Genus Urochloa Research Articles

Coexistence of soybean plants and Urochloa spp. under glyphosate and water deficit effects

In the insertion of forage plants of the genus Urochloa P. Beauv. (Poaceae) coexisting with annual crops, proper management of the intercropping becomes necessary to avoid economic losses. Among management measures, the chemical inhibition of forage plants with herbicide subdoses is highlighted. Therefore, this study evaluates the morphophysiological responses of soybean ( Glycine max (L.) Merr.) genetically modified to tolerate glyphosate (RR soybean), in coexistence with Urochloa spp., treated or not with glyphosate subdoses and subjected to water deficit. Two tests were carried out in pots with forage species Urochloa ruziziensis (R.Germ & Evrard) Crins and Urochloa brizantha (Hochst. Ex A. Rich.) R. D. Webster cv. Marandu coexisting with soybean, in randomized blocks with five replicates. The tests were arranged in a 2x2x2 factorial arrangement: the first factor was repre­sented by the absence and presence of forage; the second by the absence and use of glyphosate subdoses; and the third factor by 50% and 100% field capacity in the pots. The use of glyphosate suppressed the competitive capacity of forages, benefiting the soybean in coexistence. In the absence of suppression from glyphosate, the competition exerted by the forage promoted lower values for the physiological and morphological variables of soybean plants. Among the forages, U. ruziziensis was the most competitive with soybean plants. The root system of forages was not affected by water deficit, only the physiological and morphological characteristics of soybean, mainly rootdry mass. Glyphosate affected forage growth.

Productivity increase, reduction of nitrogen fertiliser use and drought-stress mitigation by inoculation of Marandu grass (Urochloa brizantha) with Azospirillum brasilense

Among the forage species cultivated in South America, the genus Urochloa is the most used, and the cultivar Marandu of U. brizantha is the most widely planted in Brazil. The objective of this study was to evaluate forage performance in association with Azospirillum brasilense, combined with nitrogen (N) fertilisation. The study was conducted under field conditions in Araguaína, Tocantins, in the central region of Brazil, between March 2016 and March 2017. Four N fertiliser rates (0, 12.5, 25 and 50kg/ha of N per cutting cycle) were combined with two inoculation treatments (inoculated and non-inoculated), with evaluations carried out in three periods of the year (transition, dry and wet seasons). Marandu grass plants inoculated with A. brasilense had greater plant height, number of tillers and forage production than non-inoculated plants, regardless of the N rate. Inoculation with A. brasilense allowed a 20% reduction in N fertilisation. Our results indicate that inoculation with A. brasilense in Marandu grass, as well as increasing forage production, can help to mitigate the stresses caused by the dry season.

Genotypic response of brachiaria (Urochloa spp.) to spider mite (Oligonychus trichardti) (Acari: Tetranychidae) and adaptability to different environments

Grasses in the genus Urochloa, commonly known as brachiaria, are grown as forage crops in sub-Saharan Africa, with some genotypes being used in management of insect pests. However, spider mite, Oligonychus trichardti Meyer (Acari: Tetranychidae), has recently been reported as its major pest in the region. We evaluated 18 brachiaria genotypes to identify sources of resistance to O. trichardti, and to determine their adaptability to different environments in western Kenya. Response to artificial infestation with O. trichardti was evaluated under controlled conditions in a screenhouse while adaptability to different environments and field resistance to mites was evaluated in three locations for two cropping seasons in 2016 and 2017 under farmers’ conditions. The parameters evaluated as indicators of resistance to pest damage included leaf damage, chlorophyll content reduction, plant height, leaf area, number of tillers and shoot biomass. Rainfall played a role in reducing mite infestation and increasing biomass yield of the genotypes. Significant correlations between parameters were only observed between leaf damage and yield (r = -0.50), and leaf damage and chlorophyll loss (r = 0.85). The cultivar superiority index (Pi) ranked Xaraes, Piata, ILRI 12991 and ILRI 13810 as reliable genotypes that combined moderate resistance to the mite (Pi ≤ 48.0) and high biomass yield (Pi ≤ 8.0). Since this is the first documentation of interactions between O. trichardti and different brachiaria genotypes, we propose these genotypes as potential candidates for improved forage yields in areas prone to O. trichardti infestation in Africa.

