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Ruminant livestock production in the tropics, particularly when based on pastures, is frequently blamed for being detrimental to the environment, allegedly contributing to: (1) degradation and destruction of ecosystems, including degradation and loss of soil, water and biodiversity; and (2) climate change (global warming). In this paper we argue that, rather than being detrimental, tropical forage legumes can have a positive impact on the environment, mainly due to key attributes that characterize the Leguminosae (Fabaceae) family: (1) symbiotic nitrogen fixation; (2) high nutritive value; (3) deep-reaching tap-root system; (4) wide taxonomic and genetic diversity; and (5) presence of particular secondary metabolites. Although there are also potential negative aspects, such as soil acidification and the risks of introduced legumes becoming invasive weeds, we submit that legumes have potential to contribute significantly to sustainable intensification of livestock production in the tropics, along with the provision of ecosystem services. To further assess, document and realize this potential, research for development needs in a range of areas are indicated.Keywords: Biodiversity, ecosystem services, GHG emissions, land rehabilitation, soil enhancement, symbiotic nitrogen fixation.DOI: 10.17138/TGFT(6)1-14

Aluminum ion (Al3+) toxicity is a major factor limiting plant production on acid soils. Species of zoysiagrass (Zoysia Willd.) are grown for lawn, turf, and soil conservation, especially in temperate zones. Herein, 46 zoysiagrass accessions obtained from eight provinces in China were evaluated for Al resistance using small-scale liquid culture. Each accession was grown in triplicate in nutrient solutions with 1500 μm AlCl3·6H2O (experimental) or without exposure to Al (control). The mean dry weights of the roots, shoots, and total bodies of the accessions relative to those of the nontreated controls were calculated after 60 days, and showed considerable diversity. Overall, the cv for the shoot, root, and total weights of the Al-treated accessions relative to the nontreated controls were 45.78%, 56.67%, and 42.84%, respectively. A cluster analysis based on Al resistance and subordinate function values revealed that 12 of the 46 zoysiagrass accessions (26.09%) were resistant to Al, 9 (19.57%) were moderately resistant, and 25 (54.35%) were sensitive to Al stress. These 46 zoysiagrass accessions from China have great potential for horticultural breeding and development, and for research into mechanisms that underlie Al resistance.

Molecular genetic diversity and relationships among 86 Chrysopogon aciculatus (Retz.) Trin. accessions were assessed using intersimple sequence repeat (ISSR) and sequence-related amplified polymorphism (SRAP) markers. Twenty-five ISSR markers generated 283 amplification bands, of which 266 were polymorphic. In addition, 576 polymorphic bands were detected from 627 bands amplified using 30 SRAP primers. Both marker types revealed a high level of genetic diversity, with ISSR markers showing a higher proportion of polymorphic loci (PPL; 94%) than SRAP markers (91.87%). The ISSR and SRAP data were significantly correlated (r = 0.8023). Cluster analysis of the separate ISSR and SRAP data sets clustered the accessions into three groups, which generally were consistent with geographic provenance. Cluster analysis of the combined ISSR and SRAP data set revealed four major groups similar to those based solely on ISSR or SRAP markers. The findings demonstrate that ISSR and SRAP markers are reliable and effective tools for analysis of genetic diversity in C. aciculatus.

Carpetgrass [Axonopus compressus (Sw.) Beauv.] is an important warm-season perennial turfgrass that is widely used in tropical and subtropical areas. The genetic diversity of 63 carpetgrass accessions in China was studied using simple sequence repeat (SSR) markers. Fourteen SSR primer combinations generated a total of 49 distinct bands, 48 (97.96%) of which were polymorphic. The number of observed alleles ranged from 2 to 6, with an average of 3.5. Coefficients of genetic similarity among the accessions ranged from 0.24 to 0.98. Unweighted pair-group method with arithmetic means (UPGMA) clustered the 63 accessions into three groups, and not all samples from the same region belonged to the same group. SSR markers will promote marker-assisted breeding and the assessment of genetic diversity in wild germplasm resources of carpetgrass.

