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Background: Brachiaria humidicola (Bh) has the ability to produce biological nitrification inhibitors (NIs) and release NIs from the root to the soil. Aims: To compare the effects of growing Bh with Brachiaria ruziziensis (Br, which is not able to produceNIs) on soil nitrogen (N) dynamics,Ngases and carbon dioxide (CO2) emissions and nitrifiers and denitrifiers following sheep urine application, a laboratory incubation was conducted in a He/O2 continuous flow denitrification system (DENIS). This incubation was conducted in the absence of light. Hence themeasured effects of Bh and Br on N cycling were the residual effect of biological NIs released into the soil prior to the incubation and released via root death. Methods: The treatmentswere: (1) Bhwith water application (Bh+W); (2) Bh with sheep urine (Bh + U); (3) Br with water application (Br + W); (4) Br with sheep urine (Br + U). Results: Results showed that soil NO3– concentration increased significantly in the soil with sheep urine application after the incubation. Soil nitrous oxide (N2O) and nitric oxide (NO) emissions increased immediately after the sheep urine application and peaked twice during the incubation. Cumulative emissions for the first peak were significantly lower from the Bh + U treatment (0.054 kg N ha–1) compared with the Br + U treatment (0.111 kg N ha–1), but no significant differences were observed in the total cumulative N2O and NO emissions between the Bh + U and Br + U treatment at the end of the incubation. Sheep urine addition did not affect the AOA, nirS and nosZ gene copies, but significantly increased the AOB gene copies after the incubation. Conclusions: We conclude that the residual effect of Bh to mitigate N2O emissions in a highly nitrifying soil is short-lived.

Made available in DSpace on 2021-06-25T10:58:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 BACKGROUND: Corn intercropped with ruzigrass is common in Brazil, and it can improve the physicochemical features of soils, increase water retention, and suppress the emergence of resistant weeds and soil nematodes. As both corn and ruzigrass are hosts to Spodoptera frugiperda (the main corn pest in South America), the cultivation of both these plants in the same place at one time motivates investigation into the pest population dynamics. We hypothesize that the intercropping system influences S. frugiperda pressure and leaf injury in corn. Considering that if corn hybrids with high dose toxin expression are used, ruzigrass may be a potential host to susceptible S. frugiperda larvae, consequently an alternative refuge and be included as a tool for the resistant management of Bt corn. To test these hypotheses about the use of ruzigrass as an alternative host of S. frugiperda in an intercropping system with corn, we conducted field trials in three seasons to verify S. frugiperda population dynamics and leaf injury to crop systems. In addition to phenotypic evaluation, we also characterized molecularly S. frugiperda strains collected in corn and ruzigrass to identify strain differences. RESULTS: The insects collected in both corn and ruzigrass were identified as corn strains. Ruzigrass was used as a S. frugiperda host during all crop cycles. The intercropped system did not increase the S. frugiperda population or leaf injury on Bt corn. CONCLUSION: The results suggest that the intercropped system is not prejudicial to Bt corn cultivation since high dose concept applies to all larvae instars. The results also suggest that ruzigrass may be used as a promising alternative refuge in Bt corn agroecosystems, if compliance with management strategies is followed. Department of Entomology Federal University of Grande Dourados (UFGD) Department of Biostatistics Institute of Biosciences–IBB São Paulo State University (UNESP) Department of Biostatistics Institute of Biosciences–IBB São Paulo State University (UNESP)

Background Great efforts have been made to identify grasses that are resistant to spittlebugs (Hemiptera: Cercopidae). However, the time required to develop and launch new cultivars is relatively long. The employment of resistance inducers is a current strategy that may be useful for the control of insect pests. This analysis evaluates the feasibility of using the chemical inducers silicon and nitric oxide to increase spittlebug resistance based on changes in forage grass vegetative characteristics and the biological traits of Mahanarva spectabilis (Distant, 1909). Results Mahanarva spectabilis nymphs and adults can cause significant damage to forage grasses. Furthermore, silicon and nitric oxide inducers were not sufficient to lessen this damage by positively influencing the growth and development of forage grasses. These inducers did not negatively alter the biological parameters of M. spectabilis or diminish its population. However, phenolic compound concentrations increased when forage grasses were treated with silicon or attacked by adult insects, but this parameter was not useful to predict spittlebug resistance. This fact suggests that the physiological and biochemical changes caused by silicon should be further studied. Conclusion The current analysis demonstrated that application of the chemical inducers silicon and nitric oxide is currently not a viable strategy for the effective and economic management of M. spectabilis on Brachiaria ruziziensis, Pennisetum purpureum and Digitaria sp. © 2019 Society of Chemical Industry.

