Signal Grass Research Articles

Cover crop residues decomposition, nutrient cycling and doses of mineral fertilizer in irrigated broccoli production

Abstract: The decomposition of plant residues and release of nutrients in irrigated areas cultivated with vegetables occur at a more accelerated rate. This situation can be managed to improve the efficiency of mineral fertilizers in vegetable crops. Thus, the main objective of this study was to evaluate the effects of residue decomposition and macro and micronutrients cycling of four cover crops in an irrigated broccoli production area. The experiment was conducted in factorial scheme 4x3, being four cover crops (Signal grass (SG), Pearl millet (PM), Sunn hemp (SH), PM+SH), and three mineral fertilizer doses (0, 50 and 100% of the recommended fertilizer dose: 400 kg ha -1 of P 2 O 5 , 100 kg ha -1 of K 2 O, 150 kg ha -1 of N), arranged in randomized block design with parcels of 40 m 2 (4x10 m), and four repetitions. Fresh and dry biomass, residue decomposition and nutrient cycling of cover crops, and the number of leaves, stem diameter, head height, diameter, fresh and dry biomass, and productivity of broccoli were evaluated. The greatest dry biomass of cover crops was observed when Poaceae plant species were present, particularly SG. The lowest rate of decomposition and the greatest half-life time of residues occurred where PM was present. The residue decomposition and nutrient cycling were at least three times faster in irrigated areas. The accumulation and nutrient cycling follow the sequence K>N>Ca>Mg>P>S, and Mn>Zn>B>Cu in all cover crop treatments evaluated. The greatest broccoli production was observed in the 100% mineral fertilizer dose and SH or PM+SH preceding broccoli crop farming. Keywords: Brassica oleracea var. italica ; Crotalaria juncea ; Urochloa brizantha cv marandu ; Pennisetum glaucum ; NPK

THE EFFECT OF TIME OF INITIAL CUTTING ON FORAGE YIELD AND QUALITY OF THREE PASTURE GRASSES AT SHIKA, NIGERIA

The effect of time of cutting on yield and nutritive value of three year old pastures of signal (Brachiaria decumbens), green panic (Panicum maximum var. trichoglume) and buffel (Cenchrus ciliaris ev. Gayndah) grasses were studied. The pastures were harvested for hay yield on 5th November, 1977 and allowed to rest until subjection to initial cut in June, July, August or September, 1978. Immediately after the July cut, all the plots received 100kg N/ha and 40kg P205/ha. Regrowths from the initial cuts and the control (uninterrupted growth) were all cut on 16th November, 1978. The dry matter (DM) yields of the grasses increased with increasing stage of maturity. Signal grass was more productive (P < 0.05) (17.3t/ha) than the other grasses averaged over the cutting dates. The yields of green panic and buffel grasses were 8.3 and 11.0t/ha respectively. The regrowth DM yields declined with a delay in the initial cut. Except for the increases in CP (6.9%) and IVDMD (50.1%) contents of the primary growth in August, these parameters declined as the grasses aged. Deferring the initial cutting date resulted in significant (P < 0.05) increases in CP and IVDMD contents of the regrowths. Percent increases as a result of cutting at the different date over the control for DM and CP yield were 28 and 74, respectively. Further evaluation of the three species in grazing trial is suggested.

Nutrient cycling of different plant residues and fertilizer doses in broccoli cultivation

ABSTRACT The decomposition and release of nutrients from plant residues that precede the cultivation of vegetables can positively affect the morphological parameters and crop productivity. The objective of this study was to evaluate the effects of plant residue decomposition and the cycling of macro and micronutrients of four cover crops preceding the broccoli production (single head Avenger hybrid). A 4x3 factorial scheme was implemented including four cover crops: signal grass (SG), pearl millet (PM), sunn hemp (SH), mixture PM+SH; and three doses of mineral fertilizer: 0, 50 (200 kg ha-1 of P2O5, 50 kg ha-1 of K2O, 75 kg ha-1 of N) and 100% of the recommended fertilizer dose (400 kg ha-1 of P2O5, 100 kg ha-1 of K2O and 150 kg ha-1 of N). Fresh (FB) and dry biomass (DB), residue decomposition, nutrient cycling of cover crops, the number of leaves, head height (HH), stem diameter (SD), head diameter (HD), head fresh-biomass (FB), head dry biomass (DB) and broccoli yield were evaluated. The FB production from PM (25.9 t ha-1), SG (23.3 t ha-1) and mixture PM+SH (23.9 t ha-1) were similar, while the largest production of DB occurred in the SG (11.9 t ha-1). The lowest rate of decomposition and the greatest half-life time of residues occurred where PM was present. The accumulation and nutrient cycling follow the sequence K>N>Ca>Mg>P>S and Mn>Zn>B>Cu for all cover crop treatments evaluated. The highest SD (51.95; 51.44 and 50.67 mm), HD (187.97; 187.41 and 183.48 mm), FB (1.01; 1.00 and 0.97 kg), DB (0.08; 0.07 and 0.07 kg) and broccoli yield (25.3; 24.9 and 24.7 t ha-1) was observed in the 100% dose of mineral fertilizer and on the residues of SH or PM+SH mixture, respectively.