Growth and yield of corn forage intercropped with marandu grass in an agrosilvopastoral system with eucalyptus

Corn and grass intercropping is an interesting practice, and forage plants belonging to the genus Urochloa are the most commonly used in these situations. These plants show excellent adaptation to low-fertility soil, easy establishment, considerable biomass production, as well as being an important competitor with weeds. In agrosilvopastoral systems, the yield of corn crops grown together with trees is hindered due to the reduced radiation incidence caused by tree shading. This study aimed to evaluate corn growth, light interception, and chlorophyll content when intercropped with marandu grass in an agrosilvopastoral system with one and three eucalyptus rows, and compare them with plants under full sun. The experiment was conducted in Andradina - SP (Brazil). Treatments consisted of intercropping with no eucalyptus (plants under full sun: control), one system with one eucalyptus row and another with three rows. We also assessed the effect of five distances between corn plants and eucalyptus trees (2, 4, 6, 8, and 10 m). Between eucalyptus rows, corn plants were intercropped with marandu grass. The analyzed variables were corn plant height, ear height, chlorophyll content index, light interception, dry matter, and fresh and dry forage weights. The experimental design was a randomized block in a factorial scheme plus a control, with four repetitions. Tree arrangements had no influence on corn forage, dry matter, plant height, or ear height. Lower results of yield, dry matter, plant height, and ear height were observed for plants spaced 2 m from trees. In the first two evaluations, significant differences of light interception were found for the different distances. Neither tree arrangements (one and three rows) nor the distances from the trees had any impact on corn heights, with no difference between control and the agrosilvopastoral systems. Neither plant distances from trees nor tree arrangements had an influence on chlorophyll content index of corn plants, with no difference between control and the treatments. As a result, corn growth and forage yield under agroforestry systems are similar in arrangements of 1 and 3 eucalyptus rows (15-month-old trees) and under full sun. However, corn dry matter contents were lower in systems containing trees. Intercropping corn and marandu grass in a system without trees increased light interception at harvest time, indicating a larger soil coverage. Corn forage yield and dry matter content were lower when plants were 2 m apart from eucalyptus trees since this condition provided a lower amount of light and greater competition for water and nutrients.

Genomic Constitution and Relationship in Urochloa (Poaceae) Species and Hybrids

Urochloa P. Beauv. [syn. Brachiaria (Trin.) Griseb.] belongs to the family Poaceae and comprises species presenting different ploidy levels and modes of reproduction. Specific studies on genomic constitution and relationship within the genus Urochloa are limited, despite the great economic and agronomic importance of forage species and the high frequency of polyploids. Therefore, molecular cytogenetic analyses can enhance the knowledge about genomes and their differentiation, which allows making inferences about phylogenetic and genomic relationships. The current study aimed to investigate the genomic relationships between Urochloa ruziziensis (R. Germ. & Evrard) Crins (syn. Brachiaria ruziziensis Germain & Evrard.) cultivar ‘Kennedy’, Urochloa decumbens (Stapf) R. D. Webster [syn. Brachiaria decumbens (Stapf)] cultivar ‘Basilisk’, Urochloa brizantha (Hochst. ex. A. Rich.) R. D. Webster [syn. Brachiaria brizantha (A. Rich.) Stapf] cultivar ‘Marandu’, and their interspecific hybrids by means of genomic in situ hybridization, fluorescent in situ hybridization, and nuclear genome quantification by flow cytometry. We proposed the genomic constitution of U. ruziziensis, U. decumbens, and U. brizantha, such as B2B2, B1B1B2B2, and BBB1B1, respectively. Genomes B, B1, and B2 were considered to be homoeologous, but there was less affinity between genomes B and B2.