Background Several factors may degrade pastures, in particular, inadequate nutrient application and spittlebug attacks. Mahanarva spectabilis (Distant, 1909) (Hemiptera: Cercopidae), one of the species that occur in Brazil, is a limiting pest in forage production. This study analyzes the influence of fertilization with the macronutrients nitrogen, phosphorus and potassium (NPK) on the survival of M. spectabilis nymphs, and the effects of damage by nymphs and adults on the production, quality and regrowth capacity of the forages Brachiaria ruziziensis, Pennisetum purpureum and Digitaria sp. Results Fertilization of the forages differentially affected damage due to spittlebug herbivory. Attacks by nymphs and adults decreased chlorophyll content, plant regrowth and forage quality, and increased injury, regardless of fertilization. The availability of nutrients in the soil not only decreased fiber content, but also increased crude protein, chlorophyll content and regrowth, even when pest infested. Soil fertilization increased the capacity of forage plants to lessen, albeit not eliminate, the effects of injury by M. spectabilis. Conclusion Forages in fertilized soil are more tolerant to attacks by M. spectabilis nymphs and adults. © 2019 Society of Chemical Industry.

The edible Ruspolia differens (Orthoptera: Tettigoniidae) is a widely-consumed insect in East Africa but surprisingly little is known of its host plant use in the field. We studied host plants used by non-swarming R. differens for 15 months, in central Uganda. In particular, we assessed the use of host plant species with respect to host cover in the field and host parts used by R. differens, also recording their sex, developmental stages, and colour morph. Ruspolia differens were found on 19 grass and two sedge species and they were observed predominantly (99% of 20,915 observations) on seven grasses (namely, Panicum maximum, Brachiaria ruziziensis, Chloris gayana, Hyparrhenia rufa, Cynodon dactylon, Sporobolus pyramidalis, and Pennisetum purpureum). Ruspolia differens was most frequently observed on the most common grass of each study site but P. maximum, and S. pyramidalis were used more frequently than expected from their cover in the field. Furthermore, R. differens were observed predominantly on inflorescences (97% of feeding observations) and much less frequently on the leaves (3.0%), stems (0.1%), and inflorescence stalks (0.1%) of grasses and sedges. Host use was not independent of sex, developmental stage, or colour morph. Panicum maximum was the preferred host of the youngest nymphs of R. differens. Overall, our findings indicate that a continuous supply of diverse grass resources with inflorescences is necessary for the management and conservation of wild populations of R. differens.

Chiselling has been used to alleviate soil compaction but cover crops with deep, vigorous roots can improve root growth and activity of the cash crop for a longer time. The determination of root activity in addition to root mass or length may improve the understanding of plant response to compaction. The objective of this experiment was to evaluate root growth and activity as affected by the alleviation of soil compaction using mechanical and biological methods. The experiment was conducted in Botucatu, Sao Paulo, Brazil, from 2009 to 2011, on a clay, Typic Rhodudalf soil. Crop rotations including pear millet (Pennisetum glaucum), soybean (Glycine max), grain sorghum (Sorghum bicolor), maize (Zea mays), ruzi grass (Brachiaria ruziziensis) and castor bean (Ricinus communis) in plots, either chiselled or not. Root growth was assessed by core sampling and root activity was determined indirectly using rubidium injected at several depths as a marker. Root activity was instrumental in interpreting the effects of tillage and crop rotations on soil amelioration. Compared with the initial compacted condition, chiselling increased root growth and activity just for the first 18 months of the experiment, but crop rotations, mainly including ruzi grass and castor bean, increased root growth and activity in the soil profile from the second year on. Generally, root mass was poorly correlated with root activity, except in the case of ruzi grass. Introduction of ruzi grass plus castor bean into the cropping system improves not only root growth and activity in the soil profile but also soybean yield.