Salinity is a serious limiting factor for the growth of rhizobia. Some rhizobia are tolerant to salt stress and promote plant growth, but the mechanisms underlying these effects are poorly characterized. The growth responses and osmoprotectants in four Bradyrhizobium strains were examined under salt stress in this study. Two-dimensional electrophoresis (2-DE) and mass spectrometry were conducted to investigate protein profiles in rhizobia exposed to salt stress. Subsequently, salt tolerance in stylo (Stylosanthes guianensis) inoculated with rhizobia was further detected in hydroponics. Results showed that the Bradyrhizobium strain RJS9-2 exhibited higher salt tolerance than the other three Bradyrhizobium strains. RJS9-2 was able to grow at 0.35 M NaCl treatment, while the other three Bradyrhizobium strains did not grow at 0.1 M NaCl treatment. Salt stress induced IAA production, and accumulation of proline, betaine, ectoine, and trehalose was observed in RJS9-2 but not in PN13-1. Proteomics analysis identified 14 proteins regulated by salt stress in RJS9-2 that were mainly related to the ABC transporter, stress response, and protein metabolism. Furthermore, under saline conditions, the nodule number, plant dry weight, and N concentration in stylo plants inoculated with RJS9-2 were higher than those in plants inoculated with PN13-1. These results suggest that the tolerance of RJS9-2 to salt stress may be achieved by the coordination of indole-3-acetic acid (IAA) production, osmoprotectant accumulation, and protein expression, thus promoting stylo growth.

A total of 148 accessions representing six important species of the genus Stylosanthes, including S. guianensis, S. hamata, S. scabra, S. seabrana, S. macrocephala, and S. capitata, were used to evaluate genetic variation and relationships using sequence-related amplified polymorphism markers. The results showed that the 18 selected primer pairs generated 138 distinct fragments. The fragment sizes ranged from 150 to 2000 bp. Genetic similarity coefficients among the 148 accessions ranged from 0.51 to 0.99, with an average of 0.79. The effective allele number (ne) generated by the 18 primer pairs averaged 1.3552 and ranged from 1.2069 to 1.6080; Nei’s gene diversity (He) ranged from 0.1304 to 0.3207, with an average of 0.2070; and Shannon’s information index (I) averaged 0.3213 and ranged from 0.2233 to 0.4582. The unweighted pair-group method with arithmetic averages at the 0.69 similarity level separated the 148 accessions into two distinct groups. One group belonged to S. guianensis, and the other group belonged to the non-S. guianensis type. This study verified that Stylosanthes have rich genetic variation, which is an excellent basis for Stylosanthes breeding for new cultivars. This study demonstrates that the SRAP technique is a reliable tool for differentiating Stylosanthes accessions and for discerning genetic relationship among them.

Anthracnose caused by Colletotrichum gloeosporioides is one of the most destructive fungal diseases of many plants, including stylo (Stylosanthes spp.), which is an important tropical forage legume. Although C. gloeosporioides-caused anthracnose is the major constraint limiting the growth and yield of stylo, little information is available regarding the responses of stylo during the infection process of this pathogen. This study investigated the changes in growth, the antioxidant system and gene expression in stylo in response to C. gloeosporioides treatment. Negative effects of C. gloeosporioides were observed in inoculated stylo plants, as reflected by the formation of necrotic disease lesions and the decrease in shoot fresh weight. Reactive oxygen species (ROS) accumulation increased in stylo leaves during the C. gloeosporioides infection process. The activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), glutathione peroxidase (GPX) and glutathione reductase (GR), as well as the concentrations of the antioxidant compounds ascorbate (AsA) and glutathione (GSH), increased in leaves under C. gloeosporioides treatment. Furthermore, transcriptional analysis showed that the expression of stress response genes, including NADPH oxidase (Nox), thioredoxin (Thi), pathogenesis related genes (PR1 and PR5), phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), chalcone synthase (CHS) and chitinase (Cht), was differentially enhanced in stylo leaves by C. gloeosporioides. Taken together, this study provides novel information regarding the alterations during the infection process of C. gloeosporioides in stylo at the levels of antioxidant system and gene expression.

