Abstract
Tall fescue is an important cool-season grass widely used for forage and turf, and its genotypic variation for morphological traits has not been well documented. One hundred and fifteen tall fescue accessions, including 25 commercial cultivars, were divided into five groups based on their origination. The morphological traits, including plant height, spike length, pulvinus distance, spikelet count, branch count per spike, spike count per plant, and spike weight in different accessions were determined under field conditions in 2013 and 2014. There was significant genotypic variation in morphological traits among the 115 tall fescue accessions. Wild accessions exhibited a greater variation in the morphological traits than commercial cultivars. Close correlations were found among plant height, spike length, pulvinus distance, and spikelet count. The results of this suggest plant height, spike length, pulvinus distance, and spikelet count could be used as key morphological traits for evaluating all fescue germplasm effectively.
Tall fescue (Festuca arundinacea Schreb.), a cross-pollinated, hexaploid, cool-season perennial grass, has been widely grown as an important forage and turf grass throughout the world (Aiken and Strickland, 2013; Seal, 1983). The grass belongs to the tribe Festuceae, subfamily Festucoideae, and family Poaceae (Seal, 1983). Natural populations are distributed in temperate and cool climates throughout Europe, North–West Africa, North America, and west and central Asia (Černoch et al., 2003). Tall fescue not only enhances the natural beauty of the environment and increases the value of residential and commercial property (Bonos et al., 2006; Ha et al., 1992), but also provides numerous benefits to humans including providing feed for millions of beef cattle, horses, sheep, and countless wild animals (Wang et al., 2001). Therefore, tall fescue played an important role in pastoral industry, ecological landscaping, soil conservation, and athletic industry (Wang and Xie, 2007).
The genetic variability for morphological traits is the key component of breeding programs for broadening the gene pool (Chtourou-Ghorbel et al., 2011). Variety fescue is the cosmopolitan and ubiquitous taxon, and provides the most important and diverse genetic resources in the species as forage and turf. These variations might be attributed to difference in the genetic constitutions of the population or in the environment where they grow (Dutta et al., 2013). Chtourou-Ghorbel et al. (2011) reported that substantial variation in morphological characteristics among tall fescue cultivars was currently being lost due to severe genetic erosion associated with overgrazing, irregular rainfall, and the loss of rangeland in Tunisia. Majidi et al. (2009) indicated that morphological variation in tall fescue germplasm was heritable, and that several traits including plant height and dry matter yield had a high narrow sense heritability value. Morphological traits are of great importance in selecting rational parents for hybridization breeding of many crops. The knowledge of genotypic diversity was indispensable for efficient utilization of genetic resources and breeding (Beyene et al., 2006; Finger et al., 2010).
Plant height, spike length, spikelet count, spike count per plant, and spike weight are major components of plant yield as selection criteria in breeding (Topal et al., 2004). Ebrahimiyan et al. (2012) reported significant genotypic variation in plant height, flag-leaf length, and flag-leaf width among the seventy five tall fescues. The variation of morphological traits was influenced by genotype and environment (Chtourou-Ghorbel et al., 2011). Niazkhani et al. (2014) observed that the plant height had lower direct and positive effect on dry forage yield (correlation coefficient equals to 0.051). Knowledge of relationship among the morphological traits was the basic and most important for plant selection in a breeding program (Hasan et al., 2013).
Leaf roughness, poor regeneration ability, and poor stress resistance limit wide utilization of tall fescue (Carrow, 1996; Cross et al., 2013; Xu et al., 2006). Excellent tall fescue cultivars are not only able to produce more biomass, but also survive stress conditions. Fortunately, there was tongs of tall fescue germplasm composed of landraces, commercial cultivars, and breeding lines (Li et al., 2010). Thus, improvement of tall fescue might encourage its use as a forage grass species (Easton et al., 1994). However, genetic variation in morphological traits of tall fescue has not been understood very well.
Describing the morphological traits of a large tall fescue collection is still costly and time-consuming. Selecting and describing numerous traits within smaller sample was reasonable and possible. The objectives of this study were to investigate the phenotypic variation of the morphological characteristics and to determine the correlation between the morphological traits. The findings of this study would add new information for better understanding the genetic diversity of tall fescue and therefore facilitate breeding design.
Materials and Methods
Plant materials and growth conditions.
The present research was conducted at Wuhan Botanical Garden, Chinese Academy of Science, Wuhan, China from 2012 to 2014. The climate in this region is of a northern subtropical type, with a warm, humid summer, and an obvious altitudinal change. Maximum, minimum, and mean annual temperature was 29.3 °C in July and August, 0.4 °C in January, and 17.5 °C respectively. The mean annual precipitation was 1347.7 mm. The mean annual sunshine duration was 1450–2050 h. The tall fescue accessions used in this study consisted of landraces and commercial cultivars. The distribution and origin of the 115 tall fescue accessions, including 25 commercial cultivars, were listed in Figure 1 and Table 1. The accessions were divided into five groups based on origination (i.e., Cultivar, America, Europe, Africa, and Asia).
