BIODIVERSIDADE DE BACTÉRIAS ANTAGÔNICAS A FUNGOS ASSOCIADOS À SINDROME DA MORTE DO CAPIM-MARANDU (Brachiaria brizantha)

A síndrome da morte do capim-marandu (Brachiaria brizantha) é um dos principais problemas na degradação das pastagens no bioma Amazônia. A morte das forrageiras ocorre durante a época chuvosa por suscetibilidade a fitopatógenos. Assim, objetivou-se estudar sistemas de produção e selecionar bactérias antagônicas a Fusarium spp., um dos agentes fitopatogênicos. Os isolados bacterianos foram obtidos de 10 sistemas de produção, mata nativa e pousio, na chuva e na seca. Realizou-se a caracterização molecular de isolados por sequenciamento. Dois isolados de Fusarium foram testados. Para o patógeno 1, na época da chuva, 7,5% dos isolados apresentaram antagonismo enquanto na seca foi 15%. Para o patógeno 2, nem todos os isolados positivos para o patógeno 1 foram eficientes no controle, demonstrando a ocorrência de interações entre isolados bacterianos e Fusarium spp. Na chuva, para o patógeno 1, a mata apresentou maior número de isolados positivos (20%). Na seca, os tratamentos mata, 1-Floresta e 8-integração lavoura floresta para o patógeno 1, foram os que apresentaram maior número de positivos (25%). Na identificação molecular, 8 foram os gêneros bacterianos encontrados: Burkholderia, Bacillus, Brevibacillus, Streptomyces, Pseudomonas, Escherichia, Paenibacillus e Pandoraea, em que a maioria é descrita como capaz de controlar Fusarium spp. in vitro. Palavras-chave: Burkholderia; controle biológico; integração lavoura-pecuária-floresta. Biodiversity of bacteria antagonic to fungi associated with syndrome's death palisadegrass (Brachiaria brizantha) ABSTRACT: The death syndrome of marandu grass (Brachiaria brizantha) is one of the main problems in the degradation of pastures in the Amazon biome. Plant death occurs during the rainy season due to susceptibility to phytopathogens. Thus, the objective was to study production systems and select bacteria antagonistic to Fusarium spp., one of the phytopathogenic agents. Bacterial isolates were obtained from 10 production systems, native forest and fallow, in rain and drought season. Molecular characterization of isolates was carried out by sequencing. Two Fusarium isolates were assessed. For pathogen 1, in the rainy season, 7.5% of the isolates showed antagonism, while in the dry season it was 15%. For pathogen 2, not all isolates positive for pathogen 1 were efficient in the control, showing correlations between bacterial isolates and Fusarium spp. In the rain, for pathogen 1, the forest showed the highest number of positive isolates (20%). In the dry season, the treatments forest, 1-Forest and 8-plant-forest integration for pathogen 1, were ones with the highest number of positives (25%). In the molecular identification, 8 bacterial genera were found: Burkholderia, Bacillus, Brevibacillus, Streptomyces, Pseudomonas, Escherichia, Paenibacillus and Pandoraea, most of which are described as able to controlling Fusarium spp. in vitro. Keywords: Burkholderia; biological control; integrated crop-livestock-forest.

Tillering dynamics in spring and summer of marandu palisade grass pastures previously used under deferred grazing

ABSTRACT This work was conducted to evaluate the effect of deferred pasture condition of Brachiaria brizantha cv. Marandu in the late winter on tillering during the growing season. The treatments were three pasture conditions at late winter: short pasture, tall pasture and tall/mown pasture. In September and October, tiller appearance rate (TApR) and tiller mortality rate (TMoR) were greater in the tall/mown pasture. In November and December, tall pasture presented greater TApR. From November to January the TMoR was greater in the tall pasture. The tiller stability index of short and tall/mown pastures were greater in October. The short pasture presented a greater tiller number than the tall and tall/mown pastures during the entire experimental period. Deferred and short pasture of marandu palisade grass at late winter presents in general lower tiller mortality and higher population density of tillers from the early spring onwards, in comparison to tall pasture. The mowing of marandu palisade grass with high forage mass at the late winter, although it only temporarily compromises the population stability of tillers, also stimulates its fast tillering from spring on.

