Custom services
text in 
English (pdf)
Article in xml format
Article references
Send this article by e-mail
Cited by SciELO 
Similars in
SciELO 
Permalink
Climatic fluctuations influence on morphology and productivity of plants (Ledea et al. 2017). In Cuba, there are two seasons (rainy and dry) with specific characteristics, historical mean precipitation is 1,335 mm, and more than 80 % of it falls in the rainy period. The rainfall regime is characterized by great variability, especially in the east, where more than 3,000 mm have been registered for the northern part and less than 600 mm for the southern area, mainly due to orographic influences (ONEI 2015). This variability determines, for six months in the year, a depression of productive potential of grasses and forages that are used in animal feed, and that their performance is markedly favored in the rainy season.
On the basis of the above considerations, it is pointed out that, in the eastern region, there is the Cauto river basin, with an area of 4.5 thousand km2, and four of the five eastern provinces are grouped here. In this area, more than 90 % of the eastern livestock (Fajardo 2008) is developed, where climate variability is combined and hidden by edaphic affectations (salinity, erosion, degradation, low content of organic matter, and some others).
In this same sense, Ledea (2016) stated that, in order to recover meat and milk cattle rearing, a feeding basis should be ensured that provides, at least, availability of food with quality, but before getting to this particularity, it is necessary to know and characterize productivity of the varieties used for this purpose, and even more when limiting conditions prevail. Adverse ecosystems, or degraded by degenerative processes, which is where livestock is developed in Cuba, provide few nutrients and several toxic substances to livestock that is fed in these systems. One of the alternatives to ensure the feeding basis in these ecosystems is the introduction of species or varieties that tolerate the edaphoclimatic limitations of those ecosystems.
After the above considerations, it is important to state that new varieties of Cenchrus purpureus obtained by tissue cultures from CT-115, constitute a viable alternative to expand the feeding basis before adverse conditions. Ray et al. (2016) evaluated the new varieties and determined, by comparison with their parent CUBA CT-115, that CT-601, CT-603, CT-605, CT-608 and CT-609 had the best productive performance under conditions of intense seasonal drought, characteristic of Valle del Cauto. However, this productive response can be improved with the application of irrigation in minimum doses, fertilization with organic fertilizer strategically applied, and cuts in different ages of the plant.
The cut is applied to take advantage of forage potential and pasture quality according to the development state of the plant. One of the premises in the management of pastures with the application of cuts is not to compromise the persistence of the crop by performing it when the plant has not yet accumulated reserves to ensure regrowth, nor establishing prolonged intervals of cuts, which limit their use for animal feeding due to its low quality. The moment of the cut is influenced by several factors. One of them is the edaphoclimatic characteristics of the ecosystems where crops are developed, by the strong relation they have with growth speed and tissue maturation (Ramírez de la Rivera 2010).
Therefore, the objective of this study was to evaluate the morphological and productive performance of the new varieties of Cenchrus purpureus, tolerant to droughts at different regrowth ages during the dry season.
Material and Methods
Locality, climate and soil. The study was carried out at the Estación Experimental de Pastos y Forrajes from the Instituto de Investigaciones Agropecuarias “Jorge Dimitrov”, in Granma province, during dry seasons (May-October) between 2010 and 2012 in Cuba (ONEI 2014). The station is located at 20º 18'13" North and 76º 39' 48" West.
The climate of the region, where the station is located, is classified as relatively humid tropical (Barranco and Díaz 1989). In the study area, precipitations fluctuated between 89.5 and 115 mm per year (figure 1), with at least three months as average in different years without precipitation, the maximum value was recorded in April 2011 (115mm). The accumulated of the evaluated period represented 13.6 % of the accumulated (3181.9mm) of 2000-2017 for this same season. Figure 1 shows the monthly distribution of rains in this period and the historical mean for months.
The soil of the experimental area is little differentiated fluvisol, according to the new version of genetic classification of soils in Cuba (Hernández et al. 2015), which chemical characteristics are shown in table 1. It presents good general drainage, flat topography and, generally, its natural fertility is between medium and low values with a slightly acid pH. It has very low salinity levels, up to 60 cm deep, nutrient levels are generally low, only the superior layer shows medium levels (Ledea 2016). According to this author, soil humidity in the first 60cm, during this period, ranges from 19.3 (April) to 39.9 % (March).
