Bermudagrass Accessions Research Articles

Herbage accumulation and nutritive value of new bermudagrass accessions and cultivars

AbstractBermudagrass [Cynodon dactylon (L.) Pers.] is an important forage source for ruminants in tropical and subtropical regions of the world; nevertheless, little is known about the productive and nutritional characteristics of new accessions and cultivars originating from breeding programs. Five bermudagrass cultivars (Tifton 85, Jiggs, Florida 44, Callie, and Newell) and five accessions (276, 282, 323, 286, and Missouri) were tested during the 2018 and 2019 growing seasons. Genotype × harvest interactions were detected for herbage accumulation (HA), crude protein (CP), and nitrogen yield (p < 0.05). In June, all bermudagrass genotypes showed significant variation in HA, with accession 286 being more productive than Jiggs (4.42 vs. 3.24 Mg DM ha−1 harvest−1, respectively, where DM is dry matter). In October, however, accession 323 had greater CP than Callie, accession 286, Newell, and Tifton 85, with average CP values of 155, 128, 136, and 137 g kg−1 DM, respectively. Average in vitro digestible organic matter for accession 323 (450 g kg−1 DM) was similar to that of Tifton 85 and Newell but greater than that of Missouri (393 g kg−1 DM). Genotypes displayed unique responses to all traits across harvest dates. According to the principal component analysis, the accession Missouri exhibited low productive and nutritive value properties. The accession 286 showed greater CP concentration while still productive; thus, this accession will be further examined for future release to livestock or hay producers in subtropical regions worldwide.

Cytological Pattern Reveals Genome Downsizing in Cynodon dactylon (L.) Pers along the Longitudinal Gradient

Understanding the cytological pattern of genome size and ploidy level of the bermudagrass (Cynodon dactylon) is vital to explore the evolution pattern and breeding of the species. To study the diversification of the cytological pattern of bermudagrass along the longitudinal gradient, the genome size and ploidy level were measured and explored with the relationship to climate factors. The corresponding ploidy level was verified through the mitotic chromosome counts method. Bermudagrass accessions ploidy level included diploids, triploid, tetraploid, pentaploid and hexaploid with a basic chromosome number of x = 9. The major ploidy level was tetraploid (45%) and aneuploidy was commonly discovered in collected regions. Mean genome size of bermudagrasswas was estimated to be 1.31 pg/1Cx along longitudinal gradient. The 1Cx values of diploid were higher than that of triploid and tetraploid, while the tetraploid had minimum basic genome size. In the current study, we observed that genome downsizing exists in tetraploids of Cynodon dactylon. Tetraploids have a wider distribution than other ploidy levels, especially in arid areas, occupying a relatively high proportion. In addition, at the same ploidy level, genome size was remarkably variable in the current study. The coefficient of determination analysis showed that longitude and mean annual rainfall were significantly correlated to genome size rather than ploidy level. This cytological study will be helpful for further genetic mechanisms and molecular characteristics to landscape adaptation of bermudagrass.

Genetic diversity and population structure of bermudagrass (Cynodon spp.) revealed by genotyping-by-sequencing.

Bermudagrass (Cynodon spp.) breeding and cultivar development is hampered by limited information regarding its genetic and phenotypic diversity. To explore diversity in bermudagrass, a total of 206 Cynodon accessions consisting of 193 common bermudagrass (C. dactylon var. dactylon) and 13 African bermudagrass (C. transvaalensis) accessions of worldwide origin were assembled for genetic characterization. Genotyping-by-sequencing (GBS) was employed for genetic marker development. With a minor allele frequency of 0.05 and a minimum call rate of 0.5, a total of 37,496 raw single nucleotide polymorphisms (SNPs) were called de novo and were used in the genetic diversity characterization. Population structure analysis using ADMIXTURE revealed four subpopulations in this germplasm panel, which was consistent with principal component analysis (PCA) and phylogenetic analysis results. The first three principal components explained 15.6%, 10.1%, and 3.8% of the variance in the germplasm panel, respectively. The first subpopulation consisted of C. dactylon accessions from various continents; the second subpopulation was comprised mainly of C. transvaalensis accessions; the third subpopulation contained C. dactylon accessions primarily of African origin; and the fourth subpopulation represented C. dactylon accessions obtained from the Oklahoma State University bermudagrass breeding program. Genetic diversity parameters including Nei's genetic distance, inbreeding coefficient, and Fst statistic revealed substantial genetic variation in the Cynodon accessions, demonstrating the potential of this germplasm panel for further genetic studies and cultivar development in breeding programs.