MANEJO E ADAPTAÇÃO DE PASTAGENS DO GÊNERO UROCHLOA EM SOLOS DO CERRADO

Currently, several species of the genus Urochloa have been outstanding, not only in Brazil, but also in other countries. This is due to their characteristics of good performance and adaptation, consequently, reaching production records and promoting gains for the producer. The genus Urochloa has been highlighted as an alternative of inclusion in the Cerrado biome, especially with Brazilian livestock, because its inclusion in this biome had as its main characteristic, its positive performance in soils with low fertility, which for other Cultures, because of their acidity, they present some nutritional restrictions. The genus Urochloa stands out when it comes to good performance in the production of meat and milk, because it's a grass that adapts very well to the different climates of the country and it has great values of mass production. In this way, many producers search for species of this genus, because they are plants with a high dry matter production, low disease rates and it presents effective growth during most of the year, including the period of drought, and also some species show good resistance to cigarrinha das pastagens. 277 Colloquium Agrariae, vol. 13, n. Especial, Jan–Jun, 2017, p. 276-288. ISSN: 1809-8215. DOI: 10.5747/ca.2017.v13.nesp.000233 Taking into account the economic importance and the versatility, among the species of this genus stand out U. brizantha, U. decumbens, U. ruziziensis and U. humidicola. The objective of this review was to present a study about the management and adaptation of pastures of the genus Urochloa in soils of Cerrado biome.

FORESTRY RESTORATION IN ABANDONED PASTURES OF Urochloa BY DIFFERENT SIZES OF BRUSHWOOD

ABSTRACT The brushwood is a technique of environmental complexation, which consists in the use of plant residues. This technique, when well established technically, can exert influence on seedbed quality, fostering native plant establishment and ecosystem restoration. In this way, we aimed to evaluate the efficiency of brushwood for the induction of natural regeneration of native species in an area covered by exotic inhibitory grasses of the genus Urochloa, as well as check the minimum size required to prevent the re-invasion of the forage. As a hypothesis, we adopted the minimum width of 4 m as sufficient for the establishment of natural regeneration prior to the reoccupation of grasses. The experiment was conducted between May 2014 and May 2016 in Morretes-PR in a lowland evergreen rain forest area. Seven different sizes of brushwood were compared: 6 x 1, 6 x 2, 6 x 3, 6 x 4, 6 x 5, 6 x 6 m and control treatment. Woody species were identified and counted and herbaceous cover percentage estimated after 4, 8, 12, 18 and 24 months. There was no resumption of natural succession of native species. At any size, brushwood alone was ineffective to prevent the growth by grasses from the edges of the plots, and, since it constitutes a residue pile, it further complicates the establishment of woody species. For the creation of safe sites and consequent restoration by natural regeneration, there is a need for local elimination of Urochloa forages, without which native species are unlikely to survive.

English

The intercropping of annual crops with perennial grasses is a production system that is frequently adopted in the Midwest region of Brazil due to its economic viability resulting from the use of the same area for agriculture and livestock. Most agriculture-livestock integration studies have evaluated the use of forage of the genus Urochloa in intercropped systems with corn, sorghum and sunflower. Consequently, there is a lack of information regarding pearl millet cultivation when grown simultaneously with tropical forages. Thus, the objective of this study was to evaluate the agronomic characteristics of pearl millet Pennisetum glaucum (L.) R. Br as well as the production and nutritional characteristics of Paiaguas palisadegrass (Urochloa brizantha cv. Paiaguas) under different forage systems and sowing periods in the offseason. The experiment was conducted at the Federal Institute of Goias, Rio Verde campus. The experimental design was a randomized complete block with a 5 × 2 factorial arrangement and three replications. There were two sowing periods (February and March) and five forage systems: monocropped pearl millet; monocropped Paiaguas palisadegrass; pearl millet intercropped in rows with Paiaguas palisadegrass; pearl millet intercropped between rows of Paiaguas palisadegrass and pearl millet oversown and intercropped with Paiaguas palisadegrass. The results indicated that the Paiaguas palisadegrass did not affect the pearl millet grain yield, indicating that the intercropping of pearl millet and Paiaguas palisadegrass in the offseason is a promising cultivation technique for the production of grains during the offseason in Southeastern Goias. However, the second sowing period provided better grain yields and a higher number of sacks per hectare. With respect to forage yield, the Paiaguas palisadegrass sown in oversown pearl millet was impaired by the intercropping and produced low forage yield. With respect to forage quality, the intercropped sowing system did not affect the nutritional characteristics of the Paiaguas palisadegrass. Key words: Urochloa brizantha, agriculture-livestock integration, Pennisetum glaucum (L.) R. Br.