Figura 1 Performance of precipitations during the experimental period and historical mean per months
Plant material used. Cultivars used for the study were CT-601, CT-603, CT-605, CT-608, CT-609 and CT-115. These new cultivars were obtained in the Instituto de Ciencia Animal, through mutations induced by tissue culture, from the variety Cenchrus purpureus cv. Cuba CT-115.
Design, treatment and statistical analysis. A random block design was used in a factorial arrangement with four replications, as well as 24 treatments resulting from the combination of regrowth age (60, 90, 120 and 150 days), and new cultivars of Cenchrus purpureus (CT-601, CT-603, CT-605, CT-608, CT-609 and CT-115 control). The Kolmogorov-Smirnov (Massey 1951) test was used for normal distribution of data and Bartlett (1937) test for the homogeneity of variances. The means resulting from the interactions were compared using Keuls (1952) test.
For the statistical analyzes, the Statistica on Windows package, version 10.0 (StatSoft, 2011) was used. Analysis of variance (ANAVA) was performed according to the requirements of the experimental design. The mathematical model used in each of the ANAVAs was as follows:
Where:
Yijkl |
- response variable, |
µ |
- common constant at all observations, |
Ri |
- effect of the i-th replication (i=1, ….,4), |
ERJ |
- effect of the j-th regrowth age (j=1,…., 4), |
Vk |
- effect of the k-th variety (k= 1, …,5), |
ER x Vjk |
- combined effect of the j-th regrowth age in the k-th variety, |
eijkl |
- random error ~ N (0, σ2e). |
Experimental procedure. The study began in 2010 up to 2012. Irrigation was applied (250 m3 ha-1) during the entire experimental period at intervals of 21 days. The experimental area was already established in plots of 5 x 4 m with harvestable area of 12 m2, and five furrows in each plot with plantation frames of 1 x 0.75. A cut was made to achieve uniformity in the experimental material in November 2009, and then, organic fertilization of bovine manure was applied, with 1.38 % of nitrogen, in a dose of 20 t ha-1 in the evaluated period.
For the morphological measurements, 5 plants/treatments were randomly selected from the 7 days after the uniformity cut and were representative of the plant community, for a total of 120 plants per replication.
Measurements in the plant. They were carried out in five plants per repetition, for a total of four cuts for the 60 days, three for 90 days, and two for 120 and 150 days. Height (from the base to the apical cone), leaf length (from the base to the apex), mean width of the leaves from the average of lengths of base, middle and apical portions, stem thickness and length in the fourth internode, with the use of a vernier caliper and a graduated ruler, respectively, were measured in each plant, and the amount of nodes were counted.
Yield of green matter (GM) and dry matter (DM). The cut was performed after the measurements. For this purpose, the border effect, consisting of external furrows and 50 cm at the beginning and end of each plot, was removed. Plants that were not within the border effect were cut and weighed, considering this weight as green mass. These five plants selected for agronomic measurements were sectioned into leaves and stems and a sample of 300 g was taken and dried at a variable temperature according to the recommendations of Herrera et al. (2003). From the dry weight of the sample and the green weight of each plot, yield of dry matter per hectare was estimated.
Results
Yield of GM and DM were affected by the second degree interaction during dry season (table 2). The significantly higher value in the GM yield (P≤0.001) was obtained in the CT-601 variety at the age of 150 days (10.6 t GM ha-1), and it was common for CT-605 and CT-609 varieties in this same regrowth age, but differed from CT-115 and the rest of the varieties under study in this age and in the rest that were evaluated. The significantly lower value (p≤0.001) was provided by CT-605 during the ages of 60, 90 and 120 days, at 60 days only the yield was common with the CT-601, and at 90 days with the CT- 608 For DM yield, the CT-601 showed the highest mean (p≤0.001) with respect to all varieties at the age of 150 days, and was only common to that obtained in the CT-609 at this same age. On the other hand, the statistically lower value (p≤0.001) was shown by the CT-605 at the age of 60 days, and coincided with its own means up to 120 days. It only differed with the CT-609 at 60 days and all varieties were common up to 90 days of regrowth, with values that did not exceed 0.70 t DM ha-1. After 120 days, a slight recovery of DM accumulation was observed by CT-115, CT-609, CT-603 and CT-601, with redundant values of 1.20- 1.58 t DM ha-1 (table 2).