MiRNAs and Their Target Genes Play a Critical Role in Response to Heat Stress in Cynodon dactylon (L.) Pers.

Annual global temperature is increasing rapidly. Therefore, in the near future, plants will be exposed to severe heat stress. However, the potential of microRNAs-mediated molecular mechanism for modulating the expression of their target genes is unclear. To investigate the changes of miRNAs in thermo-tolerant plants, in this study, we first investigated the impact of four high temperature regimes including 35/30°C, 40/35°C, 45/40°C, and 50/45°C in a day/night cycle for 21days on the physiological traits (total chlorophyll, relative water content and electrolyte leakage and total soluble protein), antioxidant enzymes activities (superoxide dismutase, ascorbic peroxidase, catalase and peroxidase), and osmolytes (total soluble carbohydrates and starch) in two bermudagrass accessions named Malayer and Gorgan. The results showed that more chlorophyll and the relative water content, lower ion leakage, more efficient protein and carbon metabolism and activation of defense proteins (such as antioxidant enzymes) in Gorgan accession, led to better maintained plant growth and activity during heat stress. In the next stage, to investigate the role of miRNAs and their target genes in response to heat stress in a thermo-tolerant plant, the impact of severe heat stress (45/40°C) was evaluated on the expression of three miRNAs (miRNA159a, miRNA160a and miRNA164f) and their target genes (GAMYB, ARF17 and NAC1, respectively). All measurements were performed in leaves and roots simultaneously. Heat stress significantly induced the expression of three miRNAs in leaves of two accession, while having different effects on the expression of these miRNAs in roots. The results showed that a decrease in the expression of the transcription factor ARF17, no change in the expression of the transcription factor NAC1, and an increase in the expression of the transcription factor GAMYB in leaf and root tissues of Gorgan accession led to improved heat tolerance in it. These results also showed that the effect of miRNAs on the modulating expression of target mRNAs in leaves and roots is different under heat stress, and miRNAs and mRNAs show spatiotemporal expression. Therefore, the simultaneous analysis of miRNAs and mRNAs expressions in shoot and roots is needed to comprehensively understand miRNAs regulatory function under heat stress.

Effects of low nitrogen supply on nitrogen uptake, assimilation and remobilization in wild bermudagrass

The natural mechanism of underlying the low nitrogen (N) tolerance of wild bermudagrass (Cynodon dactylon (L.) Pers.) germplasm was important for reducing N fertilizer input to turf while also maintaining acceptable turf quality. The growth, N uptake, assimilation and remobilization of two wild bermudagrass accessions (C291, low N tolerant and C716, low N sensitive) were determined under low N (0.5 mM) and control N (5 mM) levels. C291 exhibited lower reduction in shoot and plant dry weight than C716. Furthermore, C291 presented a lower decrease in 15NO3− influx compared with C716, maintained its root dry weight and root surface and showed obviously enhanced CyNRT2.2 and CyNRT2.3 expression resulting in higher shoot NO3−-N content than the control. Moreover, in C291, nitrate reductase (NR) activity had no significant difference with control, and cytosolic glutamine synthetase (GS1) protein content, glutamate synthetase (GOGAT) activity and glutamate dehydrogenase (GDH) activity higher than control, result in the soluble protein and free amino acid contents in the shoots did not differ compared with that in the control under low N conditions. Overall, the low N tolerant wild bermudagrass accessions adopted a low N supply based on improved root N uptake ability to achieve more nitrate to kept shoot N assimilation, and meanwhile increased N remobilization in the shoots, thereby maintaining a better N status in bermudagrass. The findings may help elucidate the low N tolerance mechanisms in bermudagrass and therefore facilitate genetic improvement of N use efficiency aiming to promote low-input turfgrass management.