Efeito da suplementação de proteína na produção e na composição do leite de F1 vacas Holandês x Zebu mantidas em pasto diferido de capim-braquiária

ABSTRACT The objective of this study was to evaluate different supplementation strategies concentrated to F1 Holstein x Zebu lactating cows managed in deferred signal grass pasture on the yield and composition of milk and body weight gain. Thirty six F1 Holstein x Zebu cows with an average lactation period of 267 ± 10 days, mean body weight of 548 ± 19kg were used following a completely randomized design in a 4 x 5 factorial scheme, being four feeding strategies and five days under evaluation. The treatments consisted of four nutritional strategies: deferred pasture as a source of roughage without supplementation (PDSS); deferred pasture as a source of roughage with protein supplement offer (PDCS); deferred pasture supplemented with 15 kilos of corn silage (natural base) + 1,200 grams of protein supplement (PDSP) and corn silage (ad libitum) + 700 grams of protein supplement (SMP). There was no interaction (P> 0.05) between the nutritional plans and days under evaluation for any of the variables. It was found that cows fed SMP showed milk production 26.06% higher than the other nutritional plans (mean of 11.46kg/day). F1 Holstein/Zebu cows handled in deferred pasture in a traditional way supplemented with protein maintains milk yield.

Potential of two cover crops, signal grass and ruzi grass: suggested allelopathic effect on some important weeds

There is evidence that signal (SG) and ruzi (RG) grass have an allelopathic effect on weeds. This study aim to evaluate this effects on difficult-to-control weeds: hairy beggarticks (HB), benghal dayflower (BD), horseweed (H), sourgrass (S) and tall windmill grass (TWG). The first experiment was installed in a completely randomized design with 2 donor species (SG and RG) × 4 extract concentrations (0, 75, 150 and 225 mg ml−1) in factorial scheme with four replicates. Weed germination percentage was evaluated in three-day intervals. In the second experiment, the weeds emerged in substrates previously cultivated with SG and RG, in completely randomised block design with four replicates. The emergence, shoot growth and root growth were evaluated. The results were as follows: (i) on horseweed (H), 84% germination inhibition by RG leaf extracts and 38% emergence inhibition by SG root exudates were observed; (ii) on benghal dayflower (BD), 84% germination inhibition by RG leaf extracts and 37% emergence inhibition and 4.3 times the SRL values than control by RG root exudates; (iii) on hairy beggarticks (HB) 52% germination inhibition by RG leaf extracts scored, while SG root exudates reduced 43% of the emergence, 24% shoots biomass accumulation and 11.3% root length; (iv) on sourgrass (S) 71% germination inhibition by both donor plants and 75% germination inhibition by RG leaf extracts were measured. Finally, on tall windmill grass (TWG) 69% germination inhibition was observed upon using both donor plants. It can be concluded that foliar allelochemicals inhibit the germination of: BD > S > TWG > H > HB, while root exudate allelochemicals, inhibit the emergence and root development of all weeds

Ingestive behavior and infrared thermography of Holstein × Zebu crossbreed cows in the final third of gestation in different pastoral environments

