Associative-diazotrophic-bacteria-from-forage-2019.pdf - CSIRO PUBLISHING Crop Pasture Science 2019 70 899–907 https/

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Associative diazotrophic bacteria from forage grasses in the Braziliansemi-aridregionareeffectiveplantgrowthpromoters Gabiane dos Reis Antunes A , Sheilla Rios Assis Santana A , Indra Elena Costa Escobar B , Marivaine da Silva Brasil C , Gherman Garcia Leal de Araújo D , Tadeu Vinhas Voltolini D , and Paulo Ivan Fernandes-Júnior D,E A Colegiado de Zootecnia, Universidade Federal do Vale do São Francisco, Petrolina, PE, 56300-000, Brazil. B Colegiado de Farmácia, Universidade Federal do Vale do São Francisco, Petrolina, PE, 56304-917, Brazil. C Campus Pantanal, Universidade Federal do Mato Grosso do Sul, Corumbá, MS, 79304-902, Brazil. D Embrapa Semiárido, Petrolina, PE, 56302-970, Brazil. E Corresponding author. Email: [email protected] Abstract. The study of plant growth-promoting bacteria (PGPB) can identify outstanding bacteria for crops. For forage grasses adapted to drylands, the selection of PGPB can increase the fi eld performance of pastures. The aim of this study was to isolate, and characterise at molecular, biochemical and symbiotic levels, diazotrophic bacteria obtained from buffel grass ( Cenchrusciliaris ),sorghum( Sorghumbicolor )andTifton85( Cynodon spp.)fromBrazilian semi-aridregion fi elds.Field- grown plants were collected, and the roots were surface-disinfected, crushed and inoculated in a semi-solid medium. After the formation and con fi rmation of microaerophilic pellicles, the bacteria were isolated and puri fi ed. All bacterial isolates were subjected to nifH gene ampli fi cation and identi fi ed by their partial 16S rRNA gene sequences. The bacteria were evaluated for the production of auxins and siderophores, calcium phosphate solubilisation, and diazotrophic ability as in vitro plant growth-promotion traits. A plant inoculation assay was conducted to assess the plant growth- promotion abilities of the bacterial isolates. Twenty-one bacterial isolates harboured the nifH gene ( nifH + ), among which nine were obtained from sorghum, eight from buffel grass, and four from Tifton 85. The bacterial isolates were classi fi ed as Bacillus (8), Stenotrophomonas (7), Agrobacterium (4), Cellulomonas (1) and Paenibacillus (1). All were shown to be auxin producers, with 14 isolates showing diazotrophic capacity in vitro . Fourteen isolates increased plant N content, but the bacterial strains ESA 392 and ESA 398 ( Bacillus ), ESA 397 and ESA 407 ( Stenotrophomonas ), and ESA 401 ( Agrobacterium ) were shown to promote both plant growth and N nutrition. These strains are candidates for further assays to evaluate their agronomic performance under fi eld conditions, aiming inoculant production for forage grasses in drylands. Additional keywords: biological nitrogen fi xation, Caatinga, plant growth promotion traits, strain selection. Received 21 February 2019, accepted 14 August 2019, published online 22 October 2019 Introduction The north-eastern region of Brazil is home to 65.6% of the country s sheep and 92.8% of its goats, constituting more than 22millionanimals(IBGE 2017 ).Mostoftheseanimalsareraised in the semi-arid belt on family-based farms lacking expensive
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