Microsatellite loci for Urochloa decumbens (Stapf) R.D. Webster and cross-amplification in other Urochloa species.

BackgroundForage grasses of the African genus Urochloa (syn. Brachiaria) are the basis of Brazilian beef production, and there is a strong demand for high quality, productive and adapted forage plants. Among the approximately 100 species of the genus Urochloa, Urochloa decumbens is one of the most important tropical forage grasses used for pastures due to several of its agronomic attributes. However, the level of understanding of these attributes and the tools with which to control them at the genetic level are limited, mainly due to the apomixis and ploidy level of this species. In this context, the present study aimed to identify and characterize molecular microsatellite markers of U. decumbens and to evaluate their cross-amplification in other Urochloa species.FindingsMicrosatellite loci were isolated from a previously constructed enriched library from one U. decumbens genotype. Specific primers were designed for one hundred thirteen loci, and ninety-three primer pairs successfully amplified microsatellite regions, yielding an average of 4.93 alleles per locus. The polymorphism information content (PIC) values of these loci ranged from 0.26 to 0.85 (average 0.68), and the associated discriminating power (DP) values ranged from 0.22 to 0.97 (average 0.77). Cross-amplification studies demonstrated the potential transferability of these microsatellites to four other Urochloa species. Structure analysis revealed the existence of three distinct groups, providing evidence in the allelic pool that U. decumbens is closely related to Urochloa ruziziensis and Urochloa brizantha. The genetic distance values determined using Jaccard’s coefficient ranged from 0.06 to 0.76.ConclusionsThe microsatellite markers identified in this study are the first set of molecular markers for U. decumbens species. Their availability will facilitate understanding the genetics of this and other Urochloa species and breeding them, and will be useful for germplasm characterization, linkage mapping and marker-assisted selection.Electronic supplementary materialThe online version of this article (doi:10.1186/s13104-016-1967-9) contains supplementary material, which is available to authorized users.

The Urochloa Foliar Blight and Collar Rot Pathogen Rhizoctonia solani AG-1 IA Emerged in South America Via a Host Shift from Rice.

The fungus Rhizoctonia solani anastomosis group (AG)-1 IA emerged in the early 1990s as an important pathogen causing foliar blight and collar rot on pastures of the genus Urochloa (signalgrass) in South America. We tested the hypothesis that this pathogen emerged following a host shift or jump as a result of geographical overlapping of host species. The genetic structure of host and regional populations of R. solani AG-1 IA infecting signalgrass, rice, and soybean in Colombia and Brazil was analyzed using nine microsatellite loci in 350 isolates to measure population differentiation and infer the pathogen reproductive system. Phylogeographical analyses based on the microsatellite loci and on three DNA sequence loci were used to infer historical migration patterns and test hypotheses about the origin of the current pathogen populations. Cross pathogenicity assays were conducted to measure the degree of host specialization in populations sampled from different hosts. The combined analyses indicate that the pathogen populations currently infecting Urochloa in Colombia and Brazil most likely originated from a population that originally infected rice. R. solani AG-1 IA populations infecting Urochloa exhibit a mixed reproductive system including both sexual reproduction and long-distance dispersal of adapted clones, most likely on infected seed. The pathogen population on Urochloa has a genetic structure consistent with a high evolutionary potential and showed evidence for host specialization.