This study aimed to evaluate the ingestive behavior and body surface temperature of F1 Holstein × Zebu cows that were non-lactating in the final third of gestation and managed in two pastoral environments. Forty F1 Holstein × Zebu cows divided into two pastoral environments were evaluated: signal grass (Urochloadecumbens cv. Basilisk) deferred at the beginning of regrowth and pasture of xaraés grass (Urochloa brizantha cv. Xaraés) in vegetative growth in four periods during the day (morning, afternoon, night and dawn), following the completely randomized design in a factorial scheme. Each cow is the experimental unit. The total grazing time was 32.22% higher in the signal grass than xaraés grass (average of 479.50 minutes). There was an interaction between the pastoral environments and the periods on the black globe temperature and humidity index (BGHI). In the pasture of signal grass, the BGHI was 19.07% higher in the morning and afternoon periods than the average (68.95) verified during the night and dawn. F1 Holstein × Zebu cows grazing time in the final third of gestation is influenced by the pasture condition and not by the climate since they feed in a high BGHI environment.

Assessing the nutritional status of Bunaji bulls fattened on varying inclusions of groundnut haulms and maize offal using some blood metabolites

An experiment was conducted to evaluate the effect of inclusion levels of groundnut haulms (GH) and maize offal (MO) on some blood metabolites from twenty Bunaji bulls. The bulls were divided into four groups in a completely randomized design. They were fed signal grass (Brachiaria decumbens) hay ad libitum and concentrate diets containing groundnut haulms (GH) and maize offal (MO): 80:20% GH: MO, 60:40% GH: MO, 40:60% GH: MO and 20:80% GH: MO, respectively. The animals were fed the diets over a period of 90 days and their nutritional status ascertained from the serum metabolic profile.

Stimulation action of mefenpyr-diethyl on soybean, wheat, and signal grass plants

Mefenpyr-diethyl is a safener used for protection of cereal plants under applications of ACCase and ALS inhibitor herbicides. Current studies are describing safeners using a new approach, relating these products to stimulation action on plants. The objective of this work was to evaluate the stimulation action of mefenpyr-diethyl on soybean, wheat, and signal grass plants. The experiment was conducted in a greenhouse, under a completely randomized design, with four replications, in two seasons. Mefenpyr-diethyl (50 g a.i. ha−1) was applied on soybean plants (at V4 stage), and wheat and signal grass plants (both with 15 cm height). The variables evaluated were plant height, dry matter, and lipid content of the three species, and number of tillers of wheat and signal grass plants. The application of mefenpyr-diethyl in the first season increased the number of tillers of wheat and height of soybean plants. The soybean presented 24 and 14% more dry matter than the control in the first and second season, respectively, and 0.5% more lipid content in plants treated with mefenpyr-diethyl. These results show the stimulation action of mefenpyr-diethyl on wheat and soybean plants, denoting its potential for growth promotion and indicating the need for studies with this approach. No effect was found for the signal grass plants.

Growth and Yield Response of Signal Grass (Brachiaria decumbens Stapf) Applied with Different Rates of Nitrogen Fertilizer

Application of fertilizers is essential to sustain the yield of forage crops, hence, this study was conducted to: 1) evaluate the effect of different nitrogen fertilization rates on the growth and yield of signal grass and 2) determine the appropriate nitrogen fertilization rate for optimum production of signal grass. It was laid out in a Randomized Complete Block Design (RCBD) with three replications and five treatments (T0 – Unfertilized, T1 – 30 kg N ha-1; T2 – 60 kg N ha-1; T3 – 90 kg N ha-1 and T4 – 120 kg N ha-1). The plant height, number of tillers hill-1, fresh herbage yield and dry matter yield of signal grass were significantly affected by the different rates of nitrogen fertilizer. Increasing the levels of N fertilization correspondingly improved its overall performance with plants applied with 120 kg N ha-1 having the tallest, most number of tillers and heaviest fresh herbage and dry matter yields among fertilized plants. However, the appropriate fertilization rate for optimum production was 90 kg N ha-1 as the aforementioned parameters were comparable to that of the higher rate yet of lower amount of N fertilizer needed resulting in lower production cost and higher income.