Geographical origin of 115 tall fescue accessions used in this study.
Citation: HortScience 50, 4; 10.21273/HORTSCI.50.4.512
Geographical origin of 115 tall fescue accessions used in this study.
Citation: HortScience 50, 4; 10.21273/HORTSCI.50.4.512
Geographical origin of 115 tall fescue accessions used in this study.
Citation: HortScience 50, 4; 10.21273/HORTSCI.50.4.512
Tall fescue accession and their geographical origin used in this study.
A single seed from each accession was initially placed on a layer of filter paper which soaked water in petri dishes in May, 2012. The petri dishes were placed in the dark at 20 °C until germination, and then transferred to 300–500 μmol photons per m−2·s−1 natural sunlight for 14 h photoperiod. After 2 weeks, all accessions were transferred to plastic containers (15 cm deep and 14 cm diameter) filled with a mixture of cultivation medium and sand (1:1, v/v). Each accession was cloned multiple times by tillers to maintain genetic uniformity. All accessions were established in a walk-in growth room with daily maximum and minimum temperature of 24 and 20 °C, with a 14-h photoperiod and light intensity of 300 μmol photons per m−2·s−1, respectively. They were watered daily to maintain well watered conditions, and fertilized weekly with one-half strength Hoagland’s solution (Hoagland and Arnon, 1950). The grasses were mowed weekly to 7 cm canopy height.
In Sep. 2012, the experimental plots were fertilized with 49 kg N/ha, 98 kg P/ha, and 98 kg K/ha. Peat soil (2-cm thick) was applied, and then the soil was subjected to deep-tillage (25–30 cm), raked for smoothness, and then covered with sand (2-cm deep). The 115 accessions were transplanted to the experimental field in a 1.5 × 1.5 m-lattice in Oct. 2012. The fertilizer with the ratio of N:P:K at 21:6:13 was applied in Mar. 2013 to provide 49 kg N/ha. The tall fescue was fertilized monthly from April through November in 2013 with 49 kg N/ha compound fertilizer and urea. After the data were collected in 13 June 2013, the grasses were mowed to the height of 10 cm, and no mowing was conducted at other times during the whole experimental stage. In 2014, the tall fescue was fertilized at 49 kg N/ha each time in April and May with compound fertilizer and urea. Data were collected on 28 May and 7 June in 2014. The experimental field was irrigated as needed to prevent from wilt in 2 years. When irrigated, water was applied to wet the entire root zone. The experimental sites were syringed occasionally during sunny, rain-free periods.
Measurements.
Data were collected on the plant height, spike length, pulvinus distance, spikelet count, branch count per spike, spike count per plant, and spike weight from 4 June to 13 June in 2013 and from 28 May to 7 June in 2014.
Plant height was determined as the distance from the ground level to tip of a plant. Seven uniform plants from accession per replicate were measured and the average was used for statistical analysis. Spike length was defined as the distance from the bottom to the tip of spike. Four plants with an average size from each accession per plot were measured and the average was used for analysis.
Pulvinus distance was the distance from main spike neck to flag leaf pulvinus. Four plants with an average size from each accession per plot were measured and the average was used for analysis.
The spikelet, branch per spike, and spike per plant was counted from four plants with an average size from each accession per plot, and the average was used for statistical analysis.
Spike weight was determined from four plants with an average size from each accession per plot. An average of four plants was used for analysis.
Statistical analysis.
The experiment was arranged in a completely randomized block design with four replications. All data were averaged over 2 years and subjected to the analysis of variance for accession effects using the general linear model procedure of SPSS software version 13 (SPSS Inc., Chicago, IL) (Norusis, 1998). The simple correlation coefficient between the morphological traits was calculated using Person correlation coefficient by SPSS software version 13 (SPSS Inc.) (Norusis, 1998). The analysis of variance was used to assess the effects of accessions on morphological traits. Mean separations were performed using Fisher’s protected least significant difference test (P ≤ 0.05).
Results and Discussion
The analysis for two phenotypic data (Supplemental Table 1) showed that there was no significant difference in these evaluated traits between 2 years, and therefore the average value of phenotypic data for 2 years was used for subsequent analysis. The seed yield was closely associated with spike count per plant and spike weight (Klepo et al., 2013). Therefore, excellent parental material was key factors for breeding high yield cultivars. The results in this study indicated that frequency distributions of morphological traits exhibited a normal distribution among all accessions (Fig. 2). Spike count per plant (55.68%) and spike weight (48.28%) exhibited a greater coefficient of variation (CV) than other traits. In contrast, branch count per spike showed a little CV (13.93%) (Fig. 2). Plant height, spike length, pulvinus distance, and spikelet count had a similar CV.