The autotetraploid forage Congo signal grass (Brachiaria ruziziensis) is an important component in the Brachiaria breeding programme. As with other tropical forage grass species, the association between flowering and seed yield components, the mode of inheritance and the effects of population structure on phenotypic breeding are lacking. Seventeen characteristics evaluated in 59 half-sib progeny of seven subpopulations were analysed using a mixed model methodology. According to the commonality analysis, the total seed yield (0.67) and number of days to flowering (0.22) had a greater influence on the filled-seed yield. The flowering synchrony, total number of panicles, filled-seed yield, green matter yield and dry matter yield presented statistically significant additive genetic variance between and within the subpopulations. The QST estimates ranged from 0.09 for the flowering synchrony index to 0.31 for the filled-seed yield. The effects of population structure and its use in breeding programmes are further discussed.

ruzigrass ( Urochloa ruziziensis (r. Germain & Evrard) Crins, syn. Brachiaria ruziziensis Germain & Evrard) is a tropical forage native to Africa, first introduced in Brazil in the 1960s. r uzigrass is diploid, presents sexual reproduction, and is a model species for the generation of genomic resources in the Brachiaria genus. Brachiaria species are the most important livestock forage in the tropics, covering more than 70 million ha in Brazil alone. We have used multiplex panels of microsatellite markers to characterize the genetic diversity of ruzigrass germplasm collected in Africa, and of a local population collected in Bra - zil, to obtain information for its conservation and use in breeding programs. Fifteen SS - ers were used to Genotype 114 ruzigrass sam ples. Summary statistics, as well as estimates of F ST and partitioning of genetic diversity were obtained. Clustering and genetic structure analy - ses were performed. r esults showed high val- ues of heterozygosity in the African and Brazilian populations. Although African and Brazilian sam - ples formed distinct groups in clustering analy - ses, and Bayesian analysis of genetic structure distributed samples into three clusters, estimates of pairwise F ST values showed no differentiation between African and Brazilian groups of sam - ples. results indicated that the introduction of ruzigrass in Brazil did not cause a major decrease in genetic diversity. Brazilian local populations might harbor favorable alleles that will be useful for ongoing and future breeding programs. They offer great opportunities for ruzigrass germplasm collection and conservation of genetic diversity, before attempts to access germplasm in its cen - ter of diversity are undertaken. M. Pessoa-Filho, Embrapa Cerrados, P.O. Box 08223, Brasilia, DF, Brazil 73310-970; A.L.S. Azevedo, F.S. Sobrinho, Embrapa Dairy Cattle, Rua Eugenio do Nascimento, 610, Juiz de Fora, MG, Bra

Soil waterlogging is a major abiotic stress that affects the growth and yield of forage grasses in the tropics. Brachiaria forage grasses are widely planted in the tropics to sustain livestock production. An outdoor study was conducted using plastic cylinders under drained and waterlogged soil conditions in order to identify root and shoot traits associated with waterlogging tolerance in Brachiaria ruziziensis (waterlogging sensitive) and Brachiaria humidicola (waterlogging tolerant). For that reason, dry mass, leaf chlorophyll content, photosynthetic efficiency, root morpho-anatomical traits (aerenchyma, stele proportion, suberin deposition) and total non-enzymatic antioxidant activity in leaf tissue were determined. Under waterlogging, reductions of shoot biomass, chlorophyll loss, impairment of photosynthetic efficiency and diminution of antioxidant system were found in B. ruziziensis but not in B. humidicola. In B. humidicola an increase of the antioxidant system in response to waterlogging was found. Under waterlogging, both grasses showed an increase in root aerenchyma, reduction of root stele proportion and shorter roots than plants grown under drained conditions. We conclude that a combination of greater aerenchyma formation, smaller stele proportions, increased suberin deposition in the outer part of the root and an escalation of the non-enzymatic antioxidant system acts to enhance root aeration and prevent the deleterious effect of reactive oxygen species in plants of B. humidicola subjected to waterlogged conditions.