5 Animal performance in grass monoculture or silvopasture systems using tree legumes

Abstract Silvopasture systems (SPS) area management option to enhance delivery of ecosystem services and diversification of income. This study evaluated productive responses of signalgrass (Urochloadecumbens Stapf.) in monoculture or in SPS in the sub-humid tropical region of Brazil during six months of the rainy season. The experimental design was randomized complete block with three replications. Treatments were signalgrass + Mimosa caesalpiniifolia Benth. (SPS-Mimosa); signalgrass + Gliricidia sepium (Jacq.) (SPS-Gliricidia); and signalgrass monoculture. Cattle were managed under continuous stocking with variable stocking rate. Response variables included herbage mass (HM), herbage accumulation (HA), stocking rate (SR), average daily gain (ADG), and gain per area (GPA). Herbage mass (HM) was greater (P < 0.0001) on signal grass monoculture (2045 kg DM/ha) than in SPS (1370 kg DM/ha, average for both SPS). Herbage accumulation rate was similar for signalgrass in monoculture and SPS-Gliricidia (avg. 61 kg DM ha-1 d-1), and both were greater than SPS-Mimosa (37 kg DM ha-1 d-1). Average daily gain was greater(P < 0.0001) for SPS-Gliricidia (1.1 kg head-1 d-1), followed by signalgrass in monoculture (0.9 kg head-1 d-1), and SPS-Mimosa (0.3 kg head-1 d-1). Stocking rate ranged from 0.6 animal units (1AU = 450-kg animal) per ha in April to 2.2 AUha-1 in June. Stocking rate and animal performance per area were similar for signalgrass in monoculture and SPS-Gliricidia, and both greater than SPS-Mimosa. Gliricidia enhanced animal performance and provided ecosystem services. Mimosa, however, reduced animal performance likely due to the competition with signalgrass. Mimosa trees, however, are an important source of income (timber used for fence posts) and that might overcome the losses in animal performance.

6 Animal performance in grass monoculture or silvopasture systems using tree legumes

Abstract Silvopasture systems (SPS) area management option to enhance delivery of ecosystem services and diversification of income. This study evaluated productive responses of signalgrass (UrochloadecumbensStapf.) in monoculture or in SPS in the sub-humid tropical region of Brazil during six months of the rainy season. The experimental design was randomized complete block with three replications. Treatments were signalgrass + Mimosa caesalpiniifolia Benth. (SPS-Mimosa); signalgrass + Gliricidia sepium (Jacq.) (SPS-Gliricidia); and signalgrass monoculture. Cattle were managed under continuous stocking with variable stocking rate. Response variables included herbage mass (HM), herbage accumulation (HA), stocking rate (SR), average daily gain (ADG), and gain per area (GPA). Herbage mass (HM) was greater (P < 0.0001) on signal grass monoculture (2045 kg DM/ha) than in SPS (1370 kg DM/ha, average for both SPS). Herbage accumulation rate was similar for signalgrass in monoculture and SPS-Gliricidia (avg. 61 kg DM ha-1 d-1), and both were greater than SPS-Mimosa (37 kg DM ha-1 d-1). Average daily gain was greater(P < 0.0001) for SPS-Gliricidia (1.1 kg head-1 d-1), followed by signalgrass in monoculture (0.9 kg head-1 d-1), and SPS-Mimosa (0.3 kg head-1 d-1). Stocking rate ranged from 0.6 animal units (1AU = 450-kg animal) per ha in April to 2.2 AUha-1 in June. Stocking rate and animal performance per area were similar for signalgrass in monoculture and SPS-Gliricidia, and both greater than SPS-Mimosa. Gliricidia enhanced animal performance and provided ecosystem services. Mimosa, however, reduced animal performance likely due to the competition with signalgrass. Mimosa trees, however, are an important source of income (timber used for fence posts) and that might overcome the losses in animal performance.

Implication of Urochloa spp. Intercropping and Conservation Agriculture on Soil Microbiological Quality and Yield of Tahiti Acid Lime in Long Term Orchard Experiment