Frequency distribution in morphological traits of tall fescue accessions.
Citation: HortScience 50, 4; 10.21273/HORTSCI.50.4.512
Frequency distribution in morphological traits of tall fescue accessions.
Citation: HortScience 50, 4; 10.21273/HORTSCI.50.4.512
Frequency distribution in morphological traits of tall fescue accessions.
Citation: HortScience 50, 4; 10.21273/HORTSCI.50.4.512
Significant variation in CV of morphological traits was also observed among accessions from different geographic regions (Table 2). The same results were observed in perennial ryegrass (Lolium perenne) (Bugge, 1987) and tall fescue (Sun et al., 2014). Wild tall fescue accessions had a greater CV than commercial cultivars. This was consistent with previous reports which demonstrated that morphological and agronomical variability in wild populations was greater than commercial cultivars (Belaj et al., 2010; Lumaret et al., 2004; Sun et al., 2014). Simmonds (1993) reported that plant breeding often reduced genetic variation in crop species. In addition, Africa tall fescue accessions had the lowest CV in most functional traits, and followed by wild accessions from Europe and Asia. The lowest CV in the Africa group might be attributed to the limited accessions (only seven accessions were observed).
Variation coefficient of morphological traits of tall fescue accessions from different regions.
The average spike count per plant in wild groups was generally lower than that in commercial cultivar group (Table 4). Tall fescue accessions in the Asia group had the least spike count. There was no significant difference in spike length among the wild groups (America, Europe, Africa, Asia group). Tall fescue accessions from the Africa generally had greater plant height (1.38-fold) and pulvinus distance (1.47-fold) when compared to the commercial cultivar group. The Asia accessions had a longer spike (1.35-fold), more spikelet (1.30-fold), and branch (1.30-fold) per spike, respectively, when compared to the commercial cultivar group. The spike weight in America accessions was 1.17-fold higher than that in the commercial cultivar group.
The evaluation of the genetic variation among the tall fescue cultivars, the first step in description of tall fescue germplasm, was crucial for their conservation and utilization (Gowda et al., 2012; Smith and Smith, 1989; Smith et al., 1991). The genetic variation has been investigated in many other plants, such as rice (Oryza sativa L.) (Chakanda et al., 2013), maize (Zea mays L.) (Couto et al., 2013), wheat (Triticum aestivum L.) (Li et al., 2012), and pea (Pisum sativum L.) (Jha et al., 2013). These results revealed that high diversity in morphological traits could be a useful tool for germplasm collection.
One morphological trait could be used to predict another morphological trait based on their correlation. Morphological traits are important components for the characterization of tall fescue accessions (Skinner et al., 1999). Correlation analysis showed that plant height was significantly correlated to spike length (r = 0.734), pulvinus distance (r = 0.810), spikelet count (r = 0.308), and spikelet weight (r = 0.338) (Table 3). Spike length was also correlated with most traits we observed except for spike count, with r value ranging from 0.247 to 0.757. Pulvinus distance also had significant correlations with plant height (r = 0.810), spike length (r = 0.757), spikelet count (r = 0.252), spike weight (r = 0.300). Spikelet count had significant correlations with branch count per spike (r = 0.532), spike length (r = 0.493), plant height (r = 0.308), pulvinus distance (r = 0.252). Spikelet count was negatively correlated with spike count per plant, with r value of 0.250. Similar result was also found in wheat (Triticum aestivum L.) by Ding et al. (2011) who showed that spikelet count was negatively correlated with spike count per plant. Additionally, spike count per plant had no significant correlation with most traits except for spike weight. There was a significant correlation between spike weight and spike count per plant (r = 0.567). The understanding of the relationship between the observed morphological traits is essential to the effective design in breeding strategy, and could facilitate the tall fescue breeding (Ahmadikhah et al., 2008; Milatović et al., 2010; Norman et al., 2011).
Person correlation coefficients among plant height, spike length, pulvinus distance, spikelet count, branch count per spike, spike count per plant, and spike weight for 115 tall fescue accessions.
Average value of morphological traits of tall fescue accessions from different regions.
In summary, there was a significant genotypic variation in morphological traits among tall fescue accessions. Spike count per plant and spike weight exhibited much greater CV. With regard to the geographic origin of tall fescue, wild tall fescue generally had a greater CV in most traits than commercial cultivar group. The correlation analysis showed that plant height, spike length, pulvinus distance, and spikelet count were highly correlated with each other. The variance of one trait is strongly dependent on the other traits. These findings might be considered as important for the characterization of tall fescue accessions.
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Values of morphological traits of tall fescue accessions.