Drought resistance of bermudagrass accessions collected from Eastern Mediterranean

Drought resistance of bermudagrass accessions collected from Eastern Mediterranean

Evaluation of South African common bermudagrass germplasm for shade tolerance

AbstractCommon bermudagrass (Cynodon dactylon L. Pers.) is a widely grown warm‐season turfgrass species characterized by a dense, deep‐rooted canopy and high levels of traffic tolerance. However, most cultivars have poor shade tolerance, which limits the use of these grasses in partly‐shaded areas. The identification of new sources of genetic resistance to shade will expand the germplasm pool available to breeders for developing improved bermudagrass cultivars. In this study, 24 common bermudagrass accessions recently introduced from South Africa were evaluated for their ability to persist under shade. Entries were established in a randomized complete block design with three replications at the Lake Wheeler Turfgrass Field Lab (Raleigh, NC) in the spring of 2019. Following full green‐up in summer 2020, entries were evaluated for performance under full sun, and then a 63% shade cloth was installed over the plots. Traits evaluated under shade included: turfgrass quality, turfgrass density, genetic color, ground coverage, turfgrass regrowth and the normalized difference vegetation index (NDVI). A turfgrass performance index (TPI) was calculated to identify the top performers across all traits. Under full sun, seven accessions had comparable performance with ‘Celebration’ and ‘TifTuf’ across traits. Under shade, ‘Stil03’, ‘Q 47620’, ‘TifGrand’, ‘WIN10F’, Celebration, and TifTuf exhibited the highest TPI. Accessions with superior shade tolerance identified in this study represent novel germplasm that can be used in future breeding efforts to improve shade tolerance in bermudagrass.

Identifying superior drought-tolerant Bermudagrass accessions and their defensive responses to mild and severe drought conditions

The natural variation of drought tolerance among eight Iranian bermudagrass (Cynodon dactylon L.) accessions was evaluated and compared with a commonly used variety by measuring various morphological, growth, physiological and molecular responses during mild and severe drought stress conditions. A combined multivariable analysis using principal component analysis, hierarchical clustering analysis, as well as drought-tolerance ranking measurement showed that the accessions were clustered into three groups in terms of drought tolerance. This method evaluated three accessions (Maragh, Abyaneh, and Badrood) as superior drought-tolerant, three (Karshahi, Josheghan, and Kashan) as relatively drought-tolerant, and three (Ardeha, SWI-7, and Khonb) as drought-sanative genotypes. Drought-tolerant accessions generally showed improved growth and relative water content (RWC), minor electrolyte leakage (EL) and lipid peroxidation (MDA), higher content of pigments (Chlorophyll and carotenoid) and dark green color index (DGCI), more significant up-regulation of two stress-related genes (ECERIFERUM1 and Delta 1-pyrroline-5-carboxylate synthetase), as well as higher accumulation of proline content compared to sensitive accessions under drought stress. On the other hand, drought-sensitive accessions typically had more activity of antioxidant enzymes (catalase and ascorbate peroxidase), and higher amounts of soluble sugars (glucose, mannose, and rhamnose), compared to tolerant accessions under drought stress. In conclusion, different defensive strategies may be recruited by tolerant or sensitive bermudagrass genotypes during encountering to drought stress.

Leaf photosynthesis and CO2 assimilation in response to low nitrogen supply in bermudagrass (Cynodon dactylon (L.) Pers.)