Techniques such as intercropping and minimum tillage improve soil quality, including soil microbial activity, which stimulates the efficient use of soil resources by plants. However, the effects of such practices in soil under citrus orchards have not been well characterized. In this study, we aimed to determine the effects of mowing and intercrop species on soil microbiological characteristics beneath a Tahiti acid lime orchard. The orchard was planted using minimum tillage and intercropped with two species of Urochloa species (U. ruziziensis—ruzi grass; U. decumbens—signal grass), with two types of mowers for Urochloa biomass (ecological; conventional) and herbicide applications. The study was conducted over 10 years. The ecological mower made the largest deposition of the intercrop biomass, thus providing the lowest disturbance of soil microbial activity and increasing, on average over all 10 years, the basal soil respiration (45%), microbial biomass carbon (25%), abundance of 16S rRNA (1.5%) and ITS (3.5%) genes, and arbuscular mycorrhizal fungi (30%), and providing a ca. 20% higher fruit yield. U. ruziziensis in combination with ecological mowing stimulated the abundance of the genes nifH (1.5%) and phoD (3.0%). The herbicide showed little influence. We conclude that the use of U. ruziziensis as an intercrop in citrus orchards subjected to ecological mowing can be recommended for improving and sustaining soil quality and citrus fruit production.

Agrosilvopastoral Systems and Well-Managed Pastures Increase Soil Carbon Stocks in the Brazilian Cerrado

Agrosilvopastoral systems have been promoted as sustainable models that combine crops, livestock grazing, and forestry in the same area. We hypothesize that agrosilvopastoral systems can improve soil C and N stocks over time. Therefore, in this study, we aimed to evaluate the changes in soil C and N stocks after conversion of low-productivity pasture into well-managed pasture and agrosilvopastoral land in the Brazilian Cerrado. Soil samples were collected in 2016 and 2018 at 0–5, 5–10, 10–20, and 20–30 cm depths from the following areas: integrated crop-livestock-forest (ICLF), marandu grass (Brachiaria brizantha) monoculture (MAR), low productivity pasture of signal grass (Brachiaria decumbens) monoculture (PAST), and native vegetation (NV; “Cerrado”). The C and N content and stocks, 13C natural abundance, and C contents in the physical and chemical fractions of soil organic matter (SOM) were measured. The ICLF and MAR systems promoted faster recovery of soil C and N stocks at all soil depths compared with PAST. The C content of the free light fraction of SOM under the ICLF and MAR systems increased, reaching values similar to NV up to 20 cm. The C content was higher in the humin fraction at all depths in all areas, and for this measurement, the ICLF system performed remarkably compared with PAST at a depth of 5−10 cm. Our findings support the hypothesis that conversion of low-productivity pasture into agrosilvopastoral and actively managed pasture systems leads to improvements in soil quality and C and N stocks in the Brazilian Cerrado.

Sweet corn in no-tillage system on cover crop residues in the Brazilian Cerrado

In recent years, the growth of the cultivated area with sweet corn in conventional tillage system in Brazil expanded, although crops can be grown on different residues of cover crops, which improve nutrient cycling and crop productivity. The objective of this study was to evaluate the biomass production and to quantify the rate of plant residues decomposition of different cover crops, and correlate the results with the production and grain yield of sweet corn in an area located in the Cerrado biome. The experimental design used was randomized blocks with eight treatments: PM - pearl millet; SH - sunn hemp; SG - signal grass; PM + SH; PM + SG; SH + SG; PM+ SH + SG; FW - fallow (spontaneous vegetation), which preceded the cultivation of sweet corn. Fresh biomass (FB) and dry biomass (DB) of the cover crops were evaluated, as well as the rate of plant residue decomposition. Sweet corn productivity, straw and corncob weight, and grain yield were also determined. Pearl millet presented a better performance in FB production, decomposition rate, residue half-life (T½ life) in soil, yield, corn cob strawweight and yield of sweet corn. Pearl millet, when mixed with other plants, presented reduced rate of residue decomposition and increased residue T½ life. The FW presented the lowest biomass production, with great rate of decomposition and low T½ life. Cover crops grown before sweet corn in soils of good fertility did not affect crop agronomic characteristics. Pearl millet is the best cover crop adapted to Cerrado Brazilian climatic conditions to be used in monoculture or in mixtures with other plants.