ALLELOPATHIC POTENTIAL OF AQUEOUS EXTRACT OF LEAF AND ROOT SESAME ON SICKLEPOD AND BRACHIARIA SEEDS

Sicklepod is an important weed in Brazil pastures, but control measures are not yet effective. Thus, allelopathy can be an alternative, due to its ecological importance and for being able to provide new structures sources for agrochemicals production. This research aimed to verify the allelopathic potential of sesame (Sesamum indicum L.) on germination and seedling development of sicklepod (Senna occidentalis L.) and brachiaria (Brachiaria brizantha). The treatments were root and leaf extract of sesame, and control (distilled water). Germination percentage, speed of germination, hypocotyl and radicle length were evaluated. Speed of germination, germination percentage and radicle length had no interference from the aqueous extracts. However, in brachiaria these traits had lower values than sicklepod. Hypocotyl length was not influenced by the extracts, however, the leaf extract showed lower growth of this feature. Allelopathy did not affect germination and speed of germination in both species, but interfered in brachiaria development.

Uso de corretivos do solo e a recuperação de pastagem degradada de Braquiária brizantha

A criação de bovinos no Brasil e um dos grandes pilares da economia, no qual a cada dia o foco e a maior disponibilidade de alimento ideal para consumo, gerando melhor aproveitamento das áreas, aumentando assim a produção por hectare. O objetivo com esse trabalho foi verificar a eficiência do uso de corretivos do solo na recuperação de uma pastagem degradada. O experimento realizou se na fazenda Santa Barbara no município de Orizona Goiás, em delineamento experimental de blocos casualizados, com três tratamentos de dez repetições onde os tratamentos foram: T1 testemunha sem aplicação dos corretivos de solo; T2 – aplicação de calcário 2,44 t ha-1; T3 - aplicação de calcário 2,44 t ha-1 e gesso agrícola 0,306 t ha-1. O plantio da Brachiaria brizantha foi feita a lanço no início do período chuvoso com aplicação de 10 Kg ha-1, após 90 dias do plantio foi realizado a coleta do material. Foram realizadas as coletas da forragem com o auxílio de um quadrado de ferro com diâmetro de 1,0 m2, sendo lançado sob a área da pastagens em 10 pontos aleatórios dentro de cada tratamento. Foram avaliados os teores de matéria seca, proteína bruta, umidade, extrato etéreo, fibra bruta, material mineral, Ca%, P%, NDT%. O trabalho apresentou resultado positivo na utilização dos corretivos (calcário + gesso) com aumento de 21% maior produção de matéria seca e níveis de macronutrientes adequados a alimentação animal.

Genetic Transformation of Apomictic Grasses: Progress and Constraints

The available methods for plant transformation and expansion beyond its limits remain especially critical for crop improvement. For grass species, this is even more critical, mainly due to drawbacks in in vitro regeneration. Despite the existence of many protocols in grasses to achieve genetic transformation through Agrobacterium or biolistic gene delivery, their efficiencies are genotype-dependent and still very low due to the recalcitrance of these species to in vitro regeneration. Many plant transformation facilities for cereals and other important crops may be found around the world in universities and enterprises, but this is not the case for apomictic species, many of which are C4 grasses. Moreover, apomixis (asexual reproduction by seeds) represents an additional constraint for breeding. However, the transformation of an apomictic clone is an attractive strategy, as the transgene is immediately fixed in a highly adapted genetic background, capable of large-scale clonal propagation. With the exception of some species like Brachiaria brizantha which is planted in approximately 100 M ha in Brazil, apomixis is almost non-present in economically important crops. However, as it is sometimes present in their wild relatives, the main goal is to transfer this trait to crops to fix heterosis. Until now this has been a difficult task, mainly because many aspects of apomixis are unknown. Over the last few years, many candidate genes have been identified and attempts have been made to characterize them functionally in Arabidopsis and rice. However, functional analysis in true apomictic species lags far behind, mainly due to the complexity of its genomes, of the trait itself, and the lack of efficient genetic transformation protocols. In this study, we review the current status of the in vitro culture and genetic transformation methods focusing on apomictic grasses, and the prospects for the application of new tools assayed in other related species, with two aims: to pave the way for discovering the molecular pathways involved in apomixis and to develop new capacities for breeding purposes because many of these grasses are important forage or biofuel resources.

First record of Mahanarva spectabilis (Distant) (Hemiptera: Cercopidae) in the state of Acre, Brazil

Spittlebugs are among the main insect pests of forage grasses in Brazil. In February 2021, a spittlebug infestation was verified in Xaraés palisadegrass (Brachiaria brizantha cv. Xaraés) in the municipality of Senador Guiomard, Acre state, Brazil. The specimens were captured with an entomological sweep net and identified as Notozulia entreriana (Berg) and Mahanarva spectabilis (Distant) (Hemiptera: Cercopidae). Notozulia entreriana is frequently captured in studies with spittlebugs in Acre state, though this is the first record of M. spectabilis in the state. This new record expands the species known geographical distribution in Brazil and the number of species of Mahanarva occurring in Acre state.