Table 2 Yield of Green matter (GM) and dry matter (DM) of new varieties of Cenchrus purpureus in different regrowth ages
a, b, c, d, e, f, g, h, i, j, k At least with one letter in common, there are no significant differences according to Keuls (1952)
Numbers between parenthesis belong to transformed values for log(x+1)
The highest (p≤0.001) leaf length was obtained at 90 days in CT-115 and coincided with the dimensions of this organ in CT-605 at 150 days (table 3). These means differed significantly from the rest of those obtained in the different evaluated varieties and ages, and the smallest dimension of leaves (p≤0.001) was presented by the CT-605 at 60 days. Nevertheless, except CT-603 at 60 days, CT-609 at 90 and 120 days, and CT-115 at 120 and 150 days, the rest of the values for this variable did not differ (p≥0.001) significantly from the lowest referred value.
For leaf width (table 3), the significantly superior value (2.55 cm) was obtained at 90 days on CT-115, and this was common to its own means at 120 and 150 days old and to those of CT-609 in the last three evaluated regrowth ages, and at 150 days except CT-608, all varieties provided means for leaf width that were common to that indicated by CT-115 at 90 days.
Table 3 Leaf morphology in new varieties of Cenchrus purpureus in different regrowth ages
a, b, c, d, e, f, g, h, i, jAt least with one letter in common, there are no significant differences according to Keuls (1952)
The lowest value ranged between 1.10 and 1.12 cm and was provided by CT-115 and CT-603 at 60 days, respectively, until 90 days the means were common among them for p≤0.001.
Stem morphology was also affected by the second degree interaction, the number of nodes ranged between 25.8 and 24.65 and showed up at 150 days in CT-609 and CT-601 respectively. The number of nodes of CT-609 differed from all means in all varieties at different ages, and the smaller quantity of this structure (5.52) was provided by CT-608 after 60 days, and coincided with all the means of all the varieties in this same age, and with CT-601 at 90 days.
Plant height performance was according to the number of nodes. The highest values were between 207.5 and 183.2 cm, and coincided in 150 days, the variety CT-601 had the highest value (p≤ 0.01), and it was common for CT-603 and CT-605 at regrowth age, while the lowest value (p≤0.01) of height was recorded at 60 days in CT-603, and it was not common with any of the varieties (table 4).
Table 4 Stem morphology in new varieties of Cenchrus purpureus in different ages of regrowth
a, b, c, d, e, f, g, h, i, jAt least with one letter in common, there are no significant differences according to Keuls (1952)
Numbers between parentheses belong to transformed values for log(x)
Stem thickness (table 5a) was affected by variety effect, CT-115 showed the significantly highest value (p≤0.001) and only differed with CT-605, while stem length was only affected by the effect of regrowth age (table 5b), and the ages of 90 and 120 days provided the significantly highest values (p≤0.001).
Table 5a Effect of variety on stem thickness (cm)
a, b, c, dDifferent letters differ among them according to Keuls (1952)
Table 5b Effect of regrowth age on stem lenght (cm) of new varieties of C. purpureus.
a, bDifferent letters differ among them according to Keuls (1952)
Discussion
Performance of GM yield was uniform in relation to the evaluated ages. The range of values in the last age was around 5.78 and 10.6 t GM ha-1 (table 2). These means, for dry season, markedly differed from those referred in the specialized bibliography, taking into account the high performance that characterizes the grasses, and fundamentally, to Cenchrus genus. This way, Uvidia et al. (2015) reported DM yields of 80 t ha-1 in Maralfalfa grass, under Ecuadorian Amazon conditions, which has a rainfall regime of 4,000 mm year-1, being responsible for this marked productive difference of the climate characteristics of the tropic regarding the Caribbean, and in correspondence with the specific environments, will be the development and productive performance of grass species (Álvarez et al. 2013).