Photosynthesis plays a vital role in maintaining vigorous, healthy turf under nitrogen (N)-limiting conditions. The effects of low N stress on the aboveground growth of bermudagrass (Cynodon dactylon (L.) Pers.) as well as its photosynthesis, chlorophyll fluorescence, CO2 assimilation, and carbohydrate pools were studied using hydroponic experiments. Two bermudagrass accessions, Yangjiang (low N tolerant) and C716 (low N sensitive), were used. Low N supply decreased the aboveground dry weight of both accessions. In comparison to C716, Yangjiang maintained better aboveground growth, which was attributed to its smaller reductions in leaf area and the net photosynthetic rate (Pn) at low N conditions. The Pn reduction in both accessions was on account of a reduction in stomatal conductance (Gs) and was partially due to nonstomatal limitations. Furthermore, the smaller Pn reduction in Yangjiang than in C716 was associated with the smaller decrease in CO2 assimilatory capacity in the former, and the ribulose-1,5-bisphosphate carboxylase (RuBisCO) and phosphoenolpyruvate carboxylase (PEPC) activities decreased based on leaf protein content. Although the leaf sucrose synthesis capacity and sucrose phosphate synthase (SPS) and sucrose synthase (SS) activities in Yangjiang increased more than those in C716, carbohydrates did not accumulate in the leaves of either accession to repress photosynthesis. This work provides new insights into CO2 assimilatory capacity rather than carbohydrate status under conditions of reduced leaf photosynthesis and decreasing aboveground growth in bermudagrass under low N conditions. Hence, bermudagrass accessions with low N tolerance are excellent sources of turf requiring reduced N fertilizer inputs.

Association of SSR Markers with Cold Tolerance Traits in Diverse Bermudagrass [Cynodon dactylon (L.) Pers.] Accessions

Bermudagrass [Cynodon dactylon (L.) Pers.] is a perennial and typical warm-season grass. It undergoes withering and severe damage under cold stress; thus, cold is considered as a key factor that restricts the widespread use in bermudagrass. Identification of association between molecular markers and cold tolerance-related traits would facilitate the efficient selection of cold tolerant bermudagrass cultivars. A total of 106 diverse bermudagrass accessions, including 4 commercial cultivars and 102 wild germplasms, were tested for cold tolerance and analyzed by 104 simple sequence repeat (SSR) markers. Cold significantly decreased transpiration rate, growth rate and turf quality. There were significant variations in these trait values among the accessions under cold conditions. Two subpopulations were detected in the panel of accessions based on the analysis of 1474 alleles with 104 SSR markers. Clustering analysis revealed that the genetic relationship was affected by the natural habitats. Thirty-four SSR markers were identified to be associated with two or three traits based on the corrected P values (P < 3.5 × 10−4). These markers can be used for genetic improvement of cold tolerance of bermudagrass after further validation.

Effects of low nitrogen nutrition on plant growth characteristics and nitrogen accumulation in Chinese natural bermudagrass (Cynodon dactylon (L.) Pers.) germplasm resources

ABSTRACTBermudagrass (Cynodon dactylon (L.) Pers.) is a widely used warm-season turfgrass and has the highest nitrogen (N) fertilization requirements among turfgrasses. Wild ecotype found in N-poor habitats can potentially tolerant N limiting conditions for reducing N inputs in the turf industry. However, the extent of variation in their low N tolerance has remained unclear. We conducted hydroponic experiments to evaluate the variation on growth, N accumulation, and partitioning of wild bermudagrass from China pre-core collection under normal (5 mM) and limited (0.05 mM) N levels in two experiments. The results showed that low N nutrition significantly decreased clipping growth, while had no effects on verdure and root growth; in addition, the magnitude of clippings N accumulation reduction was higher than verdure and root across all accessions. However, significant genetic variations in all studied traits except for root N content in experiment 2 were found among accessions. Using a cluster analysis, 56 accessions in experiment 1 and 12 accessions in experiment 2 were classified into four groups and two groups separately. The accessions with superior low N tolerance had improved growth and accumulated more N in the verdure and roots; it is interesting that other accessions with low N tolerance had different tolerance mechanisms and transferred more N nutrition from the roots to the clippings to maintain better turf quality. The different molds in low N tolerance suggest that there is much potential for improving low N tolerance among Chinese natural bermudagrass accessions.