The objectives of this research are to reveal the genetic variation and relationships of 29 Cynodon arcuatus accessions from different regions of China using inter-simple sequence repeat (ISSR) markers and sequence-related amplified polymorphism (SRAP) markers, and to assess the levels of polymorphisms detected by the 2 different markers and compare their efficiencies. The markers were used to provide essential information for the exploration and utilization of C. arcuatus germplasms. A total of 189 bands from 300 bp to 3000 bp were amplified by 14 ISSR primers, while 334 bands from 260 bp to 1800 bp were observed by 15 SRAP primer combinations, of which 187 (98.94%) and 316 (94.61%) were polymorphic, respectively. The ranges of genetic similarity coefficients (GSC) were 0.45–0.90 for ISSR markers, 0.48–0.94 for SRAP markers, and 0.48–0.90 for ISSR + SRAP markers. Cluster analysis using 2 methods, specifically the unweighted pair-group method with arithmetic averages and principle coordinate analysis, showed that the C. radiatus accessions clustered into 5 distinct groups using ISSR markers, 6 groups using SRAP markers, and 5 groups using ISSR + SRAP markers. The present study verified that C. arcuatus has rich genetic diversity in Hainan with the use of ISSR and SRAP markers, which provided basis for molecular breeding and germplasm creation of C. arcuatus. This study showed that the combination of both methods would be a very good way for the analysis of Cynodon accessions, which would be a good experience for further studies of the diversed Cynodon genus.

A brachiaria breeding program initiated in 1988 at CIAT (Centro Internacional de Agricultura Tropical, Cali, Colombia) combined desirable attributes found in accessions of Brachiaria brizantha and B. decumbens. Three apomictic hybrids have been released (cvv. Mulato, Mulato II and Cayman). Mulato showed agronomic potential but seed yields were low. Trials in Central America demonstrated the superiority of Mulato II, a vigorous grass with deep and branched roots, giving it excellent drought tolerance in the Brazilian Cerrado and Mexico, plus outstanding nutritional value. Following trials in Mexico and Thailand, evaluating 155 new hybrids for 7 years, cv. Cayman was released due to strong waterlogging tolerance. Research on production, quality and seed yields of brachiaria hybrids in Asia, the Americas and Africa from 2003 to 2013 is summarized in this paper.

Inter-simple sequence repeat (ISSR) markers were applied to determine the genetic relationship among 29 Cynodon radiatus accessions from different regions of China. Fifty ISSR primers were screened, and 14 primers were selected for their capability to produce clear and reproducible patterns of multiple bands to amplify specific C. radiatus genomic sequences. A total of 189 ISSR fragments from 300 bp to 3000 bp were amplified, of which 98.94% were polymorphic. Genetic similarity coefficients among the 29 accessions ranged from 0.45 to 0.90, with an average of 0.68. Cluster analysis by 2 methods, unweighted pair-group method with arithmetic averages and principle coordinate analysis, showed that the C. radiatus accessions clustered into 4 distinct groups. A high level of variation exists in C. radiatus accessions. The present study shows that the ISSR technique is a powerful method for the identification and molecular classification of C. radiatus accessions, and for the determination of their genetic relationships.

Sequence-related amplified polymorphism (SRAP) markers were used to assess the genetic relatedness among 33 Cynodon radiatus accessions from different regions of China. Fifteen primer combinations were used to amplify specific C. radiatus genomic sequences. A total of 382 SRAP fragments were generated, with fragment sizes ranging from 200 to 1800 bp. Genetic similarity coefficients among the 33 accessions ranged from 0.53 to 0.95, with an average of 0.70. Cluster analysis by two methods, the unweighted pair–group method with arithmetic averages and the principle coordinate analysis, separated the accessions into 3 distinct groups. This study shows that the SRAP technique is a reliable tool for differentiation of C. radiatus accessions and for determination of the genetic relationships among them.

Genetic variation in 55 accessions of Cynodon dactylon was estimated using inter-simple sequence repeat (ISSR) markers. The plant materials used in this study originated from 17 countries. A total of 236 ISSR fragments were generated with 14 primers. Fragment sizes ranged from 200 to 3000 bp. All scorable bands were polymorphic in nature and none of the primers used produced monomorphic bands, indicating a high level of genetic variation in this grass. The accessions were found to be clustered into eight major groups through the unweighted pair-group method with arithmetic averages. Genetic similarity coefficients (GSC) among the 55 accessions ranged from 0.52 to 0.95. The results clearly indicate that a high level of variation exists in Cynodon accessions. This study shows that the ISSR technique is a reliable tool for differentiating Cynodon accessions and for determining the genetic relationships among them.