CONTROLE CULTURAL E QUÍMICO DE Conyza spp. NO CONSÓRCIO DE MILHO COM Urochloa ruziziensis

As integrações de métodos de controle, visando o manejo de buva (Conyza spp.) passaram a ser práticas fundamentais nos sistemas integrados de produção, tais como milho (Zea mays) em consórcio com capim-ruziziensis (Urochloa ruziziensis). Os objetivos deste trabalho foram avaliar a eficácia da cobertura do capim-ruziziensis sobre a supressão da buva e avaliar opções de controle químico de buva em capim-ruziziensis. O primeiro experimento foi realizado após a colheita de milho consorciado com capim-ruziziensis, realizando avaliações da infestação de buva e sua correlação com a massa seca do capim. O segundo experimento consistiu na aplicação em mistura dos seguintes tratamentos, em esquema fatorial 3 x 7: 2,4-D (1209 g ha-1 e.a.), [halauxifen-methyl + 2,4-D] (5,76 + 780 g ha-1 i.a.) e dicamba (960 g ha-1 i.a.) compondo o primeiro fator; e metsulfuron-methyl (2,4 g ha-1 i.a.), chlorimuron-ehtyl (20 g ha-1 i.a.), diclosulam (25,2 g ha-1 i.a.), saflufenacil (35 g ha-1 i.a.), bentazon (576 g ha-1 i.a.), atrazine (1000 g ha-1 i.a.) e testemunha sem aplicação de herbicidas compondo o segundo fator. O cultivo do milho safrinha consorciado com capim-ruziziensis, reduziu respectivamente, em 80, 60 e 96% a emergência, o crescimento e a massa seca das plantas de buva durante o período de entressafra. Todos os tratamentos proporcionaram controle de buva com até 8 cm, exceto 2,4-D isolado. Para plantas de 8 a 16 cm, todos os tratamentos com associação de herbicidas foram satisfatórios. Em plantas maiores que 16 cm, houve morte total das plantas com a aplicação de saflufenacil em associação com todos os herbicidas auxínicos. Os tratamentos seletivos para o capim-ruziziensis foram 2,4-D e dicamba isolados e as associações com bentazon.

Seasonal herbage accumulation, plant-part composition and nutritive value of signal grass <i>(Urochloa decumbens)</i> pastures under simulated continuous stocking

In order to optimize the regrowth and harvest of signal grass (Urochloa decumbens) cv. Basilisk pastures it is necessary to establish more precise grazing management guidelines. The objective of this study was to evaluate herbage accumulation, plant-part composition and nutritive value of signal grass managed under contrasting levels of steady-state canopy heights. Treatments included 3 canopy height targets, i.e. 10 (S-short), 17.5 (M-medium) and 25 cm (T-tall), in a completely randomized design with 4 replications. Experimental units were 144-m2 plots which were grazed by groups of steers for short periods in an endeavor to keep canopy heights at the 3 desired targets. On average, herbage accumulation rate (HAR) in T pastures was greater than in M and S pastures, including the dry-wet season transition period in spring (September‒November). The S pastures had higher crude protein and lower acid detergent fiber concentrations than M and T pastures, especially in the first half of the calendar year. However, in vitro organic matter digestibility was similar for all treatments (612 g/kg). As S and M pastures had lower HARs than T pastures in the spring, it appears advantageous to maintain the signal grass canopy at ~25 cm in order to ensure quick regrowth with the return of the wet season. However, longer-term studies are needed with recording of animal performance before these initial findings can be promoted widely.

Potential use of Claroideoglomus etunicatum to enrich signal grass (Brachiaria decumbens Stapf.) for silvopasture preparation

Silvopasture system improvement in managing post-mining land resources has been done by searching for a quality grass. One of the selected grass species is signal grass (Brachiaria decumbens Stapf.). This research aimed to prepare signal grass through the inoculation of AMF Claroideoglomus etunicatum, as an effort to enrich its growth before being applied to post-mining soil. Research stages included the AMF inoculation on signal grass through spore culture and then transferred the colonized grass to the pot using sterile zeolite as a growth medium. The treatment on the first stage was without and with AMF inoculation (dose of 20 spores) on signal grass which was repeated for 12 times. Incubation in a spore culture was 4 weeks while incubation in a pot containing sterile zeolite medium was 8 weeks. Research data were analyzed using the Shapiro-Wilk’s normality test, Independent Sample T-test, and Pearson’s correlation test. Observation results showed that the inoculation of C. etunicatum on signal grass was significantly impact on the increase of plant height, stem diameter, number of leaves, number of tillers, shoot and root fresh weight, and shoot dry weight (p <0.05). Microscopic observation showed that there was AMF colonization on treated signal grass roots in the amount of 55 ± 0.06 % with number of spores was 252 ± 9.82 per 10 g zeolites, while AMF infection was not found in uninoculated signal grass. It is expected that by providing signal grass inoculated with AMF C. etunicatum would support its growth in post-mining land for Silvopasture system.