Molecular cloning and sequence variance analysis of the TEOSINTE BRANCHED1 (TB1) gene in bermudagrass [Cynodon dactylon (L.) Pers

TEOSINTE BRANCHED1 (TB1) encodes a TEOSINTE BRANCHED1, CYCLOIDEA, and PROLIFERATING CELL FACTOR (TCP) transcription factor that represses axillary bud outgrowth and lateral branch formation in plants. Previous studies have elucidated the essential tillering regulatory roles of TB1 in many grasses, including maize and rice; however, the functions of TB1 in turf grasses remain unclear. In this study, we cloned the CdTB1 gene from bermudagrass, an important turfgrass species, and characterized the transactivation function of the CdTB1 protein. Sequencing the CdTB1 gene locus in a mini-core germplasm collection of Chinese bermudagrasses led to the successful identification of 66 SNP and 2 indel mutations in the protein-coding region as well as 28 SNP and 11 indel mutations in the promoter region. Interestingly, mutations in the C-terminal transactivation domain of the CdTB1 protein had no significant influence on the transactivation activity, whereas a novel 335-bp insertion mutation located in the promoter region could significantly increase the expression of the CdTB1 gene. Furthermore, wild accessions of bermudagrass harboring the novel insertion mutation were found to have significantly reduced tillers compared with other accessions, suggesting a negative correlation between the mutation and tillering. The results of this study not only expanded our knowledge of TB1 gene expression regulation but also provided possible molecular markers to breed cultivars of turf and forage grasses with specific architectural features.

Genetic diversity and association mapping of forage quality in diverse bermudagrass accessions

Bermudagrass is a warm season grass widely cultivated for turf and fodder. Nonetheless, the grass has poor forage quality because animals that consume it fail to assimilate its organic matter efficiently. Thus, identification of the marker-trait association between simple sequence repeat (SSR) markers and forage-quality-related traits in diverse bermudagrass accessions would enable efficient selection of high forage quality bermudagrass cultivars. Association mapping of 8 forage-related-quality traits with 1474 markers was conducted in 60 diverse bermudagrass accessions from five geographical regions in China. Significant variations in eight phenotypic and physiological traits were observed among the 60 accessions. A total of 1474 alleles were amplified by 104 SSR primers. The average gene diversity and polymorphic information content for the study sample were 0.2097 and 0.1748 respectively. The clustering analysis suggested that geographic origin influenced genetic distances between accessions. A total of 76 markers significantly associated with traits at P < 0.01; 73 with a single trait and 3 with two traits each. Nevertheless, only 41 significant marker-trait associations (MTAs) were observed after Bonferroni test was separately conducted for each trait. Forty-one microsatellites had significant associations with 8 forage-quality-related traits. These markers provide a feasible means of genetically improving forage quality in bermudagrass after further authentication.

Genetic diversity and population structure of Chinese natural bermudagrass [Cynodon dactylon (L.) Pers.] germplasm based on SRAP markers.

Bermudagrass [Cynodon dactylon (L.) Pers.], an important turfgrass used in public parks, home lawns, golf courses and sports fields, is widely distributed in China. In the present study, sequence-related amplified polymorphism (SRAP) markers were used to assess genetic diversity and population structure among 157 indigenous bermudagrass genotypes from 20 provinces in China. The application of 26 SRAP primer pairs produced 340 bands, of which 328 (96.58%) were polymorphic. The polymorphic information content (PIC) ranged from 0.36 to 0.49 with a mean of 0.44. Genetic distance coefficients among accessions ranged from 0.04 to 0.61, with an average of 0.32. The results of STRUCTURE analysis suggested that 157 bermudagrass accessions can be grouped into three subpopulations. Moreover, according to clustering based on the unweighted pair-group method of arithmetic averages (UPGMA), accessions were divided into three major clusters. The UPGMA dendrogram revealed that accessions from identical or adjacent areas were generally, but not entirely, clustered into the same cluster. Comparison of the UPGMA dendrogram and the Bayesian STRUCTURE analysis showed general agreement between the population subdivisions and the genetic relationships among accessions. Principal coordinate analysis (PCoA) with SRAP markers revealed a similar grouping of accessions to the UPGMA dendrogram and STRUCTUE analysis. Analysis of molecular variance (AMOVA) indicated that 18% of total molecular variance was attributed to diversity among subpopulations, while 82% of variance was associated with differences within subpopulations. Our study represents the most comprehensive investigation of the genetic diversity and population structure of bermudagrass in China to date, and provides valuable information for the germplasm collection, genetic improvement, and systematic utilization of bermudagrass.