Ruzigrass (Brachiaria ruziziensis Germain et Everard cv. Kennedy) is an important forage grass in tropical and sub-tropical areas. Previously, we reported transgenic ruzigrass plants generated by our transformation system were sterile and tetraploid in spite of beginning with diploid plants. This study analyzed ploidy variation in embryogenic calli and the regenerants of diploid ruzigrass. The morphological traits and fertility were also investigated to develop a methodology for the production of stable transgenic lines. Embryogenic calli at different stages (2, 4, 6 and 12-month-old) were regenerated via somatic embryogenesis. An approach of flow cytometry (FCM) analysis was used to determine the ploidy level of embryogenic calli and regenerants of ruzigrass. FCM analysis revealed that embryogenic calli were spontaneously reduplicated at a high frequency and resulting regenerants were polyploids (tetraploid or octoploid), including 15 tetraploid regenerants (68%) and seven octoploid regenerants (32%) derived from 12-month-old embryogenic calli. These regenerants exhibited the morphological variations among different ploidy levels. The viability of pollen grains was significantly (P < 0.01) decreased in tetraploid and octoploid regenerants. Our findings indicated that clarification and resolution of ploidy variation in ruzigrass combined with ploidy level checking using FCM analysis before transformation steps is crucial for plant regeneration in transformed ruzigrass.

Tetraploid plants of ruzigrass (Brachiaria ruziziensis) have been obtained by colchicine treatment of in vitro multiple-shoot clumps and germinated seedlings. Multiple-shoot clumps were induced and maintained on MS basal medium with 0.5 mg L−1 2,4-dichlorophenoxyacetic acid (2,4-D) and 2.0 mg L−1 6-benzylaminopurine (BAP) according to a previous report. The colchicine treatment consisted of culturing multiple-shoot clumps on MS basal medium containing 0.0125–0.1% colchicine for 12 and 48 h. Surviving multiple-shoot clumps were regenerated on MS basal medium containing 2.0 mg L−1 BAP. The ploidy level of plants after colchicine treatment was determined by flow cytometry. Eight tetraploid plants were obtained from multiple-shoot clumps treated with 0.1% colchicine for 12 h. This treatment was identified as the optimum treatment and resulted in the highest frequency (28.6%) of tetraploid plants among the treatments tested on multiple-shoot clumps. Five tetraploid plants (31.3%) were obtained when seedlings were treated with 0.1% colchicine for 3 h. Although higher concentrations of colchicine and longer durations of colchicine treatment reduced the survival rate of the explants, such treatments increased the frequency of tetraploid plants. A total of 23 tetraploid plants were obtained from 900 different colchicine-treated multiple-shoot clumps, and a total of five tetraploid plants were obtained from 300 colchicine-treated seedlings. Cytological analysis affirmed the results of flow cytometry. Significant differences in leaf blade stomata were observed between diploid and tetraploid ruzigrass.

We have established a plant regeneration system via multiple shoot formation, or somatic embryogenesis from seed-derived shoot apical meristems of ruzigrass (Brachiaria ruziziensis). Shoot apices as initial explants were isolated from aseptically germinated seedlings, and cultured in vitro. The most effective treatments for multiple shoots and embryogenic calli formation were 0.5 mg L−1 2,4-dichlorophnoxyacetic acid (2,4-D) plus 2.0 mg L−1 6-benzylaminopurine (BAP) and 4.0 mg L−1 2,4-D plus 0.2 mg L−1 BAP, respectively. Plant regeneration from multiple shoot-clumps was achieved by culturing on solid MS medium containing 1.0 mg L−1 BAP or 2.0 mg L−1 kinetin plus 2.0 mg L−1 gibberellic acid. Somatic embryos regenerated plantlets on a MS medium without plant hormones. Regenerated shoots were germinated precociously on MS medium containing 0.01 or 0.1 mg L−1 naphthalene acetic acid and 2.0 mg L−1 BAP. All regenerants were successfully grown up to maturity. The plant regeneration via multiple-shoot clumps and embryogenic calli formation can be used as an alternative regenerable target tissue for genetic transformation using particle bombardment of ruzigrass.

