Taxonomic and pathogenic diversity of the blast pathogen populations infecting wheat and grasses in Minas Gerais

The blast disease of Poaceae is caused by a large species complex, among which P. oryzae is composed of several host-specialized lineages. The Pyricularia oryzae Triticum pathotype (PoT) causes the blast disease in wheat, but is also capable of infecting other grasses, which may serve as an inoculum reservoir for epidemics in wheat. In Brazil, severe wheat blast epidemics are most common in the Cerrado region. The dominant hypothesis is that signal grass (Urochloa sp.) and other gramineous plants harbor the wheat blast pathogen, thus serving as a major reservoir of inoculum for epidemics in wheat. A two-year survey of the Pyricularia blast pathogens was conducted in both wheat and non-wheat areas as well as prior (February) and during (May) the wheat growing season in Minas Gerais. A total of 1,368 plant samples representative of 31 Poaceae species, including wheat, were collected and inspected for the presence of blast symptoms. During the isolations, 932 isolates were obtained, being one fourth obtained from gramineous plants. A subset of 572 isolates was selected for identification at the species level based on portions of the CH7-BAC9 gene sequences. Most of the isolates (n = 494) were P. oryzae, within which 68% were PoT and 32% non-PoT based on two PCR assays targeting (MoT3 and C17 PCR assays). The PoT lineage was found predominantly (97%) in wheat and rarely in the other hosts, even nearby wheat fields (2.1%), as well as at longer distances from wheat regions (0.1%). The blast pathogen population isolated from signal grass grouped in different clades from PoT, and therefore referred to Urochloa lineage (PoU). A series of cross-inoculation greenhouse experiments was conducted using wheat (cv. BRS Guamirim and BR 18-Terena) and signal grass (cv. Marandu) as host and 14 PoT and six PoU isolates as pathogen factor. In the first leaf-inoculation experiment, results showed a significant interaction between host and pathogen; PoT was strongly/weakly aggressive towards wheat/signal grass and PoU was strongly/weakly aggressive towards signal grass/wheat. In inoculated wheat heads, PoT was more aggressive (>91% infected spikelets) than PoU (52% infected spikelets). In a third experiment, four signal grass cultivars (Marandu, Basilisk, Piatã, and Xaraés) were inoculated with the same set of 20 isolates. Similarly, signal grass cultivars were generally more susceptible to PoU than PoT. Severity induced by PoU was twice (7.7% severity) as high as PoT (3.8%) and so was the number of conidia/leaf produced by PoU (47,500) and PoT (23,200). Two groups of signal grass cultivars were formed, the most susceptible composed of Marandu and Basilisk and the least susceptible composed of Piatã and Xaraés. Results of our study confirm the host-specialization and the shaping of the blast populations according to the host. We further suggest that grasses in general, especially signal grass, may not play a major role as an inoculum reservoir for PoT, as it harbors mainly the PoU population. However, due to the large extent of pasture-growing regions and cross-infection ability in wheat, signal grass may harbor amounts of PoT inoculum that are sufficient for initiating leaf and head blast epidemics in wheat blast in Minas Gerais state.

Signal Grass Deferred Pastures Fertilized with Nitrogen or Intercropped with Calopo

This study aimed to evaluate the accumulation, structural characteristics, and chemical composition of deferred signal-grass pastures that were subjected to four treatments: without nitrogen fertilization, intercropped with calopo (Calopogonium mucunoides), and fertilized with urea N (50 kg ha−1 and 100 kg ha−1) for 2 years. The design was in randomized blocks, with two blocks and two repetitions of each treatment per block. There were effects of the interaction between treatment and year on green dry mass, forage accumulation, density of vegetative tillers, and crude protein content (simulated grazing). The effects of the treatments on the height, falling index, green dry mass/dead dry mass ratio, number of dead, live and total tillers, and crude protein content (direct cutting) were also observed. Signal-grass–calopo-intercropping ensured adequate mass and forage accumulation and crude protein content equivalent to those of fertilized pastures. In addition, the intercropped pasture showed a higher percentage of leaves and a higher crude protein content compared with those for the other treatments (simulated grazing). The green dry mass/dead dry mass ratio was highest in the intercropped pasture and was equivalent to only that of the pasture fertilized with a low dose of nitrogen. Therefore, signal-grass–calopo-intercropping may be recommended for deferment.

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.

Moorochloa eruciformis (sweet signal grass).

Moorochlora eruciformis is an annual herb, fodder crop and common agricultural weed, native to Africa, Asia and the Mediterranean; it has also been introduced to the Americas and Oceania. Crop seed contamination is a possible pathway for dispersal of this species. It is reported as invasive in Cuba, Spain and Australia as well as islands in Oceania. Despite this, there is limited information available about the economic and environmental impacts of this species or its dispersal potential.

Seasonal herbage accumulation, plant-part composition and nutritive value of signal grass (Urochloa decumbens) 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.

Effects of nitrogen fertilisation and irrigation on seed yield and yield components of signal grass (Urochloa decumbens)

The effects of nitrogen (N) fertiliser rate and irrigation on seed yield and its components were evaluated for signal grass (Urochloa decumbens (Stapf) R.D. Webster; syn. of Brachiaria decumbens Stapf) cv. Basilisk in a field experiment in Umuarama, Paraná, Brazil. Two water regimes (irrigated and non-irrigated) and four nitrogen (N) fertiliser rates (0, 25, 50 and 75 kg ha–1) were applied to perennial signal grass crops in a split-plot randomised complete block design with three replications. In two consecutive harvests, favourable rainfall resulted in irrigation having limited influence on most measurements, and the combined application of irrigation and N fertiliser did not improve seed yield. Compared with the nil N, the highest N application rate significantly increased seed yield for the first crop (266 vs 498 kg ha–1) and the second crop (104 vs 286 kg ha–1). Nitrogen fertilisation significantly increased number of seed per area, reproductive tiller density and plant biomass at harvest for the first and second crops. Harvest index, 1000-seed weight, reproductive tiller weight, number of spikelets per panicle and number of seeds per panicle were unaffected by N rate. Harvest index ranged from 1.10% to 3.63% and 1000-seed weight from 2.15 to 3.36 g. There were no treatment effects on number of days to flowering or anthesis. Fertilisation with 75 kg N ha–1 for the first crop and 50–75 kg N ha–1 for the second crop maximised signal grass seed yield.