Weed suppression in the formation of brachiarias under three sowing methods

The success of conservation systems such as no-till depends on adequate soil cover throughout the year, which is possible through the use of cover crops. For this purpose the species belonging to the genus Urochloa has stood out by virtue of its hardiness and tolerance to drought. Aiming ground cover for the no-till system, the objective was to evaluate the establishment of two species of the genus Urochloa, in three sowing methods, in the weed suppression and the sensitivity of these forages to glyphosate. The study design was a randomized block with a 2 x 3 x 3 factorial arrangement, in which factor A was composed of Urochloa ruziziensis and Urochloa hybrid CIAT 36087 cv. Mulato II, factor B was formed by sowing methods: sown without embedding, sown with light embedding and sown in rows, and factor C was composed of three doses of glyphosate (0.975, 1.625 and 2.275 kg ha-1 of acid equivalent). For determination of weed suppression, assessment of biomass yield and soil cover was performed, by brachiaria and weeds, at 30, 60, 90, 120 and 258 days after sowing. Visual assessment of the desiccation efficiency at 7 and 14 days after herbicide application was performed. It is concluded that embedding Urochloa seeds stands out in relation to sowing in the soil surface. Urochloa ruziziensis is more efficient in the dry weight yield, weed suppression, in addition to being more sensitive to glyphosate herbicide.

Efeito do alumínio sobre compostos nitrogenados em Urochloa spp.

Earth’s surface has, in its composition, around 7% of aluminum (Al), in the form of aluminum oxides or aluminosilicates, however, its availability is greatly dependent on soil pH. Cerrado is a biome presenting low pH soils and it has high amounts of Al+3 available; thus, plant production may become limited. Plants have mechanism to tolerate excessive amounts of Al+3 in soil; one of the mechanisms used for this purpose is the exudation of organic acids, wich are able to form complexes with Al+3, and, thus, it becomes unavailable to plants. Once available, Al+3 can affect nitrogen (N) metabolism, leading to production losses. Therefore, this study aimed to evaluate the effect of Al+3 on compounds related to N metabolism in 3 species from the genus Urochloa (U. brizantha, U. decumbens, and U. humiducola). The experimental design was completely randomized in a 2 x 3 factorial scheme (with and without Al+3 and 3 species of Urochloa); the dose of Al+3 applied was 200 µmol.L-1 in a solution with pH 4.5. Among the species evaluated, no changes were observed in compound content concentrations related to N metabolism as a response to Al+3, something which may suggest the existence of adaptation mechanisms that allow these plants to keep N metabolism unaltered even in face of a stressful situation.

Заметки о некоторых родах семейства злаков (Poaceae)

Critical notes on some genera of the family Poaceae Barnhart (Stipellula Röser et Hamasha, Panicum L., Catabrosa P. Beauv., Poa L.) are given. The genus Stipellula is treated here as monotypic, with the species S. capensis (Thunb.) Röser et Hamasha. The species Panicum maximum Jacq. (widespread in the tropics) takes an unclear posision in the genus Panicum. This species is sometimes included in the genus Urochloa P. Beauv. or treated as a monotypic genus Megathyrsus (Pilg.) B. K. Simon et S. W. L. Jacobs; we include the species in the genus Panicum subgenus Megathyrsus Pilg. We consider a small genus Catabrosa to be closer to the genus Poa than to Puccinellia Parl. Listed for Eurasia are 12 species of Catabrosa. New species Catabrosa kneuckeri Tzvelev (from North Europe), С. longissima Tzvelev (from the Caucasus), C. afghanica Tzvelev (from Afghanistan) and Poa boreorossica Tzvelev (from Leningrad Region) are described. New combinations Catabrosa minor (Bab.) Tzvelev and C. atrata (Tzvelev) Tzvelev are published.