Aluminum-resistant Brachiaria decumbens Stapf cv. Basilisk (signalgrass) and closely related, but less resistant Brachiaria ruziziensis Germain & Evrard cv. Common (ruzigrass) both accumulated high concentrations of aluminum (Al) in roots. Approximately two thirds of the total Al was complexed by soluble low-molecular-weight ligands, suggesting that it had been taken up into the symplasm. We therefore investigated whether these species might employ Al-chelating organic acids for internal detoxification of Al taken up by root apices, the primary site of Al injury. Unlike root apices of other Al-resistant plant genotypes, which secrete organic-acid anions to detoxify Al externally, apices of Brachiaria species accumulated organic acids within the tissue. A comparison with whole roots showed that this preference for accumulation (as opposed to secretion) was restricted to apices. Citric acid, and to a lesser extent trans-aconitic acid, accumulated in a uniform dose-dependent manner in root apices of both species as their Al content increased under Al-toxic growth conditions. Their accumulation was accompanied by a stimulation of malate synthesis in Al-resistant B. decumbens, while it occurred at the expense of malate in Al-sensitive B. ruziziensis. These data suggest a role of organic acids in the internal detoxification of Al in root apices of both Brachiaria species, presumably contributing to their comparatively high basal level of Al resistance. Yet internal detoxification of Al by organic acids does not appear to be the principal mechanism responsible for the superior resistance of B. decumbens. Aluminium-Stress stimuliert die Anreicherung von organischen Sauren in Wurzelspitzen von Brachiaria-Arten Sowohl das Aluminium-resistente Gras Brachiaria decumbens Stapf cv. Basilisk als auch das nah verwandte, aber weniger resistente Gras Brachiaria ruziziensis Germain & Evrard cv. Common akkumulierten hohe Aluminiumkonzentrationen in den Wurzeln. Etwa zwei Drittel des gesamten Aluminiums (Al) waren durch niedermolekulare Liganden komplexiert, was darauf hinweist, dass es im Symplasten lokalisiert war. Aus diesem Grund untersuchten wir, ob diese Pflanzenarten Al-komplexierende organische Sauren zur internen Entgiftung von Al in Wurzelspitzen (das gegenuber Al empfindlichste Organ) nutzen. Im Gegensatz zu Wurzelspitzen anderer Al-resistenter Pflanzengenotypen, die organische Saureanionen zur externen Al-Entgiftung sekretieren, reicherten beide Brachiaria-Arten organische Sauren im Wurzelspitzengewebe an. Ein Vergleich mit ganzen Wurzeln zeigte, dass diese Tendenz zur Akkumulation (im Gegensatz zur Sekretion) auf die Wurzelspitzen beschrankt war. Citrat, und in geringerem Ausmas trans-Akonitat, reicherten sich in Wurzelspitzen beider Arten mit steigendem Al-Gehalten bei Al-Angebot an. Ihre Akkumulation war in B. decumbens von einer Stimulation der Synthese von Malat begleitet, wahrend sie in B. ruziziensis auf Kosten von Malat erfolgte. Diese Ergebnisse deuten auf eine Beteiligung organischer Sauren an der internen Entgiftung von Al in Wurzelspitzen beider Brachiaria-Arten hin, was wahrscheinlich zu deren relativ hohem Resistenzniveau beitragt. Eine interne Entgiftung von Al durch organische Sauren scheint jedoch nicht der hauptsachliche Mechanismus zu sein, der fur die hohere Resistenz von B. decumbens im Vergleich zu B. ruziziensis verantwortlich ist.

Summary 1. Predictions from the Phylogenetic Constraints Hypothesis were tested for the first time in a tropical system using the pasture pest Deois flavopicta Stal, which oviposits into the ground and not into plant tissues. The prediction that there is no oviposition preference–larval performance linkage was supported. The absence of such a link provides an evolutionary basis for eruptive population dynamics. 2. The effects of host species and host plant quality on the preference of ovipositing females of D. flavopicta and performance of their offspring on the selected host plants were tested at the population level. 3. Female oviposition behaviour was affected by the presence of the host plant. Females of D. flavopicta showed a strong preference to oviposit close to host plants. The number of eggs was higher in pots containing Brachiaria ruziziensis (121.88 ± 13.70) than in pots containing only the wet oviposition substrate (5.2 ± 1.98) or dry oviposition substrate (0.067 ± 0.067). Ovipositing females did not, however, discriminate between plants of Brachiaria decumbens and Axonopus marginatus and did not show a strong oviposition preference in relation to differences in plant quality (protein and fibre content). They did show oviposition preference for plants under the high watering regime. The mean number of eggs collected from pots with non water-stressed plants was 60% higher than the mean number of eggs collected on pots with water-stressed plants. 4. Although females did not show ovipositional preference, spittlebug larval performance, measured as percentage survival and duration of nymphal period, was better on plants of high protein and low fibre content. These results indicate that there is not a linkage between female oviposition preference and subsequent nymphal performance in relation to differences in protein and fibre content in the host plants. There was, however, a limited linkage between oviposition preference and nymphal performance in relation to plant water content. Females showed preference for moist sites that have high survival of newly hatched nymphs. 5. Evidence indicates that for D. flavopicta, the influences of natality and female oviposition behaviour in response to plant quality are not the major factors driving population outbreaks, which is in accordance with the Phylogenetic Constraints Hypothesis.

