las alturas de los clones y existe tendencia general a disminuir, la
altura en el segundo año (tabla 1). Vieira da Cunha (2006) al evaluar clones e híbridos de Pennisetum sp.
encontraron variación de la altura de cada una de ellos y lo
atribuyeron a las características específica de cada planta y su
respuesta a las condiciones de clima, suelo y manejo. Este
comportamiento también lo informaron Herrera et al. (2012) al evaluar clones de Cenchrus purpureus
que presentaron mejores indicadores agronómicos que su progenitor y lo
atribuyeron a la reciente preparación del suelo, la calidad de la
semilla y la competencia con las arvenses.
Table 1.
Height of clones during the experimental period
abcd Values with dissimilar letters per column differ at P<0.05 (Duncan 1955)
En ambos períodos estacionales del primer
año el por ciento de MS de la planta íntegra difirió entre clones y
sobresalió el CT-24, mientras que, en el segundo año a pesar de diferir
entre clones, los valores estuvieron en un rango más estrecho con valor
medio de 20 % (figura 1). Este indicador es
de utilidad si la biomasa cosechada se emplea para la producción de
ensilaje, ya que es ciencia constituida que, para la obtención de
ensilajes de calidad, es preciso que el material a ensilar tenga no
menos de 25 % de MS. Al tener en cuenta lo anterior y considerar las
condiciones de manejo de este experimento, no es recomendable ensilar
directamente la biomasa de estos clones y es necesario pre-secar al sol
la masa verde para incrementar su contenido de MS.
Fig. 1.
DM percent of the clones in both seasonal periods for two years
El contenido de hojas varió significativamente entre clones (tabla 2)
y fue importante encontrar valores superiores a 50 %, cualidad que
parece heredar de su progenitor (CT-115) que se caracteriza por su
carácter hojoso. Este rasgo unido a su no elevada altura lo hacen
promisorios para la producción de biomasa y que había sido obtenido con
anterioridad en clones que se obtuvieron con mejores indicadores de
calidad y tolerantes a la sequía y salinidad (Díaz 2007 y Álvarez 2009).
Table 2.
Leaf content of the clones during the experimental period
abc Values with dissimilar letters per column differ at P<0.05 (Duncan 1955)
La longitud de la cuarta hoja totalmente
abierta difirió significativamente entre clones en ambos períodos
estacionales en los dos años experimentales donde sobresalió el CT-9.
Sin embargo, los valores del segundo año fueron, en general, inferiores a
los del primer año (tabla 3). Similar patrón de respuesta presentó el ancho de la hoja (figura 2).
En
ambos períodos estacionales y durante los dos años de evaluación, el
área foliar de la cuarta hoja completamente abierta difirió
significativamente entre clones y sobresalió el CT-9, los valores del
período lluvioso fueron superiores al poco lluvioso y se apreció cierta
tendencia a disminuir, en general, los valores del segundo año (tabla 4).
Table 3.
Length of the fourth completely open leaf of the clones
abcde Values with dissimilar letters per column differ at P<0.05 (Duncan 1955)
Fig. 2.
Length of the fourth completely open leaf of the clones
Viera da Cunha (2006) al evaluar variedades de Pennisetum sp.
señalaron que la altura y la densidad de la lámina foliar eran
indicadores fundamentales para describir y explicar la variabilidad
entre estas plantas, mientras que Romalo Faca (2008)
al estudiar 14 clones de este género informó la importancia de la
altura y la longitud de las hojas, entre otros indicadores, para
establecer las diferencias entre ellos. Fortes (2012) determinó que la longitud y el ancho de la hoja, área foliar y la altura de Pennisetum purpureum
vc. Cuba CT-115 aumentaron con la edad de rebrote, pero estos valores
disminuyeron en el segundo año de explotación en pastoreo y lo atribuyó a
las variaciones que encontró en el contenido de clorofilas y
carotenoides además del efecto de los factores climáticos. Uvidia et al. (2014) reportaron que las características de las hojas, el área foliar y la altura varía con la distancia y dosis de siembra en Pennisetum purpureum, mientras que Castañeda et al. (2015), Ray et al. (2016) y Olivera et al. (2017)
al evaluar diferentes variedades de este género mediante análisis
multivariado encontraron que la hojosidad, longitud y ancho de la hoja y
la altura eran indicadores destacados para explicar la variabilidad
entre plantas.
Table 4.
Leaf area of the fourth completely open leaf of the clones
abcd Values with dissimilar letters per column differ at P<0.05 (Duncan 1955)
El rendimiento de MS difirió entre clones (tabla 5)
y los mayores valores se registraron en el período lluvioso. Llamó la
atención que durante el período poco lluvioso del primer año los clones
CT-9, CT-24 y CT-28 superaron el rendimiento del progenitor, mientras
que, en el segundo año, en el mismo período todos los clones fueron
superiores al CT-115. Esta característica los hace promisorio para la
producción de biomasa en el período de bajas precipitaciones y es un
indicador de su posible tolerancia a la sequía, aspecto este que debe
ser estudiado en investigaciones futuras.
Table 5.
DM yields of the clones during the experimental period
abcd Values with dissimilar letters per column differ at P<0.05 (Duncan 1955)
Llamó la atención el comportamiento de las
medidas realizadas en la cuarta hoja totalmente abierta y su área foliar
en relación con el rendimiento de MS, ya que era de esperar que su
disminución en el segundo año experimental propiciara menor rendimiento y
esto no sucedió en un número de clones y concuerda con lo planteado por
Herrera (2018) quiene al estudiar el comportamiento de Pennisetum purpureum
y los factores climáticos en un período de 40 años encontraron que esta
planta incrementaba su altura pero disminuía su rendimiento con el
transcurso de los años. Sin embargo, sería de importancia estudiar esta
conducta relacionada con los pigmentos fotosintéticos, ya que todo
parece indicar que existe un proceso que está relacionado con la
eficiencia de transformación de la energía lumínica en biomasa a través
de los pigmentos fotosintéticos que debe ser estudiado.
La tabla 6
presenta el comportamiento de la población (macollas/5m) al inicio y
final de la etapa experimental. En ambos casos hubo diferencias
significativas entre clones, pero al inicio del experimento el CT-15 y
CT-24 superaron al CT-115, mientras que al final ambos clones y el CT-28
también lo hicieron.
Table 6.
Population (bunches/5m) at the beginning and end of the study
abcd Values with dissimilar letters per column differ at P<0.05 (Duncan 1955).
( ) Real value
Los resultados evidenciaron que se dispone
de un grupo de clones con características apropiadas para la producción
de biomasa forrajera y de ellos resultaron promisorios el CT-9 y CT-28
por sus rendimientos, en especial, en el período poco lluvioso. Además,
su contenido de hojas fue elevado y resultó notorio que estos clones no
se despoblaron por la frecuencia de corte empleada en los dos años
estudiados sin riego ni fertilización. Sin embargo, es necesario
realizar futuras investigaciones relacionadas con su posible tolerancia a
la sequía, conocer sus indicadores de calidad, aplicar fertilización y
riego estratégicos, así como determinar su comportamiento en la conducta
del animal que los consume.