Then, it was considered that the new varieties under Valle del Cauto conditions provide an acceptable volume of green biomass because, during dry season, the particularities of the ecosystem include a lot of short days, with short duration of light hours, low soil humidity availability (Ledea 2016) and insufficient water regime (Ramírez de la Ribera 2010). These effects predispose a low yield for cultivars, in comparison with the rainy period that is identified by a temperature regime (30-32 °C), relative humidity and residual humidity in the soil that allows cultivars to show their potential when there are no limiting factors (Rodríguez et al. 2011).
In relation to DM yield, even the highest value (2.76 t DM ha-1) obtained in this study was lower than the reports of Cárdenas et al. (2012) in Maralfalfa grass, in dry season (20.20 t M), also to those indicated by Uvidia et al. (2015) (4000 mm) in Maralfalfa (20 t DM ha-1), Luna et al. (2015) 13 t DM cut-1 (1,587.5 mm year-1), and referred by Álvarez et al. (2016) in king grass cv. Morado (14-16 t DM) at 60 days of cut under Ecuadorian Amazon conditions, where the rainfall regime determined the productive performance of the studied varieties of the different studies.
However, results of Cordovi et al. (2013), in southern Mozambique, also exceeded the means of the varieties under study. In this particular case, the conditions were in a semi-arid ecosystem, with rainfalls averaging, within three years, an amount of 220mm. These previously cited studies stated yields of 7.01, 10.24 and 15.97 t DM ha-1 in Merkeron, King grass and CT-115, respectively, suggesting that not only the availability of water limits grass yield, but temperature and relative humidity, and characteristics of the ecosystem, in a general sense, predispose considerably the photosynthetic efficiency of cultivars, and with it, the accumulation of osmotically active sugars.
In the western region of Cuba, Herrera (2015) evaluated some of the studied varieties, and obtained DM yields in the dry season, when the cut was carried out at 90 days without fertilization, similar to those referred to in table 2, fundamentally predisposed by precipitations and low temperatures. In this sense, Álvarez et al. (2013) found that, in this region, only the minimum temperature and number of days with rains, determines the yield of the cultivars that are harvested. However, in the East of the country, Ramírez de la Ribera (2010) pointed out that maximum temperatures and rainfall determine the yield of grass species that are used for animal feed, and these climate elements behave very dynamically in the weather.
Ray et al. (2016), in the establishment phase, grouped some of the varieties under study from a Principal Component Analysis (PCA), and identified the CT-601, CT-603, CT-608 and CT-115 as homogeneous in DM yield, with values of 10.5 t DM cut-1, and in the present study, under similar climatic conditions, the responses were very varied for each of the cultivars, which shows that climate and its variability will determine productive performance, and each variety responds individually to these external stimuli.
Ramírez et al. (2011), in the dry season, under the conditions of Valle del Cauto, correlated some climate variables (precipitations, days with rain, temperature, relative humidity), and found a high correlation (˃ 0.80) among the climate variables and yield. Similar results were obtained by Herrera et al. (2013), which suggests that, under the conditions of Valle del Cauto, even with conditions that prevent the persistence of other crops, the new varieties showed the ability of accumulating biomass under conditions of intense seasonal drought.
Values of leaf length (table 3), except for CT-605, are lower than those obtained by Cruz et al. (2017) (70-90cm) in a moderately saline ecosystem when clones tolerant to salinity and drought conditions (mixed) were evaluated at the age of 165 days in the establishment cut. However, these values exceeded those obtained by Díaz (2007) in the establishment period of drought-tolerant varieties, at 8 and 16 weeks with ranges of 42-52 and 49-60cm, respectively, but for week 22 (81-104.3cm), the performance was reversed. These differences lie in the adjustments that plants perform in the edaphoclimatic conditions and in the moments in which the crops were developed.