The development of irrigated pastures in the Sudan is still at its infancy. The present study determined the influence of 2 cutting heights (2.5 and 5.0 cm) and 4 cutting frequencies (4-, 6-, 8-, and 10-week) on forage yield as dry matter and forage sucrose of Rhodes grass (Chloris gayana Kunth. cv. Massaba) and Ruzi grass (Brachiaria ruziziensis Germain et Everard cv. Congo Signal) under irrigated conditions. Forage yield interactions involving species X cutting height X cutting frequency were significant. These yield interactions were attributed to differences in growth period and growth rhythm of the two species. On average, Rhodes exhibited a short growth period (13 months) compared to Ruzi grass (20 months). Forage yield and forage sucrose were, on average, superior in Ruzi compared to Rhodes grass. Forage yield and forage sucrose averaged 5.2 t ha−1 and 7.2 % fw sucrose in Ruzi compared to 2.8 t ha−1 and 6.9 % fw sucrose in Rhodes grass. Forage yield and forage sucrose of both species were negatively correlated with cutting frequency. The highest forage yield may be obtained at an 8-week cutting frequency in Rhodes (45.6 t ha−1 yr−1) compared to a 10-week cutting frequency in Ruzi grass (88 t ha−1 yr−1). Results suggest that very high forage yields as dry matter and forage sucrose of Rhodes and Ruzi grass may be possible under irrigated conditions in the Sudan at a cutting frequency of between 8 to 10 weeks.

A pomixis-asexual reproduciton through seed-provides a convenient means to faithfully propagate even heterozygous genotypes and hence exploit heterosis, in several naturally apomictic, warm-season forage grasses. Inheritance of apomixis has been shown to be monogenic dominant in at least four economically important panacoid grasses. Previously proposed breeding schemes for apomicts do not provide a means to accumulate genes contributing to nonadditive, heterotic effects over cycles of selection and recombination. Following the development of successful brachiariagrass [Brachiaria (Trin.) Griseb] cultivars by ecotype selection, artificial hybridization of brachiariagrasses began in the late 1980s with the development of a sexual tetraploidized biotype of the natural diploid, sexual ruzigrass (Brachiaria ruziziensis Germain and Evrard). A breeding scheme-recurrent selection for specific combining ability-designed to accumulate nonadditive effects, originally proposed for sexual maize (Zea mays L.), is suggested as an appropriate scheme for improvement of apomictic tropical grasses. Recurrent selection on specific combining ability or interpopulation selection schemes such as as reciprocal recurent selection should be appropriate for other asexually propagated crops.

Brachiaria ruziziensis is a sexual diploid tropical grass species of wide adaptation and good forage quality. Pachytene chromosomes were studied in morphological detail and all nine chromosomes were identified by their length, centromere position, and size and distribution of chromomeres. The idiogram prepared for the first time in this species consists of four median and five submedian chromosomes.

The importance of incorporating compatible legumes into tropical grasslands has been highlighted by many researchers. Thus an experiment was conducted to identify optimum times of establishing tropical grasses and legumes in mixtures. The species selected were Guinea grass (Panicum maximum); Brachiaria (Brachiaria ruziziensis) and Green leaf (Desmodium intortum). The grasses were established along with and 4 and 8 weeks after the legume. The growth of the species was monitored for 16 weeks. The results identified the importance of prior establishment of the legume to overcome the competitive dominance of the herbage grasses. The growth form of the grasses also had an effect on the success of legume establishment. The legume had no adverse effect on the growth of the grasses.