A deep understanding on the intrinsic mechanism is required to develop a highly specialized mechanistic model for ecosystem dynamics. However, it is usually hard to do for most of the ecological and environmental problems, because of the lack of a consistent theoretical background. Neural networks are universal and flexible models for linear and non-linear systems. This paper aimed to modeling an ecosystem using neural network models and the conventional model, and assessing their effectiveness in the dynamic simulation of ecosystem. Elman neural network model, linear neural network model, and linear ordinary differential equation were developed to simulate the dynamics of Chinese cabbage growth system recorded in the field. Matlab codes for these neural network models were given. Sensitivity analysis was conducted to detect the robustness of these models. The results showed that Elman neural network model could simulate the multivariate non-linear system at the desired accuracy. Linear neural network model may simulate such a non-linear system only in certain conditions. Conventional linear ordinary differential equation yielded divergent outputs in the dynamic simulation of the multivariate non-linear system. Sensitivity analysis indicated that the learning rate influenced the simulation performance of linear neural network model. Transfer function of the second layer in Elman neural network model would influence the simulation performance of this model, but little influence was produced when other functions were changed. Elman neural network was proven to be a robust model. Sensitivity analysis showed that the different choices of functions and parameters in neural network model would influence the performance of simulation. Sensitivity analysis is therefore powerful to detect the robustness and stability of neural network models.

A new species of Carex sect. Rhomboidales, C. jianfengensis, is described and illustrated from Hainan, China. The new species is similar to C. zunyiensis but differs in having involucral bracts sparsely hispid and with ca.1 cm long sheaths; inflorescence with 4 spikes, terminal spike ca. 2.5 cm long, lateral spikes 2-3.5 × 0.7-1 cm; staminate glumes narrowly ovate, ca. 5 mm; pistillate glumes triangular-lanceolate, 5-7 mm; perigynia 6-8 × 3 mm and pubescent on veins; nutlet 4-5 mm long, rhombic-ovoid, trigonous, base with shortly stipitate, apex abruptly contracted into a erect short beak, and not expanding into an annulate orifice.

Although Cynodon dactylon (C. dactylon) is widely distributed in China, information on its genetic diversity within the germplasm pool is limited. The objective of this study was to reveal the genetic variation and relationships of 430 C. dactylon accessions collected from 22 Chinese provinces using sequence-related amplified polymorphism (SRAP) markers. Fifteen primer pairs were used to amplify specific C. dactylon genomic sequences. A total of 481 SRAP fragments were generated, with fragment sizes ranging from 260–1800 base pairs (bp). Genetic similarity coefficients (GSC) among the 430 accessions averaged 0.72 and ranged from 0.53–0.96. Cluster analysis conducted by two methods, namely the unweighted pair-group method with arithmetic averages (UPGMA) and principle coordinate analysis (PCoA), separated the accessions into eight distinct groups. Our findings verify that Chinese C. dactylon germplasms have rich genetic diversity, which is an excellent basis for C. dactylon breeding for new cultivars.

Carex diaoluoshanica, a new species of Carex sect. Lageniformes from Hainan, China, is described and illustrated. The new species is similar to C. breviscapa but differs in having wider leaves with the leaf base gradually narrowed, 5–10 cm long and petiolelike, culms subfiliform, with only two spikes, the lateral female spikes from near the culm base.

A new species of Carex sect. Rhomboidales, Carex concava, is described and illustrated from Hainan, China. The new species is similar to C. paracheniana but differs in having wider blades and longer sheaths of bracts; inflorescence with 3 spikes; terminal spike 2–6 cm long and with a 4–14 cm long peduncle; lateral spikes 3–6 cm long, loosely flowered and with 8–15 cm long peduncles; staminate glume ovate, 1-veined costa excurrent into a shortly awn ca. 0.3 mm; pistillate glume ovate, ca. 4 mm long, 1-veined costa excurrent into a awn ca. 1 mm; perigynia fusiform and green; nutlets inclined-oval, brownish black, with 3 angles deeply constricted at the middle and the side toward of spike-stalk deeply concave at base.

Carex procumbens, a new species of Carex sect. Rhomboidales from Hainan, China, is described and illustrated. The new species is similar to C. longipetiolata but differs in culms soft and usually prostrate on the ground, having narrower leaves with the leaf base gradually narrowed, with 2–3 spikes, terminal spike 8–12 mm long, lateral spikes 5–15 mm long and loosely flowered, staminate glumes ovate with green middle vein and apex rounded, pistillate glumes ovate-lanceolate ca. 6 mm and middle vein excurrent into a short awn for ca. 2 mm, perigynia fusiform and glabrous, nutlet brown to dark brown and ovate-rhomboid, nutlet ca. 7 mm long and with a short curved beak.