Tolerance of <i>Urochloa brizantha</i> cv. MG5 to Mn Toxicity

Available information of the effects of manganese nutrition on the forage genus Urochloa is scarce. In the context, this study aims to evaluate the tolerance of Urochloa brizantha cv. MG5 to Mn toxicity. The experiment was conducted in a greenhouse at the University of the State of Sao Paulo (UNESP) in the city of Jaboticabal, SP. Plants were cultivated in vases (3.5 L) filled with soil according to a completely randomized experimental design comprising of five levels of Mn (0, 15, 30, 60 and 120 mg?dm?3) and four replications and cut in two periods: one is 42 days after sowing and the other is 30 days after the first one. Samples from both cuts were evaluated as to plant height, number of leaves and tillers, dry weight, Mn content and accumulation, and the green index was determined in the last cut. Manganese addition to soil caused an increase in chlorophyll content at the dosage of 68 mg?dm?3 observed in the second plant cut. Dosages of Mn above 15 mg?dm?3 did not induce increases in nutrient accumulation and in the number of leaves in the first and second cuts of the grass, and tillers in the first cut. The highest concentrations of manganese in the shoots did not produce visual symptoms of damage or a decrease in forage productivity demonstrating that Urochloa brizantha cv. MG5 has high tolerance to manganese toxicity.

Ornamentación del antecio superior en Urochloa y géneros vecinos (Poaceae, Panicoideae, Paniceae): su valor sistemático

Salariato, D.; O. Morrone & F. O. Zuloaga. 2008. Ornamentation pattern of the upper anthecium in Uroch- loa and related genera (Poaceae, Panicoideae, Paniceae): its systematic value. Darwiniana 46(2): 335-355. The ornamentation pattern of the upper anthecium in species of Paniceae belonging to the PCK group, in particular of the genus Urochloa, was analyzed. Nineteen different ornamentation patterns were recognized, of which 11 are reported for the first time. Several epidermal elements are described, including simple papillae, compound papillae and ridges in the anticlinal or periclinal cell walls. The ornamentation patterns were useful for infrageneric delimitation in the genus Urochloa but not to deli- mit the genus from related ones; on the contrary, this character provided more evidence to sustain the paraphyly of the genus. Systematic and phylogenetic value of this character in Urochloa and other rela- ted genera are also discussed.

A Revision of the Genus Panicum (Poaceae, Paniceae) in Belgium

Systematic research on the genus Panicum in the main Belgian public herbaria and some smaller private herbaria revealed a considerable number of new and other interesting data. Sixteen taxa have been recognized in the course of the present study: P. bulbosum*, P. capillare (incl. the subspecies capillare and barbipulvinatum*), P. chloroticum*, P. clandestinum, P. coloratum*, P. cf. decompositum*, P. dichotomiflorum (incl. the varieties dichotomiflorum and geniculatum), P. hillmanii*, P. hirticaule*, P. laevinode, P. miliaceum (incl. the subspecies miliaceum and ruderale*), P. schinzii and P. virgatum*. Several taxa (marked with * above) in part ancient and exclusive records of wool aliens originating in the Vesdre valley remained unidentified so far and are thus first mentioned for the Belgian adventitious flora. At present the following taxa are becoming more or less naturalized: P. capillare subsp. capillare, P. dichotomiflorum s.1. and P. schinzii (partially as noxious weeds in maize fields). Regularly introduced with cereals (incl. oil-seeds or commercial seeds) are P. chloroticum, P. dichotomiflorum s.1. and P. miliaceum subsp. miliaceum. Much rarer but fairly recent casuals are P. capillare subsp. barbipulvinatum, P. clandestinum, P. hillmanii, P. hirticaule and P. miliaceum subsp. ruderale. Misinterpretation within the genus led to numerous wrong identifications. P. compressum, P. flexile and P. repens need to be omitted from the Belgian adventitious flora lists. P. dichotomiflorum s.1. and P. schinzii have widely been confused; the majority of the P. dichotomiflorum collections actually belonged with P. schinzii. P. hillmanii and P. chloroticum are closely related and much confused with P. capillare and P. dichotomiflorum s.l. respectively. P. texanum is regarded as a member of the genus Urochloa, following recent nomenclatural insights. The present paper provides a dichotomous identification key for the genus Panicum in Belgium as well as additional chorological, taxonomic and nomenclatural remarks.