Contributions of intercropping systems for diversity and abundance of mite community on Jatropha curcas

Intercropping is an important strategy of pest biological control and has the potential of increasing abundance and diversity of natural enemies. Here we assessed the effect of six management crop systems on the diversity and abundance of mite pests and predatory mites associated to physic nut crops. The following crop systems were evaluated: jack beans (Canavalia ensiformis), guinea grass (Panicum maximum), signal grass (Brachiaria brizantha), cowpea (Vigna unguiculata) in succession to corn (Zea mays), physic nut free of spontaneous plants between-rows, and physic nut with spontaneous plants between-rows. Total number of mites was counted and their abundance, diversity and equitability were determined. The most abundant herbivorous mite species found in all crop systems were Polyphagotarsonemus latus and Tetranychus bastosi. Amblydromalus zannoui, Typhlodromus aripo, Typhlodromus peregrinus and Pronematus sp. were the most abundant predatory mites. Intercropping cowpea in succession to corn favoured the diversity and abundance of predatory mites in physic nut.

High-throughput phenotypic screening of random genomic fragments in transgenicriceidentified novel drought tolerance genes.

Novel drought tolerance genes were identified by screening thousands of random genomic fragments from grass species in transgenic rice. Identification of agronomically important genes is a critical step for crop breeding through biotechnology. Multiple approaches have been employed to identify new gene targets, including comprehensive screening platforms for gene discovery such as the over-expression of libraries of cDNA clones. In this study, random genomic fragments from plants were introduced into rice and screened for drought tolerance in a high-throughput manner with the aim of finding novel genetic elements not exclusively limited to coding sequences. To illustrate the power of this approach, genomic libraries were constructed from four grass species, and screening a total of 50,825 transgenic rice lines for drought tolerance resulted in the identification of 12 reproducibly efficacious fragments. Of the twelve, two were from the mitochondrial genome of signal grass and ten were from the nuclear genome of buffalo grass. Subsequent sequencing and analyses revealed that the ten fragments from buffalo grass carried a similar genetic element with no significant homology to any previously characterized gene. The deduced protein sequence was rich in acidic amino acid residues in the C-terminal half, and two of the glutamic acid residues in the C-terminal half were shown to play an important role in drought tolerance. The results demonstrate that an open-ended screening approach using random genomic fragments could discover trait genes distinct from gene discovery based on known pathways or biased toward coding sequence over-expression.

A broad diversity survey of Rhizoctonia species from the Brazilian Amazon reveals the prevalence of R. solani AG‐1 IA on signal grass and the new record of AG‐1 IF on cowpea and soybeans

AbstractLeaf blight, sheath blight, and web blight are major diseases caused by Rhizoctonia species on both Fabaceae and Poaceae plant hosts in the Brazilian Amazon agroecosystem. To determine the diversity of Rhizoctonia species associated with foliar diseases on fabaceous (cowpea and soybean) and poaceous (rice and signal grass [Urochloa brizantha]) hosts, a broad survey was conducted in Pará, Rondônia, Roraima, and Mato Grosso, in the Amazon, from 2012 to 2013. We extended our survey to Cerrado areas of Mato Grosso, and the lowlands of Paraíba Valley, in São Paulo, where these Rhizoctonia foliar diseases have not been reported so far. Our findings revealed that these diseases are caused by a diversity of Rhizoctonia solani AG‐1 complex. We detected that R. solani AG‐1 IA (sexual phase Thanatephorus cucumeris) was the predominant pathogen associated with signal grass leaf blight and collar rot diseases in the Amazon, especially in Rondônia and northern Mato Grosso. In addition, a subgroup of R. solani (AG‐1 IF), not previously reported in Brazil, was associated with leaf blight on cowpea and soybean, in Roraima. Another subgroup (AG‐1 ID) was also detected in Roraima. In Mato Grosso Cerrados we did not find any of the major Rhizoctonia foliar pathogens. Instead, R. oryzae (Waitea circinata) was the predominant species associated with a collar rot on U. brizantha. In the lowlands of São Paulo, R. oryzae‐sativae (Ceratobasidium oryzae‐sativae) was the predominant pathogen detected causing the rice sheath spot disease.