Shade response of bermudagrass accessions under different management practices

The development of cultivars ‘TifGrand’ and ‘Celebration’ has shown potential increases in shade tolerance compared to previous industry standards of bermudagrass (Cynodon spp.). Based on the literature, further improvements in shade tolerance can be attained through changes in nitrogen fertility rates, mowing heights, and the application of plant growth regulators. In this study, two South African hybrid (Cynodon dactylon (L.) Pers.×C. transvaalensis Burtt Davy) bermudagrass accessions (‘WIN10F’ and ‘STIL03’) and three standard cultivars (Celebration, Tifgrand, and ‘Tifway’) were compared for their ability to persist under 63% shade, two mowing heights, two trinexapac-ethyl (TE) treatments, and two nitrogen fertility rates. The experimental design was a strip-strip-split plot and digital image analysis was used to measure percent turfgrass cover, percent turfgrass spread after cup-cutter removal, and percent turfgrass re-growth after divot formation. Turf quality was measured using the normalized difference vegetation index (NDVI). Differences among genotypes, TE treatments, and mowing heights were observed across all response variables in 2014 and 2015. Differences in fertility treatments were observed in NDVI, percent turfgrass growth, and percent turfgrass recovery within and across years. Significant differences were observed for the interactions between entry by plant growth regulator (PGR) treatments, entry by mowing height, and mowing height by PGR. These results suggest shade management recommendations should be dependent on genotype and site-specific considerations. The development and implementation of specific management plans for certain bermudagrass varieties will contribute to the more widespread use of Cynodon spp. in shaded environments.

Cross-taxon application of sugarcane EST-SSR to genetic diversity analysis of bermudagrass (Cynodon spp.)

Bermudagrass lags in genomic and molecular breeding resources, particularly regarding a critical mass of robust, reproducible, and highly polymorphic molecular markers like simple sequence repeats (SSR). Here, 2017 sugarcane EST-SSR primer pairs (PPs) were screened for transferability and polymorphisms against commercial triploid hybrids and representatives of their parental species, tetraploid Cynodon dactylon and diploid C. transvaalensis. Fifty-four percent of PPs amplified target SSR in at least one of the two species, while 62% of these ‘transferable’ SSR were polymorphic. A subset of 228 polymorphic markers was utilized for genotyping 24 samples that included: 10 ‘Tif’ series cultivars (i.e., released from Tifton, GA), their parental species, 10 F1 hybrids between the two species, and two diverse Sorghum spp. A total of 90 and 144 PPs produced reproducible bands in the bermudagrass samples and the sorghum species, respectively. While 63 (70%) PPs were polymorphic among members of the ‘Tif’ diversity panel, 79 (54.8%) were polymorphic between the sorghum species. Further, 57 PPs polymorphic in the ‘Tif’ diversity panel were genotyped against 3 experimental lines and 7 commercial hybrids including ‘TifTuf’, a recent addition to the ‘Tif’ series. Joint analysis of 24 genotypes grouped bermudagrass accessions into two main clusters, one including C. dactylon and the other including C. transvaalensis. A small set of informative SSR readily differentiated the cultivar groups and identified potentially mischaracterized cultivars, but did not differentiate among mutants within cultivar groups. Heterologous EST-SSR from sugarcane are useful sources of polymorphic markers for cultivar identification in bermudagrass, and build on existing marker resources to facilitate genetic mapping, QTL analysis, and marker assisted selection.

Genetic diversity and association mapping of cadmium tolerance in bermudagrass [Cynodon dactylon (L.) Pers.

Identification of the association between Cd tolerance-related traits and molecular markers facilitates an efficient selection of the tolerant cultivars. The objectives of this study were to analyze the Cd tolerance and the genetic diversity of native bermudagrass accessions in China, and to identify marker-trait association with wild bermudagrass. A countrywide collection of 120 bermudagrass [Cynodon dactylon (L.) Pers.] accessions were evaluated for Cd tolerance and genetic diversity with simple sequence repeat (SSR) markers. Significant variations in 7 physiological parameters were observed among the accessions under Cd conditions. The 104 SSR primers amplified 1474 alleles. The average gene diversity and polymorphic information content (PIC) for the whole sample was 0.2270 and 0.1894, respectively. Clustering analysis showed that the distance of genetic relationship was affected by the cultivars of natural habitats and the edaphic conditions. Thirty one SSR markers were associated with more than one trait (P < 0.01), while 37 markers were identified by corrected P values (P < 3.5 × 10−4). Thirty one SSR markers were associated with a reduction in 7 traits under Cd stress. These markers can be used for genetic improvement of Cd tolerance of bermudagrass after further validation.

