RESUMORealizou-se um experimento, em casa de vegetação, em arranjo fatorial 9 x 4, com o objetivo de avaliar o efeito de substratos orgânicos comerciais e inoculação de fungos micorrízicos arbusculares (FMAs) no desenvolvimento de mudas de cafeeiro, cultivar 'Catuaí Amarelo', IAC 62. Utilizaram-se substratos à base de fibra de coco (Golden Mix 11, Golden Mix 47 e Golden Mix 80), casca de pinus (Rendmax, Vida Verde com adubação, Vida Verde sem adubação e Terra do Paraíso), solo puro e solo + esterco (70% e 30%,v/v), inoculando-se os FMAs Glomus intraradices, Glomus etunicatum e Gigaspora margarita. Manteve-se um tratamento sem inoculação. Aos 200 dias após transplante avaliaram-se: altura, diâmetro do caule, número de folhas, matéria seca da parte aérea, matéria fresca da raiz, teor de fósforo na parte aérea, colonização radicular, comprimento do micélio externo, atividade da fosfatase ácida e teores de pigmentos fotossintetizantes nas folhas do cafeeiro. Independentemente da micorrização, o melhor crescimento das mudas foi obtido no substrato Vida Verde sem adubação. Os melhores efeitos da micorrização foram constatados nas plantas colonizadas por G. margarita e crescidas nos substratos convencional (solo + esterco) e Vida Verde com adubação, nas quais se verificaram mais eficácia na utilização de P, o que reverteu em maior crescimento e produção de biomassa, resultando em maior eficiência simbiótica. No substrato solo + esterco, a micorrização favoreceu a concentração de pigmentos fotossintetizantes e diminuiu a atividade da fosfatase ácida nas folhas do cafeeiro.Palavras-chave: café, Coffea arabica, micorriza, substrato, fosfatase ácida, pigmentos fotossintetizantes. ABSTRACT ARBUSCULAR MYCORRHIZAL FUNGI ON THE DEVELOPMENT OF COFFEE PLANTLETS USING DIFFERENT ORGANIC SUBSTRATESA greenhouse experiment with an alleatory factorial 9 x 4 scheme was carried out to evaluate the effects of different substrates and species of arbuscular mycorrhizal fungi (AMF) on the development of coffee plants, cultivar Catuaí Amarelo, IAC 62. Nine substrates were used: seven commercial organic substrates -four substrates containing composted pinus peel (Rendmax, fertilized Vida Verde, nonfertilized Vida Verde and Terra do Paraíso), three containing coconut fiber (Golden Mix-11, Golden Mix-47 and Golden Mix 80) and two using soil -a mixture of 70% soil and 30% cattle manure, usually used by the producer, and soil alone. The AMF were Glomus intraradices, Glomus etunicatum and Gigaspora margarita, and a control without AMF inoculation. The plants were harvested 200 days after transplanting and the following variables were analyzed -height, number of leaves, stem diameter, shoot dry weight,

Coffee seedlings are commonly produced on substrate composed of a mixture of soil and cattle manure, supplemented with chemical fertilizers. Alternatives to reduce production costs and produce seedlings of greater quality and health include the use of commercial organic substrates, which require less handling. The use of beneficial microorganisms such as arbuscular mycorrhizal fungi (AMF) can be considered a good alternative for production of more vigorous coffee seedlings. The main goal of this study was to evaluate the effect of the inoculation of AMF isolates on coffee seedlings development in a commercial organic substrate (based on coconut fiber) and conventional substrate (mixture composed of soil and cattle manure compost). Ten AMF were tested: Rhizophagus irregularis, Glomus macrocarpum, Claroideoglomus etunicatum, Rhizophagus clarus, Glomus spp., Gigaspora margarita, Acaulospora morrowiae, Acaulospora scrobiculata, Acaulospora spp., and Dentiscutata heterogamma. Plant growth, shoot P content, mycorrhizal colonization, extraradical mycelium length, phosphatase activity, and photosynthetic pigments were evaluated. The effects of mycorrhization depended on both the inoculated fungal species and the substrate for seedling cultivation. Inoculation of G. margarita, Acaulospora spp., and Glomus spp.in the conventional substrate conferred the best growth plant responses, increasing shoot biomass by 160 to 320%. In the commercial substrate, the most efficient AMF were R. clarus, Glomus spp, A. morrowiae and A. scrobiculata, with up to 149% of shoot biomass increase.The commercial organic substrate and the inoculation of some of the AMF isolates were highly beneficial to coffee seedlings development and can replace the use of the conventional substrate. These results open new opportunities for the use of AMF as an inoculant to improve coffee seedling production in commercial organic substrates.