The greater the leaf length, the greater the capacity of photosynthesis, but also higher exposure to the loss of the border layer that guarantees the optimum temperature for the development of synthesis processes in the creation of photoassimilates (Fortes 2012). Therefore, it is intuited that, under conditions of intense seasonal drought, the new varieties moderate length of this organ to make water use more efficient within tissues. This affects the large-scale performance, but does not limit it, and also allows the crop persistence.
Likewise, the same happed for leaf width, when comparing them with the values indicated by Ramírez (2010) under pre-mountain conditions. Those obtained in the present study were inferior. However, they were similar to those of Díaz (2007), who used the same ecosystem to evaluate the establishment and development of drought-tolerant cultivars. These contrasting performances respond to the same compensatory mechanism of the demands that the edaphoclimatic characteristics of each ecosystem imposes on each crop for its development.
Plant height (table 4) showed values for 60 days lower than those indicated by Luna et al. (2015) when they evaluated Cenchrus purpureus cv. King grass and Maralfalfa in the conditions of Tropical Humid Forest in different regrowth intervals (45, 60, 75 and 90 days). At 90 days only the CT-601 reached the mean height referred by these authors, with intervals of 132-142 cm. These differences occurred because of the rainfall regime of the experimental area of that experiment, with annual rainfall of 1,587.5mm year-1, while in the study area in dry season, volumes only reached 32.7 and 9.9 % of the total precipitated in 2010 and 2012 respectively (figure 1). This was identified as a period with intense seasonal drought, but that did not limit the development of the cultivars, as their height increased to 150 days of regrowth unlike Luna et al. (2015), who found a decrease in this variable with the increase of age.
According to Beltrán et al. (2005) a high growth rate is related to an adequate radical development, but that is reduced by the period of senescence and consequent reduction of photosynthesis, although Hernández et al. (2003) explained that this performance is caused by the translocation of nutrients from the underground mass to the area, and not specifically to the phenological transition. However, under Valle del Cauto conditions, with an intensely dry period and irradiation levels above 360 cal cm- 2day-1 (Fortes 2012), these assumptions are not fulfilled, and are more related to efficiency of tropical grasses to assimilate the radiant energy that allows to accumulate carbohydrates at stem level (Ledea et al. 2017), which are later used for growth.
The described performances suggest, in the case of the varieties under study, a certain degree of tolerance to drought. Cordoví et al. (2013) obtained, in the semiarid climate of Mozambique, in dry season with the CT-115, mean heights of 158.4 cm in three years, with cuts close to 75 days in this period, 150 cm and 140 cm for King grass and Merkerón, respectively, with relative cuts of 58 and 93 days, in order. These height means are close to those obtained in the present study, and are related, according to Wencomo and Ortiz (2011), to the reserve accumulation capacity and use efficiency, besides having metabolic, physiological and morphological mechanisms that allow to minimize the effects of water lack and other limiting factors for growth, so that they can present tolerance mechanisms in a wide range (Cordoví et al. 2013) and that manifest themselves in growth increase.
Part of the reserves accumulated by plants, in this case Cenchrus genus, lies in the nodes, where soluble carbohydrates are stored, which constitute the reserves of the plants for the sprout of the offspring and the formation of new tissues for their growth and development. This is one of the reasons why this structure becomes relevant when plants are meant to be used as seeds (Calzada et al. 2014).
Also from these structures, leaves emerge during growth process and development. Fernández et al. (2015) pointed out that variations in stem morphology are stimulated by adaptive processes to the edaphoclimatic conditions of adverse ecosystems. In this sense, Cruz et al. (2017) evaluated clones tolerant to drought and salinity, and, during the evaluation period (165 days), they obtained values of number of nodes similar to those obtained in the present study. This high number of nodes is related to the height reached by plants, in which, after 120 days, they exceeded 17 nodes per plant. This gives the new varieties a particularity for dry environments, which is the accumulation of reserves in these structures.
The variety, as one of the main effects, modified stem thickness, while regrowth age influenced on their length, measured both at the level of the fourth internode.
It is concluded that, under Valle del Cauto conditions, combined effect of regrowth age with variety conditions the agro-productive performance of the new varieties of Cenchrus purpureus tolerant to drought.