Assessment of genetic diversity of bermudagrass germplasm from southwest China and Africa by using AFLP markers.

Cynodon dactylon (L.) Pers. var. dactylon (common bermudagrass) is widely distributed geographically between approximately 45°N and 45°S latitude, penetrating to approximately 53°N latitude in Europe. The extensive variation of morphological and adaptive characteristics of the taxon has been substantially documented, but information is lacking on DNA molecular variation in geographically disparate forms. The genetic diversity of 51 wild accessions of bermudagrass from southwest China (Sichuan, Chongqing, Yunnan, Guizhou, and Tibet) and 8 African bermudagrass was analyzed using amplified fragment length polymorphism molecular markers. A total of 670 polymorphic bands were detected with 11 primer combinations, of which 663 (98.74%) bands were found to be polymorphic. The genetic similarity among the accessions ranged from 0.64-0.96 with an average of 0.78. All 59 wild accessions were clustered into 5 eco-geographic groups, and nearly all accessions from the same area were classified into the same group and were found to be associated with their geographical distributions. Therefore, complex geographical and ecological environments are important factors for the genetic structure and geographical distribution of C. dactylon.

Phenotypic traits and establishment speed of 44 turf bermudagrass accessions

Breeding of turf bermudagrass (Cynodon (L.) Rich.) has made available a broad range of turf varieties with unique morphological and growth traits. Rapid establishment is necessary in order to provide the performance of a mature turf cover in the shortest time possible. The aims of the research were: (1) to determine variation of growth, morphological and biomass traits in bermudagrass accessions belonging to different phenotypic groups during establishment and (2) to relate such variations to establishment speed in order to assess whether contrasting phenotypic traits could induce different establishment patterns in bermudagrass or if a general establishment predictor can be identified for cultivars and ecotypes belonging to the same taxon. Plant material included 44 accessions of bermudagrasses that were grouped in ‘Wild’, ‘Improved’ ‘Hybrid’ and ‘Dwarf types’. Single spaced plants were transplanted in field plots in two locations in Italy (Pisa and Palermo) and allowed to establish without mowing. The following traits were determined: stolon growth rate, internode length, internode diameter and internode volume, phytomer dry weight, leaf width, colour, seed head production, above ground dry biomass, shoot density, horizontal stem density and node density. Establishment speed of accessions was also determined. Stolon growth rate was found to be the only parameter strongly correlated to establishment speed across all entries and for each of the phenotypic groups. Based on these results, stolon growth rate could be assumed as a good predictor of establishment speed for cultivars and ecotypes belonging to the Cynodon genus.

Bermudagrass adaptation in the Mediterranean climate: phenotypic traits of 44 accessions

The use of bermudagrass in the Mediterranean area is increasing for its outstanding tolerance to heat and drought, and its aggressive growth and high recuperative potential make it particularly suited to heavily worn areas and appreciated for sports turfs. However, the overall performance of a given genetic type can be affected by the adaptation to a specific environment. The objective of this research was to determine the variability of a number of phenotypic traits that can affect bermudagrass turf performance on a wide range of bermudagrass accessions grown in two locations in Italy. In May 2010, 44 accessions of bermudagrasses, grouped in “wild”, “improved” “hybrid” and “dwarf” types were transplanted in the center of field plots in Pisa and Palermo. In 2011, when the turf was completely established, the following traits were determined: shoot density, horizontal stem density, node density, leaf width, colour, quality, spring green-up, and fall colour retention. Dwarf and hybrid types yielded the best aesthetic characteristics. With respect to colour retention and spring green-up, great variability was recorded within the groups. Dwarf types presented the earliest dormancy, while the hybrid types were in general the ones to green-up first in spring.